Combination of chemical separation and data treatment for 55Fe, 63Ni, 99Tc, 137Cs and 90Sr/90Y activity determination in radioactive waste by liquid scintillation

Improved non-destructive method for 90Sr activity determination in aqueous solutions using Monte Carlo simulation

The development of new methods and improvements of existing methods for the specific activity determination of ⁹⁰Sr and other distinct beta emitters has been of considerable interest. The reason for this interest is that the notably small number of methods that are able to meet all the set criteria, such as reliability of the results, measurement uncertainty and time, and minimum production of radioactive waste, as well as applicability to various samples with reference to their nature, geometry and composition. In this paper, two methods for rapid ⁹⁰Sr activity determination based on Monte Carlo simulations are used, one for a Si semiconductor detector for beta spectrometric measurements and the other for the Geiger-Muller (GM) ionization probe. To improve the reliability of the measurement results, samples with high and low strontium activity solutions were prepared in the form of dry residues. The results of the proposed methodology were verified with a standard method using a liquid scintillation counter, and notably good agreements are achieved.

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

The obtained results showed that the Sr resin can be used for the chromatographic separation of Fe (III) and Sr (II) ions by using a mixture of HCl and HNO3. It was shown that the binding strength of Fe (III) decreases with increasing concentration of HNO3 while the binding strength of Sr (II) increases. It was found that the optimal bonding strength is achieved in 6 mol/L HCl:3 mol/L HNO3 and varying concentrations of acid in the mixture allow their selective separation. On basis of these results, a method for the separation of (55)Fe and (89,90)Sr from liquid samples which consists of binding of Fe and Sr on Sr resin and separation from a number of elements by 6 mol/L HCl:3 mol/L HNO3 and their mutual separation by eluting of Sr with 4 mol/L HCl is established. The method enables efficient simultaneous separation (with high recovery) of (89,90)Sr and (55)Fe and in combination with Čerenkov counting rapid determination of (89,90)Sr.

First approach to radionuclide mixtures quantification by using plastic scintillators. Influence of the diameter of the plastic beads

Recent studies have evaluated the capability of plastic scintillation (PS) as an alternative to liquid scintillation (LS) in radionuclide activity determination without mixed waste production. In order to complete the comparison, we now assess the extent to which PS can be used to quantify mixtures of radionuclides and the influence of the diameter of the plastic scintillation beads in detection efficiency. The results show that the detection efficiency decreases and the spectrum shrink to lower energies when the size of the plastic scintillation beads increases, and that the lower the energy of the beta particle, the greater the variation takes place. Similar behaviour has been observed for beta-gamma and alpha emitters. Two scenarios for the quantification of mixtures are considered, one including two radionuclides (14C and 60Co) whose spectra do not overlap significantly, and the other including two radionuclides (137Cs and 90Sr/90Y), where the spectra of one the isotopes is totally overlapped by the other The calculation has been performed by using the conventional window selection procedure and a new approach in which the selected windows correspond to those with lower quantification errors. Relative errors obtained using the proposed approach (less than 10%) are lower than those of the conventional procedure, even when a radionuclide is completely overlapped, except for those samples with extreme activity ratios that were not included in the window optimization process.