United States Nuclear Regulatory Commission - Protecting People and the Environment

The Programmable Logic Controller and Its Application in Nuclear Reactor Systems (NUREG/CR-6090, UCRL-ID-112900)

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Publication Information

Manuscript Completed: August 1993
Date Published:
September 1993

Prepared by:
J. Palomar, R. Wyman
Lawrence Livermore National Laboratory
P.O. Box 808
Livermore, California 94550

Prepared for:
Division of Reactor Controls and Human Factors
Office of Nuclear Reactor Regulation
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC FIN L-1867

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This document provides recommendations to guide reviewers in the application of Programmable Logic Controllers (PLCs) to the control, monitoring and protection of nuclear reactors. The first topics addressed are system-level design issues, specifically including safety. The document then discusses concerns about the PLC manufacturing organization and the protection system engineering organization. Supplementing this document are two appendices. Appendix A summarizes PLC characteristics. Specifically addressed are those characteristics that make the PLC more suitable for emergency shutdown (ESD) systems than other electrical/electronic-based systems, as well as characteristics that improve reliability of a system. Also covered are PLC characteristics that may create an unsafe operating environment. Appendix B provides an overview of the use of programmable logic controllers in emergency shutdown systems. The intent is to familiarize the reader with the design, development, test, and maintenance phases of applying a PLC to an ESD system. Each phase is described in detail and information pertinent to the application of a PLC is pointed out.

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