IMPROVEMENT OF A RADIOCHEMICAL LABORATORY THROUGH FOURTEEN YEARS OF PARTICIPATION IN AN INTERCOMPARISON PROGRAM

摘要

CNEN's radiochemistry laboratory in Pocos de Caldas has been participating in the14 years National Intercomparison Program (NIP) for the analysis of radionuclides in environmental samples. The program is conducted by the Radioprotection and Dosimetry Institute of CNEN. Three times a year, this program distributes simulated environmental samples which contain one or more radionuclides and the results of the analyses are sent for statistical and analytic performance evaluation. Each round, a report that allows performance to be evaluated and procedural or instrumental problems to be identified and corrected is sent to the participating laboratory. Participation in the program has improved analytical techniques in the determination of radionuclides and has introduced advancements in laboratory practices which have reduced many sources of uncertainty. Statistical parameters are applied to the analytical data in order to show the performance of the laboratory. The variable coefficient of three measurements that have been performed is related to standard deviation and the accuracy is precisely related to the reference value. During the period of the study, various changes in analysis methods and the acquisition of new reagents were introduced, not just to achieve better performance in the exercises but also to develop methodologies for other radionuclides which are necessary for regulatory control of the nuclear fuel cycle and are offered during the intercomparison program rounds. The improvements have been pointed out in the graphs that are included here. The data base was made up of 43 runs from 1992 to 2005, with 730 radionuclide analyses, ~(226)Ra, ~(228)Ra, ~(210)Pb, natural uranium and its isotopes, thorium, ~(90)Sr, ~(241)Am, total alpha and beta, approximately 10 gamma emitters and ~(238/239)Pu, in water, vegetation, soil and aerosol filter. The evolution of our results which were demonstrated by the results of the intercomparison allowed us to implement radiochemical analysis training programs for other CNEN laboratories and for research laboratories of both universities and private enterprises.