Abstract
Molybdenum is being considered as a potential material for future nuclear fusion experiments and power plants. It has good thermo-mechanical properties and can be easily fabricated, making it attractive as an alternative first wall material to tungsten, which is the current leading candidate. Unfortunately, according to simulations, fusion-neutron irradiated Mo may become too activated during reactor operation to maintain the objective of fusion of avoiding the generation of long-term, higher-level radioactive waste.However, these simulated predictions rely heavily on having high-quality, accurate nuclear reaction data. For example, reliable simulations of the radiological response of isotopically-tailored Mo would be required by reactor designers and eventually nuclear regulators to assess if it is a viable low-activation fusion solution (in comparison to pure Mo). In recent years, UKAEA has developed benchmarks to test and validate the FISPACT-II inventory code and the input international nuclear data libraries against experimental measurements. This paper presents nuclear code prediction comparisons to new data acquired from γ-spectroscopy measurements of Mo irradiated in the ASP 14 MeV facility at AWE in the UK.Results demonstrate that FISPACT-II predictions for Mo are remarkably accurate; particularly for activity generated from the shorter-lived radionuclides explored by these laboratory experiments, such as91Mo and97Nb, etc., and their metastable isomeric states.
Highlights
MOLYBDENUM AS A FUSION MATERIALMolybdenum is often proposed as an alternative material for the high neutron flux and high thermal load regions – the plasma-facing components (PFCs) – of nuclear fusion devices [1,2]
This paper describes recent efforts at UKAEA to test and validate the nuclear data libraries used with FISPACT-II, focussing on important nuclear reactions for Mo
The present experimental validation efforts for nuclear inventory code predictions of 14 MeVneutron-induced activity in Mo have shown that the simulation methodology (FISPACT-II) and underlying nuclear data are reasonably successful. γ-spectroscopy-derived activation estimates for radionuclides produced in Mo foils irradiated at the ASP 14 MeV-neutron source in the UK have provided a wealth of new data to test code predictions against
Summary
Molybdenum is often proposed as an alternative material for the high neutron flux and high thermal load regions – the plasma-facing components (PFCs) – of nuclear fusion devices [1,2]. High neutron capture cross sections could be a problem for fusion, in that case, molybdenum’s potential application in fusion PFCs would not be concerned with thermal neutron capture as such locations in a reactor are overwhelmingly dominated by fast, 14 MeV neutrons (i.e. the neutron energies generated as a result of the deuterium-tritium [DT] fusion reaction), but it could be a concern if Mo is used in significant concentrations in the tritium-breeding zone, where the loss of neutrons in a material with a high absorption cross section could impact on the TBR (tritium breeding ratio) [11] Predictions such as those discussed in [2] rely on accurate nuclear code simulations. This paper describes recent efforts at UKAEA to test and validate the nuclear data libraries used with FISPACT-II, focussing on important nuclear reactions for Mo
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