Interlaboratory comparison for ensuring validity of radiochemical analysis results of NPP decommissioning radioactive...

A mobile radiochemical analysis laboratory (MIRACLE) was developed to quickly characterize and classify the radioactive wastes produced during the decommissioning of nuclear power plants by their radioactivity level. To ensure the accuracy of the results produced by MIRACLE, a comparative test was conducted involving three domestic laboratories. For this purpose, one radioactive liquid reference material made from SUS 304 (SUS 304-liquid-RM), simulating the acid dissolution solution of stainless steel 304, and two certified reference materials (CRM) consisting of bead-type concrete (C-CRM)and soil (S-CRM), were used. The accuracy of the analyses for ⁶⁰Co, ¹³⁴Cs, ¹³⁷Cs, and ⁹⁰Sr, as standard radiation sources in the SUS 304-liquid-RM, C-CRM, and S-CRM, was evaluated using the En-score method as specified in ISO 13528. Results were deemed satisfactory if the En-score fell within the range of -1.0 < En < 1.0. For ⁶⁰Co and ¹³⁷Cs in the SUS 304-liquid-RM, all participating labs reported En-scores within the range of -1.0 < En < 1.0, while for ¹³⁴Cs, the En-score was greater than 1. Notably, only lab-A reported an En-score of 0.2 for ⁹⁰Sr, a beta emitter. For ⁶⁰Co and ¹³⁷Cs in the C-CRM, only lab-B reported En-scores within the range of 0 < En < 1 for ⁶⁰Co and ¹³⁷Cs across the entire radioactivity range. Finally, for ⁶⁰Co and ¹³⁷Cs in the S-CRM, all participating labs reported satisfactory En-scores across the full range of radioactivity.