Document: NUREG-0800
Document ID: 6e757273-b12b-4603-aace-b01e49e5a6da
Document Type: srp
Title: RADIOLOGICAL CONSEQUENCES OF FUEL HANDLING ACCIDENTS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350313.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.7.4
CFR Part: 
CFR Title: 

Content:
ude an examination of the type, location and redundancy of the radiation monitors intended to detect an activity release inside the containment and verification that detection is followed by automatic containment isolation. The reviewer should assess the time required to isolate the containment. This should include the instrument line sampling time (where appropriate), detector response time and containment purge isolation valve actuation and closure time. The containment is considered isolated only when the purge isolation valves are fully closed. The applicant's analysis should be reviewed regarding the travel time of any activity release starting from its release point above the refueling cavity or transfer canal and including travel time in ducts or ventilation systems up to the inner containment purge isolation valve. The time required for the release to reach the inner isolation valve is compared to the time required to isolate the containment. If the time required for the release to reach the isolation valve is longer than the time required to isolate containment, then essentially no release to the atmosphere occurs, and the reviewer's assessment should reflect this. If the time required for the release to reach the isolation valve is less than that required to isolate containment,.and no mixing or dilution credit can be given, the reviewer should assume that the entire activity release escapes from the containment in evaluating the consequences. Claims for credit for dilution or mixing of a release due to natural or forced-convection inside containment are reviewed and assessed. References 4 and 5 should be consulted and used by the reviewer for guidance in estimating dilution and mixing. Where mixing and dilution can be demonstrated within containment, the radiological consequences will be reduced by the 'degree of mixing and dilution occurring prior to containment isolation. 5. The atmospheric dispersion factors; X/Q values, to be used in analyzing the