Interlaboratory radiochemical analysis comparison on a primary waste flux

An accurate knowledge of the inventory of long-lived and radiotoxic alpha, beta and gamma-emitting radionuclides present in radioactive wastes from Nuclear Power Plants is a critical parameter for a reliable categorisation of the waste in compliance with the existing disposal site regulations. Therefore it is very important to have access to reliable radiochemical and radioanalytical procedures which provide results with a high accuracy. The objective of the project was to perform an interlaboratory radiochemical analysis campaign on the destructive measurement of radiotoxic and long-lived radionuclides in a primary waste flux. The aims of the inter-comparison test were to: determine the accuracy and reliability of the different analytical methods applied in the different participating laboratories belonging to "European Network of Testing Facilities for the Quality Checking of Radioactive Waste Packages", compare, validate and harmonise the analytical methods used, detect discrepancies and shortcomings in routine analysis, which will help to identify whether a separation or measurement method needs further improvement. The project has been structured around six work packages: Work package 1. - Definition phase. The consortium agreed on the specifications of the samples to be compared i.e. type, volume, range of activity; transport time schedule; time period for the characterisation; data evaluation procedures and results presentations. Work package 2. - Sampling. Two different waste stream samples, agreed by the consortium, were analysed: one spent cation exchange resins and one evaporator concentrate. Representative samples of the resin and concentrate were homogenised, sorted, prepared and distributed under the responsibility of El Cabril-ENRESA. The representativity of each sample prior to its delivery was checked by gamma spectrometry. Real samples from LWR's were prepared. The transport of the samples was organised by ENRESA, according to applicable regulations. Work package 3. - Analysis of samples. The analyses of the different radionuclides were carried out in the laboratories belonging to the different contractors with the procedures used on a routine base. The nuclides analysed were 3 H, 1 4 C, 5 5 Fe, 6 3 Ni, 8 9 / 9 0 Sr, 9 9 Tc, 1 2 9 I, 2 3 8 Pu, 2 3 9 / 4 0 Pu, 2 4 1 Pu, 2 4 1 Am, 2 4 2 Cm, 2 4 4 Cm, 2 3 4 U and 2 3 8 U. The procedures were carried out on two aliquots from the initial resin sample and the separations were done on three different solutions collected from each aliquot. At the end, six results per nuclide were obtained.