The influence of hydrogen isotopes on the behaviour of crystal lattice defects in tungstenPečovnik, Matic (Avtor) Markelj, Sabina (Mentor) Hydrogen isotopestungstenhydrogen isotope retentionlattice defectsdefect stabilizationmacroscopic rate-equationsTungsten (W) is one of the primary candidates for a plasma facing material in future fusion tokamak reactors, as it has good thermal properties and low intrinsic hydrogen isotope (HI) retention. Unfortunately, HI retention will be increased by many orders of magnitude due to HI trapping in lattice defects created by 14 MeV neutrons originating from the fusion reaction. To study HI retention in displacement damaged W, usually laboratory experiments are used that employ MeV W ion irradiation to create displacement damage and deuterium (D) exposures of various types to populate the created damage. The results of such experiments are modelled using macroscopic rate equations (MRE) to determine the characteristics of the interaction between the displacement damage and HI. Recently, laboratory experiments have been conducted where MeV W ion irradiation of the material was performed while the material already contained or was simultaneously exposed to D. They showed that the presence of D during W ion irradiation increases the amount of created displacement damage compared to the case when no D is present. Although efforts have been made to explain this so-called stabilization effect of D using existing MRE models, they were not able to adequately explain the observed experimental results. In this work, we have upgraded an existing displacement damage creation model by coupling a displacement damage creation model with the kinetics of D transport and trapping. The increase of the defect density due to the presence of D was parametrized by a stabilization factor. The new displacement damage creation and stabilization model’s physical meaning is based on the assumption that defects that contain at least one D have a smaller probability of annihilation as compared to D-free defects. The model was included into the existing MHIMS-R code, which was primarily designed to replicate experiments that studied HI transport and retention. We were able to reproduce the results of two laboratory experiments available in the literature where in one case the D was present during the damage creation and in the second case the D was introduced into the sample with a prior D exposure. Despite the fact that the experiments studied D-induced stabilization with different experimental procedures, the simulation reproduced the results with similar values for the stabilization factors. Using newly gained insights, we performed several follow-up experiments. These include higher D and W flux and fluence experiments and an experiment which is a combination of the previously conducted experiments. These tested the predictions made by the model, which were mostly confirmed. However, the higher flux experiment could not be adequately reproduced, as the data showed that stabilization depends on the number of trapped D in a defect which was not included in the model at the time. For this purpose, a generalized model was developed which is backwards compatible and makes the model applicable for an even wider range of W and HI fluxes and sample temperatures. We have also conducted experiments in which we studied the influence of D on defect evolution at elevated material temperatures. No significant effect of D presence was observed. The experimental results were reproduced using the MHIMS-R code with which the annealing behaviour of individual defects at temperatures between 300 and 800 K has been determined. Based on the observed behaviour, we have developed a vacancy/vacancy cluster evolution model.20212021-03-28 08:15:04Doktorsko delo/naloga125631sl