Evaluation of different methods for measuring 89Sr and 90Sr: Measurement uncertainty for the different methods as a function of the activity ratio

Detection Capability of 89Sr and 90Sr Using Liquid Scintillation Counting

ABSTRACT

We developed a new method for simultaneous determination of 89Sr and 90Sr with an emphasis on detectability. The samples were digested, and Sr was chemically purified followed by a single count on a liquid scintillation counter in three windows overlapping the 90Sr, 89Sr, and 90Y peaks. Gamma spectrometry was used to measure 85Sr, added for chemical recovery. The method was tested on 18 water samples spiked at levels from 9 to 242 Bq of 89Sr and 90Sr, with either single radionuclides or their mixtures. In addition, eight method blanks were measured. The data were analyzed numerically by solving a system of linear equations for 89Sr and 90Sr activities as analytes and 90Y activity as a participating component. The total uncertainties of the results were calculated numerically using variances and covariances. The average bias from the known activities was -0.3% (range from -3.6 to 3.1%) for 90Sr and - 1.5% (range from -10.1 to 5.1%) for 89Sr. The En-scores were within -1.0 and 1.0 at 95% confidence level. The detection capabilities of this method were determined by means of the decision threshold LC and the limit of detection referred to as the minimum detectable activity. All relevant uncertainties were propagated into the LC and minimum detectable activity. In addition, detection limits were calculated for the purpose of Safe Drinking Water Act monitoring. The detection capabilities were compared with the regulatory requirements in the US and EU for food and water. For samples spiked with either pure 89Sr or 90Sr, false positives were observed for the opposite radionuclide exceeding the above LC values. This was attributed to interference by the spiked activity. A new method was developed to calculate decision and detectability curves in the presence of interference.

Recent Development on Determination of Low-Level 90Sr in Environmental and Biological Samples: A Review

In the context of the rapid development of the world's nuclear power industry, it is vital to establish reliable and efficient radioanalytical methods to support sound environment and food radioactivity monitoring programs and a cost-effective waste management strategy. As one of the most import fission products generated during human nuclear activities, ⁹⁰Sr has been widely determined based on different analytical techniques for routine radioactivity monitoring, emergency preparedness and radioactive waste management. Herein, we summarize and critically review analytical methods developed over the last few decades for the determination of ⁹⁰Sr in environmental and biological samples. Approaches applied in different steps of the analysis including sample preparation, chemical separation and detection are systematically discussed. The recent development of modern materials for ⁹⁰Sr concentration and advanced instruments for rapid ⁹⁰Sr measurement are also addressed.