Development of Power Generation Blanket
What is the structure of the power generation blanket ?A power generation blanket consists of the envelope box and the internal breeding region. The internal breeding region consists of the tritium breeder layers (Li2TiO3 etc.) and neutron multiplier layers (Be, etc.). The envelope box receives the heat load from the plasma, therefore, it has embedded cooling channels inside the wall structure.
Tritium breeder layers and neutron multiplier layers are packed with the pebble beds whose diameters are smaller than 2mm. Helium purge gas is flown in the pebble beds to recover the generated tritium gas. Inside the breeding region, the cooling tubes were attached. Coolant which is heated by the nuclear heat of the breeder and multiplier to high temperature is sent to the power generation turbine system and produce electricity.
Why pebble beds ?
3 requirements to the tritium breeder and neutron multiplier 1) Control expansion ： Relax stress concentration to the envelope box. 2) Avoid thermal stress cracking ： Avoid plugging of the helium purge gas by micro-powder formation by the cracking. 3) High density packing ： Increase thermal conductivities of the packed beds and obtain higher tritium breeding ability. To meet such requirements, pebble beds were adopted. Thermo-mechanical performance of the pebble beds are being evaluated.