NEUTRONIC CALCULATIONS FOR A MAGNETIC FUSION ENERGY REACTOR WITH LIQUID PROTECTION FOR THE FIRST WALL

Liquids may be used between the magnetic confined fusion plasma and th e first wall of the plasma chamber to reduce the material damage throu gh displacements per atom (dpa) and helium gas production. This could extend the lifetime of the first wall in a magnetic fusion energy (MFE ) reactor to a plant lifetime of similar to 30 yr. Neutronic calculati ons are carried out in S16P3 approximation for a typical HYLIFE-II bla nket geometry, an inertial fusion energy (IFE) reactor design. This pr ovides a comparison of the damage data between compressed and uncompre ssed targets, for IFE and MFE applications, respectively, by using Fli be (Li2BeF4), natural lithium, and Li17Pb83 eutectic as both coolant a nd wall protection. In the consideration of mainline design criteria, including sufficient tritium breeding ratio (TBR = 1.1), material prot ection (dpa <100 and He<500 parts per million by atom in 30 yr of oper ation), and shallow burial index, coolant zone thickness values are fo und to be 60 cm for Flibe, 171 cm for natural lithium, and 158 cm for Li17Pb83 With Type 304 stainless steel (SS-304) as structural material . Material damage investigations are extended to structural materials made of SiC and graphite for the same blanket to obtain waste material suitable for shallow burial after decommissioning of the power plant. The dpa values and helium production rates in graphite are comparable to those in SS-304. However they are higher in SiC than in SS-304 and graphite. The average neutron heating density in the external 1.6-mm- thick SS-304 shell of the investigated blanket beyond the SiO2 insulat ion foam decreases rapidly with increasing thickness of the Flibe cool ant With DR = 60 and 80 cm, it becomes only 594 and 95 mu W/cm(3) resp ectively. The design limit for heat generation density in superconduct ing coils for magnetic fusion is 80 mu W/cm(3). A very important resul t of this work is that a blanket with liquid-curtain protection would not require extra shielding for superconducting coils around the fusio n plasma chamber. This could result in an important simplification of the design.