Radioprotection Analysis for Working Activities at the Cooling System of the Thermonuclear Fusion Experimental Facilities

Lungotevere Thaon di Revel, 76 - 00196 Roma, Italy

Abstract: The development of technologies for nuclear fusion plants in recent years has highlighted the need for the consideration of radiation protection aspects. It is important to demonstrate, for this type of plant, the lower impact on the health of workers and the population to integrate the justification for these methods, with the prospect of producing energy with alternative plants based on nuclear fission. From this point of view, a critical aspect concerns the generation of Activated Corrosion Products (ACPs) in the refrigeration systems of fusion reactors under construction or design. The refrigeration of such reactors can essentially happen with three typologies of coolant: water, liquid metals and gas. For the first case some analyses are available, conducted at international level for experimental reactor, as for example ITER (International Tokamak Experimental Reactor). In the second case studies finalized to the doses evaluation practically do not exist. For the reactors cooled with gas, the only radioactive contamination of cooling circuit is the “sputtering”, produced by the impact of the neutrons on the structural materials surface. In the case of the gas the corrosion products do not exist, because the reference gas, the helium, is chemically inactive. The present job underlines the doses results into the systems of water refrigeration, proposing procedures already used and the results achieved in some cases, and analyzing the different problem concerning the liquid metal systems. The introduced study considers the processes of activation of the constituent circuit materials for refrigeration system, the phenomena of erosion and corrosion, the transport of corrosion activated products in the circuits, the accumulation of these in the principal components. Finally, the individual dose evaluations of different working activities (safety operations and maintenance performed after the shut-down plant) are assessed and discussed.