Document: NRC Regulatory Guide
Document ID: c0dbb594-6262-4b83-96b1-366758ad9676
Document Type: regulatory_guide
Title: Interim Licensing policy on as low as Practicable for Gaseous Radiodine Releases from Light-Water-Cooled Nuclear Power Reactors (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1229/ML12298A137.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.42
CFR Part: 
CFR Title: 

Content:
etables is estimated to be 2.34 kilograms per square meter. It is assumed that over a period of 3 months of a year the adult consumes 18 kilograms of fresh leafy vegetables. As a consequence, the rate of ingestion of radioiodine via this pathway during this period of 3 months is given by 8.53 x 10-2pij curies per day. Of that ingested, 30% is re- t-2 tamed in the thyroid, or thedaily thyroid deposition is 2.56 x 1 ij curies per day. The ratios of vegetation ingestion to air doses over the course of a year for 1-131 and 1-133 are then 1.42-Cll 8 . -2 1 -(1/4)(2.56 x 10- )Pl3l,j 1I31 (02)2) = 3.9 ° (20) (0.23) (20)C1 3 1 .1 (1/4)(2.56 x 10 (2 133 (0.23) (20)(C 1 3 3 ,J) Thus, the calculation of adult thyroid dose via the vegetation ingestion pathway may be directly related to those continuous air concentrations values provided in 10 CFR 20 that correspond to air doses of 1500 millirem per year to an infant's thyroid. The breathing rate of an adult is con- sidered to be 20 cubic meters per day as compared with 3 cubic meters per day for an infant, the mass of the thyroid of an adult is 20 grams versus 2 for the infant, and the energy deposition per disintegration differs slightly from the adult to the infant thyroid. Dose corrections for the adult are provided in the table below: Annual Adult Thyroid Doses Via Nuclide Vegetation (mrem) Cl131,j 1-131 (3.9),MPC ) (0.84) (1500) a 1-133 Cl 3 3 ,j 1-13 (064)(Mr ) (0.82) (1500) a Alternative representations of the above are: D1 3 1 (mrem/yr) = 2.1 x 10 6 (X/Q)jQ1 3 1R (22) D1 3 3 (mrem/yr) = 8.3 x 10 (X/Q)jQI 3 3R (23) In Equations 22 and 23, (x/Q)j is given in seconds per cubic meter, Qi is given in curies per year, and R (from Equation 2), is dimensionless. In the above adult thyroid dose relations, the duration of exposure per year (3 months) has been taken into account. In those areas where a 1. 42-C12 greater or lesser time duration of consumption of leafy green vegetables normally occurs, the calculated dose values