Review of Light Water Reactor Regulatory Requirements: Assessment of Selected Regulatory Requirements That May Have Marginal Importance to Risk — Postaccident Sampling System, Turbine Missiles, Combustible Gas Control, Charcoal Filters(NUREG/CR-4330, PNL-5809, Volume 3)

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Publication Information

Manuscript Completed: March 1987
Date Published: May 1987

Prepared by:
W.B. Scott, J.D. Jamison, G.A. Stoetzel,
A.S. Tabatabai, T.V. Vo
Pacific Northwest Laboratory
P.O. Box 999
Richland, Washington 99352
Operated by Battelle Memorial Institute

Prepared for:
Division of Regulatory Applications
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
NRC FIN B-2894

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Abstract

In a study commissioned by the Nuclear Regulatory Commission (NRC), Pacific Northwest Laboratory (PNL) evaluated the costs and benefits of modifying regulatory requirements in the areas of the postaccident sampling system, turbine rotor design reviews and inspections, combustible gas control for inerted Boiling Water Reactor (BWR) containments, and impregnated charcoal filters in certain plant ventilation systems. The basic framework for the analyses was that presented in the Regulatory Analysis Guidelines (NUREG/BR-0058) and in the Handbook for Value-Impact Assessment (NUREG/CR-3568). The effects of selected modifications to regulations were evaluated in terms of such factors as public risk and costs to industry and NRC. The results indicate that potential modifications of the regulatory requirements in three of the four areas would have little impact on public risk. In the fourth area, impregnated charcoal filters in building ventilation systems do appear to limit risks to the public and plant staff. Revisions in the severe accident source term assumptions, however, may reduce the theoretical value of charcoal filters. The cost analysis indicated that substantial savings in operating costs may be realized by changing the interval of turbine rotor inspections. Small to moderate operating cost savings may be realized through postulated modifications to the postaccident sampling system requirements and to the requirements for combustible gas control in inerted BWR containments. Finally, the use of impregnated charcoal filters in ventilation systems appears to be the most cost-effective method of reducing radioiodine concentrations.