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Recommended bounding axial profiles in BUC applications from actual Burnup measurements in French PWR assemblies C. Riffard 1 , A. Santamarina 1 J.-F. Thro 2 F. Lavaud 3 1 CEA, DEN, DER, SPRC, CEA-Cadarache, F-13108 Saint Paul-Lez-Durance 2

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Recommended bounding axial profiles in BUC applications from actual Burnup measurements in French PWR assemblies

C. Riffard1, A. Santamarina1

J.-F. Thro2

F. Lavaud3

1CEA, DEN, DER, SPRC, CEA-Cadarache, F-13108 Saint Paul-Lez-Durance 2AREVA-NC 3EDF R&D

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

INTRODUCTION BUC Methodology Actinides + 15 Fission Products (stable and non-gazeous) Conservative hypothesis for the depletion calculation Qualification Reports for spent fuel inventory calculation and reactivity worth of BUC nuclides : Isotopic Correction Factors (cf. II, 2.5) Bounding axial burnup profile of spent fuel assemblies The previous method using a uniform mean BU gives a non realistic cosines axial flux → not conservative for BU > 30 GWd/t.

Use of burnup profile in criticality-studies necessary because of the “end-effect” Ref: OE OECD/NEA Bur urnu nup Credit c crit iticality B Benc nchmark P Pha hases II A-B

The recent BUC methodology developped by CEA in collaboration with AREVA- NC is accounting for:

Main r referen ences ces : ICNC’ C’95, 5, F FJSS’98, 98, P PHYSOR2002 2002, T TMC2005 2005, ICNC’07 7

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

French PWR UO2 BUC Calculation Route (DARWIN 2 / CRISTAL V1 / JEF2.2)

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Measurement database of axial Burnup Profiles

Origin of the data

200 PWR-UOx fuel assemblies from different NPPs (900 MWe) are considered 20 < BU < 50 GWd/t Gamma spectrometry measurement 137Cs in La Hague Reprocessing plant Curves of 512 data (1 cm pitch) on 2 opposite faces of each assembly Acquisition from the bottom to the top end of each assembly

Post-treatment

Threshold + fissile column data selection (366 cm) Normalization of the curves to 1.0 The data are classified in function of the mean BU

[20 – 30 GWd/t]
[30 – 40 GWd/t]
[40 – 50 GWd/t]
E. Cabrol
l e

et al., I ., ICNC’07

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Overview of the database (Mean BU > 30 GWd/t)

0.3 0.5 0.7 0.9 1.1 1.3 1.5 50 100 150 200 250 300 350 400

z- axis (cm)

40 - 50 GWd/t Selected Profile BU > 30 GWd/t 0.3 0.5 0.7 0.9 1.1 1.3 1.5 50 100 150 200 250 300 350 400

z- axis (cm)

30 - 40 GWd/t Selected Profile BU > 30 GWd/t

Selection o n of a bound unding p profile for F FAs s with th Me Mean BU > 3 30 G GWd/t /t Slight ht Diss ssym ymmet etry

BOTTOM

Flat BU zone

TOP

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Overview of the database (Mean BU < 30 GWd/t)

0.3 0.5 0.7 0.9 1.1 1.3 1.5 50 100 150 200 250 300 350 400

z- axis (cm)

20 - 30 GWd/t Selected Profile BU > 30 GWd/t Selected Profile TC < 30 GWd/t Selection of

f a boun
unding p

prof

file for
r F

FAs wit ith h Mean B BU < < 30 GW GWd/t (More c e conser ervative) e)

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

End-effect variability

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 200 220 240 260 280 300 320 340 360 380

z-axis (cm)

low irradiated extremity 1 high irradiated extremity 1 high irradiated extremity 2 low irradiated extremity 2 average profile BUC calculations to evaluate keff variability (shape variability in the database)

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Axial zoning

The modelization of the profiles, i.e. the number of axial zones used for their description, must be optimized to obtain a good time / precision compromise for BUC calculations.

BU profile description in 11 zones

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 50 100 150 200 250 300 350 400 z-axis (cm) Normalized Average curve 11-zones Average profile 11-zones Conservative profile Normalized Conservative curve

Axial z value (cm) Mean BU ≥ 30 GWj/t Mean BU < 30 GWj/t 11 0.52 0.49 22 0.79 0.79 33 0.96 0.95 45 1.04 1.07 73 1.05 1.08 H-98 1.089 1.116 H-63 1.05 1.03 H-42 1.01 0.98 H-23 0.83 0.74 H-12 0.66 0.55 H 0.48 0.33

60 cm 60 cm low lowest irrad adiated ed

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

BUC calculations DARWIN 2 CEA93V6 / JEF2.2 DEPLETION CALCULATION APOLLO2.5 / CEA93V6 CEA97 Optimized route (σ, φ) library Spent fuel assembly 26 BUC isotopes Concentrations BU Profile BU (i) i=1, 11 CRISTAL V1 CRITICALITY CALCULATION UOX 17x17 3.2% No intermediate shut down Cooling time 0 – 5 years Keff Pool storage (pure water)

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Criticality calculation results

Calculation results with the standard route (∆keff/keff) BUC of around 21000 pcm Keff variability 1000 pcm at BU = 30 GWd/t

Type of Profile BUC (pcm) Comparison with the average profile Ln[keff

bounding / keff av](pcm)

BU 30 GWd/t, CT 0 y BU 30 GWd/t BU 45 GWd/t CT 0 y CT 5 y CT 0 y CT 5 y Average profile (BU > 30 GWd/t)

24030
Bounding profile

BU > 30GWd/t

23180

+850 +1420 +1930 +2900

‘Simil ilar’ Burnup pr profile iles f for PWR UO UOx fuels els, c clo lose to se to th the e aver erage o

Type of Profile End-effect Ln[keff

prof / keff flat] (pcm)

BU 30 GWd/t BU 45 GWd/t CT 0 y CT 5 y CT 0 y CT 5 y Average profile (BU > 30 GWd/t)

+30 Bounding profile BU > 30 GWd/t

+640 +1380 +2940

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Criticality calculation results Calculation results with the conservative route (∆keff/keff) because of the strong conservative options of the APOLLO2 calculation sheme : BUC reduced to 15000 pcm + Variability of the keff reduced < 1000 pcm for all BU

BUC (pcm) Comparison with the average profile ∆keff/keff (pcm) BU 30 GWd/t BU 45 GWd/t Type of Profile BU 30 GWd/t, CT 0 y CT 0 y CT 5 y CT 0 y CT 5 y Average profile (FAs BU > 30 GWd/t)

15150
Conservative profile BU > 30GWd/t
15100

+10 +300 +200 +800 Conservative profile BU < 30 GWd/t +500 +1250

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International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Conclusion Use of a Burnup profile for a rigorous taking into account of the reactivity loss

f SFAs.

Bounding axial profile recommended (11 zones) Important experimental French database used Low variability of the end-effect Limited end-effect < 1000 pcm at 30 GWd/t