ENHANCING SAFETY ASSOCIATED WITH POST FUKUSHIMA MODIFICATIONS: ROLE OF RISK-INFORMED DECISION MAKING

摘要

When nuclear power plant (NPP) systems are used to support emergency functions beyond their original design purposes, without creating unintended adverse effects, safety can be enhanced. In some situations, the potential enhancements to safety can be substantial. Use of Control Rod Drive (CRD) systems to inject water into the reactor coolant systems (RCS) in Boiling Water Reactors (BWRs) and use of the feed-and-bleed strategy to remove decay heat in Pressurized Water Reactors (PWRs) illustrate substantial safety gains that may be accomplished. In light of this, nuclear safety will be best served if the regulators and industry explore additional safety gains that can be gained from the flexible and diverse mitigating strategies (referred as FLEX strategies) whose intent is to mitigate beyond design basis external events (BDBEEs). This paper provides a summary of various activities that some US NPPs have initiated to leverage FLEX capabilities to enhance public safety, and enhance operational flexibility, by using them in areas beyond BDBEE. The paper articulates how a regulators' initiatives to incorporate FLEX strategies in RIDM could manifest into increases in public safety, which in some situations may far exceed the safety gains associated with reducing risks associated with BDBEEs.