Document: NUREG-0800
Document ID: 8c2fce42-281a-4a50-9de7-513df024f27c
Document Type: srp
Title: CONTROL ROOM HABITABILITY SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340712.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.4
CFR Part: 
CFR Title: 

Content:
1, U.S. Atomic Energy Commission. 6.4-16 Rev. 2 - July 1981 SECTION 6.4 APPENDIX A ACCEPTANCE CRITERIA FOR VALVE OR DMPER REPAIR ALTERNATIVE The control room ventilation system must meet the criterion to function properly, even with a single failure of an active component. In certain cases, complex valve or damper configurations are required to meet the single failure criterion. For example, assurance of the isolation and operability of each leg of a dual inlet system at various times after a postulated accident could require a four-valve arrangement in which two pairs of series valves are con- nected in parallel. The mechnical, power, and control components of such arrangements combine to form a rather complex system. Credit will be allowed for an alternative system that allowed the failed valve to be manually reposi- tioned so that it will not interfere with the operation of the system. For example, in the case of a dual inlet system, if credit for repair is given, then two valves in series in each leg of the dual inlet would be acceptable. Where a valve fails closed but meets the criteria given below, credit would be allowed for the valve to be repositioned and locked in an open position. The approval of the repair option is contingent upon the intrinsic reliability of the internal components of the valve or damper and also upon the ease and ability to overcome the failure of the external actuating components (electrical relays, motors, hydraulic pistons, etc.). The following criteria or their equivalent will be required. 1. The valve or damper components must be listed as to which are considered internal (nonrepairable) and which external (repairable). These must be designed to meet the following criteria. a. Internal valve components (i.e., components that are difficult to repair manually without opening the ductwork) must be judged to have a very low probability of failure. The component design details will be reviewed and characteristics such as simplicity,