Document: NUREG-0800
Document ID: 2ceb30a4-38c9-442c-bd66-5a699d0e6480
Document Type: srp
Title: Appendix 7-A
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500554.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
Appendix 7-A Rev. 4 — June 1997 BTP HICB-18-1 NEW Branch Technical Position HICB-18 Guidance on the Use of Programmable Logic Controllers in Digital Computer-Based Instrumentation and Control Systems A. Background This branch technical position (BTP) provides guidelines for reviewing the use of programmable logic controllers (PLCs) in instrumentation and control (I&C) systems. These guidelines are based on reviews of licensee submittals and the analysis of PLC-related issues documented in NUREG/CR-6090, "The PLC and Its Application in Nuclear Reactor Protection Systems." 1. Regulatory Basis 10 CFR 50 Appendix A, General Design Criterion 1, "Quality Standards and Records," requires in part that "structures, systems, and components important to safety shall be designed, fabricated, and tested to quality standards commensurate with the importance of the safety functions to be performed." 10 CFR 50 Appendix A, General Design Criterion 21, "Protection System Reliability and Testability," requires in part that "the protection system shall be designed for high functional reliability . . . commensurate with the safety functions to be performed." 2. Relevant Guidance Reg. Guide 1.152, "Criteria for Digital Computers in Safety Systems of Nuclear Power Plants," provides guidance for complying with the requirements for safety systems that use digital computer systems. The guidance in Reg. Guide 1.152 refers to IEEE Std 7-4.3.2, "IEEE Standard for Digital Computers in Safety Systems of Nuclear Power Generating Stations." NUREG/CR-6090 covers the application of PLCs to nuclear reactors. The guidance in this NUREG will aid the reviewer in the evaluation of an I&C system containing one or more PLCs. NUREG/CR-6463, "Review Guidelines on Software Languages for Use in Nuclear Power Plant Safety Systems," describes recommended practices in the use of common PLC programming languages. EPRI TR-106439, "Guideline on Evaluation and Acceptance of Commercial Grade Digital Equipment for