Use of polyethylene consumables in neutron activation analysis for short-lived radionuclides

The neutron activation analysis for short-lived radionuclides at the WWR-K uses a pneumatic transport system (Austria) with specific transport capsules. The irradiated samples are not removed from the transport capsules and are measured directly in the capsule. It is necessary to take into account the fact that the induced activity of the capsule material itself acts as the background radiation in relation to the induced activity of the sample under study. A study of the capsule material and the polyethylene tubes used as sample fixing devices in the center of the transport capsule was performed. Earlier it was found that the HDPE T50 capsule material contains impurity elements Ti, Cl, Al, Na, Ca. It was found that the fixing material contains a larger amount of impurities, which leads to the increase of spectrometric equipment loading and to the increase of relative contribution of individual radionuclides to the final spectrum. The induced activity spectra were analyzed and processed, the content of elements in polyethylene was calculated and it was shown that the analytical signals of Mg-27, Mn-56 and Sb-122m, Cr-51 and Sb-122 refer exclusively to the induced activity of the fixer-tube material. This circumstance does not allow to determine small concentrations of these elements in the samples themselves. The necessity of search of other more pure material for its use as sample fixers at placement in a transport capsule is shown.