Document: NUREG-0800
Document ID: 7d56ab5c-90b1-42b4-a509-857fbfd674db
Document Type: srp
Title: review.10
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070724.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.4.9
CFR Part: 
CFR Title: 

Content:
to be the same as that in Regulatory Guide 1.77 (Ref. 2).23 6. The nuclide inventory of the fraction of the fuel which reaches or exceeds the initiation temperature of fuel melting (typically 2842 C) at any time during the course of the accident is calculated and 100% of the noble gases and 50% of the iodines contained in this fraction are assumed released to the reactor coolant. CPBSRXB should be 24 requested to review analyses which propose that fuel melting is not likely to result in significant releases prior to MSIV main steam isolation valve (MSIV) closure. 25 7. Those fuel rods presumed to fail are assumed to have operated at power levels 1.5 times that of the average power level of the core. 8. Any nuclides released to the reactor coolant from fuel cladding failures or fuel melting are instantaneously and uniformly mixed in the reactor coolant in the pressure vessel at the time of the accident. 9. For conservative analysis it is assumed that 10% of the iodines and 100% of the noble gases released in the pressure vessel reach the turbine and condensers. A more realistic analysis may be performed as needed on a case-by-case basis. Such analysis accounts for the quantity of contaminated steam carried from the pressure vessel to the turbine and condensers based on a review of the minimum transport time from the pressure vessel to the first main steam isolation valve (MSIV) and considers the MSIV closure time. 26 10. All noble gases remain in a gaseous state and are available for leakage from the turbine and condensers. 11. Of those iodines which reach the turbine and condensers, 90% are removed by partitioning and plateout in the turbine and condensers leaving 10% airborne and available for leakage. 12. The turbine and condensers leak to the atmosphere at a rate of 1% per day for a period of 24 hours, at which time the leakage is assumed to terminate. Condenser leakage rates lower than 1% per day and shorter in duration than 24 hours will be reviewed on a