Ranking of sabotage/tampering avoidance technology alternatives

Abstract

ABSTRACIPacific Northwest Laboratory conducted a study to evaluate alternatives to the design and operation of nuclear power plants, emphasizing a reduction of their vulnerability to sabotage. Estimates of core melt accident frequency during normal operations and from sabotage/tampering events were used to rank the alternatives. Core melt frequency for normal operations was estimated using sensitivity analysis of results of probabilistic risk assessments. Core melt frequency for sabotage/tampering was estimated by developing a model based on probabilistic risk analyses, historic data, engineering judgment, and safeguards analyses of plant locations where core melt events could be initiated. Results indicate the most effective alternatives focus on large areas of the plant, increase safety system redundancy, and reduce reliance on single locations for mitigation of transients. Less effective options focus on specific areas of the plant, reduce reliance on some plant areas for safe shutdown, and focus on less vulnerable targets. ; i i EXECUTIVE SUMMARY Pacific Northwest Laboratory (PNL) has conducted a study that evaluates alternatives to the basic design of nuclear power plants, based on reducing plant vulnerability to sabotage. This study was completed for the U.S. Nuclear Regulatory Commission (NRCl in support of Generic Safety Issue A-29. Nuclear Power Plant Design for the Reduction of Vulnerability to Sabotage <U.S. NRC 1978).The NRC identified a total of 25 sabotage and tampering avoidance technology <STATl alternatives to be ranked in this study. These alternatives cover a wide range of potential plant design and operational changes. Some represent alternatives for future plant designs. Others are possible design changes for all plants to reduce the threat from persons with access to plant equipment (insiders). The remaining alternatives were selected from NUREG/CR-2585, Nuclear Power Plant Damage Control Measures and Design Changes for Sabotage Protection (U.S. NRC 1982a), as examples of damage control measures to mitigate the effects of sabotage.The PNL study is an assessment of core melt frequency <CMF) for the purpose of relative comparisons between STAT alternatives. Results of probabilistic risk assessments <PRAs), vital area studies, and historic data were used to complete the analysis. Design-basis threat assessment results were not used because of their lack of frequency information, and physical protection simulations were judged to be too resource-intensive and thus were not used in the study.The approach developed assumes that STAT can reduce the frequency of accident initiating events and can improve the capability of the plant to mitigate transients prior to core damage. The effects of changes in plant operation and design were measured in terms of reduced CMF from accidents and deliberate acts of sabotage and tampering. The methodology is an extension of the CMF reduction analysis approach developed in another NRC project, the Prioritization of Generic Safety Issues (NUREG-0933, U.S. NRC 1983a...