AECL-6416 ATOMIC ENERGY ffjj^ L'ENERGIE ATOSVIIQUE OF ... · Acres Consulting Services Limited in...

AECL-6416

ATOMIC ENERGY ffjj^ L'ENERGIE ATOSVIIQUEOF CANADA LIMITED V f i j DU CANADA

A DISPOSAL CENTRE FOR IMMOBILIZED NUCLEAR WASTE:

CONCEPTUAL DESIGN STUDY

UN CENTRE DE STOCKAGE POUR LES DECHETS NUCLEAIRES FIXES:

ETUDE DE CONCEPTION

Acres Consulting Services Limitedin association with/en association avec

RE/SPEC Inc.Dilworth, Secord, Meagher and Associates

and/et

Design and Project Engineering Branchin association with/en association avecW. L. Wardrop and Associates Limited

Whiteshell Nuclear Etablissement de RecherchesResearch Establishment Nucleaires de Whiteshell

Pinawa, Manitoba ROE 1L0

February 1980 fevrier

ATOMIC ENERGY OF CANADA LIMITED

A DISPOSAL CENTRE FOR IMMOBILIZED NUCLEAR WASTE:CONCEPTUAL DESIGN STUDY

by

Acres Consulting Services Limitedin association with


and

Design and Project Engineering Branchin association with

W.L. Wardrop and Associates Limited

Whiteshell Nuclear Research EstablishmentPinawa, Manitoba ROE 1L0

1980 February

AECL-6416

UN CENTRE DE STOCKAGE POUR LES DECHETS NUCLEAIRES FIXES:ETUDE DE CONCEPTION

par

Acres Consulting Services Limiteden association avec


et

Le Service d'Ingénierie de Conceptions et Projetsen association avec


RESUME

Ce rapport décrit une étude conceptuelle d'un centre de stock-age pour les déchets nucléaires fixés. Les installations en surfacecomprennent des usines de prépara.ion des cylindres en acier contenantles déchets nucléaires fixés dans le verre, des bâtiments à chevaletd'extraction de puits et toutes les installations de soutien nécessai-res. L'enceinte de stockage souterraine est située à un seul niveau àune profondeur de 1000 m. Les cylindres de déchets sont mis er; placedans des trous de sondage des planchers de galeries. Toutes les instal-lations en surface et souterraines sont décrites, les opérations et lesprogrammes sont résumés et les prévisions de coûts et les besoins enmain d'oeuvre sont indiqués.

L'Energie Atomique du Canada LimitéeEtablissement de Recherches Nucléaires de Whiteshell

Pinawa, Manitoba ROE 1L01980 février

AECL-6416

A DISPOSAL CENTRE FOR IMMOBILIZED NUCLEAR WASTE:CONCEPTUAL DESIGN STUDY

by

Acres Consulting Services Limitedin association with

RE/SPEC Inc.Dilworth, Secord, Meagber and Associates

and

Design and Project Engineering Branchin association with


ABSTRACT

This report describes a conceptual design of a disposal centrefor immobilized nuclear waste. The surface facilities consist of plantsfor the preparation of steel cylinders containing nuclear waste immobil-ized in glass, shaft headframe buildings and all necessary supportfacilities. The underground disposal vault is located on one level at adepth of 1000 m. The waste cylinders are einplaced into boreholes in thetunnel floors. All surface and subsurface facilities are described,operations and schedules are summarized, and cost estimates and manpowerrequirements are given.

Atomic Energy of Canada LimitedWhiteshell Nuclear Research Establishment

Pinawa, Manitoba ROE 1L01980 February

AECL-6416

CONTENTS

Page

1. INTRODUCTION 1

2. THE CONCEPT 3

2.1 FUEL CYCLE AND WASTE DISPOSAL SCENARIO 32.2 IMMOBILIZED WASTE QUANTITIES, CHARACTERISTICS

AND CONTAINER DESIGN 5

2.2.1 Quantities 52.2.2 Characteristics 52.2.3 Container 6

2.3 DISPOSAL CENTRE FACILITIES AND OPERATIONS 7

2.3.1 Surface Facilities 72.3.2 Vault 8

TABLE 10FIGURES 11

3. SURFACE FACILITIES 15

3.1 SITE LAYOUT 15

3.1.1 Description 15

3.1.2 Materials Movement 16

3.2 DESCRIPTION OF FACILITIES 17

3.2.1 Waste Immobilization Plants 17

3.2.1.1 Process Description 173.2.1.2 Reference Plant Description 19

3.2.2 Wacte Shaft Headframe 203.2.3 Service Shaft Headframo. 213.2.4 Backfill Preparation Plant 213.2.5 Low-Level Liquid Waste (LLW) Treatment 223.2.6 Solid Waste Management 223.2.7 Services 233.2.8 Environmental Laboratory 24

FIGURES 25

.../cont.

CONTENTS, continued

Page

4. VAULT 35

4.1 STUDY METHODOLOGY, SPECIFICATIONS ANDDESIGN CRITERIA 35

4.4.1 General Specifications and Constraints 354.1.1.1 Setting 35U.I.1.2 Operations 36

4.2 THERMAL-ROCK MECHANICS ANALYSIS 364.3 LAYOUT 39

4.3.1 Shafts and Major Drifts 404.3.2 Panels 414.3.3 Rooms 42

4.4 VAULT DEVELOPMENT AND OPERATION 42

4.4.1 Master Schedule 424.4.2 Access and Demonstration, Phase I 444.4.3 Primary Development, Phase II 444.4.4 Panel Development and Emplacement,

Phase III 454.4.5 Maintenance and Decommissioning,

Phase IV 46

4.5 FACILITIES AND EQUIPMENT 46

4.5.1 Rock Excavation ind Handling 464.5.1.1 Access and Demonstration 464.5.1.2 Primary Development 474.5.1.3 Panel Development 48

4.5.2 Shafts and Hoists 50

4.5.2.1 Service Shaft and Hoist 504.5.2.2 Waste Shaft and Hoist 514.5.2.3 Ventilation Shafts 52

4.5.3 Container Handling 52

.../cont.

Services4.5.4.14.5.4.24.5.4.34.5.4.44.5.4.5

VentilationCompressed AirWaterDrainage and Pumping SystemPower System

CONTENTS, continued

Page

4.5.4 Services 545456575759

4.6 BACKFILLING AND SEALING 60

TABLE 63FIGURES 64

5.. COSTS AND MANPOWER REQUIREMENTS 77

3.1 COSTS 77

5.1.1 Basis for Cost Estimates 77

5.1.2 Surface Facilities 73

5.1.3 Vault 79

5.2 MANPOWER REQUIREMENTS 80

5.2.1 Surface Facilities 80

5.2.2 Vault 80TABLES 82FIGURE 92

6. SUMMARY, CONCLVSIOm AND RECOMMENDATIONS 93

6 1 SUMMARY AND CONCLUSIONS 93

6.1.1 General 93

6.1.2 Technical Feasibility 936.1.3 Schedules 956.1.4 Cost Estimates 956.1.5 Manpower Requirements 96

.../cont.

CONTENTS, concluded

Page

6.2 RECOMMENDATIONS 97

6.2.1 Surface Facilities 976.2.2 Vault 98

TABLE 100

7. REFERENCES 101

APPENDIX A BIBLIOGRAPHY OF SUPPORTING STUDIES 102

APPENDIX B THERMAL-ROCK MECHANICS 104

1. INTRODUCTION

A program has been initiated by Atomic Energy of Canada

Limited (AECL) to develop methods for the disposal of irradiated fuel

and/or high-level radioactive wastes . Since the reference concept is

burial deep underground in crystalline rock, a major segment of the

program involves the design of an underground vault which will safely

Isolate nuclear wastes from the biosphere. This report presents a

synthesis of the results of conceptual studies, carried out in fiscal

year 1978, on the deaign of a disposal centre for immobilized nuclear

waste. The main surface facility is an immobilization and packaging

plant for the waste. Shafts link the surface to the underground vault.

The wastes are emplaced in rooms underground, and the rooms are then(2)

backfilled. A companion report describes a similar disposal centre

for immobilizing and disposing of irradiated fuel.

Both irradiated fuel and immobilized waste disposal concepts

have been studied because the Canadian government has not yet determinedA

which route the Canadian nuclear program will follow. Irradiated CANDU

fuel contains fissionable material whose recoverable energy is at least

equivalent to that of natural uranium and is several times that of

natural uranium if it is used in conjunction with thorium. The key to

extracting this energy is fuel recycle, which includes chemical sepa-

ration of the true radioactive waste from the other material in the

fuel. However, there is considerable debate in the international

community concerning the future role of commercial reprocessing. Until

the government has made its decision, therefore, it is essential to

develop technologies that can immobilize and dispose of either type of

waste.

CANada Deuterium Uranium

- 2 -

The objectives of these studies were to develop a reference

design for the vault, and to develop designs fcr the attendant waste

handling, backfill and sealing operations, and for the surface immo-

bilization plants and surface services. Costs and manpower requirements

were also determined. Emphasis was placed on analysis of technical

feasibility and on studying one complete scenario in reasonable detail,

rather than on investigating a broad range of processing and disposal

alternatives. The vault layout and container emplacement designs were

derived from preliminary studies previously performed by Acres Con-(3)

suiting Services Limitedv .

The past year's studies were only one stage in the on-going

investigation. They have not developed the final designs or even neces-

sarily complete ones Other emplacement and vault layout options, as

well as surface fa iities, will be investigated in future studies.(2)

However, the des ,ns presented here and in the companion report are a

reference to which the other alternatives can be compared.

Surface facility design was performed by the Design and

Project Engineering Branch, Whiteshell Nuclear Research Establishment,

Atomic Energy of Canada Limited, in association with W.L. Wardrop and

Associates Limited. The study coordinator was M.M. Ohta (AECL).

The underground vault design and analyses were performed by

Acres Consulting Services Limited in association with RE/SPEC Inc. and

Dilworth, Secord, Meagher and Associates Limited. R.G. Charlwood

(Acres) was the study manager and A.S. Burgess was the study engineer.

The disposal centre study was funded by the Whiteshell Nuclear

Research Establishment (WNRE), Atomic Energy of Canada Limited, with

H.Y. Tammemagi acting as technical coordinator.

2. THE CONCEPT

2.1 FUEL CYCLE AND WASTE DISPOSAL SCENARIO

The disposal centre has been designed to immobilize and dis-

pose of all high-level waste which would be produced by reprocessing all

the irradiated fuel discharged from all once-through natural uranium

fuelled CANDU-PHW (CAMada IJeuterium Uranium - .Pressurized Heavy Vfater)

reactors in Canada up to and including the year 2016. The CANDU fuel

cycle, with reprocessing, is illustrated in Figure 2-1.

The rate of production of reprocessing waste, and hence of

waste packages, has been estimated based on the following assumptions:

1. All irradiated natural uranium fuel discharged from standard

CANDU-PHW reactors in Canada up to the year 2016 will be re-

processed. The separated plutonium and uranium are assumed to

be used in advanced fuel cycles. Only the waste from re-

processing the once-through fuel is considered in this report.

2. The fuel will have been irradiated to 588 GJ/kg U, and cooled

for a minimum of 10 years before reprocessing.

3. The arisings are based on a reactor development scenario with

a total once-through reactor generating capacity in Canada of

194 GW(e) in the >ear 2016.

4. Each waste immobilization plant will operate at design capa-

city for 30 years. The in-service dates will be:

Plant Capacity(Mg V/a)1500150030003000

In-Service Date(Jan. 1)2000200320C&2014

- 4 -

5. Each container will include the waste from reprocessing fuel

containing 1.45 Mg U.

6. Immobilization and packaging of the reprocessing waste will be

followed by emplacement of the containers in the vault.

The disposal centre development and operation timetable

specified for the studies was:

1. Selection of site completed 1984

2. Demonstration facility completed 1983

3. Start of construction of full scale vault 1994

4. Start of emplacement of waste packages 2000

5. End of large-scale emplacement 2043

6. Backfilling drifts and start of shaft sealing 2044

For the purposes of this study, it was assumed that the full

scale vault would be built as an extension of the demonstration facility.

Other scenarios would, of course, lead to other timetables.

The rate of production of reprocessing waste, its key proper-

ties in the immobilized form and the packaging concept are summarized in

Section 2.2.

The disposal centre layout (Figure 2-2) shows the surface

facilities required for immobilizing liquid reprocessing waste in glass

and its packaging in steel containers. The filled containers may be

temporarily stored at the surface before transfer to the underground

emplacement rooms for disposal. When full, the underground vault and

entries will be backfilled and sealed.

- 5 -

The major on-site facilities and operations are summarized in

Section 2.3. More complete descriptions of facilities and equipment are

given in Sections 3 and A.

2.2 IMMOBILIZED WASTE QUANTITIES, CHARACTERISTICS AND

CONTAINER DESIGN

2.2.1 Quantities

The disposal centre accepts reprocessing wastes from irra-

diated fuel arisings to the year 2016 for immobilization and emplacement

in containers in the vault by the year 2043. The key quantities involved

in this scenario are summarized in Table 2-1.

The maximum waste immobilization, packaging and emplacement

rate is 6210 containers per year. A cumulative total of 186 300 con-

tainers will be emplaced, derived from the waste from reprocessing

270 000 Hg U of irradiated fuel. This quantity of irradiated fuel would

arise from the generation of approximately 14x10 kW-h of electricity.

2.2.2 Characteristics

The high-level wastes processed at the disposal centre will be

a mixture of the following two streams from fuel reprocessing:

1. A concentrated aqueous stream which will contain virtually all

of the fission products and will contribute most of the initial

heat generation. This stream may contain small quantities of

actinides.

2. An alkaline stream which will contain most of the plutonlum

and actinides. This stream will contribute most of the long-

term toxicity.

- 6 -

Glass was trhe only waste immobilization form considered in the

study. An alkaline borosilicate glass was selected because:

1. Borosilicate glasses have better mechanical, chemical, thermal

and radiolytic stability than phosphate glasses.

2. Phosphate glasses and their components are highly corrosive,

requiring exotic construction materials for the processing

equipment and waste containers.

3. Borosilicate glasses are easier to process as they melt at

lower temperatures than phosphate glasses.

The reference waste glass contains approximately one percent

fission products by weight. Detailed composition of the optimum glass

for CANDU waste is a subject of ongoing research and development.

2.2.3 Container

The reference immobilized waste container is shown in Figure 2-3.

It is constructed of AISI-304L stainless steel because of the high

temperatures and oxidizing conditions to which it is exposed during the

immobilization process.

E;.ch container encapsulates a glass block with a volume of

0.43 m and a weight of 1075 kg. Total package weight is 1675 kg. It

contains fission products derived from reprocessing seventy-seven bundles

of CANDU fuel. For 10-year cooled waste, the surface radiation field of

a filled container is expected to be in the range of 100 Gy/h, requiring

radiation shielding as well as remote handling at the immobilization

plants ar.i in the vault.

- 7 -

2.3 DISPOSAL CENTRE FACILITIES AMD OPERATIONS

2.3.1 Surface Facilities

The surface facilities will receive liquid high-level repro-

cessing wastes for immobilization. Their operations are shown diagram-

matically in Figure 2-4.

The following major operations will be performed in the surface

facilities:

1. Evaporate, calcine, and vitrify the waste arisings.

2. Fill and seal the container.

3. Provide temporary storage of the container at the surface.

The highly-radioactive waste liquid will be spray-calcined and

fed into a melter, where it will be mixed with glass frit to form molten

borosilicate glass. The glass will then be poured into the container.

When it has cooled, the container will be sealed, inspected and decon-

taminated.

It has been assumed that the immobilization plants will be

located within ICO m of the headframe so transportation will be through

a shielded conveying system, and the need for on-site transport flasks

will be avoided.

Temporary storage will be provided in the headframe building

for approximately 1500 containers, thereby insulating the process oper-

ations from potential delays in the vault. The reference storage system

is a dry hot-cell.

- 8 -

The handling system will be designed for reliable operation

and will be operated to minimize the radiation exposure to the opera-

tors. As with all equipment designed for operation in a radioactive

environment, it will be simple, with few components to maintain. Those

requiring maintenance will be strategically located and easily accessed.

2.3.2 Vault

The vault is designed for construction on a modular basis.

When complete, it will consist of 16 panels each containing 24 rooms.

Each room will accommodate 500 containers emplaced in a grid of drill

holes in the floor.

Initially, the two exhaust shafts would be sunk, one to be

used for intake ana one for exhaust during the demonstration phase; the

demonstration rooms would then be excavated.

The development and emplacement operations are planned on a

retreating basis from the exhaust shafts toward the main waste-lowering

shaft and intake ventilation shaft. The perimeter drifts will be used

for waste haulage, while the central drift will be used for construction

traffic, thus providing separation between waste emplacement and exca-

vation operations.

The vault receives immobilized waste containers from the

surface for disposal. Underground operations are shown in Figure 2-4.

Operations directly related to the active material are:

1. Transfer from the surface buffer storage to cage,

2. Transport by unshielded cage to vault level.

3. Transfer to underground buffer storage.

- 9 -

4. Transport in shielded flask to emplacement room.

5. Emplacement in drill holes in room floor.

6. Backfilling holes and rooms.

There is a significant mining operation in progress under-

ground at the same time.

Each room will be backfilled on completion of the waste em-

placement. Once all the rooms in the vault have been filled, the drifts

will be backfilled and the shafts will be sealed, thus completing the

disposal operation.

- 10 -

TABLE 2-1

IRRADIATED FUEL ARISINGS, REPROCESSING AND WASTE

IMMOBILIZATION QUANTITIES

Year

2000200120022003200420052006200720082009201020112012201320142015201620172018201920202021202220232024

1 2025202620272028202920302031203220332034203520362037203820392040204120422043

Irradiated FuelArisings

Annual(Mg U/a)

9 10010 30011 40012 30013 30014 40012 90012 90012 80012 70012 50012 40012 40012 20012 10011 900

11 800

Cumulative(Mg U)

64 40073 500S3 80095 200

107 500120 400133 400146 300159 200172 000184 700197 200209 600222 000234 200246 300258 200

270 000

Reprocessing Operations

ReprocessingRate

(Mg U/a)

1 5001 5001 5003 0003 0003 0006 0006 0006 0006 0006 0006 0006 0006 0009 0009 0009 0009 0009 0009 0009 0009 0009 0009 0009 0009 0009 0009 0009 0009 0007 5007 5007 5006 0006 0006 0003 0003 0003 0003 0003 0003 0)03 0)03 000

Cumulative(Mg U)

Reprocessed

1 5003 0004 5007 500

10 50013 500

' 19 50025 50031 50037 50043 50049 50055 50061 50070 50079 50088 50097 500106 500115 500124 500133 500142 500151 500160 500169 500178 500187 500196 500205 500213 000220 500223 000234 000240 000240 000249 000252 000255 000258 000261 000264 000267 000270 000

Reprocessing WasteImmobilization and Packaging

Waste ContainerProduction Rate(Container/a)

1 0351 0351 0352 0702 0702 0704 1404 1404 1404 1404 1404 1404 1404 1406 2106 2106 2106 2106 2106 2106 2106 2106 2106 2106 2106 2106 2106 2106 2106 2105 1755 1755 1754 1404 1404 1402 0702 0702 0702 0702 0702 0702 0702 070

CumulativeNumber ofContainers

1 0352 0703 1055 1757 2459 31513 45517 59521 73525 87530 01534 15538 29542 43548 64554 85561 06667 27573 48579 69585 90592 115S8 325

104 535110 745116 955123 165129 375135 585141 795146 970152 145157 320161 460165 600169 740171 810173 880175 950178 020180 090182 160184 230186 300

- 1 1 -

FUEL FABRICATION

tORE MILLING a PROCESSING

t

CANDU REACTOR 0 D n t l D

LUJL-MIU

EXPLORATION MINING

URANIUM ORE

r

i•i

i

FUEL REPROCESSING

ITO ADVANCEDFUE:L CYCLE

VAULT SURFACEFACILITIES

DISPOSAL' VAULT

DISPOSAL BY EMPLACEMENT

vFIGURE 2 - 1 . CANDU FUEL CYCLE WITH REPROCESSING

REPROCESSED WASTECONTAINER EMPLACEMENT

WASTE PECEIVINd, PACKAGINGvAMD HANDLING

•^FACILITIES

WASTE SHAFT

*NOTEBLDGS. NOTTO SCALE

ERVICE SHAFT

EMPLACEMENT ROOM

WASTE HAULAGE DRIFT

BACKFILL RAIL HAULAGE DRIFT

MAIN DEVELOPMENT DhlFT

ROCK RAIL HAULAGE DRIFT

WASTE HAULAGE DRIFT

DOWJJCASTVENTILATIONSHAFT

FIGURE 2-2. DIAGRAMMATIC LAYOUT OF DISPOSAL CENTRE

- 13 -

TOTAL CONTAINER WEIGHT

1675 kg.

DIMENSIONS IN mm

3275•»>*N>>*'

\\\\\S \\S\ VO^N. W

FIGURE 2-3. CONTAINER FOR IMMCDILIZED WASTE

-c-I

FIGURE 2-4. SURFACE FACILITIES AND VAULT OPERATIONS

- 15 -

3. SURFACE FACILITIES

3.1 SITE LAYOUT

3.1.1 Description

The major surface facilities at the disposal centre will be

the waste immobili2ation plants, waste shaft headframe building (includ-

ing the waste storage cell), service headframe and support services.

They will be located on a 38-ha site as shown in Figure 3-1. For this

scenario, an exclusion zone excending 1 km from the mine ventilation

intake and exhaust stacks has been assumed. Figure 3-2 shows the

relative sizes cf the centre, the surface facilities and the vault, and

also shows the proposed exclusion zone.

The buildings at the centre have been arranged around the

waste shaft headframe building. Waste containers are transferred from

the immobilization plants through underground tunnels. Situating the

immobilization plants along an arc close to the waste shaft minimizes

the tunnel lengths.

The administrative buildings, stores, warehouse, inactive

maintenance workshop, mined rock handling and backfill preparation

facilities are arranged close to the vault service shaft for ease of

materials and personnel movement. A cafeteria has been provided in the

inactive area. Power and heating plant are centrally located to reduce

utility piping and power line costs, whereas water supply and inactive

liquid waste treatment systems are located near the water source.

- 16 -

3.1.2 Materials Movement

The maximum rates at which materials will be received at the

centre are as follows:

1. Vault backfill material (900-1000 m 3/d).

2. Glass frit (200 Mg/week).

3. Coal for Heating Plant (90 Mg/d).

4. Empty waste containers (217/week).

5. Miscellaneous materials including equipment, chemicals and

supplies.

Because of the large quantities of materials, rail and road

access is desirable. Economics of the specific mode will depend on the

source location. Storage areas and bins have been provided close to the

point of use, e.g., coal is stored outside in pits close to the heating

plant. Waste containers are received and stored in designated areas at

each plant. Two-week storage bins have been provided for glass frit,

and each bin serves two immobilization plants.

Most other materials are expected to be delivered to the site

by truck. A warehouse and material storage yard are available for

equipment, materials of construction and other bulk materials storage.

Chemicals will be received and stored at the points of consumption.

Small equipment, components, tools and other supplies will be received

at the stores building.

Movement of active materials within the site is generally

limited to the active zone. Inactive wastes and materials can leave the

active zone through one of the control points after monitoring. The

major inactive material which will require disposal is the mine rock.

- 17 -

A 17-hectare disposal area is provided at the site, and the rock will be

piled by scraper trucks in a pile 10 m high.

Transfer of immobilized waste containers from the plants to

the temporary storage facility will be through four independent tunnels.

Each tunnel will be approximately 4 m wide to permit maintenance.

3.2 DESCRIPTION OF FACILITIES

3.2.1 Waste Immobilization Plants

To achieve the desirable immobiliEation rates, a total of four

waste vitrification plants are provided. Since the plants are identical

in concept, only the reference plant of 1035 waste containers per annum

capacity is described below.

3.2.1.1 Process Description

The immobilization process includes the following four major

components:

1. Calcination.

2. Vitrification.

3. Off-gas treatment.

4. Secondary waste processing.

\ock diagrams of the first and second steps are presented in

Figure 3-3. High-level wastes are received and analyzed for actinide

and fission product content and fed to a spray calciner. The calciner

is an externally-heated vertical cylinder. Waste is introduced at the

top in the form of a fine spray. Drying and decomposition of nitrate

salts take place through progressive heating to 700°C as the waste falls

to the bottom of the container. The calcine flows by gravity to the

- 18 -

bottom of the calciner hopper, from where it is pneumatically trans-

ported to a melter. Off-gases generated during calcination pass through

a reinforced sintered powder metal filter, which retains 99.9 percent of

the calcine. Solids deposited on the filter are blown back and fall to

the bottom of the calciner hopper,

The calcine is mixed with the glass-making constituents, and

the mixture is vitrified in a ceramic melter. Melting is achieved by

passage of current through the glass melt, using Inconel 690 electrodes

placed at opposite ends, of the melter ceramic cavity. Product glass

overflows into the waste container, and is annealed to prevent devitri-

fication. A lid is welded on to seal the container, and the weld is

ultrasonical.'.y inspected. The container curface is decontaminated by

steam and pressurized water sprays, and inspected before the container

is transferred to the active head frame building.

A flow diagram of the off-gas treatment is shown in Figure 3-4.

Off-gases leaving the calciner filter consist mainly of atomizing air,

water and oxides of nitrogen, and carry up to 2 wt.% ruthenium and

0.5 wt.% of the nonvolatile fission product content of the calciner

feed. Treatment imst be provided to retain these constituents within

the system, and to limit the discharges from all sources at the site to

< 1% of the Derived Release Limit. The treatment system consists of

quench cooling, scrubbing in a venturi scrubber, condensation of excess

moisture, and mist elimination. The bulk of the volatilized ruthenium

is then removed in a ferric oxide filter. This is followed by a cata-

lytic decomposer for the oxides of nitrogen, a roughing filter, an

iodine adsorber and a final high efficiency filter. The remaining off-

gases are mixed with the plant ventilation flow and discharged through

the plant stack.

The secondary waste processing flow diagram is illustrated in

Figure 3-5. During off-gas treatment, all volatile radionuclldes,

- 19 -

particulates and most of the water and oxides of nitrogen are retained

in a liquid stream. This secondary waste stream is concentrated and the

concentrate recycled to the calciner. Overheads from the concentrator

consist of water and nitric acid which are treated further in ion-

exchange columns. Column effluents are transferred to the low-level

liquid waste treatment facility for further decontamination or monitor-

ing before discharge to the environment.

3.2.1.2 Reference Plant Description

The reference waste immobilization plant is located in a

building 70 m long, 45 m wide and 18 m high. The main floor, and sec-

tions through the building are shown in Figures 3-6 and 3-7, respec-

tively. The building can be divided into the following four zones:

1. Process Area.

2. Decontamination and Maintenance Zone.

3. Analytical Wing.

4. Administration Area.

Process cells a e located at the heart of the facility, and

are arranged in order of increasing activity. Entrance to the plant is

through the administration area where change rooms, offices and control

room are also located. The analytical area and decontamination area are

accessible through change rooms. The laboratory is connected to the

process area by a flight of stairs.

Filled waste containers are dispatched to the active head-

frame building through a tunnel from the end of the process area. Solid

low-level wastes are dispatched through a truck bay in the decontamina-

tion area. Transfer of equipment and material between the process area

and the decontamination area is by an overhead crane and air-lock

arrangement. Smaller tools and equipment can also be transferred

between the two zones through a mechanical gallery and airlocks.

- 20 -

A combination of remote- and direct-contact maintenance is

employed. Remote replacement is used for highly active equipment which

may require occasional replacement. Direct maintenance, after decon-

tamination to reduce radiation fields to acceptable levels, is used for

the remaining equipment. Cells are designed and handling equipment is

provided throughout the plant to meet these maintenance objectives.

Contamination control is provided by the cell walls and venti-

lation air flow. The plant is divided into four ventilation zones,

depending on personnel movement requirements and potential contamination

risks. Ventilation flows take place from areas of no or low-level

activity potential to areas where high activity levels may be present.

Air is finally extracted by the exhaust blowers, filtered, monitored and

discharged through the plant stack. A total 15 m /s of air will be

discharged from each waste immobilization plant during active operation.

3.2.2 Haste Shaft Headframe

The waste shaft headframe building will receive containers of

immobilized waste. The building contains the hoist headframe structure,

temporary storage cell, associated operating galleries and all required

services and facilities (Figures 3-3 and 3-9).

The temporary storage facility is a hot cell with a total

available area of 640 m . Storage capacity is provided for up to 1500

containers to prevent shut-down of the immobilization plant during vault

maintenance downtime. Waste containers will be received through four

tunnels from the immobilization plants on railmounted trolleys. Con-

tainers will be transferred one by one, using a 2-Mg remotely-operated

overhead crane, to storage or directly to the cage loading area. In the

storage area, containers will be stored in racks for retrieval when

required for vault emplacement.

- 21 -

Containers will be moved within the storage area by remotely-

operated overhead cranes. Transfer into the cage utilizes an indexing

table and a hydraulically-operated boon crane.

3.2.3 Service Shaft Headframe

The service shaft headframe will consist of a reinforced

concrete structure on a base incorporating the shaft collar (Figure

3-10). The headframe will accommodate the rock skip, service cage and

emergency man-riding cage hoists and all associated control equipment.

The base of the headframe will provide approximately 1200 t of rock-

storage capacity, acting as a surge facility between the underground and

surface operations.

For the installation of hoist machinery in the headframe and

their subsequent servicing and maintenance, a heavy-duty jib crane will

be installed on the skip hoist floor. The crane will be capable of

hoisting the heaviest pieces of equipment from ground level to the upper

floor of the frame and pcsitioning them, in a single operation. Supple-

mentary lifting equipment will be provided from the various levels for

equipment that is not directly accessible to the jib crane.

Rail access will be provided to the service cage for transfer

of large pieces of equipment between surface and underground.

3.2.4 Backfill Preparation Plant

To prepare the material required for the final backfilling of

the vault, rock will be reclaimed from the service headframe bin by a

conveyor and transferred to the intermediate rock storage pile. Rock

which is to be disposed of will be loaded from this pile by a front-end

loader into dump trucks for transfer to the disposal area. Rock re-

quired for crushing will be Tiken by conveyor to the preparation plant

- 22 -

for screening and crushing. Following crushing, coarse aggregate will

be stored in a bin in the preparation plant.

Pit-run sand and gravel will be brought to the site by means

of dump trucks, discharged into a bin and fed by a stacker to a surge

pile. It will be reclaimed and fed by conveyor into the crusher and

screen house where it will be screened as necessary and stored in a bin.

The crushed rock, sand and gravel will be blended and the aggregate

conveyed to the headframe of the service shaft. Bentonite will be

transferred underground via the service cage and mixed with the blended

aggregates just prior to backfill placement.

3.2.5 Low-Level Liquid Waste (LLW) Treatment

Up to 250 m /day of low-level liquid wastes will be generated

by the active facilities at the centre. Generally, these wastes will

have a sufficiently low activity level to be acceptable for discharge to

the environment. However, if monitoring indicates unacceptable activity

levels, treatment will be provided at the LLW facility. It will include

flocculation and sedimentation followed by ion-exchange treatment.

Expected decontamination factors are in the order of 10 . The treated

waste will be discharged once per day, after monitoring to ensure that

the release does not exceed the site license limits.

3.2.6 Solid Waste Management

Active solid wastes generated at the centre will be pre-

treated, segregated, packaged and tagged. Additional processing will be

provided at the solid-waste processing building. This will include

sorting, compaction or incineration, and packaging. It is expected that

containers, similar to those selected for the reactor wastes for final

disposal at the low- and medium-active waste vault, will be used for

these wastes. At this stage, it is assumed that the waste will be

- 23 -

packed in 200-dm drums and stored in concrete bunkers similar to those

used at the Bruce* Waste Management Site.

Ashes from the incinerator, ion-exchange resins, sludge from

the LLW facility and other suitable waste residues will be incorporated

into bitumen. The bitumen plant will be located at the LLW building.

Packaged wastes from the LLW plant will be shipped directly to the

concrete bunkers for storage.

3.2.7 Services

The centre is provided with inactive services common to all

active facilities, the head frame buildings and the vault. These

include:

1. Heating and standby power plant which will supply the chilled

water, hot water and compressed air requirements for the site.

2. Substation for power transformation and distribution to the

various facilities.

3. Inactive workshop.

4. Store for equipment and other supplies.

5. Central administration building.

6. Vault spoil storage area.

7. Water pumping station and treatment plant.

8. Sewage treatment facility.

The site is provided with domestic sewer, storm sewer, domes-

tic and service water, and utility distribution lines.

- 24 -

3.2.8 Environmental Laboratory

A laboratory is provided for monitoring the site and the

environment for radioactivity. The laboratory will be set up before the

active facilities start up to gather background data for subsequent

monitoring of the environmental impacts of centre operation.

I

bo

FIGURE 3-1. WASTE DISPOSAL CENTRE LAYOUT

6.1km

VAULT -VENTILATION " > l

SHAFTS S |

EXCLUSION

3.6km

VAULT BOUNDARY

ZONE BOUNDARY

iI11

_Ji

SURFACEFACILITIES

FIGURE 3-2. IMMOBILIZED WASTE DISPOSAL CENTRE SITE LAYOUT(Not to scale)

ACCOUNTTA

I

ABILITYNK

RECEPTIONTflN"

MIXED WASTE

i

ATOMIZING

FEEDTANKS

f

AIR

ED WASTE:ROM FIGURE

3.5 TRANSPORT AIR

DECONTAM-INATIONGROUP

CALCINERS FILTERS

t tCALCINE

\

1

SOLIDTRANSPORT

CONTAINERFILLING AMDWELDING OF

TOP

T

— 1

CYCLONES

\ t

MtLl LH

tGLASS

-RIT

D OFF GAS TREATMFNT

•

FIGURE 3.4

i 1

OFF-GASES

FIGURE 3-3. CHEMICAL FLOW DIAGRAM OF THE CALCINATION AND VITRIFICATION STEPS

FROM FIGURE 3.3

OFF-GASES^.

TO

ATMOSPHEREVIA PLANTSTACK

COOLING

HEPA

FILTRATION*i

SCRUBBING CONDENSATIONMIS1

SEPARA'

TO SECONDARY WASTE RECYCLING

NOx

DECOMPOSITION

FIGURE 3.5

RUTHENIUM

ADSORPTION

rnow

HEATING

00

I

FIGURE 3-4. OFF-GAS TREATMENT

TO OFF-GASSYSTEM

FROM _ _ .FIGURE 3 . 4 *

RECEPTION8. FEEDING

FROM Ru FILTER

FROM FILTER LEACH __,

FROM OFF-GAS SCRUBBE?

EVAPORATOR CONDENSER

TO FIGURE 3.3

ACTIVATEDIRON BED NEUTRALIZATION

FURTHERDECON-

TAMINATION

ZEOLITEDEMINERALIZFR

HNO3

TO LOH-LEVELWASTE SYSTEM

DISCHARGE TOENVIRONMENT

FIGURE 3 - 5 . CHEMICAL FLOW DIAGRAM OF SECONDARY WASTE PROCESSING

oI

FIGURE 3 - 6 MAIN FLOOR PLAN OF THE WASTE IMMOBILIZATION PLANT

MECHANICAL GALLERY

LOADINGP I T LOADING

DOCK[RARE

SECTION A-A

TRUCKBAT

LOADINGDOCK

LOADINGPIT

OPERATINGGALLERY

DISPATCH

CHEMICALSTORAGEROOM

VENTILATI01ROW

CHEMICALPREPARATION

ROOM

LABORATORIES ACTIVE

MAINTENANCE

SHOP

TRUCK

BAY

SECTION B-B

FIGURE 3 - 7 CROSS SECTIONS OF THE K4STE IMMOBILIZATION BUILDING SHOWNIN FIGURE 3 - 6

-OVERHEAD DOOft

OPERATING GALLERY

SI I

ho

I

• * • ' ' f * * -

SCALE IN METRES

FIGURE 3-8. WASTE SHAFT HEADFRAHE BUILDING PLAN

- 33 -

SKIP HOIST

CAGE HOIST

EQUIPMENT aWORKERS CAGE

WASTEROCK

BACKFILL

FIGURE 3 -10 . SERVICE SHAFT HEADFRAME

- 35 -

4. VAULT

4.1 STUDY METHODOLOGY, SPECIFICATIONS AND DESIGN CRITERIA

The vault design study methodology is shown in Figure 4-1 and

consists of the following general sequence of tasks:

1. Determination of preliminary design criteria.

2. Determination of preliminary design concepts.

3. Thermal-rock mechanics analysis.

4. Design of vault layout, services and operation.

5. Estimates of cost and manpower requirements.

6. Design Concept Report.

4.1.1 General Specifications and Constraints

AECL specifications for this design study were based upon pre-(3)vious conceptual studies , available data, and constraints used by

other study groups. Those which have not been described in Section 2.2

are summarized below.

4.1.1.1 Setting

The vault is located on a single level at a depth of 1000 m in

a crystalline rock whose properties are either those of granite or

gabbro. It consists of rooms for waste emplacement, connected by

drifts. Containers are emplaced in drill holes in the floor of the

rooms.

- 36 -

4.1.1.2 Operations

All construction and development operations for the vault use

standard and accepted mining industry techniques.

Emplacement procedures and handling equipment for containers

are designed to ensure that radiation doses received by personnel will

be consistent with current design target levels for nuclear workers.

Conventional worker safety standards will also be met.

Vault development and waste emplacement operations are kept

separate. Ventilation of the vault is designed to provide air flows for

worker protection and comfort during both construction and waste emplace-

ment phases. Provision is also to be made for temporary ventilation in

those areas which may require short-term worker access. The ventilation

system either draws air through the construction area and then through

the waste emplacement ar^a, or provides separate systems.

All air flowing from the "active" part of the vault flows

through a radioactive particulate monitoring system. In the event of

airborne radioactive contamination, the airflow is directed through a

filter system before discharge into the environment.

The containers are emplaced in drill holas in the room floor

with one container per drill hole. Backfill is placed above the con-

tainer in the drill hole. Each room is completely backfilled after

waste containers have been emplaced in all drill holes in that room.

4.2 THERMAL-ROCK MECHANICS ANALYSIS

A thermal-rock mechanics analysis of the reference concept was

undertaken to establish the criteria for use in the layout and design

studies for the vault. Specifically, this required establishing the

- 37 -

thermal loadings which would be acceptable within the limitations of the

specifications and design options. Details of the thermal-rock mechanics

analysis are contained in Appendix B.

For the purpose of this study, the vault area has been divided

into three regions.

1. The container (near-field) region, which includes the back-

filled cavity and the volume of rc<c along the room and

pillar extending from the room floor to a few metres below the

container.

2. The room-and-pillar region, which includes the rock mass in

the room-and-pillar unit and extends to several room diameters

both above and below the room.

3. The far-field region, which extends vertically from the surface

to two or more times the vault depth below the level of the

vault and horizontally to at least a vault's length beyond the

edges of the vault.

The thermomechanical constraints which were agreed for these

regions with AECL at the initiation of the study are summarized in

Table 4.1. The waste heat generation as a function of time relative to

the heat generation at the time of emplacement is illustrated in

Figure 4-2.

During the far-field analyses, the potential for the devel-

opment of a perturbed fissure zone (defined as the zone of rock where

existing fissures may be opened due to the action of tensile stresses)

was recognized. For the purposes of this study, the acceptable depth of

the zone was limited to 100 m.

- 38 -

The design was such that modifications to the thermal loadings

could be achieved within this concept by:

1. Varying the spacing of the rooms (extraction ratio).

2. Varying the spacing of the containers along the room (pitch).

Revisions to capacity requirements may be met by the extension

of panels or addition of further panels. The transverse spacing and the

number of containers across the room was fixed for these studies.

Two specific rock types, granite and gabbro, were considered.

No distinction was made between the rock types with regard to their

mechanical properties. The thermal conductivity and coefficient of

thermal expansion were considered to provide the distinction between the

two rock types.

A matrix of the important variables (extraction ratio, pitch

and panel thermal loading (PTL) for near-field and room-and-pillar

analyses, or gross thermal loading (GTL) for far-field analyses) was

used to deiine the required thermal analyses. The extraction ratio,

pitch and PTL satisfying the thermal constraints for all three regions

of the vault were chosen for the subsequent rock mechanics analyses.

For the two-dimensional plane-strain rock mechanics analyses,

a linear Mohr-Coulomb failure criterion was used for both the intact

rock and joints. In addition, a 'no tension' criterion was employed in

all the analyses.

For both granite and gabbro, the preferred PTL-pitch-extrac-

tion ratio combinations are controlled by the minimum drill-hole spacing

and the backfill temperature constraints. However, the container skin

temperature constraint could become significant if the acceptable back-

fill temperature were increased (backfill constraint) or the acceptable

- 39 -

container skin temperature were reduced ^container skin temperature con-

straint). This would apply particularly to a vault in gabbro. Varia-

tion in effects of far-field constraints were not examined parametrically,

but are not anticipated to be significant at the thermal loadings

required by the other constraints. Room stability and pillar strength

ratio criteria do not appear to be critical for any of the thermal

loadings considered.

Based on tb<=" analyses described, the thermal and thermomecha-

nical constraints and restrictions, and the common extraction ratio of

25Z, the following configuration was selected for the vault design

criteria.-

Granite and Gabbro - extraction ratio - 25%2

- PTL <_ 24 W/m

- GTL <_ 23.6 W/

- pitch _> 1.5 m

For gabbro, the selected configuration is controlled by the

allowable container spacing and backfill temperature constraints at an

extraction ratio of 25%. The selected configuration for the granite

vault is defined by the minimum container spacing constraint and the

common extraction ratio value of 25% established by the gabbro case.

4.3 LAYOUT

The detailed vault layout was developed using the design

criteria developed from the thermal-rock mechanics analyses.

In addition, the following factors were considered:

1. The number of penetrations of the pluton should be minimized

consistent with economic development of the vault.

- 40 -

2. The layout should be flexible so that it could be readily

modified to suit changes in waste management practices or

geological conditions, by extending a panel or by construction

of additional panels.

3. Development and emplacement operations should retreat toward

the main shafts to avoid working in active and heat-generating

areas.

4. Separation of development and emplacement operations would be

achieved by physical barriers and/or operating procedures.

5. The conceptual design should be workable, although not necess-

arily optimal.

The layout for the vault is shown in Figure 4-3. Design

considerations which led to this layout are discussed below.

4.3.1 Shafts and Major Drifts

The shafts are indicated on Figure 4-3. The service shaft,

waste shaft and downcast ventilation shaft will be at one end of the

vault. At the opposite end, two upcast shafts will provide ventilation

air exhaust. All shafts are located outside the vault area with a

minimum distance to the nearest panel of 200 m. This was determined

from thermal analyses to restrict the temperature rise at the shafts to

less than 5°C with the maximum rise occurring 50 years after emplacement.

Rock handling and container handling facilities will be sep-

arated vertically in the shaft area, with common maintenance facilities

on the main vault level.

The development and operation of the vault will require drifts

for access and materials transport. These will be:

- 41 -

1. Main drift for access during primary development and panel

development.

2. Waste transport drifts to permit transport of containers

separate from development operations.

3. Rock rail haulage and backfill rail haulage drifts located

30 m below and above the main drift, respectively, with

raises driven to the vault level for transfer of materials.

4. Panel drifts to provide access for room development, waste

emplacement and backfilling.

All drifts will be driven on a 0.5% upgrade from the main

shaft group to facilitate drainage. Cross sections are based on single-

lane operation, widened for passing areas at suitable locations. Turning

points will be provided at approximately 200-m intervals in panel drifts

to assist in traffic operations during waste emplacement. Intersections

will be offset to reduce roof spans and, in the case of panel drift/main

drift intersections, to permit installation of security grills for

operations separation.

4.3.2 Panels

The vault will contain 14 full panels with 2 half panels at

each end as shown in Figure 4-3. Each full panel contains 24 rooms, 12

on either side of the panel drift, and provides space for the emplace-

ment of 12 000 containers. Room/panel drift intersections are offset to

reduce roof spans.

The room spacing was determined from the results of thermal-

rock mechanics analyses which defined an extraction ratio of 25%. The

panel dimensions (430 m by 450 m) were determined from consideration of

- 42 -

rock excavation and haulage methods. Rock will be loaded into trucks in

the room using front-end loaders, and will be hauled to the rock raise

for dumping to the rock rail haulage level.

Development and emplacement activities will not take place

concurrently in the same panel. Development of each panel will begin

with excavation of the panel drift from the main drift to the waste

transport drift. Rooms will be developed beginning at the main drift.

4.3.3 Rooms

The rooms are designed to permit location of four containers

at 1.5 m centre-to-centre spacing across the room, as shown in Figure 4-3.

Each room will contain 500 containers. The room height is determined

primarily from hole drilling and container handling considerations. The

room entry is "dog-legged" to reduce the possibility of direct radiation

in the panel drift during emplacement and hole backfilling operations.

Rooms will be driven on a 2% upgrade from the panel drift to facilitate

drainage. All rooms will be single entry to minimize possible hydro-

geological interconnection through the vault. At the room entrance the

rock surface will be cleaned and the surrounding rock grouted as neces-

sary to form the foundation for a backfill "plug" to minimize intercon-

nection between rooms and drifts.

4.4 VAULT DEVELOPMENT AMD OPERATIOM

4.4.1 Master Schedule

The master schedule for development and operation of the vault

during the period 1984 to 2050 was developed to meet the project mile-

stones defined in Section 2.1. The schedule is composed of the follow-

ing phases:

- 43 -

Phase I Access and Demonstration 1984 - 1993.*

Phase II Primary Development 1994 - 1999.

Phase III Panel Development and Emplacement 2000 - 2043.

Phase IV Decommissioning 2044 - 2050.

Milestones and activities for Phases I and II are given in

Figure 4-4. The start of construction has been taken as early 1984 in

order to have the demonstration vault available for operation in 1988.

Bidding and selection of contractors will have to be complete in advance

of this date.

Development of the demonstration vault was not within the

scope of work of this study and, therefore, only an outline schedule has

been prepared. This indicates that 6 years of demonstration is avail-

able before commencing full-scale vault construction, if full-scale

waste emplacement is to start in year 2000.

The primary development start date has been established as

1994 in order to allow time for an orderly construction program. The

waste emplacement schedule has been established to suit the delivery

rates of containers from the immobilization facility at the surface.

Backfilling of each room follows immediately after emplacement of the

containers in that room is complete. The decommissioning phase follows

completion of waste emplacement.

It has been assumed that contractors would be appointed for

carrying out the Phase I and Phase II construction activities. The

Phase III and Phase IV activities have been planned on the basis that

the owner would operate the facility.

* See disclaimer on inside of front cover.

- 44 -

4.4.2 Access and Demonstration, Phase I

The start date for this phase is early 1984. The contractor

will have to have been selected and all detailed engineering required

for shaft sinking will need to be done in advance of this date.

The initial construction activity will commence in 1984 with

the sinking of a small construction shaft at the opposite end of the

vault from the service shafts area. From this shaft, an 850-m long

drift will be driven to the location of a second small shaft which,

subsequently, will be excavated to the surface by raising techniques.

These two shafts will later serve as permanent exhaust ventilation

shafts. In the area between these two shafts the demonstration and

testing facilities can be developed. From the interconnecting drift

between the shafts, an exploration drift will be driven along the centre

axis of the future vault to the location of the future service shaft at

the opposite end. This will permit exploration of the rock mass during

the early stages of activity on the site.

4.4.3 Primary Development, Phase II

Around 1992, a decision must be made as to whether to proceed

with the construction and development of the vault on the selected

provisional site. This is necessary to allow the detailed design of all

service facilities, shafts and vault to be carried out and to prepare

tender specifications for construction activities to begin in 1994.

A critical path diagram for these activities is shown in

Figure 4-4. The construction of the large service shaft will start in

1994. This shaft construction will be carried out by raising a pilot

raise from vault level to surface. At the same time, the concrete

headframe will be erected and the necessary shaft-sinking equipment

installed, allowing the shaft to be slashed to full size once the pilot

- 45 -

raise is completed. The excavated rock will be dropped to the vault

level where it will be brought by rail cars to the temporary construc-

tion shaft for hoisting to surface. Once the various shaft levels have

been cut, the backfill and rock bins excavated and all necessary shaft

and hoist equipment installed, the two adjacent shafts, the waste shaft

and the downcast ventilation shaft, will be raised to the surface.

The underground vault development will start as soon as the

rock hoisting facilities are ready in the service shaft. This devel-

opment activity consists of driving the five major drifts to the oppo-

site end of the vault. In addition, excavation and installation of the

necessary service and waste handling facilities around the shaft will be

carried out.

Inspection of the critical path shows that the service shaft

construction controls the date for the start of the primary underground

vault development in 1997. Construction of the service and downcast

shafts will require ventilation air from the pilot main drift which is

planned for prior construction during the demonstration phase. Thi;

remainder of the critical path lies on the main drift development,

leading, on completion, to the initial panel development.

4.4.4 Panel Development and Emplacement, Phase III

The detailed schedule and sequence of activities in this phase

are shown in Figure 4-5 for the period 2000 to 2043.

Four principal activity streams are planned for the panel

development and emplacement phase. These are:

1. Room excavation.

2. Room preparation and emplacement hole drilling.

3. Container emplacement.

4. Room backfilling.

- 46 -

It has been assumed that these operations will be handled by

the owner's staff, The equipment requirements and rates of operation

have been set to isuit the container delivery rates. It appears that the

resulting schedule is quite flexible and should be capable of adjustment

to suit the active materials handling requirements, monitoring, etc.

4.4.5 Maintenance and Decommissioning, Phase IV

The final backfilling of drifts and shafts, sealing and de-

commissioning of the vault is scheduled for the period 2044 - 2050.

Project completion after decommissioning is scheduled for

2050.

4.5 FACILITIES AMD EQUIPMENT

4.5.1 Rock Excavation and Handling

4.5.1.1 Access and Demonstration

This will involve excavation of the two upcast shafts, a

demonstration vault, and driving a pilot drift along the line of the

main drift for access and exploration purposes. Drill and blast methods

will be used for excavation with trackless and/or rail haulage as appro-

priate. Upcast shaft 1 will be furnished with a temporary headframe for

skip hoisting. Rock excavation quantities are summarized below.

Depth/Length Quantity(m) (m3)

Upcast Shafts (2) 1000 22 000Drifts 4450 40 050

- 47 -

4.5.1.2 Primary Development

Rock excavation for primary development will comprise:

1. Sinking of service, downcast and waste shafts.

2. Enlarging main drift to final cross section.

3. Driving waste transport drifts.

4. Driving rock and backfill rail haulage drifcs.

5. Excavation of shaft levels for rock and waste handling facil-

ities, and installation and commissioning of equipment.

Details of the shaft excavation are given in Section 4.5.2.

The excavation of service facilities around the shaft group

and of the major drifts will be carried out as soon as the service shaft

is completed and ready for double-skip hoisting.

Excavation rates have been based upon conventional drill-and

blast-methods using currently available trackless electric-hydraulic

drill jumbos. Mucking and haulage to the service shaft will be by Load-

Haul-Dump (LHD) units and diesel-powered trucks or rail equipment as

appropriate.

Excavation quantities are summarized below:

SHAFTS

Description

Service

Wasty

Downcast

Depth(m)

1 075

1 000

1 030

Diameter(m)

7.3

3.6

4.6

Volume

~WT45 000

10 000

17 000

- 48 -

HAULAGEWAYS ANDSHAFT PILLARDEVELOPMENT

Main drift

Rock rail haulage drift

Backfill rail haulage drift

Waste transport drifts (2)

Shaft levels

TotalLength

(m)

3 900

4 000

4 000

8 900

Volume

(m3)

108 000

86 000

86 000

247 000

27 000

4.5.1.3 Panel Development

Rock excavation for panel development will comprise:

1. Excavation of panel drifts.

2. Excavation of emplacement rooms.

3. Drilling of emplacement holes.

Excavation of the first panel will begin in mid-1998 in order

to be prepared for container emplacement at the beginning of 2000.

Individual panel development will begin with driving the panel drift

from the main drift to the waste transport drift. A number of rooms

will be excavated simultaneously for efficJ°ncy id scl.eule require-

ments. The excavation cycle comprises:

1. Drilling.

2. Hole loading.

3. Blasting.

4. Mucking and hauling.

5. Ground support.

These activities are shown in Figure 4-6.

- 49 -

Excavation rates and cost estimates are based upon conven-

tional drill-and-blast methods using cjrrently available trackless

electric-hydraulic drill jumbos. LHD units will load the blasted rock

into trucks for haulage to the rock passes located at the main drift.

Two independent train sets with 25-t trolley-battery electric locomo-

tives will haul muck cars from the rock passes to the service shaft.

Rock will be dumped into a large rock bin for automatic hoisting to the

surface by a double skip friction hoist.

Equipment for drilling the 0.61 m diameter, 4.75 m deep,

emplacement holes has been based on available small diameter raise

boring rigs. The drill rig will be an electrically powered, reverse

circulation, water-flush unit mounted on a crawler chassis which will

also contain rod stem storage and handling equipment. The height will

be less than 4 m when fully extended. For stability while drilling,

the drill rig will be equipped with hydraulic roof and floor jacks.

Panel development excavation quantities are summ?rized below,

and annual rates are shown on Figure 4-7.

Volume

(m3)

165 000

2 956 000

258 000

Panel

Rooms

Drill

TOTAL

drifts

holes

VOLUME

Total length

(m)

5 960

84 210

884 920

Averagecross sectional

area (m2)

27.7

35.1

0.292

3 379 000

Preparation of the room for container emplacement will require:

1. Geological mapping of the room.

2. Placing screeded concrete pad at hole locations for flask

seating.

- 50 -

3. Drilling emplacement holes.

4. Testing drill hoJes and significant fractures, and remedial

grouting if required.

5. Removing loose rock and muck from the room.

6. Placing guidance markers for waste transporter.

7. Placing of bedding backfill in emplacement drill holes.

4.5.2 Shafts and Hoists

Five shafts will be required between the surface and vault

level:

At the main shaft group - service shaft

- waste shaft

- downcast ventilation shaft

At the exhaust end of the vault - two upcast ventilation

shafts

4.5.2.1 Service Shaft and Hoist

The service shaft is required to provide for:

1. Efficient hoisting of excavated rock.

2. Conveyance of large units of mechanized equipment and under-

ground supply material with maximum weights of 10 t.

3. Expedient conveyance of underground personnel at start and end

of working shifts. The number of people to be handled at one

time is estimated at 50.

- 51 -

4. Auxiliary man-riding cage for supervisors and emergency

situations during the shifts.

5. Regulatory ladder escape way to surface.

6. All the necessary service pipes and cables from surface to the

underground vault.

The shaft will be 7.3 in diameter, concrete lined and divided

into three sections as shown in Figure 4-8. These will contain:

1. Two 13-t balanced skips for rock hoisting.

2. Service cage.

3. Ladder escape way, service pipes and cables and emergency

cage.

The rock hoisting system will be designed for a capacity of

410 t/h.

For the purpose of this study, it is assumed that the shaft

will be excavated by Alimak raising from vault level followed by slash-

ing to full diameter and lining. A typical shaft sinking operation

sequence is shown in Figure 4-9.

The service shaft headframe is described in Section 3.2.3.

4.5.2.2 Waste Shaft and Hoist

The waste shaft will be dedicated for handling containers

between the surface and the vault. The maximum container production

rate will be 6210 containers per annum from 2014 through 2029.

- 52 -

The shaft will be 3.6 m diameter, concrete-lined. The cage

will be a single-deck unit of steel construction with ar enclosed deck,

safety doors and container restraining equipment. Roof structural

members will be thickened for shielding in the event that work is

necessary near a loaded cage. Safety devices will be provided to arrest

the cage upon cable failure. The cage will have a weight of approxi-

mately 9 t and a load capacity of 10 t.

The waste shaft headframe is described in Section 3.2.2. It

has been assumed that the shaft will be excavated by full-face raising

from vault level, using an Alimak or similar system.

4.5.2.3 Ventilation Shafts

Ventilation shafts will be required to handle 283 m /s. A

single 4.6-m concrete-lined downcast and two 3.65-m concrete-lined

upcast shafts will be required.

The present schedule allows for the development of a demon-

stration vault at the exhaust end of the vault. The first upcast shaft

will, therefore, be sunk by conventional methods. It has been assumed

that the second upcast shaft and the downcast shaft will be excavated by

full-face raising from the vault level, using an Alimak or similar

system.

4.5.3 Container Handling

The containers will be sealed and decontaminated at the waste

immobilization plant, so surface contamination will not be an opera-

tional problem in the vault. Neutron fluxes are sufficiently low that

the gamma-ray shielding will be adequate for neutron-flux shielding.

Shielding requirements will be determined primarily by the gamma radi-

ation levels. The surface dose rate will be about 100 Gy/h. At 4 m

from the container surface, the dose rate is estimated to be 3.75 Gy/h.

- 53 -

The waste immobilization plant will produce containers at a

maximum rate of 6210 containers per year. On the basis of two shifts

per day, approximately 14 containers will be emplaced per shift.

Containers will be moved from storage into the waste shaft

cage by means of a remotely-operated overhead crane, indexing table and

hydraulically-operated boom crane for loading the container into the

cage.

Each container will be mechanically secured in the cage and

transported, one at a time, unshielded, from the head-frame storage to

vault level down the waste shaft. It will be unloaded from the cage

onto an indexing table with a capacity for 8 containers, using a hydrau-

lically-operated boom crane. Details of the underground transfer station

are shown in Figure 4-10. The container will be removed from the

indexing table using the transporter hoist and grapple, and will th^n be

transported in a flask by a manned diesel-powered transporter through

the waste haulage drifts and panel drifts.

The transporter design is based upon existing 4-wheeled arti-

culated diesel mine vehicles. Containers will be loaded one at a time

with the flask located over the transfer room port. The flask will be

closed by a sliding door at the base. For transport, the flask will be

rotated to the horizontal position.

The transporter will be reversed into the room to the emplace-

ment hole location. With the transporter stationary the flask will be

raised to the upright position and final alignment will be performed.

After lowering the shielding sleeve and opening the flask, the container

will be lowered into the emplacement hole and the grapple released.

After emplacing the container, a temporary shielded plug will be placed

in the drill hole. Backfilling of the drill hole is described in

Section 4.6. The transporter will return to the underground transfer

station and the cycle will be repeated.

- 54 -

To meet emplacement schedules and maintenance conaider.itions

four transporters will be required.

4.5.4 Services

4.5.4.1 Ventilation

The underground ventilation system will serve the following

purposes:

1. To maintain dust concentrations below acceptable levels.

2. To provide the required air volumes for the operation of

diesel-powered equipment so that concentrations of harmful

gases and particles are kept within regulatory limits.

3. To provide a good underground working environment for all

personnel within the limits and standards set for working

temperature, humidity, and dust and gas concentrations.

4. To ensure that any airborne radioactive contamination arising

in an extreme accident is removed in a controlled manner with

minimum risk of exposure to workers.

The use of ventilation for control of thermal effects in the

rock has not been considered in this study.

In general, raining experience has shown that the ventilation

requirements for the operation of diesel equipment will also satisfy

personnel criteria for temperature, humidity, and airborne particulates.

The design of the ventilation system has therefore been hased on the

requirements for diesel equipment operation underground.

- 55 -

The total ventilation supply of 283 m /s is tabulated below by

functional requirement and distribution.

Function

Panel Development

Waste Handling

Backfilling

Rail Haulage

Service Installations

TOTAL

Enginepower (kW)

1 600

1 000

530

-

_

3 130

VentilationRequirement (m3/s)

127

80

43

10

23

283

Distribution (m3/s)

Downcast Ventilation Shaft 283

Central Shaft Group - Upcast in Waste and Service Shafts 23

Upcast Ventilation Shafts 260

Main Drift 127

Waste Transport Drifts 123

Rock and Backfill Rail Haulage Drifts 10

The sequence of operations described in Section 4.4.4 permits

separation of ventilation flows between emplacement and development

activities.

The ventilation flow diagram is shown in Figure 4-11. In the

ventilation intake building over the downcast shaft, a single 1081-kW

fan will operate; during wintertime, gas burners will heat the intake

air to 2°C.

Over each upcast shaft, a surface structure will house a dam-

per arrangement, a filter section end an axial flow fan. During normal

- 56 -

operations, exhaust air will bypass the filter chambers and be exhausted

by a f an.

In an emergency condition in which radioactive material might

enter the ventilation airstream underground, bypass dampers will close

and the air will be exhausted through the filter bank. This will con-

sist of medium-efficiency filters and high-efficiency (95 percent)

filters. Each filter bank, prefliter and high-efficiency filter will be

approximately 12 m wide and 2.3 m high.

For each operating panel, it will be necessary to use auxi-

liary fan installations and ventilation ducts to provide the required

ventilation in the individual rooms. The maximum requirements for

ventilation in the individual rooms are identical for panel development,

waste handling and backfilling activities. This amounts to approxi-

mately 19 in Is, which is governed by the use of an LHD unit and a

diesel truck during mucking for panel development, and by the simultan-

eous operation in a room of the waste transport truck and emplacement

service vehicle. This ventilation is also desirable in rooms during

backfilling to remove and dilute the dust.

4.5.4.2 Compressed Air

A pipe distribution of compressed air will be required through-

out the vault. The main need for compressed air will be for rock

bolting, shotcreting and minor excavations such as the rock and backfill

passes, which might be carried out using air-operated drilling or

mucking equipment, particularly during primary development. The prin-

cipal rock excavation drilling will be undertaken using electric-hydrau-

lic jumbos and will not require a compressed air supply. The surface

compressor station will comprise three reciprocating compressors, each3 2

rated for 0.6 m /s at 860 kN/m , driven by 225-kW electric motors.

- 57 -

Distribution system from the compressor station through the

service shaft and along the major drifts will employ steel flange bolted

pipes. In the panel drifts and emplacement rooms, portable pipes with

quick couplings will be used. At the collar of each panel in operation,

a water-trap receiver will be installed.

At the central shaft group, a compressed air distribution

system will be required to the various service installations for the

operation of air tools and equipment.

4.5.4.3 Water

The requirement for water during the vault operation will be

for drilling equipment, watering-down of blasted rock before mucking

operations commence, emplacement-hole drilling and room preparation

using air-water jets for flushing the excavation faces and floor. The

total maximum water demand has been estimated at 22 L/s.

Water will be supplied from the main surface distribution

system. In the service shaft, the pipe will be equipped with a pres-

sure-sensing device and an emergency shutoff valve located at the shaft

collar to close off in the event of a break in the water pipe in the

shaft. A pressure-reducing station will be located at the bottom of the

service shaft to provide 400 kN/m at points of usage. Distribution

pipes will run along each of the five major drifts. For each panel,

portable quick-coupled sections will be used in the panel drifts and the

emplacement rooms. As the rooms are completed, these pipes will be

removed and reused in other rooms.

4.5.4.4 Drainage and Pumping Systems

The requirements for the underground drainage and pumping sys-

tems will be determined by the water inflow into excavated openings from

- 58 -

the surrounding rock formation, and by the consumption of supplied water

in various vault operations. A capacity of 63 L/s has been established

as a minimum pumping requirement to handle these flows.

To ensure that natural drainage will take place through the

entire vault area toward the central shaft group, the major drifts will

slope 0.5% upward from the central shaft group. All panel drifts will

slope 2% down toward the central main drift with the individual emplace-

ment rooms sloping 2% down toward the panel drifts.

The main collection sump or basin at the main shaft group will

be sized to provide adequate depth of submergence over the pump suction

for satisfactory hydraulic performance, and to provide an operating

volume which will limit the motor start frequency to not more than once

per hour. Two high-pressure multistage cartridge-type centrifugal

pumps, each rated to deliver 63 L/s against the system design head, will

be located in a dry-sump arrangement adjacent to the collection sump.

Normal operation will consist of one pump operating under start-stop

level control from the collection sump, with the second pump functioning

as a standby unit. However, these pumps will be capable of simultaneous

operation in the event of high inflow to the collection sump. Discharge

piping from the pump to the surface will be installed in the service

shaft.

On the surface, the pumped mine water will be discharged into

a settling pond. Routine sampling and monitoring will be undertaken for

the detection of radioactive contaminants in the drainage water. If an

unacceptable level of radioactivity is detected in the drainage water,

mine water discharge will be redirected to an emergency holding pond on

the surface. The point of inflow of the radioactive drainage water into

the collector ditch in the rock rail haulage drift will be located, and

the contaminated water redirected into a permanently-installed lOO-mm

emergency drainage pipe installed along the wall of the rock rail

- 59 -

haulage drift. The standby pump and spare discharge pipe will be used

for segregated pumping.

4.5.4.5 Power System

The main underground distribution will be through two 13.8 kV

cables, one located in the service shaft and the other in either of the

upcast shafts, and two 13.8 kV cables running the entire length of the

centre main drift. All of these cables will be rated such that the

entire underground load can be supplied through one shaft and one main

drift cable.

The drainage pumps, skip hoists, downcast fan and backfill

blower will operate at 4.16 kV. Most of the other AC loads will operate

at 600 V. Power for stationary loads will be provided from distribution

boards located near the service shaft and one of the upcast shafts on

the surface, and near the ends of the main drift. Power to the mobile

loads will be provided by portable power centers to be located in the

panel drifts. The power for the locomotives at each level will be

provided by three 500 VDC rectifiers connected to each end and center

point of the trolley cables.

In all main and panel drifts, lighting will be provided by

high-pressure sodium vapor fixtures, spaced at 50-m centres. Illumi-

nation for the emplacement rooms will be provided by portable flood-

lights.

In case of failure of the main power distribution system, a

diesel-powered generator will automatically provide temporary power to

critical surface and underground installations, such as the service

cage, waste hoist and handling system, main fans and the underground

drainage pumps.

- 60 -

4.6 BACKFILLING AND SEALING

Backfill material within the vault will serve two principal

purposes.

1. It will act as a relatively impermeable barrier to the flow of

water in both the rooms and drifts.

2. It will serve as a conductive medium for the transfer of heat

from the container to the surrounding host rock within the

emplacement rooms.

The sorption properties of the backfill will also be bene-

ficia1 in retarding nuclide transport. The drill hole concept developed

in this study, however, was specifically designed to limit the reliance

on the geochemical buffer characteristics of the backfill as a contain-

ment mechanism. The overall sealing of the vault will also be a func-

tion of the nature of the interface area between the rock and backfill.

Room preparation will therefore be necessary to ensure that the per-

meability of this area is satisfactory relative to the backfill and rock

permeability properties.

Backfill will be placed in emplacement drill holes after com-

pletion of each row of four holes. The room will be backfilled upon

completion of container emplacement.

Backfilling and sealing of shafts and drifts is scheduled to

begin in 2045, following completion of container emplacement, and be

completed by 2050.

For the purpose of the conceptual design study it has been

assumed that only natural materials will be used for backfill. In addi-

tion, the use of as much excavated rock as possible has been incorpo-

rated.

- 61 -

The proposed backfill consists of:

Crushed rock coarse aggregate 55%

Pit run sand and gravel fine aggregate 35%

Bentonite clay 10%.

The surface backfill preparation plant is described in Section

3.2.4. Blended fine and coarse aggregates will be delivered via a pipe

in the service shaft to a bin at the backfill rail haulage level. The

bentonite will not be added to the backfill until immediately before em-

placement. The aggregates will be transported in the rail haulage drift

to the backfill passes.

Backfilling of emplacement holes will take place one row at a

time, sequentially with the waste emplacement, using a specially de-

signed service vehicle. The operation for each hole will be as follows:

1. The service vehicle shield will locate over the emplacement

hole.

2. The temporary hole plug will be removed and a batched quantity

of silica sand placed in the drill hole to backfill the

annulus between the container and drill hole wall.

3. The remainder of the drill hole will be backfilled with a

sand/cl>!y mixture, with compaction by a drop ram.

4. The shield will be raised and the process repeated at the next

hole.

The emplacement and drill-hole backfilling operations will

take place concurrently in different rooms. This will minimize the

interdependency of the two operations.

- 62 -

Placement of backfill in the rooms and drifts will employ a

pneumatic method, shown in Figure 4-12. Ben';onite will be blended with

the aggregates at the mixer, but water will be added to the backfill at

the nozzle to ensure placement at a satisfactory moisture content. The

placement machine will be electric powered to eliminate the need for

refuelling in the emplacement room. The 1.5 m of backfill above the

container will be sufficient to ensure shielding during room backfilling.

Shaft sealing may require breaking out the concrete lining at

selected locations to ensure intimate contact between the backfill and

rock. Pneumatic or mechanical methods may be used for placement and

compaction.

TABLE 4-1

INITIAL THERMOMECHANICAL CONSTRAINTS

Geometric Region of V&ult

1Container near field

Room and pillar

Far field

Thermomechanical Constraint

Container skin temperature

Container cavity stability

Near-field rock mass stability

Backfill volume - average temperature

Roof and rib failure/support

Integrated average of strength-stress

i ratio in the pillar

Rock mass stability

Quantification

150°C

(135°C rise)

Open and stable hole

Not supported

100°C

(85 °C rise)

Conventional rock

bolting requirements

> 2

No irreversibledeformation

TASK 1

PreliminaryDesignCriteria

Define constructionand operationalrequirements anddesign constraints

Define thermalrock mechanicsdesign constraints

TASK 2

PreliminaryDesignConcepts

Define pre-liminarydesign conceptusing modifiedPhase I and IIbaselineconcept

TASK 3Analysis

The fieldthermal-rockmechanicsanalyses

Room andpillarthermal androckmechanic sanalyses

Containernear fieldzonethermaland thermalrockmechanicsanalyses

TASK 4Design Vault

Long-termcreep rupture-prelimianryassessment

Seismicresponsepreliminaryassessment

Synthesize andsummar izethermal rockmechanics resultsand specifiedconstraintsinto designcriteria

TOSHEET 2

FIGURE 4-1: VAULT STUDY METHODOLOGY (Sheet 1)

TASK 4 CONTINUED

RockExcavation and

Handling

Sheet 1

*

i

Room Layout

BackfillingandSealing

ContainerHandling and

SafetyAssessment

UndergroundServices

(Ventilation,Water, Drain-age, Power,

etc.)

tVatLay

i

Itout

TASK 5

Schedule andCost Estimate

TASK 6

Summary Reports

DesignConceptReport

FIGURE 4-1. VAULT STUDY METHODOLOGY (SHEET 2)

- 66 -

1.0

0.1

0.01

0.001 \10 100 1000 10,000

TIME SINCE FUEL DISCHARGED FROM REACTOR (YEARS)

FIGURE 4-2. RADIOGENIC HEAT GENERATION OF IMMOBILIZEDWASTE AS A FUNCTION OF TIME

4 UPCAST VENTILATION| SHAFT200._

" "CPANEiT

t SERVICESHAFT

3600 300

~==—J-PANELDRIFT(TYP)

HALF FULL PANELPANEL(TYP)

DRIFTHAULAGE

223

ISOnlSOa

T1

CONTAINER0.457m » ~

f DETAIL

ALL DIMENSIONS IN METRES

o l l l SPACESR 30

LEL.IOOO

<t. PANELDRIFT

FIGURE 4-3. VAULT LAYOUT AND ROOM DETAILS

COLL** SHM-T, eeecrS M C S " * " " , CUT W

INSTALL SHUT

NSTAJJ. PCEMANEWT EXHAUST =»N '

COLL AC S**APT,

LLOPMEXT

WASTE EMPLA.CEK>EJ»JT

iT CAL PATH ITNP)

FIGURE 4-4. PRIMARY DEVELOPMENT CRITICAL PATH DIAGRAM

PANEL1 No.

o Excavationb Preparation<f Emplacementd Backfilling

(DETAIL OF SHADED AREA)

2025

85 90 95 05 102000

Emplacementstarts

16 20 25 30 35 40 45

YEARS

Emplacementcomplete

FIGURE 4-5. PANEL DEVELOPMENT AND EMPLACEMENT SCHEDULE

7 /LOAD FOR BLASTING ROCK BOLTING

oi

FIGURE 4-6. PANEL DEVELOPMENT AflD ROCK EXCAVATION SYSTEM

ROCK EXCAVATION ( 1 0 6 m3)

oo

985 90

totn

8oootn

o

Ol

20 25

wo

OJ

o

rv

tn

-

-

\

V\\

—•

Plant 1(20001

Plant 2(2U03)

v Plant 3\ (2006)

\ \

\

Start

Start

Start

Plant

\

N

\

no OJ

up

up

up

4 Start up(2014) 1

\ Plant 1 \\ Shutdown (2T830)

\ Plant 2 \

a 3,379,000

\ Shutdown (2033>lY Plant 3\ Shutdown (2036)

\

V Plant 4Shutdown (2044)

tnOOOO

OO-oOO

o'ooo

J o

WASTE CONTAIHERS

SERVICEPIPES

[EMERGENCYCAGE

EQUIPMENT aWORKERS CAGE

ROCKHAULAGESKIP

ROCKHAULAGESKIP

BACKFILL DOWNCOMER

FIGURE 4-8. SERVICE SHAFT CAGE AND ROCK HAULAGE SKIPS

- 73 -

DRILLING MUCKINGGROUNDSUPPORT

FIGURE 4-9. SERVICE SHAFT EXCAVATION METHOD

WASTESHAFT,

IMMOBILIZEDWASTECONTAINER

FIGURE 4-10. UNDERGROUND TRANSFER STATION

WASTE HAULAGE DRIFT

EXHAUSTFAN

AEXHAUSTFAN

MAIN DRIFT

ROCK RAILHAULAGE DRIFTBACKFILL DRIFT

WASTE HAULAGE DRIFTHEATER

VENTILATINGDOWNCASTSHAFT

FIGURE 4-11. VENTILATION FLOW SYSTEM

- 76 -

EMPLACEMENT HOLE DRILLING

EMPLACEMENT HOLE TESTING

ROOM SURFACE PREPARATION(washing, drill ing S grouting)

© WASTE EMPLACEMENT

SPREADING a COMPACTING

(6) FINAL BACKFILLING

FIGURE 4-12. IMMOBILIZED WASTE EMPLACEMENT AND BACKFILLING IN VAULT

5. COSTS AND MANPOWER REQUIREMENTS

5.1 COSTS

5.1.1 Basis for Cost Estimates

The basis for estimating the costs of both the surface facili-

ties and tisS undeiground vault is summarized below.

1. All costs are expressed in 1979 January Canadian Jcliars.

2. The centre was assumed to be located 300 km from a major urban

centre and within daily commuting distance of a town capable

of housing all employees.

3. Ic was assumed that construction of the centre would be car-

ried out by contractors and that the centre owner would erect

a construction camp to provide board and lodging for all

construction personnel.

4. There is no allowance for the operating costs of the demon-

stration vault.

5. For major cost items such as buildings, shafts, etc., detailed

estimates of labour, equipment capital, equipment operating,

supply, service and overhead costs were prepared.

6. For other items such as Hiiuor build >gs and services, the

estimate was based on unit d.st statistics and comparisons

with existing similar installations.

7. Interest charges during construction have not been included in

the budget cost estimates.

- 78 -

5.1.2 - Surface Facilities

These cose estimates are applicable only to the concept

described in this report. The costs can not be directly compared with

the vitrificatioa and packaging costs quoted by other nations because of

major differences in some of the design assumptions. Some assumption'

specific to this study are:

1. The burnup of CANDU fuel is 588 GJ/kg U.

2. The fuel is stored for 10 years prior to processing and

packaging.

3. There is no storage of high- and medium-level radioactive feed

liquid.

4. High- and medium-level radioactive liquid wastes from i:he

reprocessing plants are immobilized simultaneously.

The capital cost estimates for the centre facilities are shown

in Table 5-1. The total direct costs of constructing the facilities and

associated services would be $245 million. Indirect costs, which in-

clude construction indirect, engineering, administrative overheads,

taxes and commissioning, would amount to $184 million. This gives a

total estimated capital cost of ^ $429 million. Including a contingency

of 20%, the budget capital cost would be $515 million or $1.91/kg U.

The annual operating costs of the surface facilities are shown

in Table 5-2. The estimated lifetime operating cost would be $2940

million; so, including a contingency of 22.5%, the total budget lifetime

operating cost would be $3602 million or $13.36/kg U.

The cost to decommission the surface facilities is estimated

to be approximately $30 million, and the cost to provide surveillance

- 79 -

and security of the centre for a limited period after decommissioning

would be approximately $7 million.

The cash flow for the surface facilities is presented in

Table 5-3.

5.1.3 Vault

The capital cost estimates for the vault are given in Table 5-4.

The direct capital cost of the vault and associated structures and

services would be $175 million. Indirect costs would amount to $23

million for a total estimated capital cost of $198 million. Including a

contingency of 20%, the budget capital cost for the vault would be $238

million or $0.88/kg U.

It should be noted that costs incurred during exploration and

demonstration (Phase I, 1984 - 1993) ana during pri.nary development

(Phase II, 1994 - 1999) have been capitalized. Initial nurchase and

replacement of major equipment has been capitalized during panel devel-

opment and emplacement (Phase III, 2000 - 2043) and during decommis-

sioning (Phase IV, 2044 - 2050).

The annual operating costs of the vault are shown in Table 5-5.

The total estimated lifetime operating cost of the vault, including an

administrative overhead of 20%, would be $765 million. Including a

contingency of 22.5%, the total budget lifetime operating cost would be

$937 million or $3.48/kg U. All expenditures in Phases III and IV are

considered to be operating costs, with the exception of initial and

replacement purchases of major equipment. For the panel development,

emplacement, backfilling, maintenance and decommissioning phases, the

rates for various job classifications were set at approximately the same

as those used in the uranium mines in the Elliot Lake area. These rates

include all fringe benefits, vacation pay, shift work compensation and

bonuses where applicable.

- 80 -

The cash flow for the vault is presented in Table 5-6.

5.2 MANPOWER REQUIREMENTS


The construction of the surface facilities would take place in

four stages with each stage representing the addition of a plant. Based

on the capital costs and assumed construction duration, the construction

labour force *rould peak at 300 workers during the first stage, 150

during the second stage and 250 during the third and fourth stages.

The personnel required for the operation of the surface facili-

ties would peak at 940. These can be broken down as follows:

Immobilization Plants 1 and 2 360 (180/plant)

Immobilization Plants 3 and 4 490 (245/plant)

Support Svaff 90

A breakdown of the skill levels of the operating personnel is

shown in Table 5-7.

5.2.2 Vault

The vault development and operation manpower schedule, includ-

ing both owner and contractor staffs, is summarized in Table 5-8. The

manning estimates are budget estimates and include allowances for oper-

ations, administration and contingencies.

During Phase I (initial access and demonstration) and Phase II

(primary development) the manpower requirements fluctuate considerably.

The estimates shown are approximate and will be subject to smoothing

during the planning stages. It has been assumed that a contractor will

- 31 -

perform the work with some supervision of the owner's staff. Staff

requirements for the demonstration project have not been included.

The peak manning level during Phase I will be in the range 60

to 120. The peak during Phase II will be in the range 260 to 400.

During Phase III (panel development and emplacement), the

staff will increase to between 300 and 350 and then begin to decrease in

about 2029. A breakdown of the manpower skill levels is shown in

Table 5-9. The manpower skill levels distribution in Phase III is only

approximate, but is included to indicate the mix and the opportunities

for utilization of local labour, in terms of training and experience

requirements, for the main vault operation.

Phase IV (backfilling and sealing operations) (2044 - 2050) is

estimated to require about 135 personnel. These activities could be

extended in duration in order to minimize the impact on employinent at

the completion of the project.

Figure 5-1 shows the total manpower requirements for con-

tracting and operating the complete disposal centre.

- 82 -

TABLE 5.1

SURFACE FACILITIES CAPITAL COST

(1979 January Canadian Dollars)

Direct Costs

Site-related Work and Equipment

Site-related Services

Two Immobilization Plants (1500 Mg/a)

Two Immobilization Plants (3000 Mg/a)

Temporary Storage Building

Tunnels

Ventilation Exhaust Buildings

Auxiliary Buildings

Site Selection, Environmental and SafetyAssessment

First Year's Operating Supplies

TOTAL DIRECT COST (TDC)

Indirect Costs

Construction Indirect?? (22% of TDC)

Engineering (j0% of TDC)

Administrative Overhead

Taxes (5% of TDC)

Commissioning

TOTAL INDIRECT COST

TOTAL ESTIMATED CAPITAL COST

Contingency (20%)

TOTAL BUDGET CAPITAL COST (TBC)

Total($ x 1000)

8 572

32 500

61 990

94 225

7 500

8 293

2 016

21 813

6 000

2 420

245 329

53 972

73 599

1 600

12 266

42 644

184 081

429 410

85 882

515 292

TABLE 5.2

SURFACE FACILITIES ANNUAL OPERATING COSTS

•'.'.''. ' January Canadian Dollars x 1000)

Year

2000-2002

2003-2005

2006-2013

2014-2029

2030-2032

2033-2035

2036-2043

MiscellaneousRaw Materials

100

150

300

450

350

250

150

Coal andElectricity

1 371

1 947

2 840

3 733

3 153

2 577

1 681

TOTAL ESTIMATED LIFETIME OPERATING

CONTINGENCY (22. 5%)

C O S T

Maintenance

1 772

2 469

3 657

4 837

4 507

4 175

1 900

COST

TOTAL BIIDGET LIFETIME OPERATING COST

S

Manpower

9 380

14 280

20 200

26 320

21 700

16 940

10 640

ContractorManpower

2 016

3 024

3 954

5 040

4 032

3 024

2 016

$2940 million

$ 662 million

$3602 million

Taxes andInsurance

4 430

6 173

9 143

12 093

11 268

10 438

4 750

Total

25 862

41 529

67 220

93 231

78 975

64 530

34 723

- 84 -

TABLE 5.3

CASH FLOW FOR SURFACE FACILITIES

(1979 Canadian Dollars with no Financing Chargesincluding 20% conL::-','gen;.;)

•

Year

199419951996199719981999200020012002200320042005200620072008200920102011201220132014

t202820292030203120322033203420352036

1 -2043204420442045

Total

CapitalExpenditure($ million)

193142364234313334332012

212122322012

515

OperatingCost

($ million)

32.032.032.051.051.051.082.582.582.582.582.582.582.582.5

113.5

t113.5113.598.098.098.079.579.579.543.0

t43.0

3601.5

Others

5X

5X

iox

iox

o.ixx

o.ixx

30j

Decommissioning CostSurveillance and Security Cost

- 85 -

TABLE 5.4

VAULT CAPITAL COSTS


Phase

DIREC

I

II

ii':

IV

I t e m

C COSTS

Initial upcast shafts and ventilation

Exploration and initial development

Service shaft

Downcast shaft

Primary and auxiliary ventilation

Waste shaft

Major drifts

Underground services

Waste handling installations

Backfill plant

Panel development

Waste handling

Backfilling

Room sealing and vault sealing

TOTAL DIRECT COST

TOTAL INDIRECT COST

TOTAL ESTIMATED CAPITAL COST

CONTINGENCY (20%)

TOTAL BUDGET CAPITAL COST

Total($ x 1000)

10 860

8 137

24 907

5 400

3 444

8 630

37 736

9 450

4 200

4 200

29 960

20 372

5 600

2 086

174 982

22 748

i97 730

39 .545

237 275

TABLE 5.5

VAULT ANNUAL OPERATING COST


Phase

III

IV

Year

1999

2000-2002

2003-2005

2006-2013

2014-2028

2029

2030-2032

2033-2035

2036-2043

2044-2049

Annual Base Cost ($ x 1000)

PanelDevelopment

1045

1045

2090

3480

6265

6265

4870

3480

3965

WasteHandling

245

490

975

1460

14'60

1220

870

805

Backfilling

940

1880

3760

6160

5755

4700

3760

3760

16180

Services

5500

5500

5520

5845

5845

5500

5500

11000

5500

TOTAL ESTIMATED LIFETIME OPERATING COST $765 million

CONTINGENCY (22.5%) $172 million

TOTAL BUDGET LIFETIME OPERATING COST $937 million

- 87 -

TABLE 5.6

CASH FLOW FOR VAULT

(1979 January Canadian Dollars,

including 20% contingency)

Phase

I

Phase I

II

Phase II

III

Year

198419851986198719881989199019911992

Subtotal

1993199419951996199719981999

Subtotal

199920002001200220032004200520062007200820092010

Capital

634432

25

181324312924

132

34

31.

12

380732841842343022200200200

760

000512074706964227361

844

797746_---

797898---

340

(S x 1000)

Operating

19991212121616161616

__--__--

-

-_--_-

-

279464464464192192192796796796796796

Total

634432

25

18

1324312924

132

514991212151816161629

380732841342343022200200200

760

000512074706964227361

844

076210464464192192989694796796796136

.../cont.

- 88 -

TABLE 5 .6 , concluded

Phase Year

2011201220132014201520162017201820192020202120222023202420252026202720282029203020312032

| 2033

Phase 113

IV

Phase IV

20342035203620372038203920402041204220432044

Subtotal

20452046204720482049

Subtotal

Capital

---

4 746----

12 340----

4 746----

12 340----

7 403----

7 690----

75 343

2 828-__-

2 828

($ x 1000)

Operating

16 79616 79616 79624 17124 17124 17124 17124 17124 17124 17124 17124 17124 17124 17124 17124 17124 17124 17123 67719 95119 95119 95116 66816 66816 66811 97911 97911 97911 97911 97911 97911 97911 97911 932

804 478

26 55826 55826 55826 55826 558

132 790

Total

16 79616 79616 79624 17128 91724 17124 17124 17124 17136 51124 17124 17124 17124 17128 91724 17124 17124 17123 67732 29119 95119 95116 66816 66824 07111 97911 97911 97911 97919 66911 97911 97911 97911 932

880 321

29 38626 55826 55826 55826 b58

135 618

- 89 -

TABLE 5.7

SKILL LEVEL DISTRIBUTION OF SURFACE FACILITIES

OPERATING PERSONNEL DURING PEAK OPERATION

Professional

Skilled trades

Semiskilled trades

Labourer

Clerical

TOTAL

105

430

275

80

50

940

- 90 -

TABLE 5.8

VAULT MANPOWER LEVi^S SCHEDULE

Phase

I*

ri*

in**

IV*

Time

1984-1993

1994-1999

1999

2000-2002

2003-2005

2006-2013

2014-2028

2029

2030-2032

2033-2035

2036-2043

2044-2049

Administrationand Supervision

25

35

5

37

47

65

94

92

78

65

47

40

Operation

55

280

13

93

120

165

237

232

195

163

117

95

Total

80

315

18

130

167

230

331

324

273

228

164

135

* Estimates in Phases I, II and IV are approximately ± 30%

** Estimates in Phase III are ± 16%

- 91 -

TABLE 5.9

SKILL LEVEL DISTRIBUTION OF VAULT OPERATING

PERSONNEL DURING PHASE III OPERATIONS

Professionals

Skilled Trades2

Semiskilled Trades

Laborers

TOTALS

3t£ff

26

61

7

94

Labour

_

73

134

30

237

Total

26

134

141

30

331

1. Management, engineering, geological and other professionals

2. Mining, mechanical and waste-handling technician!-? and

supervisors with several years training and experience

3. Mining and mechanical equipment operators possibly trained

on the job

4. General laborers starting without previous training or

experience

1500

1990 2000 2010 2020(YEAR)

2030 2040 2050

FIGURE 5 - 1 . MANPOWER PROJECTIONS FOR THE IMMOBILIZEDWASTE DISPOSAL CENTRE

- 9J -

6. SUMMARY, CONCLUSIONS AND RECOMMENDATIONS

6.1 SUMMARY AMD CONCLUSIONS

6.1.1 General

This study has developed a conceptual design of a centre to

immobilize waste from reprocessing of natural uranium CANDU fuel and

dispose of it in an underground vault. The principal facilities and

equipment have been identified, construction and operation schedules

developed to meet the project milestones, and cost estimates prepared.

The quantities of waste which could be immobilized in the

proposed centre are those which would arise from what is presently

considered to be an optimistic projection of nuclear generation to the

year 2016. The design of the centre is modular in concept and can be

readily adapted to other scenarios.

It must be emphasized again, however, that the designs of

these facilities and equipment have not been optimized, but are offered

only as a possible design concept based on the stated assumptions and

constraints.

6.1.2 Technical Feasibility

The high-level wastes processed in the surface facilities will

be a mixture of the following two streams:

1. Concentrated high-level waste stream from fuel reprocesaing.

This stream will generate heat and will contain most of the

fission products.

2. An alkaline stream generated during solvent scrubbing oper-

ations in the reprocessing plant. This stream can carry up to

0.5% of the original plutonlum content of the irradiated fuel.

The feasibility of the process to immobilize this mixture has

not been demonstrated. Several countries in the world have the tech-

nology to immobilize the first stream but no one has immobilized the

second stream in large quantities. Considerable research effort is

being expended on this topic at WNRE. The remainder of the operations

at the centre are feasible with some expansion of technologies currently

available in Canada.

The shafts, hoists and underground facilities can be con-

structed using state-of-the-art mining technology. The influence of

heat generation by the waste on rock stability (granite or gabbro) has

been kept at acceptable levels through the selection of appropriate

container spacings, room-and-pillar design and vault layout.

Container surface and room backfill temperatures can also be

controlled never to exceed the assumed design maxima of 150°C and 100°C,

respectively. The container and backfill temperatures decay to close to

ambient geothermal levels within 1000 years.

Waste handling, emplacement and room backfilling can be

accomplished using adaptations of standard mining and material-handling

equipment. Radiation exposures during handling can be kept within

allowable limits.

The thermal-rock mechanics analyses have provided detailed

predictions of the initial state, transient thermal effects and non-

linear rock response and failure. Parametric studies of key parameters

have demonstrated the adaptability of the concept to suit actual rock

conditions and properties.

- 95 -

6.1.3 Schedules

The development cf the immobilization facilities has 1500

Mg U/a plants scheduled to start in years 2000 and 2003. 3000 Mg U/a

plants are scheduled to be in-service in 2006 and 2014. Modifications

to this schedule are possible if the waste arisings are different from

those assumed. The initial shafts and underground facilities should be

constructed in the period 1984 to 1987 to allow underground demonstra-

tions in the main vault area to commence in 1988. Adequate time must be

allowed before construction for bids, planning, detailed engineering,

mobilization and equipment procurement.

The main vault construction should commence in 1994 if em-

placement is to commence in 2000. Six years are available for demon-

strations before starting the main vault development for this particular

scenario.

The room and panel development, hole drilling, waste emplace-

ment and backfilling operations can be scheduled to suit the waste

immobilization rates. Considerable flexibility is available in oper-

ating rates.

The final drift and shaft backfilling and vault decommis-

sioning operations which, for the purposes of this study, are planned to

commence in 2045, can be scheduled at various rates to suit the avail-

able resources. Durations of 5 to 10 years appear realistic.

6.1.4 Cost Estimates

The capital and operating costs for the centre are summarized

in Table 6-1. For the surface facilities the capital cost is estimated

to be $515 million ($1.91/kg U) (1979 dollars) and the operating costs

to be $3602 million ($13.33/kg U ) , resulting in a total of $4117 -million

($15.24/kg U ) .

- 96 -

The capital cost of the vault is estimated to be $237 million

($0.88/kg U) and total operating costs at $937 million ($3.47/kg U ) ,

resulting in a total of $1174 million ($4.35/kg U ) .

The cost of decommissioning the centre and for surveillance

and security is estimated at $43 million ($O.16/kg U ) .

The total centre cost is therefore estimated to be $5335

million ($19.75/kg U). This cost is distributed over wastes arising

from 14 TW-h oi electrical generation, giving a unit cost of 0.40

mills/kW-h.

The surface facilities account for almost 70% of the capital

cost of the centre and approximately 80% of the operating cost. Of the

total cost of immobilization and disposal, $15.40 is accounted for by

the surface facilities and $4.35 by the underground activities.

Of the surface facility operating costs, the stainless steel

containers contribute $1680 million, and the immobilization plant man-

power contributes $1540 million (32% and 29% of the total centre cosf ,

respectively).

In the vault the cost of mining rooms, drilling holes, em-

placing wastes and backfilling are categorized as operating costs. The

cost of drilling the emplacement holes would be $110 million and the

total backfilling cost $318 million, of which $200 million was the cost

of bentonite supplies (6%, 3.7% and 2% of the centre total, respectively).

6.1.5 Manpower Requirements

The surface facilities construction labour force will build up

to a maxi.mim of 300. The vault construction labour force in the same

period (1994 - 2000) will peak at 300. The total construction labour

- 97 -

force in this period will therefore be approximately 600 and will be

primarily contractors' personnel.

The surface facilities operation manpower will peak at 940

during the period 2000 - 2035. The vault operation labour force in this

period will peak at 340, resulting in a total of 1280 on site. Of this

number 607 will be required at the site for the full operating period,

20(10 - 2043.

6.2 RECOMMENDATIONS

The following have been identified as study areas where

further attention could be useful. These are restricted to questions

which could have major impact on the design concept and its feasibility.

Optimization requirements have not been identified except in certain key

instances.


1. Separate immobilization of high-level and alkaline waste

streams. - This study would investigate the cost and tech-

nical impacts of separate waste immobilization for the same

scenario as developed for the mixed wastes.

2. Effects of reprocessing and waste immobilization systems

integration. - Following completion of the International Fuel

Cycle Evaluation (INFCE) study, this study could be updated to

consider a complete CANDU fuel cycle scenario, including

reprocessing, fuel fabrication and waste immobilization.

3. Future experimental work on waste immobilization should

include testing of alternative schemes for the solidification

of separate and mixed high-level and alkaline waste streams.

- 98 -

6.2.2 Vault

1. Further construction-scheduling studies of the primary devel-

opment phase could be undertaken to try to reduce the con-

struction time before emplacement.

2. Occupational radiation dose assessments of the reference and

other waste-handling and emplacement concepts should be made.

Analyses should also be made of accident scenarios.

3. The development of specially adapted emplacement hole drilling

equipment to suit the minimum room height and drilling rates

is important and can benefit from development work.

4. Backfilling and sealing methods for the shafts should be

developed in detail once the material, shaft liners and rock

response in the hydrogeological system have been established.

5. The drill-and-blast method for emplacement room excavation

should be assessed versus a possible tunnel-boring machine

method. This would include an investigation of the effect of

the blast-fractured zone on hydrogeology.

6. In view of the high cost, investigations should be made into

the effect of varying the bentonite content in the backfill.

Alternate backfill materials should also be investigated.

7. In-situ data should be acquired to confirm assumed conditions

and properties (in-situ stress, geothermal regime, joint

patterns, groundwater chemistry, etc.).

8. Laboratory, analytical and in-situ tests are required to

confirm the thermal-ror.k mechanics response around the con-

tainers in the medium term. The long-term potential for creep

rupture around the emplacement hole and room periphery requires

- 99 -

further assessment in terms of its impact on groundwater flow

in the vault zone.

9. Studies and tests are required to verify the maximum allowable

backfill temperatures.

10. Further definition is required of the far-field thermal-rock

mechanics criteria.

- 100 -

TABLE 6.1

COST SUMMARY WITH NO FINANCIAL CHARGES


Item

iSURFACE FACILITIES*

Capital

Operating

TOTAL

VAULT

Capital

Operating

TOTAL

Total Capital

Total Operating

Decommissioning,Surveillance andSecurity

TOTAL

Total Cost

$ x 1000 $/kg U

515 292 1.91

3 601 778 13.33

4 117 070 15.24

237 275 0.88

937 268 3.47

1 174 543 4.35

752 567 2.79

4 539 046 16.80

43 200 0.16

5 334 813 19.75

* These cost estimates are applicable only to the

concept described in this report. They should

not be compared directly with the vitrification

and packaging costs quoted by other nations.

- 101 -

7. REFERENCES

1. J. Boulton (Ed.)» "Management of Radioactive Fuel Wastes: TheCanadian Disposal Program", Atomic Energy of Canada LimitedReport, AECL-6314 (1978).

2. Acres Consulting Services Limited and Associates, and WNREDesign and Project Engineering Branch and Associates, "ADisposal Centre for Irradiated Nuclear Fuel: ConceptualDesign Study", Atomic Energy of Canada Limited Report, AECL-6415 (1979).

3. Acres Consulting Services Limited and Associates, "RadioactiveWaste Repository Study, Parts I, II and III", Atomic Energy ofCanada Limited Report, AECL-6188-1, -7 and -3 (1978).

- 102 -

APPENDIX A

BIBLIOGRAPHY OF SUPPORTING STUDIES

TR-No. Title

47 Immobilized Fuel and Reprocessing Waste Vaults: Design

Specification and Scope of Work

48 Immobilized Fuel and Reprocessing Waste Vaults: Preliminary

Design Concepts

53 Reprocessing Waste Vault: Container Near-Field Thermal-Rock

Mechanics Analyses

54 Reprocessing Waste Vault: Room and Pillar Thermal-Rock

Mechanics Analyses

55 Reprocessing Waste Vault: Far-Field Thermal-Rock Mechanics

Analyses

56 Immobilized Fuel and Reprocessing Waste Vaults: Long-Term

Creep Rupture - Review and Assessment

57 Immobilized Fuel and Reprocessing Waste Vaults: Seismic

Response - Review and Assessment

58 Immobilized Fuel and Reprocessing Waste Vaults: Design

Criteria and Synthesis of Thermal-Rock Mechnics Analyses

60 Reprocessing Waste Vault: Design Concepts and Layouts

61 Immobilized Fuel and Reprocessing Waste Vaults: Rock

Excavation and Handling System

- 103 -

TR-No. Title

62 Immobilized Fuel and Reprocessing Waste Vaults: Shafts and

Hoists

64 Reprocessing Waste Vault: Container Handling System

65 Immobilized Fuel and Reprocessing Waste Vaults: Underground

Services

66 Immobilized Fuel and Reprocessing Waste Vaults: Backfilling

System

68 Reprocessing Waste Vault: Development and Operation -

Schedule and Cost Estimates

74 Conceptual Design Study of the Surface Facilities at the

Immobilized Waste Disposal Centre

- 104 -

APPENDIX B

THERMAL ROCK MECHANICS

B.I INTRODUCTION AND OBJECTIVES

The objective of the thermal rock mechanics study was to

establish the criteria for use in the conceptual design studies for the

vault. Specifically, this requires establishing the thermal loadings

that are acceptable within the limitations of the specifications and

design options .

For the purpose of this study, the vault area has been divided

into three regions :

1. The container (near-field) region which includes the container

emplacement hole and the volume of rock along the room and

pillar, extending from the room floor to a few metres below

the container.

2. The room-and-pillar region which includes the rock mass in the

room-and-pillar unit and extends to several room diameters

both above and below the room.

3. The far-field region which extends vertically from the surface

to two or more times the vault depth below the level of the

vault, and horizontally to at least a vault's length beyond

the edges of the vault.

Specified thermal and mechanical constraints for these regions

are summarized in Table B-l.

- 105 -

The design specification requires that the containers (3.03 m

in length and 0.457 m in diameter) be emplaced in he'> s drilled in the

floor of the room. Retrieval of the containers is not considered in the

design studies, and the room will be backfilled immediately after em-

placement of the waste containers.

Preliminary layouts were developed prior to undertaking the

thermal mechanical analyses. The arrangements were based primarily on

construction and operational considerations, with individual panels

400 m wide by 800 to 1400 m in length.

The design was such that modifications Co the thermal loadings

could be achieved within this concept by varying the spacing of the

rooms (extraction ratio) or by varying the spacing of the containers

along the room (pitch).

In addition, revisions to capacity requirements may be met by

the extension of panels or addition of further panels. The transverse

spacing and the number of containers across the room was fixed for these

studies.

B.2 MATERIAL PROPERTIES

The thermal and mechanical properties used in this study are

summarized in Table B-2.

Two specific rock types, granite and gabbro, were considered.

These were differentiated by differences in their thermal conductivity

and coefficient of thermal expansion. For the rootn-and-pillar analyses,

the variation of rock strength was also examined.

The vertical in-situ stress in the models was assumed to

result from gravitational load only. The horizontal stress was taken

as a function of depth, based qn Herget^ " , and equal to 1.5 times the

- 106 -

vertical stress at a depth of 1000 m. The g&othermal gradient was

assumed to be 15°C/km, with an average surface temperature of 0°C.

Detailed data on the geometry of rock jointing in plutons of

the Canadian Shield are not available. For this study, three models

have been used.

1. Unjointed Rock Material - representing the upper end of the

range of strength of rock masses

2. Ubiquitously-Jointed Model - in which two vertical sets and

one horizontal set were assumed over the entire rock mass,

representing the lower end of the range of rock mass strength

3. Blast-Fractured Zor.e/Discrete Joint Models - used in the

room-and-pillar analyses as being a reasonable approximation

for anticipated conditions.

For the 2-dimensional plane-strain rock mechanics analyses,

a linear Mohr-Coulomb failure criterion was used for both the intact

rock and joints. In addition, a "no-tension" criterion was employed

in all the analyses. "No-tension" modelling involve:- reversing any

tensile forces arising during the analyses and transferring these

forces to adjacent rock. This procedure is repeated until no tensile

stresses remain. This load transfer mechanism is described in detail

by Zienkiewicz^B"2).

In each region the ratio of available shear strength to

shear stress was computed for both intact rocks and joints, and ex-

pressed as the "strength ratio". Regions with strength ratios of

unity thus represent zones of strength failure. Areas of the models

in which the "no-tension" criterion was applied have been referred to

as a "perturbed fissure zone". These represent areas in which

existing fractures may be opened.

- 107 -

B.3 GENERAL CONSIDERATIONS

The thermal rock mechanics analyses of the three regions of

the vault were performed using two-dimensional finite-element models and

the material properties listed in Table B-2.

A matrix of the important variables, extraction raclo, pitch

and panel thermal loading (PTL) for near-fi°ld and room-and-pillar

analyses, or gross thermal loading (GTL) for far-field analyses, was

used to define the required thermal analyses. The heat-generation

characteristics of the wastes are presented ir Section 4.2. The

extraction ratio, pitch and PTL satisfying the thermal constraints for

all three regions of the vault were chosen for the subsequent rock

mechanics analyses. All analyses considered hoth granite and gabbro

as potential host rocks.

It was recognized that a complete parametric analysis of the

vault alternatives would be excessively time-consuming and expensive.

At the present conceptual stage of design, such studies could not,

therefore, be justified. Some parameters such as backfill temperature

and container skin temperature were limited by maximum values in the

initial specification. Parameters such as room dimensions, container

numbers and spacing across the room and minimum pitch were set at the

preliminary layout study stage.

A hierarchy of constraints and restrictions was therefore

established for the analyses.

The first level was represented by the geometric restrictions

which were developed during the preliminary layout study stage. Thus,

only layouts which satisfied these geometric restrictions were con-

sidered for analysis.

- 108 -

The second level was represented by thermal constraints,

typically container skin temperature and average backfill temperature.

Thermal analyses were, therefore, undertaken and combinations of pitch

and extraction ratio which satisfied the thermal constraints were

defined. These analyses were undertaken primarily with the container

near-fields and room-and-pillar models.

The third level was represented by stress and deformation

constraints and restrictions. These required nonlinear-coupled thermal-

mechanical analyses of the three vault regions. Because of the com-

plexity, it was advantageous to limit the number of analyses as much as

possible. Only combinations of pitch and extraction ratio which

satisfied the thermal constraints were, therefore, selected for the

thermal mechanical analyses.

Examination of the proposed layout indicates that to achieve

the same GTL, reduction of the extraction ratio would be less expensive

than an increase in the pitch; the former requires lengthening the

limited number of panel drifts, but the latter requires lengthening all

the rooms. The thermal loadings for the design criteria satisfied all

thermal and thermal-mechanical specified constraints, as well as the

restrictions developed in the course of the study.

B.4 ANALYSES OF THE VAULT

B.4.1 Container Near-Field

The thermal-mechanical analyses of the container used a two-

dimensional model of a horizontal section through the vault floor at the

mid-plane of the container drill hole (Figure B-l). Thermal analyses

were performed using the principle of superposition. In this method,

the container mid-plane radial temperature distribution is determined

from a finite-element model of an idealized single container in an

- 109 -

infinite medium. The temperature in a field of multiple containers is

then determined by summation of temperature rises from contributing

containers. The principal criteria addressed in this model were:

1. The maximum container skin temperature should not exceed 150°C

2. Irreversible thermal mechanical responses within the drill

hole should be minimal.

A variety of extraction ratios and pitch which satisfied the

constraint skin temperature criterion for both the granite and gabbro

concepts were developed. The allowable ranges are shown in Figures B-2

and B-3 for granite and gabbro, respectively. These indicate that the

minimum container drill-hole spacing constraint is the governing cri-

terion for extraction ratios up to 25% for gabbro and up to 35% for

granite. These cori

gabbro and granite.

granite. These correspond to PTL's of 24 and 33 W/m , respectively, for

For the rock-mechanics analyses, both intact and jointed rock

were modelled. The jointed rock contained two vertical, orthogonal and

ubiquitous-joint sets, with strikes of 0°, 90°, 45° and -45° with

respect to the axis of the room. The ratios of the horizontal in-situ

stresses (normal versus parallel to the longitudinal axis of the room)

were assumed to be 1.5, 1.0 or 0.67. In all cases, one of the two

horizontal stresses was taken as 1.5 times the vertical geostatic stress.

The results showed that for either granite or gabbro the depth

of penetration of failure zones radially into the rock mass around the

drill holes was as follows:

1. Intact Rock - No intact-rock failure was predicted on excava-

tion. Strength failure occurred due to the thermal stresses

and penetrated a maximum distance of 5 cm at 10 years after

emplacement

- 110 -

2. Jointed Rock - Joint-strength failure was predicted for the

ubiquitous joints up to a penetration of 5 cm on excavations.

The joint-strength failure zone increased to a maximum depth

of 10 cm due to thermal stresses at 20 years after emplacement

(Figure B-4).

Only insignificant changes in these results were produced by

varying the joint orientations or the ratio of the horizontal stresses.

The minor extent of the strength-failure region is considered

to be acceptable from the point of view of stability or support of the

container near-field region. While no backfill is specifically required

in the annulus between the container and the drill-hole wall, the results

indicate that it would be prudent to include some to support any frac-

tured rock around the drill hole.

B.4.2 Room and Pillar

The thermal and thermal-mechanical analyses of the room-and-

pillar region were performed using the two-dimensional finite-element

model shown in Figure B-5.

The principal constraints to be satisfied were:

1. Maximum volume-averaged room backfill temperature to be 100°C-

2. Room stability to be achieved by conventional mining practices.

3. Average pillar strength ratio to be greater than 2.

These are summarized in Table B-l.

The parametric thermal analyses defined the allowable ranges

of extraction ratio, pitch and PTL which met the constraint that the

Ill -

volume-average room backfill temperature shall not exceed 100°C. These

are shown in Figures B-2 and B-3 for granite and gabbro, respectively.

The temperature-time history for the room backfill is shown in Figure

B-6. For the granite vault, the backfill temperature constraint limited2

the maximum allowable PTL to about 27 W/m . For the gabbro, the same

constraint United the maximum allowable PTL to about 24 W/m .

Based on the results of the container near-field and room-and-

pillar thermal analyses, for analytical expediency the following single

configuration was selected for thermomechanical analyses for both the

granite and gabbro vault concepts:

extraction

PTL

pitch

vatio =

>

25%

24 W/m2

1.5 m.

The nonlinear finite-element analyses of the room-and-pillar

concept were performed using the following three models:

1. Unjointed rock model.

2. Ubiquitously-jointed model.

3. Blast-fractured zone/discrete joint model.

Of these models, the blast-fractured zone/discrete joint model

is believed to best represent conditions of openings in hard-rock mining,

as evidenced by core drilling, stress determination and seismic

tests ' ' " . The analyses showed that the incremental changes in the

extent of the region of strength failure due to the thermal cycle were

small compared to the effects of the initial excavation. This is illus-

trated for the blast-fractured zone/discrete-joint model in Figures

B-7, B-8, B-9 and B-10. The average strength ratio in the pillar is

always well in excess of the required value of 2, as shown in the figures.

- 112 -

The regions of strength failure indicated by the analyses are

considered similar to those which can be expected in typical hard-rock

excavation at the proposed depth. Conventional rock-support methods

used in mining are considered adequate for the support of these regions.

B.4.3 Far-Field

The principal criterion addressed in the far-field analyses is

the requirement for no irreversible strains in the far-field rock mass.

For the far-field analyses, che thermal loading considered was

a GTL =23.6 W/m (this is equivalent to PTL = 24 W/m ) . This was

selected on the basis of the container near-field and room-and-pillar

thermal analyses. With this thermal loading, the maximum temperature at

the mid-plane of the vault was found to occur 50 years after emplacement

of the waste. Maximum temperatures were 87°C for granite and 102°C for

gabbro. The room-and-pillar and far-field analyses thus showed good

agreement in terms of maximum temperatures within the vault.

The thermal-mechanical analyses of the far-field region used

the no-tension type of analyses. No regions of perturbed fissure zones

were noted for this vault. In addition, no region of shear strength

failure was observed for either the granite or gabbro rock. The maximum

vertical displacement of the ground surface occurred for both rock types

approximately 2000 years after emplacement and was 10 cm for gabbro and

13 cm for granite.

B.5 SUMMARY OF ANALYSES

The t» rmal-mechanical constraints and allowable ranges for

pitch and extract!. •• ratio for the vault concept are summarized in

Figure B-ll.

- 113 -

For both granite and gabbro the preferred PTL-pitch-extraction

ratio combinations are controlled by the minimum drill-hole spacing and

the backfill temperature constraints. However, an increase in the

backfill temperature constraint or reduction in the container skin

temperature constraint could make this latter constraint significant,

particularly for a vault in gabbro. Variation in effects of far-field

constraints were not examined parametrically, but are not anticipated to

be significant at the thermal loadings required by the other constraints.

Room stability and pillar strength ratio criteria do not appear to be

critical for any of the thermal loadings considered.

Based on the analyses described, the thermal and thermome-

chanical constraints and restrictions and the common extraction ra io of

25%, the following configuration was selected for the vault design

criteria in both granite and gabbro:

Extraction ratio - 25%

PTL - 24 W/m2

GTL - 23.6 W/m2

Pitch - 1.5 ra

For gabbro, the selected configuration is controlled by the

allowable container spacing, container skin temperature and backfill

temperature constraints at an extraction ratio of 25%. The selected

configuration for the granite vault is defined by the minimum container

spacing constraint and the common extraction ratio value of 25/S estab-

lished by the gabbro case.

- 114 -

REFERENCES

B.I Herget, G., "Variations of Rock Stresses with Depth at aCanadian Iron Mine", Int. J. Rock Min. Sci. 10, No. 1, 37(1973).

B.2 O.C. Zienkiewicz, B.E. Valliappan «md J.P. King, "StressAnalysis of Rock as a No-Tension Material", Geotechnique 18.55 (1968).

B.3 D.F. Coates, "Rock Mechanics Principles", Mines Branch Mono-graph 847, Ottawa, 1967.

B.4 L. Obert and W.I. Duvall, "Rock Mechanics and the Design ofStructures in Rock", J. Wiley and Sons, 196 7.

B.5 Geller, L.B., "A New Look at Thermal Rock Fracturing", Trans.Institution of Mining and Metallurgy 79_, A133 (1970).

TABLE B-l

SPECIFIED THERMAL AND MECHANICAL CONSTRAINTS FOR VAULTS

Geometric Regionof Vault

Containernear-fieId

i

I

j Room andpillar

i

ii

Far-field

Thermomechanical Constraint

Container skin temperature

I

Container cavity stability

Near-field rock mass stability

Backfill volume-averagetemperature

Roof and rib failure/support

Integrated average of strength-stress ratio in pillar

Sustained long-term temperature

Rock mass stability anddeformation

Ground surface movement

Allowable Magnitude

150°C

(135°c rise)

open and stable hole

not supported

100 °C

(85°c rise)

conventional rock-bolting requirements

> 2

i not applicable

negligible irreversibledeformation and per-

J turbed fissure zoneI < 100 m deep

comparable to long-termregional movements

TABLE B-2

THERMAL AND THEEMOMECHANICAL MATERIAL PROPERTIES

Property

Thermal Conductivity

Specific Heat

Density

Young's Modulus

Poisson's Ratio

Angle of Internal Friction- Peak- Residual

Cohesion- Peak- Residual

Coefficient of ThermalExpansion

Units

W/m/K

J/kg/K

kg/m3

MPa

DegreesDegrees

MPaMPa

K"1

Intact

3

800

2800

40000

0

4535

191

8 d0" 6

Granite

Rock

ol,2

1

1

1

.21

33

2

.92

,1.*

Joints

_

-

-

-

-

4035

10.

-

33

2

32

Intact

2.

800

2800

40000

0.

4535

191

1

Gabbro

Rock

01'2

1

1

1

21

33

2

92

.,1.4

Joints

-

-

-

-

4035

10.

-

3

2

32

Acres Consulting Services Limited, "Radioactive Waste Repository Study",Parts 1, 2 and 3, for Atomic Energy of Canada Limited, Atomic Energy of CanadaLimited Report, AECL-6188/1, -2 and -3 (1978).

H. Stille, A.S. Burgess and U. Lindblom, "Groundwater Movement Around aRepository - Geological and Geotechnical Conditions", KBS Technical Report 54:01 (1977).

Acres Consulting Services Limited, "Atomic Energy of Canada Limited Radioactive WasteRepository Study", Topical Report II - Room Stability (1977).

L,B. Geller, "A New Look at Thermal Rock Fracturing", Trans. InstitutionMining Metallurgy, 79; A133-A170 (1970).

- 117 -

PIT.JAR

30m

PILLAR

O O O Oo o o oo o o oo o'o-oo o o oO o O Oo o o o

7.5 m

FIGURE B-l. COMTAINER NEAR-FIELD MODEL REGION

- 118 -

Container Surface Constraint: 150°C(135°C rise)

Backfill Constraint: 100°C(85°c rise)

10 W/m

ALLOWABLERANGE

1.5 2.5

FIGURE B-2. THE RANGES OF PITCH AND EXTRACTION RATIOTHAT MEET THE THERMAL AND DRILL-HOLESPACING CONSTRAINTS FOR A GRANITE VAULT

- 119 -

en

o

Container SurfaceConstraint: 150°C

(135°c r ise)Backf i l l Constraint:

100°C (85°c r ise)

^LE SPAC-

CONSTRAINT

0.5 1.5PITCH (m)

2.0 2.5

10 W/ni

ALLOWABLERANGE

FIGURE B-3. THE RANGES OF PITCH AND EXTRACTION RATIOTHAT MEET THE THERMAL AND DRILL-HOLESPACING CONSTRAINTS FOR A GABBRO VAULT

10cm SCALEH +

oI

Time = 0.0 a Time = 0.1 a Time = 1.0a Time = 10 a Time = 20 a Time = 100 a

FIGURE B-4. GRANITE VAULT: NEAR-FIELD STRENGTH RATIO CONTOURS AT VARIOUS TIMESAFTER EMPLACEMENT WITH EQUAL INITIAL HORIZONTAL STRESSES

- 121 -

20 n aboveroom free tomove verticallyfor stress —analyses

Room centrelineinsulated forthermal analyses

Room centrelinefixed horizon-tal ly for stressanalyses

1,000 m belowground surface

Immobilizedwaste

20 m below roomfixed verticallyfor stressanalyses

150 m abovecentre of roomfixed at 0°Cfor thermalanalyses

Pillar centrelineinsulated forthermal analyses

Pillar centrelinefixed horizontallyfor stress analyses

150 m below centreof room fixed atD°C

FIGURE B-5. FINITE-ELEMENT MESH FOR THERMAL-ROCKMECHANICS ANALYSIS OF ROOM-AND-PILLAR REGION

90

80

70

60

50

40

30

20

10

0

.

^,

/

J

ER ?5

**>

"0 k =

N\

X\

3 l / ra K

MM —m. —

TMAX = 83 K,S = 2.3m ,

PTL = 27 .2 W/ITI

TMAX = 73 KS = 1.5m ,

PTL = 2 3 . 9 W/rn

TMAX = 55KS = 2.On ,

PTL = 1 7 . 9 H/ni

6 8 10 20 40 60 80 100

TIME (YLAR?)

200 400

FIGURE B-6 . BACKFILL TEMPERATURE RISE AS A FUNCTION OF TIME FORVARIOUS VALUES OF PITCH, S, FOR A GRANITE VAULT

- 123 -

ER = 25%DEPTH = 1,000m

Blast-Fracturedwith 90° Joint,

DISCRETE VERTICAL JOINT

FIGURE B-7. ROOM-AND-PILLAR REGION CONTOURS OF STRENGTH RATIO AT EXCAVATION(TIME = 0) , WITH A BLAST-FRACTURED ZONE AROUND THE ROOM HAVINGUBIQUITOUS VERTICAL JOINTS, A DISCRETE VERTICAL JOINT AT 4 mFROM CENTRE OF ROOM, AND WEAK UNJOINTED ROCK ELSEWHERE (GRANITEOR GABBRO)

- 124 -

PITCH = 1.5 mER = 25% ,

PTL = 24 V/m

UHJOINTED ROCK


FIGURE B-8. ROOM -AND-PILLAR REGION CONTOURS OF STRENGTH RATIO 10 YEARSAFTER EMPLACEMENT, USING MODEL OF FIGURE B-7 (GRANITE OR GABBRO)

- 125 -

WSTE

PITCH = 1.5mER = 25% ~

PTL = 24 V/mDEPTH = 1,000m


FIGURE B-9. GRANITE VAULT: ROOM-AND-PILLAR REGION CONTOURS OFSTRENGTH RATIO 75 YEARS FROM EMPLACEMENT, US IMG MODELOF FIGURE B-7

- 126 -

PTL = 24 W/mDEPTH = 1,000m


FIGURE B-1O. GABBRO VAULT: ROOM-AND-PILLAR REGIONCONTOURS OF STRENGTH RATIO AT 1 YEAR AND 75 YEARSFROM EMPLACEMENT, USING MODEL OF FIGURE R-7

1.5 2.0PITCH On)

FIGURE B-ll. THERMALMECHANICAL CONSTRAINTS

ISSN 0067-0367 ISSNOO67-0J67

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