Document: NUREG-0800
Document ID: 240b218f-0879-4774-a145-71a59b902d69
Document Type: srp
Title: RADIOLOGICAL CONSEQUENCES OF A DESIGN BASIS LOSS-OF-COOLANT
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350160.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.6.5
CFR Part: 
CFR Title: 

Content:
that the recirculation mode is initiated. For a plant that does not provide an ESF atmosphere filtration system, the dose assessment should also include the leakage from a gross failure of a pas- sive component. This leakage should conservatively be assumed to be 50 gallons per minute, starting at 24 hours after the accident and lasting for 30 minutes. For a plant that does provide an ESF atmosphere filtration system in the areas of potential leakage from a gross failure of passive components, such dose assessment need not be performed. The applicant's information on the time-dependent temperature of the sump water circulating outside containment after the LOCA is evaluated. For a water temperature above 2126F, the fraction of the leakage that flashes to steam is determined assuming a constant enthalpy process. If the flash frac- tion is greater than 10%, then this fraction is taken as the fraction of iodine in the leakage that becomes airborne.. If the calculated flash fraction is less than 10% or if the water is less than 2126F, then 10% of the iodine in the leakage is assumed to become airborne unless a smaller amount is justified based on actual sump pH history and ventilation rates. The airborne iodine is assumed to be released immediately to the environment. The atmospheric dispersion is based upon the ground level X/Q values deter- mined under SRP Section 2.3.4. Atmosphere filtration system filters are evaluated by the ETSB with respect to the guidelines of Regulatory Guide 1.52 (Ref. 5) for appropriate credit to be given for iodine removal by the filters. The doses at the nearest exclusion area boundary and LPZ outer boundary are calculated using appropriate assumptions and methods as described in Appendix A to SRP Section 15.6.5. The doses calculated by the staff are reported in the dose table of the sec- tion, "Radiological Consequences of a LOCA," which is prepared in accordance with SRP Section 15.6.5, Appendix A. IV. EVALUATION FINDINGS The reviewer