Publications

Nuclear power plants have experienced actuations of fire protection systems (FPSs) under conditions for which these systems were not intended to actuate. They have also experienced advertent actuations with the presence of a fire. These actuations have often damaged nearby plant equipment. A review of past occurrences of both types of such events on nuclear power plant safety has been performed. Thirteen different scenarios leading to actuation of fire protection systems due to a variety of causes were identified. These scenarios range from inadvertant actuation caused by human errors to hardware failures and include seismic root causes and seismic/fire interactions. A quantification of these thirteen scenarios, where applicable, was performed on a BWR4/MKI. This report estimates the contribution of FPS actuations to core damage frequency and to risk.

Nuclear power plants have experienced actuations of fire protection systems (FPSs) under conditions for which these systems were not intended to actuate and also have experienced advertent actuations with the presence of a fire. These actuations have often damaged safety-related equipment. A review of the impact of past occurrences of both types of such events and their impact on plant safety systems, an analysis of the risk impacts of such events on nuclear power plant safety, and a cost-benefit analysis of potential corrective measures have been performed. Thirteen different scenarios leading to actuation of fire protection systems due to a variety of causes were identified. These scenarios ranged from inadvertent actuation caused by human error to hardware failure, and include seismic root causes and seismic/fire interactions. A quantification of these thirteen root causes, where applicable, was performed on generically applicable scenarios. This document, Volume 2, contains appendices A,B, and C of this report.

Nuclear power plants have experienced actuations of fire protection systems (FPSs) under conditions for which these systems were not intended to actuate and also have experienced advertent actuations with the presence of a fire. These actuations have often damaged nearby plant equipment. A review of the impact of past occurrences of both types of such events, a quantification of the risk of FPS actuation, a sensitivity study of the quantification of the risk of FPS actuation and risk calculations in terms of person-REM have been performed. Thirteen different scenarios leading to actuation of fire protection systems due to a variety of causes were identified. A quantification of these thirteen scenarios, where applicable, was performed on a 3-loop Westinghouse Pressurized water Reactor (PWR). These scenarios ranged from inadvertent actuation caused by human error to hardware failures, and include seismic root causes and seismic/fire interaction. This report estimates the contribution of FPS actuations to core damage frequency and risk.

Nuclear power plants have experienced inadvertent actuations of fire protection systems (FPS) under conditions for which these systems were not intended to actuate. They have also experienced advertent actuations with the presence of a fire. These actuations have often damaged plant equipment. This document provides a review of the impact of past occurrences of both types of such events on nuclear power plant safety. Thirteen different scenarios leading to actuation of fire protection systems due to a variety of causes were identified. These scenarios ranged from inadvertent actuation caused by human error to hardware failure and includes seismic root causes and seismic/fire interaction. A quantification of these thirteen scenarios, where applicable, was performed on a Babcock and Wilcox Pressurized Water Reactor (lowered loop design). This report estimates the contribution of FPS actuations to core damage frequency and to risk.

This volume presents the methodology and results of the internal event accident sequence analysis of the LaSalle Unit II nuclear power plant performed as part of the Level III Probabilistic Risk Assessment being performed by Sandia national laboratories for the Nuclear Regulatory commission. This report describes the new techniques developed to solve the very large and logically complicated fault trees developed in the modeling of the LaSalle systems, for evaluating the large number of cut sets in the accident sequences, for the application of recovery actions to these cut sets, and for the evaluation of the effects of containment failure on the systems and the resolution of core vulnerable accident sequences.

In keeping with the philosophy of the external events analyses for NUREG-1150, which are intended to be smart probabilistic risk assessments (PRAs) making full use of all insights gained during the past 10 years of development in risk assessment methodologies, the Savannah River K-Reactor fire analysis was performed using newly developed and simplified methods. These methods have been under development at Sandia National Laboratories under sponsorship of the Nuclear Regulatory Commission (NRC) Division of Risk Assessment as part of the Dependent Failure Methodology Development Program. A detailed screening analysis was performed which showed most plant areas had a negligible contribution to fire-induced core damage frequency. Detailed analysis of the fire risk resulted in a total (mean) core damage frequency of 1.35E-7 per year. 18 refs., 12 figs., 17 tabs.

A complete external events probabilistic risk assessment has been performed for the N-Reactor power plant, making full use of all insights gained during the past ten years' developments in risk assessment methodologies. A detailed screening analysis was performed which showed that all external events had negligible contribution to core damage frequency except fires, seismic events, and external flooding. A limited scope analysis of the external flooding risk indicated that it is not a major risk contributor. Detailed analyses of the fire and seismic risks resulted in total (mean) core damage frequencies of 1.96E-5 and 4.60E-05 per reactor year, respectively. Detailed uncertainty analyses were performed for both fire and seismic risks. These results show that the core damage frequency profile for these events is comparable to that found for existing commercial power plants if proposed fixes are completed as part of the restart program. 108 refs., 85 figs., 80 tabs.