Messung und Analyse von neutroneninduzierten Aktivitäten in Materialien zukünftiger Kernfusionsreaktoren

The radioactivity induced by neutrons in the materials of future fusion devices represents a central topic of safety- and environmental-related investigations. For the design and operation of future fusion devices, like the International Experimental Thermonuclear Reactor ITER or power plants like DEMO, the activation performance of the materials during operation and after shut-down has to be simulated. The European Activation System (EASY), consisting of the inventory code FISPACT and the activation library EAF, is the world wide reference system for these calculations. The activation of the fusion reactor materials, as well as the EASY system have to be tested experimentally. In the present work several samples of materials from the European fusion technology program were irradiated in neutron fields of DT neutron generators at TU Dresden and at Sergiev Posad near Moscow. The radioactivity following irradiation was determined several times during decay by ?×-spectroscopy. The results are analysed with EASY and ratios of the calculated-to-experimental activation (C/E) are determined, to find limits for the experimental validation of EASY. For the future improvement of EASY integral cross sections are obtained from these C/E and discussed in connection with the EAF data, energy differential measurements from the EXFOR System of the International Atomic Energy Agency (IAEA), other energy integral measurements and evaluated data from libraries in the JANIS system of the Nuclear Energy Agency (NEA). The investigated materials of the present work are Tungsten, Yttrium, CuCrZr and Lead. Tungsten is the preferred material for the divertor plates of fusion devices an a constituent of reduced activation structural materials. Yttrium is used in the ODS steels, which are candidate materials for the first wall and blanket structure of. The characteristic feature of ODS steels is to introduce Y2O3 oxide particles into structural materials like EUROFER to improve the high-temperature strength and to maintain superior radiation resistance. CuCrZr alloys are used as a heat sink in the first wall of the blanket and in the divertor. The CuCrZr alloys contain impurities in consequence of the production technology, which can have an influence on the activation performance and thus have to be known accurately. In this work the neutron activation analysis has proved to be an appropriate instrument to measure the amount of some special impurities. Lead acts as a neutron multiplier and coolant in breeding blanket concepts such as the European Test Blanket Modules (TBM) with liquid Pb-17Li. Due to some large discrepancies between the measured activities and those calculated with EASY for tungsten, these cross sections are analysed with recent models of the nuclear reaction mechanisms. The sensitivity of the obtained cross sections with respect to different reaction models and parameters is investigated and limits for new evaluations are obtained with respect to the experimental results.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Technische Universität Dresden

Year

2004

Author dc:creator

• Eichin, Randy

Contributors dc:contributor

• Freiesleben, Hartwig
• Fischer, Ulrich
• Vonach, Herbert

• Aktivierungsexperimente
• DT-Neutronen
• ITER
• Kernfusion
• Neutronenaktivierungsanalyse
• gering aktivierbare Materialien
• Activation measurement
• DT neutron field
• Nuclear Fusion
• low activation materials
• neutron activation analysis