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:
number distribution, (݊(݀௔)) of particles of aerodynamic diameter (݀௔) is given in Reference A-18 as: ݊(݀௔) = ଵ ௗೌ√ଶ஠୪୬൫஢ౝ൯ܧݔ݌቎− ୪୬൬೏ೌ ೏೒൰ మ ଶ୪୬൫ఙ೒൯ మ቏ , Equation A-4 where: ߪ௚= geometric standard deviation ݀௚= geometric mean (which, for a log-normal distribution, is the same as the median diameter) According to the Hatch-Choate equations, the AMMD is related to the median diameter (݀௚), in meters, is by the relation: d୥= ܣܯܯܦ ܧݔ݌[−3 ln൫ߪ௚൯ ଶ], Equation A-5 Discretize the range of particle diameters, da, from 1E-9 to 1E-3 microns in to 150 groups. For each group, apply Equation A-4 to compute the normalized number distribution, (݊(݀௔)). Then, for each discretized group: (1) compute its settling velocity by applying Equation A-1; (2) use Equation 3 from Reference A-19 to compute inboard and outboard concentrations of particles leaving the volumes; (3) sum up the inboard and outboard concentrations using an appropriate numerical integration technique (such as the trapezoidal method); (4) utilize Equation A-2 to then DG-1389, Appendix A, Page A-12 compute the filter efficiencies. Finally, utilize Equation A-3 to convert filter efficiencies, ߟ௙௜௟௧, into removal coefficients, hr-1. A-5.6.4 Aerosol deposition removal coefficients for the condenser using a multi-group method and numerical integration will be evaluated on an individual case basis. A-5.7 Reduction of the amount of released elemental iodine by plateout deposition on steam system piping may be credited, but the amount of reduction in concentration allowed will be evaluated on an individual case basis. The model should assume well-mixed volumes. Reference A-20 provides guidance on an acceptable model. A-5.8 Reduction of the amount of released organic iodine (e.g., Brockman-Bixler model in RADTRAD (Ref. A-4)) should not be credited. A-5.9 In the absence of collection and treatment of releases