Integration of DEMO hazard piping into the tokamak building

•An overview of the main design issues of DEMO Tokamak building is given.•The functions of the Tokamak building and the layout criteria are defined.•The lesson learned from ITER tokamak layout definition are discussed and preliminary solutions are presented.•The potential hazards present in the Tokamak building and the relevant mitigation systems are outlined.•The importance of an early and integrated development of the main DEMO systems (included the variants) and of the Tokamak building is pointed out. Because of the complexity of the design of a Fusion Power Plant like the EU DEMOnstration power plant the study of the plant layout must proceed in parallel with the design of the major systems. This is necessary to ensure that the design of the plant incorporates from the very beginning sound considerations on: •Safety and licensing,•Personnel security in context with operation and maintenance,•Adequate plant availability, and•Safe performance operation including delivery of few hundred MW net electric power to the electrical grid. Though it is a process of trial and change that follows the design evolution, this approach allows a better and continuous control of the numerous physical and functional interfaces among the systems and structures assuring an optimization of the overall design focused on the above targets. Some of the fluid systems inside the tokamak building are activated e.g., water coolant circuits of in-vessel components containing activated corrosion products (ACPs), radioactive N16 and N17 isotopes generated from neutron irradiation of oxygen, as well as the Lithium-Lead (LiPb) system containing ACPs and radioactive isotopes generated by neutron activation of the LiPb alloy. The layout of the corresponding circuits must consider constraints such as shielding, inspection, maintainability and irradiation lifetime of some equipment of other plant systems located in the tokamak building, e.g. electric and electronic equipment, organic seals of valves, and relevant actuators. Furthermore the personnel exposure during operation and maintenance has to be as low as reasonable achievable. The experiences of Nuclear Power Plants and ITER (International Thermonuclear Experimental Reactor) are an important input to the layout of the DEMO coolant circuit. This paper presents some initial considerations on the criteria to be used for the layout criteria inside the tokamak building.