Document: NUREG-0800
Document ID: 4865fc6d-b85f-4173-9bca-162fa9fe67d2
Document Type: srp
Title: Appendix 7-A
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500555.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
to the same software requirements. Other considerations, such as functional and signal diversity, that lead to different software requirements form a stronger basis for diversity. Rev. 4 — June 1997 Appendix 7-A BTP HICB-19-6 Manual displays and controls provided for compliance with the fourth point of the NRC position on D-in-D&D should be sufficient to both monitor the plant states and to actuate systems required by the control room operators to place the nuclear plant in a hot-shutdown condition. In addition, the displays and controls should monitor and control the following critical safety functions: reactivity level, core heat removal, reactor coolant inventory, containment isolation, and containment integrity. This additional manual capability is necessary in advanced reactors because all of the protection and control systems are digital-computer-based, and thus vulnerable to common-mode failure. The manual capability should consist of hardwired, system-level controls and displays. These controls provide plant operators with information and control capabilities that are not subject to common-mode failures caused by software errors in the plant's automatic digital I&C safety system. The point at which the manual controls are connected to safety equipment should be downstream of the plant's digital I&C safety system outputs, but should not compromise the integrity of interconnecting cables and interfaces between local electrical or electronic cabinets and the plant's electromechanical equipment. To achieve system-level actuation at the lowest possible level in the safety system architecture, the controls may be hardwired either to analog components or to simple (e.g., the component function can be completely demonstrated by test), dedicated, and diverse, software-based digital equipment that performs the coordinated actuation logic. These displays may include digital components that are exclusively dedicated to the display function. The functional