United States Nuclear Regulatory Commission - Protecting People and the Environment

Reviewing Real-Time Performance of Nuclear Reactor Safety Systems (NUREG/CR-6083, UCRL-ID-114565)

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Publication Information

Manuscript Completed: July 1993
Date Published:
August 1993

Prepared by:
G.G. Preckshot
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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The purpose of this paper is to recommend regulatory guidance for reviewers examining real-time performance of computer-based safety systems used in nuclear power plants. Three areas of guidance are covered in this report. The first area covers how to determine if, when, and what prototypes should be required of developers to make a convincing demonstration that specific problems have been solved or that performance goals have been met. The second area has recommendations for timing analyses that will prove that the real-time system will meet its safety-imposed deadlines. The third area has descriptions of means for assessing expected or actual real-time performance before, during, and after development is completed. To ensure that the delivered real-time software product meets performance goals, the paper recommends certain types of code-execution and communications scheduling. Technical background is provided in the appendix on methods of timing analysis, scheduling real-time computations, prototyping, real-time software development approaches, modeling and measurement, and real-time operating systems.

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