Impact of the flowing activated water on maintenance and electronic functioning for the pre-conceptual design of the European DEMO fusion reactor

This paper is devoted to provide generic guidelines to facilitate the characterization of an important contribution to the radiation environment during operation and after the shutdown. This is fundamental to plan safe operation and maintenance of the European DEMO Fusion Power Plant. The study is focused on the estimation of activation responses to electronics and workers, in representative rooms of the DEMO building housing those pipes carrying activated water coming from the water cooled breeding blankets (WCLL BB). The prediction of some radiation-related quantities is needed in order to evaluate feasibility for functioning of rad-sensible components (e.g. electronic and electrical equipment) as well as for manual maintenance planning. The feasibility for placing rad-sensible equipment near the activated water pipes is determined by calculating the accumulated dose in silicon (due to both neutrons and photons), and neutron fluence rate. Besides, the viability for manual maintenance activities is evaluated by calculating residual dose rate for workers. These quantities are assessed in a representative room containing the pipes as well as in an adjacent room. In view of future developments on DEMO designs a parametric study has been performed and a compendium of different configurations is considered: several numbers of pipes, pipes dimensions and thickness of the wall separating both rooms are examined, as well as different delay times. Additionally, a study dedicated to the shielding improvement of both rooms is presented considering such parametric variations.