recommended bounding axial profiles in buc …international workshop on advances in applications of...
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1International 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-Durance2AREVA-NC
3EDF R&D
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2International 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 calculationQualification 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: OECD/NEA Burnup Credit criticality Benchmark Phases II A-B
The recent BUC methodology developped by CEA in collaboration with AREVA-NC is accounting for:
Main references : ICNC’95, FJSS’98, PHYSOR2002, TMC2005, ICNC’07
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3International 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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4International 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 data200 PWR-UOx fuel assemblies from different NPPs (900 MWe) are considered
20 < BU < 50 GWd/tGamma 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-treatmentThreshold + fissile column data selection (366 cm)Normalization of the curves to 1.0The data are classified in function of the mean BU
• [20 – 30 GWd/t]• [30 – 40 GWd/t]• [40 – 50 GWd/t]
E. Cabrol et al., ICNC’07
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5International 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
0 50 100 150 200 250 300 350 400z- axis (cm)
40 - 50 GWd/tSelected Profile BU > 30 GWd/t
0.3
0.5
0.7
0.9
1.1
1.3
1.5
0 50 100 150 200 250 300 350 400z- axis (cm)
30 - 40 GWd/t Selected Profile BU > 30 GWd/tSelection of a
bounding profile for FAs with Mean
BU > 30 GWd/t Slight Dissymmetry
BOTTOM
Flat BU zone
TOP
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6International 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
0 50 100 150 200 250 300 350 400z- axis (cm)
20 - 30 GWd/t
Selected Profile BU > 30 GWd/t
Selected Profile TC < 30 GWd/t
Selection of a bounding profile for FAs with Mean BU < 30 GWd/t(More conservative)
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7International 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 380z-axis (cm)
low irradiated extremity 1high irradiated extremity 1high irradiated extremity 2low irradiated extremity 2average profile
BUC calculations to evaluate keff variability (shape variability in the database)
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8International 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
0 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 lowest
irradiated
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9International Workshop on Advances in Applications of Burnup Credit for Spent Fuel Storage, Transport, Reprocessing and Disposition – Cordoba, 27-30, Oct. 2009
BUC calculations
DARWIN 2CEA93V6 / JEF2.2
DEPLETION CALCULATION
APOLLO2.5 / CEA93V6CEA97 Optimized route
(σ, φ) library
Spent fuel assembly26 BUC isotopes Concentrations
BU ProfileBU (i) i=1, 11
CRISTAL V1CRITICALITY CALCULATION
UOX 17x17 3.2%
No intermediate shut downCooling time 0 – 5 years
Keff
Pool storage (pure water)
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10International 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 pcmKeff variability 1000 pcm at BU = 30 GWd/t
Type of Profile
BUC (pcm)Comparison with the average
profileLn[keff
bounding / keffav] (pcm)
BU 30 GWd/t, CT 0 yBU 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 profileBU > 30GWd/t -23180 +850 +1420 +1930 +2900
‘Similar’ Burnup profiles for PWR UOx fuels, close to the average one
Type of Profile
End-effectLn[keff
prof / keffflat] (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) -920 -780 -550 +30
Bounding profile BU > 30 GWd/t -70 +640 +1380 +2940 Recommended
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11International 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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12International 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 of SFAs.Bounding axial profile recommended (11 zones)
Important experimental French database usedLow variability of the end-effectLimited end-effect < 1000 pcm at 30 GWd/t