Air systems problems at US light water reactors

This paper provides a review and evaluation of the potential safety implications associated with air system problems at US light water reactors. It provides an analysis of operating data, focusing on degraded air systems and the vulnerability of safety-related equipment to common-mode failures associated with air systems. The data are analyzed from the perspectives of trends and patterns, risk assessments, and cost/benefit studies. Several recommendations are presented to reduce risk, enhance safety, and improve plant performance. Air systems are not safety grade systems at most operating plants. As a result, plant accident analyses assume that safety-related equipment dependent upon air systems will either fail safe upon loss of air or perform its intended function with the assistance of backup accumulators