Development of a Neutron Activation Analysis station at the Lund Ion Beam Analysis Facility

Detta är en Kandidat-uppsats från Lunds universitet/Kärnfysik; Lunds universitet/Fysiska institutionen

Sammanfattning: This report outlines the first stages of the development of the Neutron Activation Analysis station at the Lund Ion Beam Analysis Facility in the Division of Nuclear Physics, Lund University. The motivation for this project is to use the Neutron Activation Analysis detection technique for environmental monitoring around the European Spallation Source, soon to come into operation. In the event of an emergency scenario, some radiotoxic isotopes may be released into the environment from the Tungsten spallation target, including the difficult to detect lanthanide, 148Gd. In normal operation, a variety of radionuclides may also be released. In this initial stage, the aim was to build a measurement station which is able to measure very short-lived activation products, and to investigate if it is possible to trace gadolinium isotopes in environmental samples using neutron activation analysis. The measurement station was constructed over the span of one semester, and a selection of metal foils and environmental samples were activated and analysed. The samples were irradiated using a portable neutron generator with a maximum production rate of 4.71 ·10E8 n/s. Two methods of measurement were utilised: one which used irradiation- and measurement- times of longer than one hour, and another which used a fast pneumatic transport system with irradiation- and measurement-times of less than 1 minute. High Purity Germanium detectors were used to measure the γ-rays emitted from the activated samples. Results showed that with the selection of tested samples, it was possible to measure activation products with half-lives as short as two seconds using the fast pneumatic line. In the environmental samples, it was seen that amounts larger than several grams were needed in order to see activation and that longer irradiation time was more suitable. The results obtained show that the station has the potential to be developed for use with the Compact Accelerator-driven Neutron Source under development at the facility, which is anticipated to achieve a neutron production rate of 10E11 n/s.

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