Asymmetric blowdown loads on PWR (pressurized-water-reactor) primary systems: resolution of generic task action plan A-2

NRC staff, after being informed of newly identified asymmetric loadings resulting from postulated ruptures of primary piping, initiated a generic investigation, Task Action Plan A-2, limited to pressurized-water-reactor (PWR) plants because of their higher primary system pressures. The intent of the investigation was to develop acceptable criteria and guidelines for evaluating plant analyses. The staff concludes that an acceptable basis is provided in this report for performing and reviewing plant analyses. Criteria were developed for evaluating loading transients, structural components, and the fuel assembly. The staff approved computer programs and modeling techniques submitted by each PWR vendor for development of the subcooled blowdown and cavity-pressure loading transients. Audit models were developed to evaluate the structural computer programs and modeling techniques. Methods have been approved for the structural-analysis method submitted by Westinghouse for the Indian Point Unit 3 plant. Criteria and guidelines are provided to perform a detailed evaluation of the fuel assembly. Acceptance criteria are also provided so deformed fuel-assembly spacer grids may be evaluated.