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:
lution derived from drawing in equal amounts of clean and contaminated air through two open inlets. 6.4-10 Rev. 2 - July 1981 (1i) Dual Inlet designs limited to manual selection control - equation (6) of Reference 5 may be used with respect to the more favorable inlet location to estimate the X/Q's. The estimated values can be reduced by a factor of 4 to account for dilution effects associated with a dual inlet configuration and the relative probability that the operator will make the proper inlet selection. The reduction factor is contingent upon having redundant radiation detectors within each air inlet. The reduction factor is based on the judgment that trained control room operators, in con- junction with radiation alarm indication, will select and close the contaminated air inlet. (lii) Dual inlet designs with automatic selection control fea- tures - equation (6) of Reference 6 may be used with resect to the more favorable Inlet location to estimate the X/Q s. The estimated values can be reduced by. about a factor of 10 to account for the ability to select a "clean" air inlet. The actual factor may be somewhat higher if the inlet con- figuration begins to approach the remote air inlet concept such that the probability of having one clean air inlet is relatively high. Plant configuration and meteorological conditions should be used as the principal basis for reduction factors greater than 10. The reduction factor of 10 or more is contingent upon having redundant detectors in each inlet and the provisions of acceptable control logic which would be used in the automatic selection of a clean air inlet. Because damage to the ducting might seriously affect the system capability to protect the operators, the ducting should be seismic Category I and should be protected against tornado missiles. In addition, the number and placement of dampers must be such as to assure both flow and isolation in each inlet assuming one single active componentTaillure (see Appendix A for