Modeling a Digital Feedwater Control System Using Traditional Probabilistic Risk Assessment Methods (NUREG/CR-6997)

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Publication Information

Manuscript Completed: June 2008
Date Published: September 2009

Prepared by:
T.L. Chu, M. Yue, G. Martinez-Guridi,
K. Mernick, and J. Lehner, BNL
A. Kuritzky, NRC

Brookhaven National Laboratory
Upton, NY 11973-5000

A. Kuritzky, NRC Project Manager

NRC Job Code N6413

Office of Nuclear Regulatory Research

Availability Notice


The United States Nuclear Regulatory Commission (NRC) is currently performing research on the development of probabilistic models for digital instrumentation and control systems for inclusion in nuclear plant probabilistic risk assessments. The desired goal of this research is to develop regulatory guidance for the use of risk information in regulatory decisions for new and operating reactors. This report documents the development of a reliability model of a digital feedwater control system using Markov methods supported by an automated failure modes and effects analysis (FMEA) tool. In general, the approach developed in this study should be applicable to both control and protection systems. Although the objective of the study is only to demonstrate the feasibility of the state of the art of traditional methods and data, the development of the automated FMEA tool can be considered an enhancement to the state of the art. Due to limitations in the scope of the study and the state of the art, the current model is not suitable to support regulatory decision-making. Additional research is needed to further enhance the state of the art, and potential areas of research are documented, for example, modeling of software failures.

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