Fusion power studies provide insight into physics and technology issues that need addressing to develop fusion as an optimal electricity generation alternative in the near future. As part of them, calculations are performed of different parameters important for the safety and environmental assessments of power plant concepts based on magnetically confined burning plasmas. These assessments help optimise such concepts, and involve many different physics disciplines and the use of large computational codes and nuclear databases. The work presented in this thesis has been developed within the Fusion Technology group of the UKAEA Fusion Division, under the framework of the European Power Plant Conceptual Study. For the safety and environmental assessment of four different fusion power plant concepts, estimations were made of the amount, characteristics and radiotoxicity of the activated material arising from neutron irradiation of the structures. Results were used to analyse: (a) public safety, through the bounding accident analysis, obtaining maximum temperature excursions following hypothetical, internally-driven, worst-case accidents, and (b) the radioactive waste arising from the operation of the plant, and in particular the possibility to re-utilise some of the irradiated material. Calculations were assisted by, and helped in the development of, a new computational tool coupling the neutron transport, activation and thermal analyses to the same three-dimensional geometry