PSAM 16 - Paper Overview

PSAM 16 Conference Paper Overview

Welcome to the PSAM 16 Conference paper and speaker overview page.

Lead Author: David Blanchard

Use of a Risk-Informed Performance-Based Advanced Reactor Design Standard to Categorize and Classify Components for a Current Generation Nuclear Power Plant
A number of standards and guidelines have been developed for use in the US for the purpose of risk informing the design of advanced reactors. Some of these documents are directed at specific reactor types, others are technology neutral. The objectives of each of these standards and guidelines are directed at appropriately combining deterministic, probabilistic, and performance-based design methods during development of the plant design. This paper describes the application of one of these risk-informed performance-based (RIPB) design standards to the categorization and classification of components for a current generation light water reactor. While the selected standard was developed for use in the design of an advanced reactor, the purpose of this exercise was to identify what components would have been classified as safety related, non-safety related (with special treatment requirements) and non-safety related (no special treatment requirements) had insights from the plant specific PRA been available at the time the plant was licensed. The plant is a PWR that began operation in the early 1970s. The RIPB design standard that was selected was ANS/ANSI 30.3, ‘Light-Water Reactor Risk-Informed Performance-Based Design-202x’ which recently concluded final balloting. ANS/ANSI 30.3 permits the selection of licensing basis events using any of a spectrum of approaches from traditional deterministic methods supplemented by PRA to starting with risk significant accident sequences of the PRA and adjusting them deterministically. For the purpose of this exercise, the licensing basis for the PWR under examination was set aside and the accident sequences of the at power Level 1 internal events PRA considered as candidates for licensing basis events. A blend of deterministic and probabilistic methods were used in performing the categorization and classification of plant components. ANS/ANSI 30.3 endorses the deterministic criterion of ANS/ANSI 58.14 for initial classification of SSCs. For the subject PWR, the ANS/ANSI 58.14 criterion was applied to the cut sets from the accident sequences of the PRA. This provided a measure of plant capability defense-in-depth in selecting components that are candidates for being relied upon in managing safety. ANS/ANSI 30.3 provides flexibility in the determination of risk significance of components in that it does not endorse specific measures of importance or thresholds. In this exercise, categorization of components was performed simply by requantifying the accident sequences of the PRA to demonstrate the collective effectiveness of the ANS/ANSI 58.14 selected components in managing risk. Risk importance measures were used, but only to identify candidates for addition to or deletion from the list of selected components. In accordance with ANS/ANSI 30.3 requirements, engineering rationale based on plant design features and operating characteristics were developed when changes were made to the initial ANS/ANSI 58.14 defense-in-depth based selection of components. The paper provides definitions for ‘plant capability defense-in-depth’ and ‘risk significance’ that were used in the evaluation. Also described are the methods used to apply the ANS/ANSI 58.14 deterministic criterion using the logic models of the PRA. The final list of components classified as safety related and non-safety related with special treatment were found to be necessary and sufficient only for a subset of the accident sequences of the Level 1 internal events PRA. The paper discusses methods for pruning the PRA accident sequences to identify those that might be candidates for design basis and licensing basis events. While the plant under investigation is not likely to change its current licensing basis, the methods used in performing this categorization and classification can be beneficial in other applications of the PRA (e.g., implementation of 10CFR50.69, risk-informed cyber security, etc.).

Use of a Risk-Informed Performance-Based Advanced Reactor Design Standard to Categorize and Classify Components for a Current Generation Nuclear Power Plant

A number of standards and guidelines have been developed for use in the US for the purpose of risk informing the design of advanced reactors. Some of these documents are directed at specific reactor types, others are technology neutral. The objectives of each of these standards and guidelines are directed at appropriately combining deterministic, probabilistic, and performance-based design methods during development of the plant design. This paper describes the application of one of these risk-informed performance-based (RIPB) design standards to the categorization and classification of components for a current generation light water reactor. While the selected standard was developed for use in the design of an advanced reactor, the purpose of this exercise was to identify what components would have been classified as safety related, non-safety related (with special treatment requirements) and non-safety related (no special treatment requirements) had insights from the plant specific PRA been available at the time the plant was licensed. The plant is a PWR that began operation in the early 1970s. The RIPB design standard that was selected was ANS/ANSI 30.3, ‘Light-Water Reactor Risk-Informed Performance-Based Design-202x’ which recently concluded final balloting. ANS/ANSI 30.3 permits the selection of licensing basis events using any of a spectrum of approaches from traditional deterministic methods supplemented by PRA to starting with risk significant accident sequences of the PRA and adjusting them deterministically. For the purpose of this exercise, the licensing basis for the PWR under examination was set aside and the accident sequences of the at power Level 1 internal events PRA considered as candidates for licensing basis events. A blend of deterministic and probabilistic methods were used in performing the categorization and classification of plant components. ANS/ANSI 30.3 endorses the deterministic criterion of ANS/ANSI 58.14 for initial classification of SSCs. For the subject PWR, the ANS/ANSI 58.14 criterion was applied to the cut sets from the accident sequences of the PRA. This provided a measure of plant capability defense-in-depth in selecting components that are candidates for being relied upon in managing safety. ANS/ANSI 30.3 provides flexibility in the determination of risk significance of components in that it does not endorse specific measures of importance or thresholds. In this exercise, categorization of components was performed simply by requantifying the accident sequences of the PRA to demonstrate the collective effectiveness of the ANS/ANSI 58.14 selected components in managing risk. Risk importance measures were used, but only to identify candidates for addition to or deletion from the list of selected components. In accordance with ANS/ANSI 30.3 requirements, engineering rationale based on plant design features and operating characteristics were developed when changes were made to the initial ANS/ANSI 58.14 defense-in-depth based selection of components. The paper provides definitions for ‘plant capability defense-in-depth’ and ‘risk significance’ that were used in the evaluation. Also described are the methods used to apply the ANS/ANSI 58.14 deterministic criterion using the logic models of the PRA. The final list of components classified as safety related and non-safety related with special treatment were found to be necessary and sufficient only for a subset of the accident sequences of the Level 1 internal events PRA. The paper discusses methods for pruning the PRA accident sequences to identify those that might be candidates for design basis and licensing basis events. While the plant under investigation is not likely to change its current licensing basis, the methods used in performing this categorization and classification can be beneficial in other applications of the PRA (e.g., implementation of 10CFR50.69, risk-informed cyber security, etc.).

PSAM 16 Conference Paper Overview

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