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Sequential separation of Fe and Sr from liquid samples by using Sr resin and rapid determination of 55Fe and 89, 90Sr

As a rule, the determination of 55Fe and strontium isotopes is complicated and time-consuming, especially the determination of 89, 90Sr. In last decade a number of methods have been developed for radioactive strontium isolation and determination in various kinds of samples, but only few methods for 55Fe determination mainly in liquid radioactive waste samples. One reason for this lies in the fact that strontium isotopes are highly radiotoxic fission product (especially 90Sr with long half life), and as such they were an interesting subject for various kinds of investigations, from their distribution and behavior in natural systems to the influences on the human health. In distinction from strontium isotopes, 55Fe is an activation product, low energetic emitter with approximately 2.74 year half life. As such, it was not as interesting as strontium, but environmental concerns prompted the responsible institutions in the radiological monitoring program to include 55Fe determinations in their procedures. In almost all published methods, isolation and determination of 89, 90Sr and 55Fe are separated and a method for simultaneous isolation of 55Fe and 89, 90Sr in one step does not exist. Therefore, the goal of paper is to present a method for the isolation of 55Fe and 89, 90Sr from liquid sample in one step by using Sr resin and mixture of nitric and hydrochloric acid. It is well known that Sr resin is very specific and selective for Sr ions so that Sr can be separated from number of elements on Sr resin column by using HNO3 solution including Fe. However Fe and Sr can be bound on Sr resin from mixture of HNO3+HCl. Namely Sr resin was primarily developed as Sr specific resin which enables very efficient separation of Sr from Ca as well as Pb and many other elements and main focus in literature was directed to its application in separation and determination of 89, 90Sr (and 210Pb) in different kind of samples while Fe was not in focus from above mentioned reason. Therefore it will be shown how Fe and Sr can be bound and mutually separated (and from many other elements) on Sr resin column and how this separation can be used for the development of rapid method for their determination in liquid samples. Namely binding strength and selectivity depend on concentration of HCl and HNO3 and by changing of eluent composition separation of Fe from Sr as well as Fe(II) from Fe(III) ions can be achieved. On the base of these results methodology for rapid determination which involves, binding of Fe and Sr on the Sr column from the mixture of HNO3+HCl, elution of Sr with HCl, Fe with HNO3 and detection on LSC is created. It will be shown that 55Fe can be easily determined by liquid scintillation counting while activity of 89, 90Sr can be obtained by Cherenkov counting in 5M HNO3. It will be shown how successive counting enables rapid determination of low level activities of 89, 90Sr in different activity ratio of 89Sr/90Sr and how some parameters can influence on detection limits and uncertainty. Methodology is tested by determination of 55Fe and 89, 90Sr in proficiency testing samples and radioactive waste samples and obtained results will be presented and discussed in detail.

55Fe; 89; 90Sr; Sr resin; Fe and Sr separation; 55Fe; 89; 90Sr determination

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