Twenty years of experience in handling sodium in ... Documents...Sodium – Water Reaction Test...

IAEA Workshop on Challenges for Coolants in Fast Neutron Spectrum system:

Chemistry and materials

Twenty years of experience in handling sodium in experimental sodium facilities

B. Babu

Scientific Officer ‘H’ and Head – Device Development and Rig Services Division

Indira Gandhi Centre for Atomic Research, Kalpakkam

Department of Atomic Energy, India.

Presentation layout

• Introduction

• Experimental sodium facilities

• Large component test rig

• Experiments in other sodium facilities

• Sodium loop operation experience

• Operation philosophy

• Impurities in sodium and purification

• Sodium leak detection

• Minor sodium leak incidents

• Sodium fire and extinguishing methods

• Handling of sodium components

• Safety aspects

• Improvements proposed for future facilities

• Summary

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Stage – I

PHWRs

• 18- operating

• 4 - under construction

• Scaling to 700 MWe

• Gestation period

being reduced

• 10 more planned

LWRs

• 2 BWRs operating

• 2 PWRs operating

Stage - II

Fast Breeder Reactors

• 40 MWth FBTR - Operating

Technology Objectives

realised

• 500 MWe PFBR-

under commissioning

• high power potential

Stage - III

Thorium Based Reactors

• 30 kWth KAMINI- operating

• 300 MWe AHWR- under

regulatory examination

• power potential Very

large.

• Availability of accelerator

driven neutron sources can

convert Thorium on a large

scale

Three Stage Nuclear Power Program

13.5 MWe

Fast Breeder Test Reactor

Flow Diagram of FBTR

5

Prototype Fast Breeder Reactor

Flow Diagram of PFBR

Engineering R & D in Support of PFBR

IGCAR is actively involved in development of Fast reactor technology

Design validation, testing and qualification of various components of FBRs

is achieved through experiments in sodium or water using scaled down

models.

In-sodium experiments are carried out in the different sodium facilities of

IGCAR

Major Sodium Facilities

Large Component Test Facility (LCTR)

Sodium – Water Reaction Test Facility

SILVERINA Sodium Loop

In-Sodium Test Facility

Bi-Metallic Sodium Loop

Steam Generator Test Facility

LEENA Test Facility

SADHANA sodium loop

Thermal Hydraulic Studies

Sub-Assembly Test Loop

Ganga – Water Loop

1/4th Reactor Assembly Model

(SAMRAT)

Pool Hydraulics Loop

Component Testing

Absorber Rod Drive Mechanism

Fuel Handling Equipments

Heat Transfer Studies in LCTR

Failed Fuel Location Module

Components & Instruments Developed

Sodium Centrifugal Pumps

Electromagnetic Pumps

Electromagnetic Flowmeters

Sodium Instruments such as

level probes, leak detectors,

Ultrasonic under sodium scanner

Sodium Facilities In IGCAR

• Large Component Test Rig: Sodium inventory -100 tonnes

Testing of full scale reactor components

• Sodium Water Reaction Test Facility: Sodium – 10 tonnes

Specifically for sodium water reaction experiment and developmental activities of

hydrogen meters.

• Steam Generator Test Facility – Sodium - 18 tonnes

Testing of Steam Generator model, Regeneration experiment on cold trap

• SADHANA test facility : [LCTR Storage tank]

Testing of simulated model of SGDHR system, DHX, AHX-Type-B

• Thermal Shock Test Facility [SOWART storage tank]

Thermal shock testing of small components

• In Sodium Test Facility [Fatigue Loop and Creep loop] - Sodium - 1 tonne

Material testing

• Bi-Metallic loop - Sodium – 0.5 tonne

Carbon transfer behaviour studies on materials

• SILVERINA sodium loop – Sodium inventory- 1.3 tonnes

Small component test facility

Large Component Test Rig

• Five test vessels in which

independent test

conditions can be

maintained

• Electro Magnetic Pump

for sodium circulation and

online purification

• Heater Vessel with 200 kW

power immersion heater

• Commissioned in 1994 – completed more than 20 years of operation

• Cumulative operating hours till date is more than 70,000 h

• Total sodium hold up: 100 tonnes

• Pipe lines and components are provided with surface heaters,

• Sensors

• thermocouples

• wire type leak detectors

• MI type Continuous and Discontinuous level sensors

• Sodium Ionisation detectors.

• PLC based Data Acquisition and Control system is used for monitoring

all the parameters in the control room.

• Maximum operating temperature of the test facility is 550 °C and the

maximum sodium flow rate is 20 m3/h.

• Material of construction is Austenitic Stainless steel, grade 316.

Large Component Test Rig

Major Experiments in LCTR

Tests/Experiments conducted for PFBR in Sodium

• Development and testing of in-sodium sensors for PFBR

• Calibration of Continuous & Discontinuous Sodium level probes of PFBR

• Testing and Qualification of Under Sodium Ultrasonic Scanner for PFBR.

• Performance testing of Prototype CSRDM

• Performance testing of Prototype DSRDM

• Performance testing of Primary Ramp & Primary Tilting Mechanism of

Inclined Fuel Transfer Machine of PFBR.

• Performance testing of In Vessel Fuel Transfer Machine Transfer arm of

PFBR.

• Testing of Annular Linear Induction Pump, DC Conduction Pump &

Sodium vapor condenser

• Heat transfer and temperature distribution studies in roof slab model and

control plug model of PFBR and studies on effectiveness of cooling circuit

of top shield

• Sub-Assembly wetting and washing

Mutual Inductance type Leak Detector for detecting sodium leaks in Main vessel, safety

vessel and double wall pipes of PFBR

1) In-sodium Sensors developed for PFBR

Eddy Current Flow Meter to measure primary discharge flow in PFBR

Extended Spark Plug type Leak Detector for detecting

sodium leak in main and safety vessels of PFBR

Mutual Inductance type discrete and continuous level probes for sodium level measurement in various sodium capacities of PFBR

Sodium Aerosol Detector for area monitoring of

sodium leak in PFBR

Permanent Magnet Flow Meter for measuring sodium

flow rate at various locations in PFBR


2) Calibration of MI type continuous level probe in sodium

• Mutual inductance type Continuous Level Probes for monitoring sodium level in sodium tanks and vessels.

• Probes of active length 6000 mm and total length of 9600 mm.

• During calibration the secondary voltages recorded at constant primary current of 100 mA,

At frequencies from 2 to 4 kHz

Zero level and full level

At temperatures from 200°C to 550°C.

29 nos. each of continuous and discrete probes of PFBR calibrated

Level probe calibration set up erected in TV-1 of LCTR


• High temperature piezoelectric transducers developed for

viewing protrusion, growth and bowing of the Fuel SA before

Fuel handling

• 4 nos. each of Side Viewing and Downward Viewing

Transducers .

(b)

(c)

(a) Methodology (b)Transducer holder (c) Experimental setup (d) USUSS

(a) Protrusion of a subassembly

• Qualification testing of transducers –

in water and in sodium, Validation in

radioactive environment.

• A reference target inside the reactor

for proper alignment of scanner.

(d)


3) Testing and Qualification of Under Sodium Ultrasonic Scanner of PFBR.

4) Performance Evaluation of Shutdown Systems of PFBR

Lower part storage vessels Upper parts in storage room

Testing of 3 nos. of DSRDMs and 9 nos. of CSRDMs completed.

Functional tests carried out:

Torque measurement, Straightness of travel measurement, Verification of inter seal

leak tightness, Measurement of Frictional force during translation, Verification of

scram operation & deceleration (CSRDM only), Verification of EM minimum holding

current & response time


IFTM is for • Transfer of spent fuel subassemblies

from IVTP to EVTP • Loading of fresh subassembly from

EVTP to IVTP The primary side of IFTM consists of • Primary Tilting Mechanism (PTM) • Primary Ramp (PR) • Primary Gate Valve • Shield Plug • PR liner • Rotatable Shielded Leg (RSL) • Hoisting mechanism Secondary side of IFTM consists of • Secondary Gate Valve • Secondary Ramp

• Secondary Tilting mechanism.

• Testing was carried in air and sodium at two phases – primary and secondary

IFTM assembly


5) Testing of Inclined Fuel Transfer Machine

6) Testing of Electromagnetic Pumps

Reflux Annular Linear Induction Pump (ALIP)

Once through ALIP

DC Conduction Pump

Sodium Submersible ALIP

A.C. Conduction Pump

• EM pumps – Pumping of sodium

• Fleming’s left hand rule

• EM pump types

• DC conduction pump

• AC conduction pump

• Annular Linear Induction pump

• Performance validation of pumps carried out by testing the pump in sodium.

• During sodium testing of ALIP Head Vs Flow, Input power vs. Flow and Efficiency Vs

Flow characteristics are obtained.

• Long term endurance testing also carried out.


• Self wastage studies

were carried out at

different steam leak

rates in the range of 10-

50mg/s

• Model Cold Trap Testing

SOWART

• SGDHR Scaled down

model

• A Decay Heat

Exchanger

• An Air Heat Exchanger

(AHX) for heat removal

at an elevation of 19 m

from the Test Vessel.

• A Chimney for

inducing the natural

draft connected to AHX.

• Natural Circulation of

sodium was achieved

as per rated conditions.

SADHANA LOOP

Other Sodium Test Facilities

• DSRDM magnet testing

• Transfer arm bearing testing

• SID performance testing

• Eddy current type DSR position

sensor

• Tribological studies on materials

• Sodium aerosol compatibility of

inflatable seal rubber material.

SILVERINA LOOP

Other Sodium Test Facilities

BI-METALLIC LOOP • 16,000 h of exposure Mod.

9 Cr. 1 Mo. - SS 316 LN

specimens

completed in flowing

sodium

• Self welding experiments on

material specimens in

sodium

LEENA LOOP • Qualification of Wire type leak detectors

layout for PFBR

• Lowest leak simulated is 214 g/h

detected in 50 minutes

• Maximum quantity of sodium leaked

1.3 kg -detected in 6 h (leak rate

222g/h)

• 100 g/h to be detected in 20 h.

SGTF

• Experimental data utilised for

FBR SG design

• Total operating hours 6000.

• Development of acoustic leak

detection system

• Flow Induced Vibration of SG

tubes

• LCF and Creep fatigue interaction

studies on Mod 9Cr-1Mo and 316 LN

materials & weld joints at 550 – 600˚C.

• Creep rupture tests on 316 LN

• Tribology, thermal striping and fretting

and wear studies on material specimens

IN-SODIUM TEST FACILITY

Major Experiments in other facilities

• Experiments on Adjacent tube wastage studies at different steam leak rates

• SG endurance test at rated conditions

• Estimation of SG heat transfer area margin

• Flow Induced Vibration studies of SG tubes

• Fatigue and creep experiments

• Testing of Integrated Cold trap and Integrated Plugging Indicator

• Development & Testing of in-sodium and cover gas hydrogen meter

(a) Impingement wastage test section

(b) Model SG – SGTF

(c) Integrated cold trap

(a)

(b)

(c)

20

A new sodium loop at Engineering Hall-I

The facility is commissioned in January 2017.

Objectives

• Testing and calibration of medium length MI type

continuous/discrete level probes and RADAR level probes.

• In-sodium testing of small and medium size reactor components

which are part of reactor.

• Sodium freezing studies simulating the secondary circuit of

future FBRs.

• Performance testing of different types of EM pumps and

flowmeters.

Sodium Facility For Component Testing (SFCT)

Material of construction is SS 316LN.

Sodium inventory is 6 tonnes.

50 m3/h capacity EM pump for heating and cooling circuit

170 m3/h capacity EM pump for testing at high flows.

220 kW heater capacity, designed for operation up to 600 °C.

Sodium Technology Complex (upcoming facility)

• Qualification and Testing of CSRDM/CSR and DSRDM/DSR with improved safety features

• Qualification of third shut down system for reactor operations

• Testing of any other lengthy components of FBR-1 and 2. • Under Sodium Ultrasonic Scanning System & Sweep Arm

Scanner, Developmental studies on In Vessel Under

Sodium Examination techniques for in service inspection.

• Maximum Operating Temperature: 550 °C.

• Material of Construction: AISI 316 LN • Three test vessels • 50 m3/h Annular Linear Induction

Pump • Sodium Purification Circuit • Heating & Cooling systems • Interconnecting pipe lines of varying

sizes

• High bay of 40 m length, 21 m width and 43 m height

• Large sodium test facility • Full scale assembling of full scale

reactor components • Air test facility, Sodium cleaning,

chemical cleaning • Dismantling and safe storage of

advanced shut down mechanisms. • 25T & 10T capacity cranes for high

bay • Electrical Power Requirement : 4.8

MW

Sodium Loop Operation Experience

Operation philosophy

• An established operating sequence followed meticulously.

• Key operational sodium parameters such as the flow, temperature and purity

are monitored and maintained

• Sodium purity maintained at reactor grade by cold trap

• Plugging runs taken weekly to monitor and maintain the oxygen level less

than 2 ppm.

Impurities in sodium & purification

• Impurities (Ca, O, H and C) ingress into sodium from air, moisture, Carbon-di-

oxide, oils, and greases.

• Due to reactive nature of sodium, Oxygen would be present not only as

dissolved oxide, but also as surface coating (solid oxide).

• Even though carbon solubility is low, carbon can be present as dispersed

particulates.

• Periodic sampling of loop sodium is carried out annually/ between test

campaigns using the overflow type sodium sampler

• Impurity levels of oxygen, carbon and trace elements determined by

chemical analysis.


Sodium leak detection

• Liquid sodium reacts violently with air / water.

• It requires a leak tight containment and specialized sensors to detect leak in

the incipient stage itself to ensure safety.

• Leakage of sodium can be detected in multiple ways

• Sodium aerosol detection

• Sodium Ionisation Detector (SID)

• Sodium leak detection

• wire type

• spark plug type

• Mutual Inductance type Leak Detector

• SID detects minute quantity of sodium leak and tests demonstrated that it can

detect 1 mg of sodium per m3 of carrier gas instantaneously.

• Wire type leak sensors detect leak in the pipelines

• Spark plug type leak sensors detect the leak in sodium capacities, bellow

sealed valves and double envelope.

• MILD works on the principle of decrease in mutual inductance between two

coils when sodium surrounds it.


Minor sodium leak incidents

• Incidence of leak in LCTR - less

• Maximum sodium leak was 2.8 kg – from sodium to air heat exchanger due to

failure of a finned tube to tube sheet weld joint.

• Other sodium leaks < 100 g in bellows sealed valves due to stress corrosion

Sodium fire and extinguishing methods

• Sodium fire is characterised by short flame golden yellow in colour and dense

white oxide smoke.

• Sodium oxidizes spontaneously in air, with the evolution of heat. As sodium

temperature increases, the rate of oxidation also increases, resulting in

sodium catching fire.

• Sodium fire extinguished by

• application of dry chemical powder.

• Flooding with Argon or nitrogen to smother the fire. This method is slow

and effective but is difficult in inaccessible areas.

• Blanketing or oxygen starvation


Handling of sodium components

• During introduction and removal of components into Test vessel - positive

pressure and continuous Argon purging are maintained to eliminate the

ingress of atmospheric air into the system.

• Cleaning of sodium exposed components is necessary for reuse of

components and its safe storage.

• Cleaning methods

• involving chemical reactions - dangerous and the resulting phenomena

are complex.

• Alcohol and thermo fluid oil - piping and small components like valves.

• Dry steam along with nitrogen purging

• Jet of water - parts with very simple geometry

• Process of carbon dioxide bubbled through hot water – Large

components

Safety Aspects

• Operation of the rig is carried out based on approved technical specifications

and by trained manpower.

• Dyke of 0.6 m height provided around the storage tanks in dump pit - to

avoid entry of water into the pit under conditions of inundation

• Dump tanks and all other sodium system components are of helium leak tight

construction

• Floor area and side walls (upto 2m) inside dump pit are steel lined with 5 mm

thick MS plate – to avoid contact / reaction of sodium with concrete

• Accumulation of small quantity of water over long periods under the MS liner

removed using a small pump.

• Water level in the sump is indicated by a level detector and in turn linked to a

level alarm.

• All the test vessels are provided with over flow lines which are linked to dump

tank.

• Covered leak collection trays are provided below test vessels to collect the

leaking sodium and extinguish the fire by passive means.

Safety Aspects

• All the major capacities like sodium storage tanks and test vessels are

provided with wire type leak detectors.

• Povisions are made to handle two types of fires - sodium metal fire and

conventional fires.

• Proper functioning of all the instrumentation systems, safety inter locks,

dump valves, sodium leak detection system, diesel generator operation, Un

Interrupted Power Supply (UPS) and battery banks are checked periodically

as per operation procedure and technical specifications.

• Any significant event / leak was analysed and corrective action taken.

• All industrial hygiene and safety requirements as stipulated in the Atomic

Energy (factories) rules are complied with during all operations in the sodium

facilities.

• Periodic review / inspection by regulatory bodies

• Preventive / breakdown /surveillance tests were meticulously followed with

approved procedure

Improvements Proposed For Future Facilities

• Material of construction: AISI 316 LN is better compared to AISI 316.

• Storage tanks: vertical tanks due to easier design, low thermal shocks and

easier supporting.

• Cold trap: Larger capacity for faster purification after experiments

• Operating experience of EM Pumps has been satisfactory and suggested to

use ALIP in future facilities.

• Recommended to have a level probe in the priming vessel for the priming of

the pump

• Failure of 50 % of the heaters in vertical Heater Vessel [HV] had occurred

after 15 years of operation. So a vertical HV with additional heaters with

dished ends will be suitable.

• Alternate dump paths for the large sodium capacities should be provided.

• Mineral Insulated Sheathed heaters shall be used as surface heaters.

• Unbreakable bead type sleeves to be used to avoid spurious leak signals

• At the outlet of the Plugging indicator blower, a smoke detector and sodium

ionization flute pipe for aerosol detection is recommended.

Improvements Proposed for Future Facilities

• Periodical check of the leak port of bellows sealed valves for any blockage

like foreign particles and cleaning ensures prompt leak signal

• Cleanliness shall be maintained to reduce the probability of blockage of the

SID sampling flute holes and frequent surveillance/ cleaning of the flute pipes

is necessary.

• Mutual Inductance type discrete sensors instead of Resistance Type Level

Probes to be used.

• Air drier unit needs to be utilized in the compressed air circuit to reduce the

moisture carryover to the solenoid actuated pneumatic valves.

• Diesel Generator set shall be positioned at a higher elevation on a pedestal

above FFL to take care of any revision in the DBFL in future.

• Single crane in high bay lead to queuing of the experimental activities. Two

cranes of different load carrying capacities are recommended.

Summary

• Comprehensive picture of the Sodium facilities in operation and planned at

IGCAR are given

• Large Component Test Rig was operated successfully for more than 20

years without any major incidents.

• PFBR components were tested in sodium, qualified and installed in the

reactor.

• Experiments on R&D for development of sodium technology continuously

pursued for future FBRs

• In-sodium sensors and devices were developed and tested for FBR

applications

• Experience gained during the course of operation of LCTR.

• Experience gained on methods of handling of components for testing in

sodium and effective cleaning thereafter for reuse

• Feedback of the experience provided as input to the design of new sodium

test facility.

• Overall experience in operating the sodium loops at high temperature has

given us the confidence to continue further experiments and design and

commissioning of new sodium facilities.

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