Sensitivity and Uncertainty Analyses Applied to Criticality Safety Validation: Illustrative Applications and Initial Guidance(NUREG/CR-6655, Volume 2)

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Publication Information

Manuscript Completed: October 1999
Date Published: November 1999

Prepared by:
B.L. Broadhead, C.M. Hopper, R.L. Childs, C.V. Parks

Oak Ridge National Laboratory
Managed by Lockheed Martin Energy Research Corporation
Oak Ridge, TN 37831-6370

C.W. Nilsen, NRC Project Manager

Prepared for:
Division of Systems Analysis and Regulatory Effectiveness
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code W6479

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This report presents the application of sensitivity and uncertainty (S/U) analysis methodologies developed in Volume 1 to the code/data validation tasks of a criticality safety computational study. Sensitivity and uncertainty analysis methods were first developed for application to fast reactor studies in the 1970s. This work has revitalized and updated the existing S/U computational capabilities such that they can be used as prototypic modules of the SCALE code system, which contains criticality analysis tools currently in use by criticality safety practitioners. After complete development, simplified tools are expected to be released for general use.

The methods for application of S/U and generalized linear-least-squares methodology (GLLSM) tools to the criticality safety validation procedures were described in Volume 1 of this report. Volume 2 of this report presents the application of these procedures to the validation of criticality safety analyses supporting uranium operations where the enrichments are greater than 5 wt %.

Specifically, the traditional keff trending analyses are compared with newly developed keff trending procedures, utilizing the D and ck coefficients described in Volume 1. These newly developed procedures are applied to a family of postulated systems involving U(11)O2 fuel, with H/X values ranging from 0 to 1000. These analyses produced a series of guidance and recommendations for the general usage of these various techniques. Recommendations for future work are also detailed.

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