Spallation Target R&D for the EU Accelerator-Driven Sub-critical System Project

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BENE04, DESY Hamburg, Germany Y.KADI November 2-5, 2004

Spallation Target R&D for the EU

Accelerator-Driven Sub-critical System Project

Y. Kadi(AB/ATB)

European Organization for Nuclear Research, CERNCH-1211 Geneva 23, SWITZERLAND

[email protected]

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ISOL thick target

Protons

+/- 8V500A

+/- 9V1000A

*

RILIS laser beams

Nb cavity

Tantalum oven

Transfer line

Mass-Separation

Ionisation

Effusion

DiffusionDiffusion

Nuclear reaction

UC2 pills Graphite sleeve

UC2 target

Tim

e

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Refractory compounds:Oxides, carbides, chlorides

Molten metals,Molten salts,Thins foils, powders

0

20

40

60

80

100

C Al Si Ca Sc Ti V Mg Ge Sr Zr Nb Sn Te Ba La Ce Gd Ta W Ir Au Pb Th U

ISOL targets materials

spallation - fissionZ

Si

Ca

Ti

Sr

Zr

Nb

Sn

LaTa

W

Pb

Th

U

C

Al

Ce

MgUsers’ request frequency

Target thickness: 4-220 g/cm2

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High energy protons fission of 238U and n-induced fission of 235U

Fission probability

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

0 50 100 150 200

A [amu]

Fission probability [%]

238U, 1.4 GeV p,f (2.59 barn) CASCABLA

238U, 600 MeV p,f (2.25 barn) CASCABLA

235U, Thermal n,f ( 582 barn)

Fission

Spallation

Fragments

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ISOLDE target handling.

Class A laboratory (2004)Isotopes (Activity/LA) > 10’000

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Use of Spallation Neutrons

• Spallation neutrons can be used to transmute the highly-radiotoxic nuclei which are present in nuclear waste into stable or very short lived isotopes that can be disposed off safely.

• The techniques developed for ADS can be applied to optimize the production of fission products of the EURISOL-DS.

……. A long way to go but clear synergies in the neutronics …….

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Transmutation of Nuclear Waste ?

•Europe : 35% of electricity from nuclear energy

•produces about 2500 t/y of used fuel: 25 t (Pu),

3.5 t (MAs: Np, Am, Cm) and 3 t (LLFPs).

•social and environmental satisfactory solution

is needed for the waste problem

•The P&T in association with the ADS can lead

to this acceptable solution.

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Transmutation of Nuclear Waste ? (2)

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Sub-Critical Systems (1)

• In Accelerator-Driven Systems a Sub-Critical blanket surrounding the spallation target is used to multiply the spallation neutrons.

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Sub-Critical Systems (2)

ADS operates in a non self-sustained chain reaction mode

minimises criticality and power excursions

ADS is operated in a sub-critical mode stays sub-critical whether

accelerator is on or off extra level of safety against

criticality accidents

The accelerator provides a control mechanism for sub-critical systems

more convenient than control rods in critical reactor

safety concerns, neutron economy

ADS provides a decoupling of the neutron source (spallation source) from the fissile fuel (fission neutrons)

ADS accepts fuels that would not be acceptable in critical reactors

Minor Actinides High Pu content LLFF...

ADS operates in a non self-sustained chain reaction mode

minimises criticality and power excursions

ADS is operated in a sub-critical mode stays sub-critical whether

accelerator is on or off extra level of safety against

criticality accidents

The accelerator provides a control mechanism for sub-critical systems

more convenient than control rods in critical reactor

safety concerns, neutron economy

ADS provides a decoupling of the neutron source (spallation source) from the fissile fuel (fission neutrons)

ADS accepts fuels that would not be acceptable in critical reactors

Minor Actinides High Pu content LLFF...

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The FEAT Experiment (1)

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The Energy Amplifier Concept

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The Energy Amplifier Concept (2)

Method: A high energy proton beam interacts in a molten lead (Pb-Bi) swimming pool. Neutrons are produced by the so-called spallation process. Lead is “transparent” to neutrons. Single phase coolant, b.p. ≈ 2000 °C

TRU: They are introduced, after separation, in the form of classic, well tested “fuel rods”. Fast neutrons, both from spallation and fission, drift to the TRU rods and fission them efficiently. A substantial amount of net power is produced (up to ≈ 1/3 of LWR), to pay for the operation.

LLFF: Neutrons leaking from the periphery of the core are used to transmute also LLFF (Tc99, I129 ....)

Safety: The sub-criticality (k ≈ 0.950.98) condition is guaranteed at all times.

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The Energy Amplifier Concept (3)

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The Three Levels of ADS Validation

Three different levels of validation of an ADS can be specified:

• First, validation of the different component concepts, taken separately (accelerator, target, subcritical core, dedicated fuels and fuel processing methods). In Europe: The FEAT, TARC & MUSE experimental programs and the MEGAPIE project are significant examples.

• Second, validation of the coupling of the different components in a significant environment, e.g. in terms of power of the global installation, using as far as possible existing critical reactors, to be adapted to the objectives.

• Third, validation in an installation explicitly designed for demonstration (e.g. the ADS installation described in the European roadmap established by the Technical Working Group, chaired by prof. Rubbia). This third step should evolve to a demonstration of transmutation fuels, after a first phase in which the subcritical core could be loaded with “standard” fuel.

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ADS VALIDATION: Level 1

• Physics Basic underlying physics has been thoroughly checked at zero power in particular by experiments at CERN and elsewhere

Spallation process and neutron yields with proton beam in a wide range of energies

Fission rates and lead nuclear properties: a sub-critical arrangement with k≈0.9 has demonstrated energy gain in agreement with calculations (FEAT Experiment)

Transmutation rates for most offending LLFP. Fast elimination by “adiabatic resonance crossing” has been demonstrated experimentally for 129I and 99Tc. (TARC Experiment)

Most key reactions fully tested at low power level

A comprehensive programme of neutron induced cross-section measurements has been started (nTOF Project)

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ADS VALIDATION: The TARC Experiment (1)

Simulation of neutrons produced by a single 3.5 GeV/c proton

(147 neutrons produced, 55035 scattering)

Simulation of neutrons produced by a single 3.5 GeV/c proton

(147 neutrons produced, 55035 scattering)

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• We are now at a turning point in terms of programme co-ordination and resource deployment in Europe. For the coming five to seven years, the R&D should concentrate on:

• The development of high intensity accelerators and megawatt spallation sources, and their integration in a fissile facility

• The development of advanced fuel reprocessing technology

Throughout Europe, the main facilities or experiments of relevance are:

– IPHI (High Intensity Proton Injector) in France and TRASCO (TRAsmutazione SCOrie) in Italy, on the design of a high current and reliable proton linear accelerator.

– MEGAPIE (MEGAwatt PIlot Experiment), a robust and efficient spallation target, integrated in the SINQ facility at the Paul Scherrer Institute in Switzerland. The SINQ facility is a spallation neutron source fed by a 590 MeV proton cyclotron.

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• MUSE-4 (At the MASURCA installation in CEA-Cadarache, using the GENEPI Accelerator), as a first image of a sub-critical fast core fed by external neutrons.

• JRC-ITU The Minor Actinide (fuel fabrication) and advanced aqueous and pyro-processing Laboratories at JRC-ITU in Karlsruhe.

• JRC-IRMM Neutron data activity at Gelina TOF Facility in Geel.

• N_TOF (Neutron Time of Flight) experiment at CERN, Geneva, for nuclear cross-section measurements.

• KALLA (KArlsruhe Lead LAboratory) and

• CIRCE (CIRCuito Eutettico) facilities for Pb and Pb-Bi Eutectic technology development in Brasimone, Italy.

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ADS VALIDATION: CIRCE Pb & PbBi test facility

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ADS VALIDATION: MEGAPIE test

• MEGAPIE Project at PSI

• 0.59 GeV proton beam

• 1 MW beam power• Goals:• Demonstrate

feasablility• One year service

life• Irradiation in 2005

Proton Beam

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• First, validation of the different component concepts, taken separately (accelerator, target, subcritical core, dedicated fuels and fuel processing methods). In Europe: The MUSE experimental program and the MEGAPIE project are significant examples.



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ADS VALIDATION Level 2: TRADE Project

• The TRADE experiment suggested by C. Rubbia, first worked-out in an ENEA/CEA/CERN feasibility study and presently assessed by a wider international group (lead: ENEA, CEA, DOE, FZK), is a significant step towards the ADS demonstration, i.e. within the second step of ADS validation

• Coupling of a proton accelerator to a power TRIGA Reactor via a spallation target, inserted at the center of the core.

• Range of power :– in the core : 200 - 1000 KW,– in the target : 20 - 100 KW.

• The main interest of TRADE, as compared to the MUSE experiments, is the ability of incorporating the power feedback effects into the dynamics measurements in ADS and to address ADS operational, safety and licensing issues.

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The TRADE Facility - Reactor and Accelerator Buildings

Core ReactorCyclotron (section)

Beam Pipe

Shielded Beam Pipe Tunnel

Control Room Window

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Overall Lay-out of the TRADE FacilityOverall Lay-out of the TRADE Facility

Core cross-sectionCore cross-section

Top view & bending magnetsTop view & bending magnets

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TRIGA MARK II REACTOR

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TRIGA MARK II REACTOR

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The main characteristics of TRADE

• A proton cyclotron delivering a beam of 140 MeV protons (option investigated 300 MeV).

• A three sections beam transport line: Matching section/Straight transfer line/Final bending line.

• A solid Ta target (back-up : W clad in Ta).

• Forced convection of the target cooling with a separate loop.

• Natural convection for the core cooling.

• Range of subcritical levels : k = 0.90 0.99

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The Spallation Target System

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Primary Flux

Thick Ta Target (protons/cm2/s) per mA

- 140 MeV -

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Primary Flux

Thick Ta Target (protons/cm2/s) per mA

- 300 MeV -

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H-E Neutron Flux @ 140 MeV

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H-E Neutron Flux @ 300 MeV

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Radiation Damage

Gas production and the displacement rates per kW of beam

Target

(Ta)

Average

Prot. Ener(MeV)

Average

Neut. Ener(MeV)

H3

Production(appm/dpa)

He

Production(appm/dpa)

HE proton(dpa/yr)

HE neutron(dpa/yr)

Max Ave

140 MeV 90 51 0.99 54.8 0.6 0.07

200 MeV 115 65 2.92 130. 0.5 0.05

300 MeV 155 88 6.93 275. 0.4 0.04

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Target cooling system in forced convection

Coarse Dimensioning of the circuit:

•Thermal power = 40kW•Design ΔT ~ 5 - 20 °C

Pumps and circuit characteristics:

•Pumps flow-rate ~ 8 - 2 m3/h•Water max speed (3 holes of Φ =

18 mm) ~ 3 - 1 m/s

Coarse Dimensioning of the circuit:

•Thermal power = 40kW•Design ΔT ~ 5 - 20 °C

Pumps and circuit characteristics:

•Pumps flow-rate ~ 8 - 2 m3/h•Water max speed (3 holes of Φ =

18 mm) ~ 3 - 1 m/s

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In presence of the design mass flow-rate of water (2.24 Kg/s), the maximum thermal flux at the outer wall of the target is 135 w/cm2 thus assuring a margin large enough to prevent the occurrence of Critical Heat Flux. Moreover the maximum temperature is 80°C which is significantly lower than the TRIGA saturation temperature

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Test loop configuration to be built at FzK

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• First, validation of the different component concepts, taken separately (accelerator, target, subcritical core, dedicated fuels and fuel processing methods). In Europe: The MUSE experimental program and the MEGAPIE project are significant examples.



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Spallation Target: Boundary Conditions

• 350 MeV, 5 mA proton beam for fast neutron fluxes for transmutation, i.e. 1.75 MW of which 80 % is heat

• 130 mm penetration depth for 350 MeV - Bragg peak

• 72 mm ID radial extent of the beam tube + 122 mm OD radial extent of the feeder - limited by neutronics

• Windowless target due to high beam load - despite vacuum

• Pb-Bi because of neutronic and thermal properties

1.4 MW heat in ~ 0.5 l to be removed while meeting thermal and vacuum requirements

MYRRHA Project: 50 - 80 MWth (k≈0.97)

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Spallation Target: Desired Target Configuration

Volume-minimized recirculation zone gets lower ‘tailored’ heat input

Example of radial tailoring

0%

100%

-3,5 -2,5 -1,5 -0,5 0,5 1,5 2,5 3,5

r (cm)

High-speed flow (2.5 m/s) permits effective heat removalIrradiationsamples

Fast coreBEAM

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Spallation Loop Technical Lay-Out

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Spallation Target:Design and R&D Approach

Interaction between:

• Experiments with increasing complexity and correspondence to the real situation (H2O–Hg–PbBi)

• CFD simulations to– predict experimental results – optimize nozzles for experiments– simulate heat deposition which can not yet be simulated experimentally

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Hg Experiments at IPUL

Main flow Adding/Removing Hg from cylinder Vacuum system

• 8 ton Hg

• Q up to 11 l/s

• Vacuum above free surface < 0.1 mbar

• Minimal pump load is necessary (to avoid pump cavitation)

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DG16.5 Hg Experiments

nominal volume flow 10 l/s60

16.5°

Close to desired configuration ! intermediate lowering of level some spitting axial asymmetry

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DG16.5 H2O Experiments

nominal volume flow 10 l/s

vacuum pressure 22 mbar

Similarity check: OK !

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Spallation Target: Future Steps

• Pb-Bi Experiments at FZK (KALLA)

Similar size as IPUL loop Similar complexity as MYRRHA loop: 2

free surface + mechanical impeller pump

fall 2005

• Pb-Bi Experiments at ENEA (CHEOPE)

Minimum closed loop configuration MHD pump Speed feedback regulation test fall 2005

•Proton beam heating Simulation with CFD code (e.g. FLOW-3D)

Simulated or measured flow field

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R&D Program Partnership Network

• Accelerator IBA (B) • Spallation source

– Basic spallation data NRC Soreq (I) + PSI (CH)– Feasibility of the windowless design UCL (B) + FZR (D) +

FZK(D) + NRG (NL) + CEA (F) + ENEA (I) + IPUL (Latvia)– Compatibility of the free surface with the proton beam line vacuum

ATL (UK) , SDMS (F)

• Subcritical assembly ENEA (I) + CEA (F) + BN (B) + UoK-UI (LT), IPPE & GIDROPRESS (Russia), TEE (B), CIEMAT (Sp), RIAR (Russia)

• Safety TEE (B), AVN (B) & FANC (B) (Information & contacts)

• Robotics OTL (UK) • Building IBA (B), OTL (UK)

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Outline of the results WP4/Target studies

Design accommodate different target styles

LBE reactors can accommodate liquid LBE target with

both window and windowless concepts

Gas cooled XADS relies on liquid LBE window target

with solid target as back-up solution

Different engineering variants have been developed to

account for specific requirements

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Design accommodate different target styles

Lifetime of the window cannot be established (at 6 mA / 600 MeV max. damage of window is 54 dpa/Gas production in 3 months) (viability to be reconsidered after MEGAPIE integral test and R&D)

beamscanning LBE flow8 cm scan12cm duct width

Figure 5 - LBE-cooled XADS Figure 6 - LBE-cooled XAD Windowless Target

Window Target

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For the LBE-cooled XADS and MYRRHA, the

Windowless Target Unit option presents more merits

in term of less Reactor Roof activation, longer lifetime

and reduced need of material qualification (to be

further developed & supported by R&D : CFD/Vacuum

system/pumps)

For the Gas, the solid Target cooled by He seems the

most coherent choice and shall improve the window

integrity/maintenance aspects. Very early stage , shall

be developed (focus on beam shutdown aspects)

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"Cold window concept"

750

180

267

307

Di 370 Ep. 10

840

9755

170

200

200

200

Interface with WP 4.3 – Preliminary solid target arrangement

200

252

3

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FP6 IP-EUROTRANS

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SP4: DEMETRA

The objective is to develop and assess the heavy liquid metal (HLM) technologies for ADSapplications, the heavy liquid metal being both the spallation material and/or the primarycoolant. The main results obtained during FP5 are a first screening on the compatibility ofstructural materials with the HLM, comprehension of basic corrosion phenomena, oxygencontrol, measurement techniques, and thermalhydraulics (TECLA), preliminary evaluationon the mechanical behaviour of martensitic steels irradiated both in proton and neutronfields and simulation of spallation element effects (SPIRE), design and operation of a 1 MWspallation target (MEGAPIE-TEST). The proposed work plan address the following tasks:

– Performance of ETD relevant large-scale experiments in the CIRCE and KALLA facilities for the characterisation and validation of primary system components and a full size spallation target module, in combination with a detailed thermalhydraulic-thermomechanic assessment under steady-state and transient conditions.

– Characterisation of structural materials in terms of corrosion kinetics, corrosion protection and mechanical properties degradation, with and without combined proton and neutron irradiation.

– Development and demonstration of measurement techniques to be applied in large-scale facilities and their feasibility of upgrade for future industrial applications.

– Performance and assessment of the MEGAPIE post test analysis and post irradiation examination (PIE); quantification of the transferability of the results to ETD conditions.

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Worldwide Programs

Project Neutron Source Core Purpose

MUSE(France)

DT(~1010n/s)

Fast(< 1 kW)

Reactor physics of fast subcritical system

TRADE(Italy)

Proton (140 MeV)+ Ta (40 kW)

Thermal(200 kW)

Demonstration of ADS with thermal feedback

TEF-P(Japan)

Proton (600 MeV)+ Pb-Bi (10W, ~1012n/s)

Fast(< 1 kW)

Coupling of fast subcritical system with spallation source including MA fueled configuration

SAD(Russia)

Proton (660 MeV)+ Pb-Bi (1 kW)

Fast(20 kW)

Coupling of fast subcritical system with spallation source

MYRRHA(Belgium)

Proton (350 MeV)+ Pb-Bi (1.75 MW)

Fast(35 MW)

Experimental ADS

MEGAPIE(Switzerland)

Proton (600 MeV)+ Pb-Bi (1MW)

----- Demonstration of 1MW target for short period

TEF-T(Japan)

Proton (600 MeV)+ Pb-Bi (200 kW)

-----Dedicated facility for demonstration and accumulation of material data base for long term

Reference ADSProton ( ≈ 1 GeV)

+ Pb-Bi (≈ 10 MW)Fast

(1500 MW)Transmutation of MA and LLFP

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Conclusions

• Transmutation of nuclear waste is establishing the case for the development of new high-power proton drivers.

• High-power targets are necessary for the exploitation of these new machines.

• Target systems have been developed for the initial 1MW class machines, but are as yet unproven.

• No convincing solution exists as yet for the envisioned 4 MW class machines.

• A world wide R&D effort is under way to develop new high-power targets.

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Spallation Target R&D for the EU Accelerator-Driven Sub-critical System Project

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