Document: NRC Regulatory Guide
Document ID: 4d46a966-d280-43da-9b03-8b0abe7b29ce
Document Type: regulatory_guide
Title: Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2120/ML21204A065.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.183
CFR Part: 
CFR Title: 

Content:
ve iodine. Step 4—Evaluate release as an overall release. The removal coefficient is used to model the time-dependent concentration of radionuclides released from the pool as follows: Qe = λe Vpool (Equation B-14) 2 Combined speciation rate from NUREG/CR-5950, “Iodine Evolution and pH Control,” issued December 1992 (Ref. B-3). DG-1389, Appendix B, Page B-5 a. λf is used if recirculation filtration is credited. b. Alternatively, a loop and filter can be modeled instead of using λf. B-4. Noble Gases and Particulates The retention of noble gases in the water in the fuel pool or reactor cavity is negligible (i.e., DF of 1). Particulate radionuclides are assumed to be retained by the water in the fuel pool or reactor cavity (i.e., infinite DF). B-5. Fuel Handling Accidents within the Fuel Building For fuel handling accidents postulated to occur within the fuel building, the following assumptions are acceptable to the NRC staff: B-5.1 The radioactive material that escapes from the fuel pool to the fuel building is assumed to be released to the environment over a 2-hour time period for the initial fuel gap gas release which considers time-independent releases from the fuel pool. The release rate is generally assumed to be a linear or exponential function over this time period. For the time-dependent releases from the fuel pool from the re-evolution of iodine, these releases are to be considered directly to the environment outside the fuel building as they are released from the pool. B-5.2 A reduction in the amount of radioactive material released from the fuel pool by engineered- safety-feature (ESF) filter systems may be taken into account, using the guidance in Regulatory Guide 1.52, Revision 4, “Design, Inspection, and Testing Criteria for Air Filtration and Adsorption Units of Post-Accident Engineered-Safety-Feature Atmosphere Cleanup Systems in Light-Water-Cooled Nuclear Power Plants,” issued September 2012 (Ref. B-4). The radioactivity release analyses