Determination of HTM-nuclides in Materials from Research Reactor Decommissioning

During the dismantling of the ASTRA-research reactor in Seibersdorf, Austria, materials were accumulated that must be either disposed of as radioactive waste or released for reuse or disposal as ordinary waste. Radiological assessments are necessary for all of these materials, thus gamma counting has to be performed, and for pure beta-emitters, nuclide vectors have to be established on a limited number of samples. The methods and results for two types of samples, aluminum metal and barite concrete, both irradiated with neutrons, are presented. The analyses were accomplished by gamma spectrometry and by LSC after appropriate chemical separation. In order to estimate the activation processes, a simple mathematical model was set up, enabling a check for the plausibility of the results and an assessment of the neutron flux. There was a fair agreement of the measured and calculated activity concentrations for most of the nuclides.