Heating rates in blankets of fusion reactors

Abstract

Spatially dependent neutron and gamma fluxes and their associated heating rates have been calculated for two separate breeding blankets of a conceptual fusion reactor. Both designs incorporate liquid lithium as the major coolant, but one has a structure of niobium, while the second is constructed of stainless steel, with some liquid sodium cooling. Calculations involving various energy group structures and degrees of anisotropy are also made to determine the effect of these parameters on the heating rates. All calculations were made with a program system specifically developed to determine the heating rates in conceptual CTR blankets. In the program system, transport theory is used to determine the gamma and neutron fluxes. For a 10 MW/m² loading of incident 14 MeV neutrons on the first wall, the maximum total heating rate obtained is on the order of 108 w/cm³ of which 100 w/cm³ are due to gamma ray interactions. This heating rate occurs in the first wall of a conceptual blanket which uses niobium as the structural material. The first energy group neutron flux (13.5 - 14.9 MeV) plays a dominant role in determining the heating rates in the blanket, not only in the energy deposited by this group itself, but also in producing the high energy gamma rays (12 - 14 MeV) which are responsible for 67% of the energy deposited by gamma rays in the first wall of a blanket of niobium construction.