Estimating the Effect of Isotopic Uncertainties in Spent Nuclear Fuel

88 Pages·2001·105.018 MB·English

ORNL/TM-2001/83

A Stochastic Method for
Estimating the Effect
of Isotopic Uncertainties
in Spent Nuclear Fuel

M. D. DeHart
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ORNL/TM-2001/83

Computational Physics and Engineering Division (10)

A Stochastic Method for Estimating the Effect of Isotopic
Uncertainties in Spent Nuclear Fuel

M. D. DeHart

Oak Ridge National Laboratory,
P.O. Box 2008,
Oak Ridge, TN 37831-6370

Date Published: September 2001

Prepared by the
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37831
managed and operated by
UT-Battelle, LLC
for the
U.S. DEPARTMENT OF ENERGY
under contract DE-AC05-00OR22725

CONTENTS

LIST OF FIGURES.......................................................................................................................v
LIST OF TABLES......................................................................................................................vii
ACKNOWLEDGMENTS............................................................................................................ix
ABSTRACT.................................................................................................................................xi
1. INTRODUCTION................................................................................................................1
2. STATISTICAL BACKGROUND........................................................................................3
3. APPROACH........................................................................................................................7
4. PARALLEL PROCESSING..............................................................................................11
5. RESULTS...........................................................................................................................13
5.1. Convergence..............................................................................................................17
5.2. Distribution of Eigenvalues.......................................................................................19
5.3. Actinide-Only vs. “Full” Burnup Credit...................................................................23
5.4. Conservatism of Bounding Approach.......................................................................26
6. CONCLUSIONS................................................................................................................31
7. REFERENCES...................................................................................................................33
APPENDIX A.............................................................................................................................35
KRONOS Fortran-90 Program Listing..............................................................................37
APPENDIX B: SAMPLE BASELINE INPUT MODELS USED BY KRONOS.....................53
Sample 1: KRONOS KENO Cask model, non-uniform axial profile, actinides only,
20 GWd/MTU..................................................................................................55
Sample 2: KRONOS KENO pin model, non-uniform axial profile, actinides + fission
products, 40 GWd/MTU..................................................................................63
iii
Sample 3: KRONOS XSDRN pin-cell model, actinides + fission products,
60 GWd/MTU .............................................................................................72

iv
LIST OF FIGURES

Figure Page
1. Convergence of mean value of k for 60 GWd/MTU cask models...........................................18
2. Convergence of population standard deviation for 60 GWd/MTU cask models.....................19
3. Distribution of k values for Case 1, 20 GWd/MTU.................................................................20
4. Distribution of k values for Case 2, 40 GWd/MTU.................................................................21
5. Distribution of k values for Case 3, 60 GWd/MTU.................................................................22
6. Fission product reactivity worth as a function of burnup.........................................................25
7. Uncertainty due to fission products as a function of burnup....................................................26
8. Probability plot for KENO cask calculations, actinides + fission products.............................27
9. Probability plot for KENO cask calculations, actinides only...................................................28

v
vi
LIST OF TABLES

Table Page
1. Validation results used in uncertainty analyses..........................................................................8
2. Results of KRONOS calculations for various configurations and burnups.............................14
3. Reactivity worth of fission products and associated uncertainties...........................................24

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