Determination of Th, U and K contamination in materials used in a low background detector by nuclear measures

In a low background detector high contamination of U, Th and K in the materials used couldn’t be accepted. All materials furnished should be tested and measures optioned have a sensibility of E-11/E-12 g/g. Such measures need an adequate irradiation time and flux. An optimum cooling time and other parameters should be optimised in order to reach the goal. Analysis are made by Neutron Activation Analysis (NAA) while analysis of the natural gamma activity are made by long time measures in a low background detector.