Discussion on results of national measurement capability comparison assessment for gross α and gross β radioactivity in water and calculation formulas for spike recovery
Objective To summarize and analyze the difficulties and key points in the measurement of gross α and gross βradioactivity in water based on the results of national measurement capability comparison assessment,and provide the basis and reference for the future work and the development of new local standards.Methods The research team participated in the comparison assessment for measurement of the gross radioactivity in water samples organized by National Institute for Radiological Protection,Chinese Center for Disease Control and Prevention.According to the comparison assessment res-ults and the content in the national standard GB/T 5750.13-2023(published draft),the steps of spike recovery involved dur-ing the measurement were analyzed and discussed.Two different formulas used for spike recovery calculation were ana-lyzed for their impact on the final measurement results.Results When the spike recovery F(derived)derived from the formu-las was used for result calculation,the spike recovery ranged as follows:gross α:63.00％-84.60％,and gross β:95.0％-99.1％;3/6 of the comparison results were determined as excellent and 3/6 as pass as a whole(among them,4 were excellent and 2 were pass for both single gross α assessment items and single gross β assessment items).When the spike re-covery F from the GB/T 5750.13-2023(published draft)was used for result calculation,the spike recovery ranged as fol-lows:gross α:39.69％-71.57％,and gross β:90.25％-98.21％;5/6 of the comparison results were determined as fail and 1/6 as pass(among them,5 were fail and 1 was pass for single gross α assessment items;5 were excellent and 1 was pass for single gross β assessment items).When two different formulas were used for spike recovery calculation,there was a signific-ant difference in gross α radioactivity measurement(t=4.27,P=0.03＜0.05),but there was no significant difference in gross β radioactivity measurement(t=0.667,P=0.524＞0.05).Conclusion In the measurement of gross α and gross β ra-dioactivity in water,appropriate reference to the spike recovery has a great influence on the measurement results.Therefore,quality control should be strengthened to further ensure the accuracy of measurement.
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