Nuclear Data Needs for the Assessment of Generation IV Nuclear Energy Systems G. Rimpault

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FRENCH ATOMIC ENERGY COMMISION (CEA) - NUCLEAR ENERGY DIVISION

CEA/DER Cadarache Centre Gérald Rimpault Nuclear Data Needs, SG26, NEA data bank, 3 May 2006

Nuclear Data Needs for the Assessment Nuclear Data Needs for the Assessment

of of

Generation IV Nuclear Energy SystemsGeneration IV Nuclear Energy Systems

G. RimpaultCommissariat à l’Energie Atomique (CEA) Cadarache Center

13108 Saint-Paul-lez-Durance Cedex, [email protected]

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The current presentation is aiming at describing the methodology for defining nuclear data needs and the short list of high priority ones.

Items covered

• Target accuracies for GEN-IV neutronic characteristics

• The covariance data

• The integral uncertainties due to nuclear data

• Uncertainties Requested for Nuclear Data

• Integral Experiments: A way to Assess Nuclear Data

• Experimental Data Base

• Conclusion and Perspectives

SummarySummary

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Target accuracies for GEN-IV neutronic characteristicsTarget accuracies for GEN-IV neutronic characteristics

The design of the cores and fuel cycles of the Gen IV systems relies on some neutronic characteristics.

Target accuracies are requested at the different stages of the design studies (1st stage: viability; 2nd stage: performance).

Uncertainties at 1 System Development Phase

Parameter Viability Perf ormance

Multiplication f actor, keff BOL < 0.7% < 0.3%Local power density < 5% < 3%Structure Damage < 15% < 9%Reactivity Swing (keff EOL) (<1.0%) (< 0.5%)Breeding Gain <+/-0.06 <+/-0.04Void Reactivity Eff ect on each component

(leakage; non-leak.) < 16% < 10%Doppler Reactivity Eff ect < 16% < 10%Delayed Neutron Fraction < 13% < 7%Control Rod Worth < 16% < 10% heating < 16% < 10%

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Target accuracies requested for the performance stage of the design studies are indicative and are under improvement in:

Na-cooled FR with CRP on AIEA on « updated codes and methods to reduce the calculational uncertainties of the LMFR reactivity effects » with:

•Phase 4 : Check the safe behaviour of the BN600 core fully loaded with MOX using weapon grade Plutonium (already performed)

•Phase 6 : Check the safe behaviour of the BN600 core fully loaded with MOX from Thermal Reactor spent fuel cooled down 50 years (in progress)

Objective: Check the Safety Behaviors with increase MA content up to 6% and associated method and nuclear data uncertainties

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Results for BN600 Phases 4 and 6 variants with JEF2.2

Diffusion Transport Diffusion Transport Diffusion TransportK-eff 1.00182 1.00941 K-eff 0.98827 0.99519 K-eff 0.01355 0.01422Kd -0.00795 -0.00787 Kd -0.00408 -0.00398 Kd -0.00388 -0.00389

Sodium density

coefficient-0.00199 -0.00294

Sodium density

coefficient-0.01802 -0.01939

Sodium density

coefficient0.01603 0.01645

Phase 4 - Phase 6Phase4 Phase 6

JEF-2.2

Large difference on K-eff between Phase 4 and Phase 6

Doppler constant reduced by a factor 2

Sodium density coefficient significantly increased

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Results for BN600 Phases 4 and 6 variants with JEFF3.1

Diffusion Transport Diffusion Transport Diffusion TransportK-eff 1.00426 1.01194 K-eff 1.00386 1.01096 K-eff 0.00040 0.00098Kd -0.00803 -0.00794 Kd -0.00408 -0.00396 Kd -0.00396 -0.00398

Sodium density

coefficient0.00067 -0.00098

Sodium density

coefficient-0.01489 -0.01664

Sodium density


Phase 4 - Phase 6

JEFF-3.1

Phase4 Phase 6

No more difference on K-eff between Phase 4 and Phase 6

Doppler constant reduced by a factor 2

Sodium density coefficient significantly increased

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Differences between JEFF-3.1 and JEF-2.2

BN600Diffusion Transport Diffusion Transport Diffusion Transport

K-eff 0.00244 0.00253 K-eff 0.01559 0.01577 K-eff -0.01315 -0.01324Kd -0.00008 -0.00008 Kd 0.00000 0.00002 Kd -0.00008 -0.00010

Sodium density


Sodium density


Sodium density

coefficient-0.00047 -0.00079

Phase6 Phase 4 - Phase 6

JEFF-3.1 - JEF-2.2

Phase4

No difference on K-eff between JEFF-3.1 and JEF-2.2 on Phase 4

Large difference on K-eff between JEFF-3.1 and JEF-2.2 on Phase 6

Doppler constant remains insensitive to nuclear data libraries

Sodium density coefficient increased uniformally

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Target accuracies requested for the performance stage of the design studies are indicative and are under improvement in:

He-cooled FR with EU GCFR core physics group CRP with objectives:

• Assessing the method uncertainties

• Defining the nuclear data uncertainties on reactivity coefficients

(includes EOC composition changes)

Objective: Check the safe behavior of the GCFR 2400MWth CERCER with associated method and nuclear data uncertainties (in progress)

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Base data sensitivity and integral uncertaintyBase data sensitivity and integral uncertainty

In order to get uncertainty on integral characteristics of the coresensitivities and variance covariance matrices are needed.

Works already performed by

•G. Aliberti et al. “Nuclear Data Sensitivity, Uncertainty and Target Accuracy Assessment for Future Nuclear Systems” and

•S. Ohki “Target accuracy of MA nuclear data”

can be considered as a basis for current task.

Further work, however is still required for:

•The anisotropy of scattering

•The impact of burn up xs on reactivity coefficients and other characteristics (this includes the FP xs)

This work is planned at CEA with a PhD student

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Variance-covariance matrix Variance-covariance matrix BB associated to nuclear data associated to nuclear data

The variance-covariance matrix B associated to nuclear data should be associated to nuclear data evaluation and this is the first request for evaluators since values at the moment are scarce.

However, in order to make progress on the design request lines, simple variance- covariance matrices have been estimated for a few nuclides

More fundamental work is in progress at CEA/Cadarache at the evaluation level

(see next viewgraph)

However, caution should exist if integral measurements are taken as a source of information for setting an evaluation.

Users should be aware of it, not to double count the information in their assessment studies

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Thermal and epithermal energy range

produced with SAMMY

or CONRAD

Produced with TALYS*

« Full correlation matrix »

0.01 meV 10 keV 20 MeV0.01 meV 20 MeV

0.01 meV 10 keV

10 MeV 10 MeV10 keV

Nuclear data file developments – Future workNuclear data file developments – Future work

Uncertainties and covariance data

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Integral Uncertainties due to current Nuclear DataIntegral Uncertainties due to current Nuclear Data

Clean core measurements (critical mass, buckling, K-infinity, spectral indices)

performed in MASURCA, ZEBRA and SNEAK facilities for fast systemsbut also EOLE and MINERVE facilities for thermal systemsare used to assess the performance of nuclear data libraries.

There are also post irradiation experiments which provide more information on capture xs

The results obtained are associated with large uncertainties due to current nuclear data librariesand hide the existence of compensating errors

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Adjusted Nuclear Data LibrariesAdjusted Nuclear Data Libraries

In the past getting the required target accuracies was achieved through adjustment of nuclear data on integral measurements.

Recent differential measurements give evidence of the validity of such an approach

while others show difficulties in achieving the desired goal

Convergence on Nuclear Data between values deduced from the adjustment and recent differential measurement is observed.

Most spectacular examples are illustrated by: Na cross sections Pu240 cross sections

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Sodium Inelastic Cross Sections: Adjusted and EvaluatedSodium Inelastic Cross Sections: Adjusted and Evaluated

Na I nelastic Cross- section

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

J EF2

ERALIB1

J EFF3

Na MeasurementsPerformed at Geel

Resonance structurecoherent with

total cross sectionmeasured at ORNL

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Uncertainties on SFR Critical Masses due to the Nuclear DataUncertainties on SFR Critical Masses due to the Nuclear Data

Predictability of Critical Masses

the obtained adjusted ERALIB1 uncertainties are consistent

with the target accuracy required for sodium-cooled oxide fast reactors

Uncertainties at 1 (values expressed in pcm)

Core PHENI X SUPER- PHENI X CMP

SUPER- PHENI X C1D

Calculation method

Approximations

Project Special

assemblies (1.5 %)

51

38

40

30

40

30

85

Base data Core Special

assemblies

100 150 150

85

ERANOS f ormulaire total 140 158 200

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Uncertainties on SFR Power Map due to the Nuclear DataUncertainties on SFR Power Map due to the Nuclear Data

Predictability of Power Map Distribution

the obtained adjusted dERALIB1 uncertainties are consistent

with the target accuracy required for sodium-cooled oxide fast reactors

Uncertainties at 1 (values expressed in %)

Core PHENI X SUPER- PHENI X fuel assemblies

Calculation method 0.54 % 1.93 %

Data base 1.78 % 1.50 %

ERANOS f ormulaire total

1.86 % 2.44 %

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Uncertainties Requested for Nuclear DataUncertainties Requested for Nuclear Data

The uncertainties on nuclear data

as they have been obtained with ERALIB1 fulfil

the SFR and GFR design requests for those major nuclides of interest

Pu239, Pu240, Pu241, U238, U235 , Fe, Cr, Ni, Na, O.

It is therefore worth looking at the standard deviations before and after adjustment to find out where new differential measurements are needed

The approach is approximate since correlations within ERALIB1 offer a way to significantly reduce the impact of standard deviations.

And there are still pending problems associated to some ERALIB1 nuclides such as the one on structural materials (Fe, Cr, Ni) which need to be considered and might be due to adjustment approximation

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Integral Experiments: A Way to Assess Nuclear DataIntegral Experiments: A Way to Assess Nuclear Data

Integral Experiments can be used as an evidence of insufficiency in existing evaluations. Cautious should be given to potential bias which exist in integral experiment as it exists in differential measurements.

Integral Experiments have a complementary role to differential measurements for meeting some nuclear data needs (for instance Pu239 fission).

Standard deviations need to account for the uncertainties due to integral measurements as well as differential measurements.

This way to proceed offers a way to better evaluations which might be usable in Monte Carlo codes as in deterministic ones.

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XS & Branching Ratios

MASURCAKeff, indices

BFS67,69,71

Fast SpectrumThermal spectrumCOSMO

OSMOSE

PROFIL1&2

PROFILM

UOX(3.1%, 4.5%)

MOX

SUPERPROFIL

JOYO

TRAPU

SUPERFACT

Critical Experiments

Post IrradiationExperiments

Experimental Base for Actinides Nuclear Data Validation

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XS & Branching Ratios

STEKoscillations

SEGoscillations

Fast SpectrumThermal spectrum

DIMPLE

MINERVE

PROFIL1&2

PROFIL- M

SUPERPROFIL

Critical Experiments

Post IrradiationExperiments

Experimental Base for FP Nuclear Data Validation

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Conclusion and PerspectivesConclusion and Perspectives

The methodology for defining nuclear data needs has been briefly covered.

Target accuracies for GEN-IV neutronic characteristics is an important point to start with

The covariance data is of significant importance for quantifying the needs and evaluators should provide them with their nuclear data.

Nuclear Data Requests should be associated to uncertainty values.

Integral Experiments have a complementary role to differential measurements for meeting some nuclear data needs (for instance Pu239 fission).

A list of potential requests is existing, quantifying their uncertainties remain a significant effort particularly when looking at fuel cycle quantities.

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Nuclear Data Needs for the Assessment of Generation IV Nuclear Energy Systems G. Rimpault

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