U.S.N.R.C. Containment Performance Research Program

The major source of risk to the public from the operation of nuclear power plants stems from accident scenarios that lead to a containment failure. The regulatory concern is that the failure modes and associated load levels for containment structures cannot be predicted with any real confidence by state-of-the-art methods. This is especially so if the contemplated failure mode is localized leakage. Both assessments of the risk posed by loads outside the design basis and estimates of the effectiveness of proposed mitigative steps require an ability to predict the way in which a containment will fail. USNRC research on containment failure is based on the observation that excessive leakage can occur from four sources: (1) failure of the shell; (2) leakage at large penetrations; (3) leakage at electrical penetrations; and (4) leakage through valves