More on 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 non-linear 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 ICONE16-20 categorized the design rules in the code into linear 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, is given. In particular, several changes of these rules in the current edition of the codes and their applications are addressed, and several rules which are intensively applied but often found to be inconsistent and confusing in Sweden are discussed. It is suggested that the design evaluation can be made directly through non-linear transient finite element analysis using a strain-based criterion for time-history dynamic loads of either reversing or non-reversing type.