Considerations on neutron/environment characteristics in inertial fusion ignition (NIF) and reactor (KOYO) facilities

This paper reviews reported calculations on the assessment of some environmental questions related to neutron activation in ignition (National Ignition Facility, NIF) and reactor (KOYO Project) inertial fusion facilities. NIF results on the availability of the target chamber after different gain shots, inventories of activated gases in the bay area, and comments on radiological impacts from normal operations have shown the good environmental qualifications of this facility. The laser fusion conceptual reactor KOYO, developed by the ILE Osaka, uses liquid LiPb film protection flowing through ceramic SiC-base porous tubes in two different packing fraction blankets. It is shown the availability of a large fraction of the SiC with impurities to be considered as class C shallow land burial (SLB); however, the complete solution for SLB is the use of porous woven graphite (C) fabric tubes. An important effect in the activation of the chamber wall, composed by the ferritic steel HT-9, is demonstrated by using an intermediate graphite reflector. A good activation performance in the chamber is demonstrated allowing SLB and different recycling options. Hypothetical environmental releases of 1 kg of target-emissions-facing SiC tubes and HT-9 materials have also been simulated indicating optimum performances.