Isolation of iron and strontium from liquid samples and determination of ~(55)Fe and ~(89,90)Sr in liquid radioactive waste

摘要

This paper describes the method of isolating iron and strontium from liquid samples with a low concentration of ions that enables simple and rapid determination of ~(55)Fe and ~(89,90)Sr. The method consists of binding (concentrating) Fe and Sr at the cation exchanger Amberlite IR-120, their elution from cation exchanger with 4M HC1 or 8M HNO_3,isolating Fe on the TRU extraction chromatographic column with4 M HC1 or 8 M HNO_3, and isolating Sr on the Sr.spec column with the mixture of 8 M HNO_3+2 M HC1 or 5 M HNO_3.After the isolation, ~(55)Fe is determined by liquid scintillation counting with scintillation solution, while activity of ~(89,90)Sr is obtained by Cherenkov counting in5 M HNO_3.It was shown that successive counting can be used for simultaneous determination of ~(89,90)Sr activity. The activity ratio of ~(89)Sr/~(90)Sr (up to 20:1) and vice versa does not impact the determination. ~(55)Fe is also determined immediately after isolation. The measurements in alpha,beta mode can be used to verify any presence of alpha-emitter (americium) in the fraction of iron and to correct the result. The method was tested by determining ~(55)Fe and ~(89,90))Sr in model samples and radioactive waste samples. The paper also shows that Fe and Zn can be bound to the TEVA and TRU resins from the solutions of HC1, HNO_3, and mixture of HC1 + HNO_3. The binding strength depends on the type of resin and the concentration of the acid or the concentration of acids in the mixture. These resin and acids can be used for mutual separation of Fe and Zn and their separation from other elements.