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:
lated hood. 4. Proceed with caution in this step. Excessive gas formation during the extraction can cause the stopcock or cap on the separatory funnel to "pop" with consequent loss of samp!e. Start by gently swirling the solution to effect mixing. Invert the separatory funnel with the stopcock pointing up and release the pressure by opening the stopcock. Close the stopcock, shake, and repeat the pressure release sequence. 5.. Organic phase should be deep red: if not, add additional gram of NH2 OH.lHCI. 6. After back extraction into water, CC14 should be colorless; if not add additional NaHS.03 and reextract. 7. HASL 300 "Procedure Manual" Health and Safety Laboratory, U.S. Atomic Energy Commission, 376 Hudson St., New York, New York 10014. Calibration and Standardization of Beta Counter Counter standardization should be performed with 1-131 standard obtained from the National Bureau of Standards (NBS)or with one which Is relatable to NBS. An example of a relatable standard is a secondary or tertiary standard which has been calibrated against a primary NBS standard. A self-absorption calibration curve should be constructed using at least 4 points. A useful curve can be constructed by plotting counter efficiency against mass. The counter efficiency can then be read off the curve as a function of the gravimetric yield. .4.3-4 I Example of Calculation of Results The activity in picocurics per liter at the time the milk was collected is determined by calculations based tn the observed net counts per minute of 1-131. The calculation requires correction for chemical yield, protein-bound iodine, counter efficiency, decay since sampling, and the sample volume. An example of a calculation of the 1-131 concentration in a sample and the error (standard deviation )Iassociated with tile measurement follows: Wl of ppt. mg Chem ical yield = ,, .8 I 14.83" F'nh! ppt is not Stoichii n ntrically Pdlt. and determined weight of PdIc for 10 ml! of I. I. Chemical yi!J 2. Counter