In-house re-calibration method of Plutonium-236 by radiochemical analysis and alpha spectrometry.

The accuracy and precision of a radiotracer's activity concentration is essential in obtaining credible and sustainable analytical data. This study illustrated the in-house re-calibration method of an unknown Plutonium-236 (236Pu) solution by radiochemical analysis and alpha spectrometry that have been completed in our laboratory. The objective of this study was to recalibrate and determine the accurate activity of the unknown radioactive solution, which was a challenging task for five years experienced radiation measurement laboratory (RML). Six non-sustained consecutive test points data were below 3σ in the weekly quality control chart of 236Pu blank samples. The cause and effect tool was implemented to investigate the discrepancy in data by evaluating several parameters. The tracer was the most probable parameter that needed to be verified due to some uncontrolled laboratory and vial storage conditions. It was assumed that radioactive hot particles could be formed, producing a concentric fraction of Plutonium in the unknown 236Pu solution. Therefore, the recalibration of the unknown 236Pu activity concentration solution was proposed and implemented. To confirm this observation, triple blank samples underwent a radiochemical analysis, and they were found to be less than the certified value. The verified recalibration method was approached through a full radiochemical pre-preparation (triple full digestions, triple purifications). Then, a certified Plutonium-242 reference (242Pu) was used as across calibration source, and measurements were done using spectrometry measurements. The average of the recalibrated values and the associated uncertainties were estimated to be 0.632 ±0.024 in the 236Pu solution. The new verified concentration value was validated with the analysis of two different International Atomic Energy Agency (IAEA) Certified Reference Materials (CRMs), and the obtained results were found to be in good agreement with the IAEA certified values. Therefore, the method used to recalibrate the activity concentration was successful and it can be implemented for recalibrating unknown activity sources in the future. The newly derived 236Pu activity concentration can be used as a verified radiotracer for future plutonium radioisotopes analytical applications. Conclusively, professional and decent practice of radio analytical laboratories should be conducted following quality management systems. [ABSTRACT FROM AUTHOR]