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:
uick-acting toxic gas detectors, (2) automatic emergency zone isolation, (3) emergency zone leaktightness, (4) limited fresh air makeup rates, and 6.4-12 Rev. 2 - July 1981 (5) breathing apparatus and associated bottled air supply. The best solution for a particular case will depend on the toxic gas in question and on the specific ventilation system design. c. Confined Area Releases The reviewer studies the control building layout in relation to potential sources of radiation and toxic gases inside the control | building or adjacent connected buildings. The following is considered: V (1) Storage location of CO or other firefighting materials should be such as to eliminate the possibility of significant qyanti- ties of the gases entering the emergency zone. The review will be coordinated with the Chemical Engineering Branch (CMEB). (2) The ventilation zones adjacent to the emergency zone should be configured and balanced to preclude air flow toward the emer- gency zone. (3) All pressurized equipment and piping (e.g., main steam lines and turbines) that could cause sign ficant pressure gradients when failed inside buildings should be isolated from the emer- gency zone by multiple barriers such as multiple door vestibules or their equivalent. 6. Radiation Shielding Control room operators as well as other plant personnel are protected from radiation sources associated with normal plant operation by a com- bination of shielding and distance. The adequacy of this type of protection for normal operating conditions is coordinated with the RAB. To a large extent the same radiation shielding (and missile barriers) also provides protection from DBA radiation sources. This is especially true with respect to the control room walls which usually consist of at least 18 inches of concrete. In most cases the radiation from external DBA radiation sources is attenuated to negligible levels. However, the following items should be considered qualitatively in assessing the ade- quacy of