Modelling neutron damage effects on tritium transport in tungsten

Abstract

A damage-induced hydrogen trap creation model is proposed, and parameters for tungsten are identified using experimental data. The methodology for obtaining these parameters using thermo-desorption analysis spectra data is outlined. Self-damaged and optionally annealed tungsten samples have undergone TDS analysis, which has been analysed to identify the properties of extrinsic traps induced by the damage and to determine how they evolve with damage and annealing temperature. A parametric study investigated the impact of the damage rate and temperature on tritium inventories in tungsten. Tritium transport simulations have been performed with FESTIM considering a 1D model of a 2 mm sample of tungsten with damage rates and temperatures varying from 0– ${10^{2}}$ dpa/fpy and 600–1300 K, respectively. The results show that after 24 h simultaneous exposure to neutron damage at ${10^{2}}$ dpa/FPY and tritium implantation at 700 K, tritium inventories can increase by up to four orders of magnitude when damaged at a rate of ${10^{2}}$ dpa/FPY compared to undamaged, defect-free tungsten, increasing further to five orders of magnitude after one full power year. The time taken to reach retention saturation shows the need for kinetic models of trapping properties on time scales relevant to reactor operation. The trap-creation model parameterisation procedure can be used to investigate neutron damage effects on other fusion-relevant materials such as EUROFER, Inconel and more.

Keywords

• tungsten
• neutron damage
• annealing
• trapping
• tritium transport