Evaluation of the safety benefits and costs of proposed revisions to inservice testing requirements for pumps and valves. Final report

This report documents the results of an evaluation of the potential safety benefits and costs associated with a set of proposed revisions to ASME Code requirements for the inservice testing of pumps and valves. In September of 1991, the NRC requested that the ASME Operations and Maintenance Committee consider the incorporation of revisions to the Code which would require that inservice pump and valve testing verify all safety functions, and be performed at or near design basis conditions. Probabilistic risk assessment models developed for the NRC and the failure data used in performing these probabilistic risk assessments were evaluated to estimate the potential reduction in public risk. Pump and valve failures which might be prevented by the proposed testing were identified. Estimated potential reductions in core damage frequency and associated reductions in public risk were calculated. The results of this evaluation indicate that the proposed revisions to the ASME Code requirements for inservice testing would result in minimal safety benefits which would not meet the ``significant additional protection`` standard established in the backfit rule. Safety benefits estimated in this analysis are several orders of magnitude lower than those which would be required for the proposed revisions to be cost effective.