Rate theory modelling of radiation effects in bbc Fe at low temperature

Abstract

Consulta en la Biblioteca ETSI Industriales (7979)

[EN] Recent modelling has shown that irradiation effects at low temperatures, between 20¿100 oC, may differ in important ways from those at higher temperatures, typical for reactor applications. The reason is that phase stability between secondary-phase particles, e.g., copper precipitates, and the host material, is different. Some cases where this may be of importance, are the long-term storage of nuclear waste, with temperatures below 100 oC, and future fusion reactors, with temperatures down to room temperature. The aim of this project is to use reaction rate theory to model the evolution of defect clusters or secondary-phase clusters, in a varying irradiation environment, e.g., electron irradiation, neutron irradiation or ion irradiation, and specifically at low temperatures. In order to achieve this, an initial analysis to radiation effects is needed. It will help to better understand how the microstructure and composition of irradiated materials are affected by irradiation and as a consequence, the changes that it can produce on the macroscopic properties of materials: swelling, deformation and embrittlement. Many studies and investigations have been done and are still being carried out in order to determine the significance of these effects, for example, experimental studies and modelling of copper precipitation under neutron and electron irradiation. This work will try to go further focussing on the modelling of vacancy clustering at the crystalline lattice of Fe at low temperatures. With the new model simulating the point defect formation and diffusion during irradiation, all the assumptions and mathematical relationships taken into account were introduced in a computer code using, due to its great efficiency in computational physics, Fortran 90 language. It implements the solution of ordinary differential equations (ODE) by means of different iterative methods commonly found in the literature. As it will be displayed in the last chapters of this thesis, a cluster dynamics model is employed to obtain the evolution with the time of vacancy clusters as well as the effects of the changing environment on these cluster size distributions. Two main parameters are of great interest and depending on the adopted values the final result will be one or another. These are temperature and dose, and due to their importance, a special treatment of them will be done in the final part of this study.