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:
ng the fractal scaling factor (Fnuclide) by the predicted Kr-85m R/B using Equation 13 of NUREG/CR-7003, as follows: The R/B fraction for isotope I-132 should be calculated using this fractal equation even though its half-life is less than 6 hours (2.28 hours) because its precursor of tellurium (Te)-132 has a half- life of 3.2 days, which controls the release of I-132. J-2.1.4 Table J2 lists the fractal scaling factors for each nuclide calculated using the following equation from NUREG/CR-7003: m Kr i m Kr i nuclide nuclide i D V S F B R 85 85 , − −       =       λ α 25 .0 85 85       = − − m Kr nuclide m Kr nuclide nuclide F α λ λ α DG-1389, Appendix J, Page J-5 Table J-2. Fractal Scaling Factors for Short-Lived Nuclides NUCLIDE NUREG/CR-7003, TABLE 1 FRACTAL SCALING FACTOR Half-Life Decay Constants Alpha Xe-133 5.243 days 1.53x10-6 1.25 2.276 Xe-135 9.10 hours 2.12x10-5 1.85 1.301 Xe-135m 15.3 months 7.55x10-4 23.50 1.005 Xe-137 3.82 months 3.02x10-3 1.07 0.328 Xe-138 14.1 months 8.19x10-4 1.00 0.447 Xe-139 39.7 seconds 1.75x10-2 1.00 0.208 Kr-85m 4.48 hours 4.30x10-5 1.31 1.000 Kr-87 1.27 hours 1.52x10-4 1.25 0.721 Kr-88 2.84 hours 6.78x10-5 1.03 0.840 Kr-89 3.15 months 3.35x10-3 1.21 0.330 Kr-90 32.3 seconds 2.15x10-2 1.11 0.203 I-131 8.04 days 9.98x10-7 1.00 2.395 I-132 2.28 hours 8.44x10-5 137* 2.702 I-133 20.8 hours 9.26x10-6 1.21 1.439 I-134 52.6 months 2.20x10-4 4.40 0.900 I-135 6.57 hours 2.93 x10-5 1.00 1.029 * The I-132 alpha term accounts for significant contribution from precursor Te-132. J-3. High-confidence, upper tolerance release fractions should be calculated using an NRC-approved fuel rod thermal-mechanical code, along with quantified model uncertainties. J-3.1 For short-lived isotopes, the 2011 ANS-5.4 release model standard recommends multiplying the best estimate predictions by a factor of 5.0 to obtain upper tolerance release fractions. DG-1389, Appendix J, Page J-6