Overview on Neutronics, Safety and Radiological Protection of HiPER Facility

Full text: The HiPER facility is conceived to be a high repetition inertial fusion experiment dedicated to demonstrate the feasibility of the laser driven fusion. The most demanding irradiation scenario could consist in 100 MJ neutron yields, with 10 Hz repetition rate, 100 shots per burst and one burst every month, and 20 years of lifetime. The target bay should be defined to withstand this scenario. For this paper we consider that the target bay consists on the reaction chamber, a shielding for the chamber, disposable lenses, and an optical final assembly with its own shielding. The study is divided in three phases linked to different moments of the reactor lifetime: irradiation periods, cooling time between bursts and waste management after 20 years of operation. A major attention is paid in this paper to the waste management of the facility. The waste management assessment is made considering the alternatives: Near-Surface Burial, Clearance and Hands-on and Remote Recycling. The quantities identified as relevant are: Contact Dose Rate, Decay Heat and Waste Disposal Rate and Clearance indexes. Taking into account the waste management assessment, we suggest a choice for the reaction chamber material among several candidates (aluminum alloys, ferritic and austenitic steels and their reduced-activation versions). Special attention is paid to the presence of impurities. During the irradiation periods, we have studied the prompt dose rates, as well as the primary damage component, such as gas production, deposited energy, atom displacement and materials activation. Derived from this study, we calculate and propose different shielding for the reaction chamber and for the final optic assembly. It is possible also to offer an estimation of the lifetime of some pieces. In the cooling time between burst we have studied problems associated to the activation of the materials. With calculations of the residual dose rate in the whole target bay, we propose possible maintenance and replacement planning and strategies (hands-on or remote). (author)