Document: NRC Regulatory Guide
Document ID: 0cfc3978-32da-4370-9f31-8a3547d82846
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating the Potential Radiological Consequences of a Fuel Handling Accident in the Fuel Handling and Storage Facility for Boiling and Pressurized Water Reactors (Rev. 0)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0833/ML083300022.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.25
CFR Part: 
CFR Title: 

Content:
on product inventories are calculated assuming full power operation at the end of core life immediately preceding shutdown and such calculation should include an appropriate radial peaking factor. The minimum acceptable radial peaking factors are 1.5 for BWRs and 1.65 for PWRs. f. The iodine gap inventory is composed of inorganic species (99.75%) and organic species (.25%). g. The pool decontamination factors for the inorganic and organic species are 133 and 1, respectively, giving an overall effective decontamination factor of 100 (i.e., 99% of the total iodine released from the damaged rods is retained by the pool water). This difference in decontamination factors for inorganic and organic iodine species results in the iodine above the fuel pool being composed of 75% inorganic and 25% organic species. h. The retention of noble gases in the pool is negligible (i.e., decontamination factor of 1). i. The radioactive material that escapes from the pool to the building is released from the building3 over a two hour time period. j. If it can be shown that the building atmosphere is exhausted through adsorbers designed to remove iodine, the removal efficiency is 90% for inorganic species and 70% for organic species.4 k. The effluent from the filter system passes directly to the emergency exhaust system without mixing5 in the surrounding building atmosphere and is then released (as an elevated plume for those facilities with stacks6). 2 For release pressures greater than 1200 psig and water depths less than 23 feet, the iodine decontamination factors will be less than those assumed in this guide and must be calculated on an individual case basis using assumptions comparable in conservatism to those of this guide. 3 The effectiveness of features provided to reduce the amount of radioactive material available for release to the environment will be evaluated on an individual case basis. 4 These efficiencies are based upon a 2-inch charcoal bed depth with ¼ second residence