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:
the use of beta-gamma coincidence counting techniques. Also since Regulatory Guide 4.3 was issued, there has been a recognition of the need to consider the effects of relatively high and variable con- centrations of stable iodine in milk on the calculated radiochemical recovery and of the resultant need for determinations of stable iodine in milk. Because of the existence of acceptable alternative procedures, and the general recognition of the practicality of determining low levels of iodine-131 in milk, the detailed procedural guidance of Regu- latory Guide 4.3 is no longer needed. Current licensing commitments based on Regulatory Guide 4.3 will not need to be reexamined as a result of this withdrawal. Regulatory guides may be withdrawn when they are superseded by the Commission's regulations, when equivalent recommendations have been incorporated in applicable approved codes and standards, or when changes in methods and techniques have made them obsolete. Sincerely, Robert B. Minogue, Director Office of Standards Development APPENDIX IODINE-131 ANALYSIS OF MILK AT CONCENTRATIONS DOWN TO 0.25 PICOCURIE PER LITER The direct ion exchange method fCo separating iodine from raw milk requires that the iodine he in a readily exchangeable anionic form. Radiviodine tracer experiments on cows' 2 -' have shown that 0-10 percent of the iodine in milk may he protein bound, rendering this fraction essentially unavailable for exchange with the ion exchange resin. However, this uncertainty of up to 10 percent in the 1-131 determination will not significantly affect data interpretation and therefore is considered to be acceptable. Nevertheless, for the sake of accuracy, it is recommended that a fixed correction factor of 1.05(1/0.95 = 1.05) be applied to the counting data to compensate 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