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:
additional factor that is used to modify the base infiltration rate is the enhancement of the infiltration occurring at the dampers or valves upstream of recirculation fans. When closed, these dampers typically are exposed to a pressure differential of several millimeters (inches) water gauge. This is accounted for by an 61 additional infiltration contribution over the base infiltration of 3.2- mm (1/8-in) water gauge. 62 The use of an infiltration rate that is based on calculation is acceptable except in the case where the applicant has assumed exceptionally low rates of infiltration. In these cases, more substantial verification or proof may be required. For instance, if an applicant submits an analysis that shows a gross leakage rate of less than 0.06 volume changes per hour, the reviewer would require that the gross leakage be verified by periodic tests as described in Regulatory Position C.5 of Regulatory Guide 1.95. (3) Zone isolation with filtered recirculated air and a positive pressure. This system is essentially the same as the preceding one. However, an additional operational mode is possible. Makeup air for pressurization is admitted. It is filtered before entering the emergency zone. Pressurization reduces the unfiltered inleakage that is assumed to occur when the emergency zone is not pressurized. Assuming a filter fan capacity of 2400 L/s (5000 cfm) and a filter efficiency of 95%, the 63 following protection factors result (flows in L/s (cfm) ): 64 Makeup Air Recirculated No Infiltration) Infiltration ) Air IPF (Assuming IPF (Assuming ***65 190 (400) 2200 (4600) 238 159 66 67 350 (750) 2000 (4250) 128 101 68 69 470 (1000) 1900 (4000) 96 80 70 71 The makeup flow rate should have adequate margin to assureensure that the control room will be maintained at a pressure of at least 3.2-mm (1/8-in) water gauge. The applicant should indicate that an acceptance 72 6.4-13 DRAFT Rev. 3 - April 1996 test will be performed to verify adequate pressurization. If the