Development of 'on-site' measurement methods for assay of plutonium isotopes.

Over the past decades, radioanalytical methods for environmental monitoring of plutonium (Pu) isotopes from contaminated soils were developed to respond in case of a nuclear accident but also for routine analyses. In this paper we prove the possibility of on-site analysis of plutonium using alpha particle spectrometry. Tests are performed with two types of soils: a "brown" soil and a "sandy" soil, both spiked with 242Pu. The proposed method starts with leaching the soil, then separating the radionuclides of interest through a TEVA column and finally preparing counting planchets for alpha-spectrometry analyses. The aim of this work was to obtain a fast and reliable procedure, from the sample preparation to the analysis, applicable directly in the field and lasting no longer than a working day. The testing involved several parameters, such as the soil-to-liquid ratio, the acid molarity, the influence of a purification step, the source preparation. For each procedure defined, the time and the recovery rates of 242Pu were recorded and compared. Results have proven that the recovery rates increase with the solid-to-liquid ratio, with the acid molarity, with the purification step but decrease with the mixing time. The two methods used for source preparation showed similar results and the sources were measured by alpha spectrometry, using two different counting devices. The final selected sample preparation procedure has a throughput of 3 h, with recovery rates of 33.8 ± 3.1% for the "brown" soil and 77.3 ± 9.2% for the "sandy" soil and is suitable for a field application.

EURADOS intercomparison on emergency radiobioassay.

Nine laboratories participated in an intercomparison exercise organised by the European Radiation Dosimetry Group (EURADOS) for emergency radiobioassay involving four high-risk radionuclides ((239)Pu, (241)Am, (90)Sr and (226)Ra). Diverse methods of analysis were used by the participating laboratories for the in vitro determination of each of the four radionuclides in urine samples. Almost all the methods used are sensitive enough to meet the requirements for emergency radiobioassay derived for this project in reference to the Clinical Decision Guide introduced by the NCRP. Results from most of the methods meet the requirements of ISO 28218 on accuracy in terms of relative bias and relative precision. However, some technical gaps have been identified. For example, some laboratories do not have the ability to assay samples containing (226)Ra, and sample turnaround time would be expected to be much shorter than that reported by many laboratories, as timely results for internal contamination and early decisions on medical intervention are highly desired. Participating laboratories are expected to learn from each other on the methods used to improve the interoperability among these laboratories.