Non-Linear Design Evaluation of Nuclear Power Piping Subjected to Time-History Dynamic Loads According to ASME B&PV III

A nuclear piping system which is found to be disqualified, i.e. overstressed, in design evaluation in accordance with ASME B&PV code, Section III, can still be qualified if further nonlinear design requirements can be satisfied in refined non-linear analyses in which material plasticity and other non-linear conditions are taken into account. Our work presented earlier in ICONE16-19 categorized the design rules in the code into linear design and non-linear design rules and attempted to clarify the corresponding design requirements. In this paper, an in-depth review of these rules and relevant requirements for time-history dynamic loads designated in Service Limit Levels C and D, such as those caused by e.g. water-hammer effects and others, is given. In particular, several rules which are currently intensively applied but often found to be inconsistent and confusing in Sweden are studied and discussed in detail. Suggestions for a reasonable application of these rules, which are currently practiced in several ongoing projects for the power uprate and life-extension of BWR power plants, are given.