Sensitivity and Parametric Evaluations of Significant Aspects of Burnup Credit for PWR Spent Fuel Packages
| Attachment | Size |
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| ORNL_TM_12973.pdf (85.49 MB) | 85.49 MB |
Spent fuel transportation and storage cask designs based on a burnup credit approach must
consider issues that are not relevant in casks designed under a fresh-fuel loading assumption. For
example, the spent fuel composition must be adequately characterized and the criticality analysis
model can be complicated by the need to consider axial burnup variations. Parametric analyses are
needed to characterize the importance of fuel assembly and fuel cycle parameters on spent fuel
composition and reactivity. Numerical models must be evaluated to determine the sensitivity of
criticality safety calculations to modeling assumptions. The purpose of this report is to describe
analyses and evaluations performed in order to demonstrate the effect physical parameters and
modeling assumptions have on the criticality analysis of spent fuel. The analyses in this report
include determination and ranking of the most important actinides and fission products; study of the
effect of various depletion scenarios on subsequent criticality calculations; establishment of trends
in neutron multiplication as a function of fuel enrichment, burnup, cooling time; and a parametric
and modeling evaluation of three-dimensional effects (e.g., axially varying burnup and
temperature/density effects) in a conceptual cask design. The sensitivity and parametric evaluations
were performed with the consideration of two different burnup credit approaches: (1) only actinides
in the fuel are considered in the criticality analysis, and (2) both actinides and fission products are
considered.
Calculations described in this report were performed using the criticality and depletion
sequences available in the SCALE code system and the SCALE 27-group burnup library. Although
the results described herein do not constitute a validation of SCALE for use in spent fuel analysis,
independent validation efforts have been completed and are described in other reports. Such
validation is necessary in the acceptance of the results and conclusions included in this report.
