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:
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 Nuclear Safety Applications," provides more detail on the characteristics of an acceptable process for qualifying existing software, and discusses the use of engineering judgment and compensating factors. NUREG/CR-6421 discusses graded acceptance processes for commercial off-the-shelf software used in reactor applications. The guidance in this NUREG will aid the reviewer in the evaluation of acceptance processes that are part of commercial dedications of PLC embedded, operating system, and programming tools software. Rev. 4 — June 1997 Appendix 7-A BTP HICB-18-2 3. Purpose The purpose of this BTP is to provide guidance for NRC staff to verify conformance with the previously cited regulatory bases and standards in the design of digital computer systems using PLCs. This BTP has two objectives: • To ensure that embedded and operating system software and programming tools are reviewed, and the appropriate acceptance criteria are applied. • To ensure that the PLC application programs (e.g., ladder-logic programs) are developed using an appropriate software development process. B. Branch Technical Position 1. Introduction The PLC is typically a commercial-grade computer system that employs a particular high-level language, such as ladder logic, for the purpose of monitoring and controlling industrial processes. The PLC is a computer system, and as such, the software used on it should be designed and implemented using a process that conforms with the guidance in BTP HICB-14. The detailed design and implementation activities of such a process, however, may be easier to implement for applications produced using the high-level languages typical of PLCs. PLC applications are usually coded using ladder logic or sequential function charts. The resulting programs can be