Document: NUREG-0800
Document ID: 21b37b7c-b45c-4247-b4a5-c2f28df75be4
Document Type: srp
Title: INSTRUMENTATION AND CONTROLS (Tier 1)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070663.pdf
Revision Date: 2023-06
Chapter: 14
Section ID: 14.3.5
CFR Part: 
CFR Title: 

Content:
ia for the development of the design. Tier 1 should be written to incorporate the most impor- tant and general aspects (top-level requirements) from the standards. The set of standards and criteria in DCD Tier 2 encompass the guidance for generating the plans that will be used in the I&C system design process throughout the lifecycle. The certified design description and design development process continue for the lifetime of the plant. Any safety-related software that is changed or added after plant startup is required to either be developed using the certified design development process described in the computer Tier 1, or the licensee must submit a design process description (together with the design bases) that will produce software of the same or higher quality than the original certified design process, consistent with Tier 1. The licensee will be required to use the approved software change procedure (SCP) based upon the certified design development process for the operation stage of the lifecycle. A. Diversity and Defense-In-Depth Tier 1 should address the concern that software design faults or other initiating events common to redundant, multidivisional logic channels of I&C protection systems (or between different systems (safety and/or non-safety) could disable a significant portion of the plant's safety functions at the moment when these functions are needed to mitigate an accident, and addresses the diverse features that are provided for the primary automatic logic. SRP Section 7.1, 7.8 and BTP-HICB-19 describe the staff guidance for the review of the defense-in-depth and diversity provisions in the I&C system design. B. Electromagnetic Interference (EMI) Tier 1 should address the process to ensure that I&C equipment is able to function properly when subjected to an electromagnetic environment that is characteristic of the plant environment. An EMI compliance plan to confirm the level of immunity to DRAFT Rev. 0 - April 1996 14.3.5-6 electrical noise