Comparison of Handbook and 3-D Finite Element Analysis LEFM Solutions for a Threaded Fastener

As part of license renewal activities, many Boiling Water Reactor utilities must assess the integrity of bolted components within the reactor pressure vessel. Since inspection techniques capable of identifying cracking in the threaded regions of the core plate bolting do not currently exist it is important for flaw tolerance evaluations to be performed with as much accuracy as possible in order to obtain realistic inspection intervals and to assess the degree of redundancy in the bolted joint designs. Both 3-D finite element analysis and handbook linear elastic fracture mechanics solutions are used to assess the flaw tolerance of a core plate bolt design. Consideration of the relevant degradation and crack growth mechanisms is given for both initial crack configuration(s) and crack growth calculations. The 3-D finite element analysis is performed to investigate the effects of various simplifications in the available handbook solutions presented in the literature. The results of the flaw tolerance evaluations using both methods are compared and conclusions drawn regarding the applicability of the available handbook solutions for similar work in the future.