United States Nuclear Regulatory Commission - Protecting People and the Environment

Risk Informing Emergency Preparedness Oversight: Evaluation of Emergency Action Levels — A Pilot Study of Peach Bottom, Surry and Sequoyah (NUREG/CR-7154, Volume 2)

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Publication Information

Manuscript Completed: October 2012
Date Published: January 2013

Prepared by:
M. Azarm, T. Gitnick, S. Herrick, J. Kratchman,
M. Morell-Gonzalez, R. Sullivan, J. Zamanali

Project Manager: Sandra L. Herrick
Principal Investigator: M. Ali Azarm

Prepared for:
Division of Risk Analysis
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

The Evaluation of Emergency Action Levels (EALs) project applied probabilistic risk assessment (PRA) methods to selected emergency action levels (EALs). The objective of this study is to explore the feasibility of using PRA to provide risk insights about EAL schemes. This study is the first effort to apply PRA methodology to nuclear power plant (NPP) EAL schemes. Peach Bottom, Surry and Sequoyah were selected as the pilot plants as they represent, respectively, 1) boiling water reactors (BWRs) with a Mark I containment, 2) pressurized water reactors (PWRs) with a large dry containment, and 3) PWRs with an ice condenser containment. EAL threshold conditions, as stated in the plant-specific emergency plan documents, are mapped into scenarios specific to the Standardized Plant Analysis Risk (SPAR) models for these plants. Conditional core damage probability (CCDP) is used as the risk metric to evaluate each EAL scenario. The results of this study provide generic and plant specific insights to be considered when developing future risk informed emergency planning (EP) regulatory activities. The results show that the current EAL schemes are generally logical in that plant risk increases as the emergency classification (EC) severity increases. However, the results also suggest that there are inconsistencies in the EC ranking of some EALs. These inconsistencies are identified for further consideration. The risk insights from this report may be applied to improve the current NRC approved EAL schemes. Nevertheless, it is important to note that regulatory decisions for EP are complex and should not be made solely considering CCDP values, but should be substantiated by deterministic approaches along with the PRA insights.

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