RESUMO
A systematic evaluation of activity concentrations of 3H, 63Ni and 14C by using the CIEMAT/NIST method has been carried out over time intervals of 4, 2.4 and 2.3 years, respectively. It proves that the CIEMAT/NIST method can compensate, with no need for additional checking sources or procedures, for count losses and quench parameter reduction in long-term measurements with LSC spectrometers and allows one to obtain very accurate activity concentration values by using a quench curve close to the nuclide measurements. If this requirement of the method is not fulfilled, significant discrepancies, up to 5.6% for 3H, 1.5% for 63Ni and 0.35% for 14C, can be obtained in only 1-year time difference.
RESUMO
In order to make quantitative assessments about the usefulness of different gamma-ray emitting radionuclide cocktails to carry out efficiency calibrations of gamma-ray spectrometers, a method has been developed that allows the comparison of their different performances and to optimize the choice of gamma energy lines for the radionuclides within a specific cocktail. The method has been applied to compare different cocktail configurations obtained from measurements made in the laboratory with monoenergetic radionuclides, and their relative performances are presented and discussed.
Assuntos
Algoritmos , Calibragem/normas , Teste de Materiais/métodos , Teste de Materiais/normas , Radioisótopos/análise , Radioisótopos/normas , Espectrometria gama/métodos , Espectrometria gama/normas , Teste de Materiais/instrumentação , Controle de Qualidade , Radiometria/métodos , Radiometria/normas , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Espanha , Espectrometria gama/instrumentaçãoRESUMO
Two solutions, one of 32P with a significant contribution of 33P, and another one of 204Tl were standardized by liquid scintillation counting in the frame of two intercomparison exercises organized by the BIPM in 2002. For the 32P solution, the counting efficiencies for 32P and 33P were obtained by the CIEMAT/NIST method. The individual contributions of 32P and 33P were determined by fitting a set of measurements to a function of the half-lives and counting efficiencies of both component nuclides. 204Tl was also standardized by the CIEMAT/NIST method using two counters, three scintillators, HiSafe 3, Insta-Gel Plus and Ultima-Gold, and two different kinds of samples. A total of 480 samples were measured over 45 days with results in full agreement within the uncertainties considered. The efficiency values are also compared to those used in the previous 204Tl intercomparison (1997).
