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:
for that group. b. Compute each group, aerosol filter efficiency using the following method. By rearranging Equations 2 and 3 from Reference A-16, the filter efficiency, ߟ௙௜௟௧, is computed by utilizing the group settling velocity, settling area, volumetric flow rate, and volume of the well-mixed region being modeled as follows: ߟ௙௜௟௧= 1 − ஼೚ೠ೟ ஼೔೙= 1 − ଵ ଵାഊ∗ೇ ೂ = 1 − ଵ ଵାೠೞ∗ಲ ೂ Equation A-2 where: ߟ௙௜௟௧ = removal, or filter efficiency; ݑ௦ = settling velocity (ft/hr); DG-1389, Appendix A, Page A-11 A = settling area (ft2); ܥ௢௨௧ = outgoing concentration of nuclides in the pipe segment volume; ܥ௜௡ = initial concentration of nuclides in the pipe segment volume; and, Q = volumetric flow rate into pipe segment volume (ft3/hr); λ = equivalent removal coefficient (hr-1). Account for the effect of the changing settling velocity distribution in the downstream volumes by adjusting the downstream volume efficiencies by multiplying them by the prior volume aerosol filter removal efficiency. c. Compute the TEAREs (i.e., filter efficiencies) and equivalent removal coefficients, λ (hr-1), for a credited volume by the following method. Compute the probability-weight aerosol filter efficiency by multiplying the aerosol filter efficiency by the group probability from Step 1. Then sum all the probability weighted aerosol removal efficiencies to obtain the TEARE. By solving for λ in Equation A-2, the removal coefficients are computed to yield: ߣ= ିఎ೑೔೗೟∗ொ ൫ఎ೑೔೗೟ିଵ൯∗௏ Equation A-3 where: ηfilt = TEAREs Q = volumetric flow rate into credited volume V = well-mixed pipe free volume A-5.6.3 Numerical Integration: The equation for a normalized number distribution, (݊(݀௔)) of particles of aerodynamic diameter (݀௔) is given in Reference A-18 as: ݊(݀௔) = ଵ ௗೌ√ଶ஠୪୬൫஢ౝ൯ܧݔ݌቎− ୪୬൬೏ೌ ೏೒൰ మ