Influence of high magnetic field on fusion reactor blanket processes

During operation of a fusion reactor, materials and processes of blanket zone will be subject to high temperatures, intense fast neutron radiation and action of intense magnetic field. MF changes kinetics of chemical reactions of high energy as a result of spin transformation, diffusion parameters of charged particles. An alternating MF can induce e.m.f. in materials. Changeable processes of this kind in the blanket may be radiolysis of ceramic materials (colloid Li and O2), tritium release from ceramic and Be pebbles, corrosion processes between ceramics and structural materials, tritium permeation. Up to now, influence of MF was studied for the most part on previously irradiated materials (PIE). The following research results are described in this study: influence of MF on radiolysis of Li4SiO4 and Li2TiO3 pebbles, tritium release from irradiated ceramic and Be pebbles, preliminary results about mutual corrosion of ceramics and EUROFER 97 at high temperature under radiation. Irradiating the ITER and DEMO relevant Li4SiO4 (FZK) and Li2TiO3 (CEA) pebbles at different temperatures with fast electrons (5 MeV), MF of 1.4 T increases the radiolysis by 20%-25%. The effect is related to the change of spins of primary excitons of the matrix in MF, resulting in an increase in the efficiency of formation of radiation-induced defects and products of radiolysis. MF of 2.4 T delayed by 40% the tritium release at thermo annealing to 1120 K of the Li4SiO4 pebbles (FZK) irradiated in the EXOTIC-8/8 experiment. The effect may be related to lengthening of the diffusion path of T+, as a main form of localised tritium, in the volume of ceramic grains (the grain size 30-40 μm). In the Be pebbles irradiated in the BERYLLIUM experiment, tritium is localised in the T2 and T0 chemical forms. As, for the most part, diffusion of T0 ensures the tritium transfer in the Be grain volume, MF delays the tritium release. The delaying effect of MF is related to the decrease of T0 as a result of spin change of an uncorrelated T0 ... T0. On the other hand, under the simultaneous action of ionising radiation, MF increases considerably the tritium release by up to 80%. The facilitating effect of MF may be caused by spin change from singlet to triplet state in a correlated pair of radicals generated as a result of T2. (author)