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:
, ASME Code AG-1 including the AG-1a-92 Addenda to evaluate the system. The procedures are as 48 follows: a. The type of system proposed is determined. The following types of protection provisions are currently being employed for boiling water reactor (BWR) or pressurized water reactor (PWR) plants: (1) Zone isolation, with the incoming air filtered and a positive pressure maintained by the ventilation system fans. This arrangement is often provided for BWRs having high stacks. Airflow rates are between 190 and 1900 L/s (400 and 4000 cfm).49 (2) Zone isolation, with filtered recirculated air. This arrangement is often provided for BWRs and PWRs with roof vents. Recirculation rates range from 950 to 14,200 L/s (2000 to 30,000 cfm).50 (3) Zone isolation, with filtered recirculated air, and with a positive pressure maintained in the zone. This arrangement is essentially the same as that in (2), with the addition of the positive pressure provision. (4) Dual air inlets for the emergency zone. In this arrangement two widely spaced inlets are located outboard, on opposite sides of potential toxic and radioactive gas sources. The arrangement guarantees at least one inlet being free of contamination, except under extreme no-wind conditions. It can be used in all types of plants. Makeup air supplied from the contamination-free inlet provides a positive pressure in the emergency zone and thus minimizes infiltration. (5) Bottled air supply for a limited time. In this arrangement a flow rate of 190 to 290 L/s (400 to 600 cfm) is provided from compressed air 51 containers for about 1 hour to prevent inleakage. It is used in systems having containments whose internal atmospheric pressure becomes negative within an hour after a DBA (subatmospheric containments). b. The input parameters to the radiological dose model are determined (see Item 5 below). The parameters are emergency zone volume, filter efficiency, filtered makeup airflow rate, unfiltered inleakage (infiltration), and