Document: NRC Regulatory Guide
Document ID: 5f67f910-de21-4629-9b03-b5a9f09c3c66
Document Type: regulatory_guide
Title: 
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML0037/ML003739544.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.6
CFR Part: 
CFR Title: 

Content:
d, the use of Sr-85 tracer for radiochemical yield determination is recommended, but if both Sr-90 and Sr-89 analyses are required, Sr-85 tracer should not be used because it interferes with the Sr-89 measurement. It is necessary in the latter case to do the yield determination by a gravimetric technique. One of the most .important steps in the analysis is the early exchange of strontium carrier and/or tracer with the Sr-89 and Sr-90 in the sample. Equilibration can be considered to have been attained when the radiostrontium in the sample has been completely solubilized in the presence of strontium carrier and/or tracer.,Once this equilibrium has been established, any subsequent loss of radiostrontium can be accurately assessed through yield determination of carrier or tracer. It is important, therefore, that all steps leading to equilibration be performed with extra care to avoid losses in these steps. If a significant amount (several milligrams) of stable strontium is present in the sample, as is the case for sea water, somc shellfish, and certain soils, the gravimetric yield determination will be in error if a correction is not made for the additional strontium. Most other bioenvironmental media of concern have small concentrations of stable strontium which are not expected to cause a problem and in general can be ignored. Calcium, however, is present in significant amounts in most bioenvironmental media, and its separation from small amounts of added strontium'carrier can be tedious; if this separation is not performed properly, however, the gravimetric yield will be biased in proportion to the amount of calcium remaining in the strontium fraction. Since Sr-90 and Sr-89 concentrations in normal bioenvironmental media are expected to be low, appropriate low-level techniques should be used in making these measurements. Some of the better high precision radiochemical procedures for low-level Sr-90 assay depend on counting the Y-90 daughter activity, rather than