Recommended bounding axial profiles in BUC applications from actual - PowerPoint PPT Presentation

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 AREVA-NC 3 EDF R&D International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 1 Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

INTRODUCTION BUC Methodology The recent BUC methodology developped by CEA in collaboration with AREVA- NC is accounting for: 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 Main r referen ences ces : ICNC’ C’95, 5, F FJSS’98, 98, P PHYSOR2002 2002, T TMC2005 2005, ICNC’07 7 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 International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 2 Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

French PWR UO 2 BUC Calculation Route (DARWIN 2 / CRISTAL V1 / JEF2.2) International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 3 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 137 Cs 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 E. Cabrol ol e et al., I ., ICNC’07 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] International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 4 Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Overview of the database (Mean BU > 30 GWd/t) 1.5 1.3 1.1 0.9 0.7 Selected 30 - 40 GWd/t Profile BU > 0.5 Selection o n of a 30 GWd/t 0.3 bound unding p profile 0 50 100 150 200 250 300 350 400 for F FAs s with th Me Mean z- axis (cm) BU > 3 30 G GWd/t /t Slight ht Diss ssym ymmet etry 1.5 Flat BU zone 1.3 1.1 0.9 0.7 Selected 40 - 50 GWd/t Profile BU > 0.5 30 GWd/t BOTTOM TOP 0.3 0 50 100 150 200 250 300 350 400 z- axis (cm) International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 5 Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Overview of the database (Mean BU < 30 GWd/t) 1.5 Selected 1.3 Profile BU > 30 GWd/t 1.1 0.9 0.7 Selected 20 - 30 GWd/t Profile TC < 0.5 30 GWd/t 0.3 0 50 100 150 200 250 300 350 400 z- axis (cm) Selection of of a boun ounding p prof ofile for or F FAs wit ith h Mean B BU < < 30 GW GWd/t (More c e conser ervative) e) International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 6 Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

End-effect variability 1.3 BUC calculations to evaluate keff variability 1.2 (shape variability in the database) 1.1 1.0 0.9 0.8 0.7 low irradiated extremity 1 0.6 high irradiated extremity 1 high irradiated extremity 2 0.5 low irradiated extremity 2 average profile 0.4 0.3 200 220 240 260 280 300 320 340 360 380 z-axis (cm) International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 7 Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Axial zoning The modelization of the profiles, i.e. the Axial z Mean BU ≥ Mean BU < number of axial zones used for their value 30 GWj/t 30 GWj/t (cm) description, must be optimized to obtain a good time / precision compromise for 11 0.52 0.49 BUC calculations. BU profile description in 11 zones 22 0.79 0.79 1.2 33 0.96 0.95 1.1 45 1.04 1.07 1.0 73 1.05 1.08 0.9 0.8 H-98 1.089 1.116 Normalized Average curve 0.7 11-zones Average profile H-63 1.05 1.03 11-zones Conservative profile 0.6 Normalized Conservative curve 0.5 H-42 1.01 0.98 0.4 H-23 0.83 0.74 0 50 100 150 200 250 300 350 400 z-axis (cm) 60 cm 60 cm lowest low H-12 0.66 0.55 irrad adiated ed H 0.48 0.33 International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 8 Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

BUC calculations UOX 17x17 3.2% APOLLO2.5 / CEA93V6 CEA97 Optimized route ( σ, φ ) library BU Profile BU (i) i=1, 11 DARWIN 2 CEA93V6 / JEF2.2 DEPLETION CALCULATION No intermediate shut down Cooling time 0 – 5 years Spent fuel assembly 26 BUC isotopes Concentrations CRISTAL V1 CRITICALITY CALCULATION Pool storage (pure water) Keff International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 9 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 Comparison with the average BUC (pcm) profile bounding / k eff av ]  (pcm) Ln[k eff Type of Profile BU 30 GWd/t BU 45 GWd/t BU 30 GWd/t, CT 0 y CT 0 y CT 5 y CT 0 y CT 5 y Average profile -24030 - - - - (BU > 30 GWd/t) Bounding profile -23180 +850 +1420 +1930 +2900 BU > 30GWd/t ‘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 one End-effect Ln[k eff prof / k eff flat ] (pcm) Type of Profile 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) -920 -780 -550 +30 Recommended Bounding profile BU > 30 GWd/t -70 +640 +1380 +2940 International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 10 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 Comparison with the average profile BUC (pcm) ∆ keff/keff (pcm) Type of Profile BU 30 GWd/t BU 45 GWd/t 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 International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 11 Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009

Conclusion Use of a Burnup profile for a rigorous taking into account of the reactivity loss of 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 International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, 12 Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009