Intra- and inter-laboratory comparison on radiocesium in radiation-contaminated waste samples: Results for surface soils, fly ash, bottom ash, and molten slag

Abstract

Radiation leaks from the Fukushima Daiichi nuclear power station has occurred after the Japan's Tohoku earthquake on March 11, 2011. Since then, by using validated analytical procedures, the behavior of radioactive materials, especially radiocesium ( 134 Cs, 137 Cs), should be investigated for not only government-initiated areawide waste management, but also for routine waste management and recycling. To confirm the necessity to improve the accuracy and precision of the current analytical procedures of radicesium in radiation-contaminated wastes, such as soil and incineration ash samples, we have conducted research for intra- and inter-laboratory comparisons on radiocesium with six participants. During an inter-laboratory study, radiocesium in activity concentration-prepared samples was measured by a Ge semiconductor detector, a NaI(TI) scintillation detector and a LaBr 3 (Ce) scintillation detector. The mean activity concentrations (n =14) in roadside soil, plantation soil, agriculture soil, fly ash, bottom ash, and molten slag were 63900, 5610, 356, 21200, 3640, and 670 Bq kg -1 (the sum of 134 Cs and 137 Cs), respectively. The standard for Special Measures concerning the Handling of Pollution by Radioactive Materials Act in Japan is 8000 Bq kg -1 (the sum of 134 Cs and 137 Cs) within the obtained activity concentration range. The results demonstrated that the relative standard deviations (RSDs) for intra- and inter-laboratory data from tested samples were less than 10 %, indicating participants in this research could obtain reproducible results based on intra- and inter-laboratory comparisons. In this study, small variations in the data were observed as follows: 1) variation in the intra-laboratory data for agriculture soil; the lowest activity concentration of radiocesium tended to be comparably higher than other samples. 2) A detector-dependent variation in the inter-laboratory data was also indicated. © 2013 The Japan Society for Analytical Chemistry.