Effect of containment venting on the risk from LWR meltdown accidents

Technical Report · Mon May 01 04:00:00 EDT 1978

OSTI ID:6675712

Cybulskis, P; Wooton, R O; Denning, R S

Many of the high-consequence accident sequences in the Reactor Safety Study (WASH-1400) involved containment failure by overpressurization. One way to relieve pressure and avoid containment failure is by venting of the containment atmosphere. The study undertook to develop some quantitative insight into the potential effect on public risk of venting and filtering the containment atmosphere for this class of accidents. The results of the Reactor Safety Study were examined to identify the dominant accident sequences in which containment venting could be expected to have an impact. The effects on fission product release for these sequences due to various modes of venting and/or filtering were then evaluated. The results for these selected dominant sequences were then used as a guide to infer the overall effects of containment venting on reactor accident risks. The potential impact on both the Reactor Safety Study PWR and BWR designs were considered. The results indicate that for the PWR design considered venting alone will not lead to an appreciable reduction in overall risk of reactor meltdown accidents. Filtered venting could reduce the likelihood of the accidents with very high consequences that were found to dominate the risk in WASH-1400. IN PWR accidents involving loss of containment heat removal containment venting could significantly delay the start of core melting and thus offer the possibility to effect repairs and avoid core melting. For the BWR design considered, filtered venting will not lead to an appreciable reducton of overall risk due to the dominance of several transient accident sequences in which venting was found to have little beneficial effect. The maximum benefit that could be derived from filtered venting appears to be about an order of magnitude reduced in risk; beyond this containment modes not affected by venting appear to be controlling.

• Research Organization: Battelle Columbus Labs., OH (USA)
• OSTI ID: 6675712
• Report Number(s): NUREG/CR-0138; BMI-2002
• Country of Publication: United States
• Language: English

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