Document: NRC Regulatory Guide
Document ID: 7fa0e9f9-cb40-463b-adc5-53fe2057e43f
Document Type: regulatory_guide
Title: Fresh and Spent Fuel Pool Criticality Analysis + HISTORY - HISTORY 08/2020 – DG-1373 , Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2018/ML20182A788.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.240
CFR Part: 
CFR Title: 

Content:
llowing statement: For pressurized-water reactor (PWR) spent fuel pools that credit soluble boron, the limiting misload will be the accident which requires the highest soluble boron to ensure that the maximum keff does not exceed 0.95. The NRC agrees that the limiting abnormal condition will be the one which requires the highest soluble boron to meet regulatory requirements. However, while misloading events are typically the limiting abnormal condition, that is not always the case; therefore, licensees or applicants should consider all credible abnormal and accident conditions. k. Section 9.4 lists some parameters that may need to be verified as part of post irradiation fuel characterization activities. One of the parameters is “soluble boron (burnup averaged).” The NRC endorses use of cycle burnup averaged soluble boron, consistent with Section 4.2.1, but the NRC does not endorse other interpretations of the phrase “burnup averaged,” such as averaging across the whole burnup range for a given fuel assembly. l. Section A.1 provides recommendations for the validation of computer codes used for nuclear criticality safety analyses, as well as referencing NUREG/CR-6698, “Guide for Validation of Nuclear Criticality Safety Calculational Methodology,” issued January 2001 (Ref. 21), for additional information. An important aspect of validation that is not covered in much detail is the importance of selecting appropriately representative benchmarks and critical experiments, especially when performing trend evaluation. Licensees or applicants may need to consider smaller sets of data to avoid confounding effects that obscure trends or that lead to conclusions based on data that are not highly representative of the spent fuel pool geometry and compositions of interest. m. Section A.2.2 states that startup critical data from boiling-water reactors (BWRs) can be used to benchmark depletion codes and compute a bias and bias uncertainty. NEI 12-16, Revision 4, does