Document: NUREG-0800
Document ID: e1169529-d2cb-4947-9efe-b23d927f4aa9
Document Type: srp
Title: NUREG40800
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350520.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8
CFR Part: 
CFR Title: 

Content:
cating the bypass or inoperable status of portions of the prot'ection system, systems actuated or controlled by the protection system, and auxiliary or supporting systems that must be operable for the protection system and the system it actuates to perform their safety- related functions. This appendix gives more specific guidance on meeting the provisions of Regulatory Guide 1.47 as they pertain to diesel-generator units. Diesel-generator units, as defined in Regulatory Guide 1.108, "Periodic Testing of Diesel Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants," consist of the engine, generator, combustion air system, cooling water system up to the supply, fuel supply system, lubricating oil system, starting energy sources, autostart controls, manual controls, and diesel- generator breaker. Operating experience has shown that there have been incidents where diesel- generator units failed to respond to an automatic start signal because control switches or lockout and shutdown relays (which require manual reset) were left in the shutdown condition without control room operators being aware of their status. The principal reasons for this lack of awareness were the (a) sharing of annunciator stations for both disabling and nondisabling alarm conditions; (b) wording on annunciator windows for disabling conditions that did not specifically say a diesel-generator unit was unavailable for an automatic emergency start; and (c) disabling conditions that were not annunciated in the control room. In order that the operator can act appropriately to supply emergency power when required in the operation of diesel-generator units, it is esential that he has accurate and sufficient information about the status of the units (e.g., is a unit under test; is a unit locked out for repair, maintenance, or otherwise unavailable) on which to base his decisions. 2. BRANCH TECHNICAL POSITION 2.1 Diesel-generator unit bypass or deliberately induced inoperability