Experimental validation of transmutation products calculations in neutron irradiated tungsten

Abstract

Neutron irradiation can significantly alter the elemental composition of a material by generating transmutation products through nuclear reactions between neutrons and atomic nuclei. These changes in composition can substantially impact the material's physical and mechanical properties. Therefore, accurately assessing the buildup of transmutation products in neutron-irradiated materials is essential for understanding and predicting these effects. Tungsten (W) is particularly critical for the first wall and divertor components in fusion reactors. As such, an accurate assessment of transmutation products in neutron-irradiated tungsten is crucial for the safety and lifespan of future fusion power plants. The scope of the present work is to experimentally validate calculations of transmutation products buildup in tungsten after neutron irradiation at the Materials Test Reactor (MTR) BR-2 at SCK CEN, Belgium. Tungsten specimens were irradiated to doses of 0.12 and 0.19 displacements per atom (dpa) within the temperature range of 600 to 1200 °C. Nuclide inventory calculations were performed using the FISPACT-II code and the TENDL-2019 cross-section library. γ-ray spectroscopy was employed to determine the specific activity levels of ${}^{181}W$, ${}^{185}W$, ${}^{188}W$, ${}^{188}Re$ and ${}^{182}Ta$ in order to validate the transmutation products calculations for rhenium (Re), osmium (Os) and tantalum (Ta). It is shown that the theoretical calculations for Re and Os concentrations are in good agreement with the experimental data, while the Ta concentration is underestimated by a factor of approximately 1.5.