Software Reliability And Safety In Nuclear Reactor Protection Systems

UCRL-ID-114839 Software Reliability and Safety in Nuclear Reactor Protection Systems Prepared by J. Dennis Lawrence Prepared for U.S. Nuclear Regulatory Commission FESSP Fission Energy and Systems Safety Program Lawrence Livermore National Laboratory Disclaimer This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. This work was supported by the United States Nuclear Regulatory Commission under a Memorandum of Understanding with the United States Department of Energy. UCRL-ID-114839 Software Reliability and Safety in Nuclear Reactor Protection Systems Manuscript date: June 11, 1993 Prepared by J. Dennis Lawrence Lawrence Livermore National Laboratory 7000 East Avenue Livermore, CA 94550 Prepared for U.S. Nuclear Regulatory Commission ii ABSTRACT Planning the development, use and regulation of computer systems in nuclear reactor protection systems in such a way as to enhance reliability and safety is a complex issue. This report is one of a series of reports from the Computer Safety and Reliability Group, Lawrence Livermore National Laboratory, that investigates different aspects of computer software in reactor protection systems. There are two central themes in the report. First, software considerations cannot be fully understood in isolation from computer hardware and application considerations. Second, the process of engineering reliability and safety into a computer system requires activities to be carried out throughout the software life cycle. The report discusses the many activities that can be carried out during the software life cycle to improve the safety and reliability of the resulting product. The viewpoint is primarily that of the assessor, or auditor. iii iv CONTENTS 1. Introduction ..........................................................................................................................................................1 1.1. Purpose ....