Document: NRC Regulatory Guide
Document ID: 535957c7-1203-410d-b709-8e4d381f00de
Document Type: regulatory_guide
Title: Measurements of Radionuclides in the Environment, Analysis of I-131 in Milk
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML1335/ML13350A246.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.3
CFR Part: 
CFR Title: 

Content:
te for this effect. Also, there may be instances where milk samples • may curdle to varying degrees in the interim between collection arid analysis. Milk in this condition is unsuitable for analysis by the direct ion exchange method. A fresh sample should be obtained should this occur. If clabbering continue. it) be a problem, the ion exchange separation should be performed at the sample collection point and the ion exchange resin column shipped to the laboratory for processing. If this cannot be done, the milk sample should be frozen prior to shipment to the analytical laboratory. The procedure described in this appendix was adapted from a procedure entitled "Determination of 1-129 in Milk and Water Samples" developed by the Radiological Sciences Laboratory. Division of Laboratories and Research, New York State Department of Health It was tested at the Battelle Memorial Institute Pacific Northwest Laboratories and shown to be adequate to measure 1-131 in milk at the 0.25 picocurie per liter concentration level. This sensitivity is • based on using a 4.liter milk sample and beta counting • for 1000 minutes or longer in a low-background counter with a nominal background count rate of 0'5.1 count per minute (cpm). The analytical sensitivity can be further improved by using more than 4 liters of milk and counting for longer than 1000 minutes. . A recount for decay check should be performed 7-10 days after the first count. However, because it is not practical to do. this for net counting rates of less than about 0.3 cpm, a recount should be made only when the initial net counting rate is greater than 0.3 cpm. If. after the second count, it is determined that the activity is not decaying with a half-life of 8 days, a third count should be made 4.5 days after the second count. 'Murthy. G. K.. ei at "Method for Removing Iodine-131 from Milk," Journal or Dairy Science. 45:1066 (1962) 2Salki' M.. Omomo. Y.. "Determination of Iodine-131 in Milk, Quick Mcthod. for