Document: NUREG-0800
Document ID: 9f13abda-ee55-4fa1-8276-db55ac2094ef
Document Type: srp
Title: CONTROL ROOM HABITABILITY SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070449.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.4
CFR Part: 
CFR Title: 

Content:
the site which may pose a threat to the plant operators upon a postulated accidental release. The method used to determine whether the quantity or location of the toxic material is such as to require closer study is described in Regulatory Guide 1.78. This guide also discusses the methods for analyzing the degree of risk and states, in general terms, the various protective measures that could be instituted if the hazard is found to be too great. In the case of chlorine, specific acceptable protective provisions have been determined (Ref. 8)are provided in Regulatory Guide 1.95.88 In summary, the following provisions or their equivalent are required for the emergency zone ventilation system: (1) quick-acting toxic gas detectors, (2) automatic emergency zone isolation, (3) emergency zone leaktightness, (4) limited fresh air makeup rates, and (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: (1) Storage location of C0(2)CO or other firefighting materials should be 2 such as to eliminate the possibility of significant quantities of the gases 6.4-17 DRAFT Rev. 3 - April 1996 entering the emergency zone. The review will be coordinated with the Chemical Engineering Branch (CMEB)EMCB.89 (2) The ventilation zones adjacent to the emergency zone should be configured and balanced to preclude airflow toward the emergency zone. (3) All pressurized equipment and piping (e.g., main steam lines and turbines) that could cause significant pressure gradients when failed inside buildings should be isolated from the emergency zone by multiple barriers such as multiple door vestibules or their equivalent. 6. Radiation Shielding