PNNL

Abstract

A rapid, automated, microanalytical procedure for the determination of 90Sr in aged nuclear waste has been developed. It is based on a sequential injection analysis (SIA) system which rapidly seperates 90Sr from 90Y, 137CS, and other radionuclides. The isolated 90Sr is then detected on-line with a flow-through liquid scintillation counter. The seperation is achieved using a sorbent extraction minicolimn containing a resin (EIChrom, Sr-Spec) that selectively binds 90Sr as a crown ether complex under acidic conditions. The 90Sr is eluted with water, mixed with liquid scintillation cocktail, and detected in quantified from peak areas, giving linear calibration curves. The instrument can also be operated in a stopped-flow mode for longer counting times. Analyses of aged nuclear waste samples from the Hanford site by the SIA method and a manual method were in excellent agreement: correlation coefficient R=0.994. Sample analysis by the SIA method is complete in less than 40 min. The advantages of the new 90Sr analyzer include faster analysis, greater precision, reduced labor costs, and reduced secondary waste. Worker safety is improved because solution handling operations are fully automated and contained.