Radiolysis Experiments for the Aqueous Self-Cooled Blanket. Final report

The results of Fusion Technology Task NAB 1.1 (Radiolytic Experiments for the ASCB), are reported . In the Aqueous Self-Cooled Blanket (ASCB) concept, an aqueous 6Li solution in a metallic structure is used as a shielding-breeding blanket for fusion reactors. Radiolysis could be very important with respect to the design and the use of an ASCB. The objectives of this project were to quantify the radiolytic decomposition of neutron irradiated aqueous lithium solutions and to demonstrate, if possible, the suppression of this decomposition by the initial addition of a small amount of hydrogen. Closed capsules, with the solutions and an inert gas or hydrogen as cover gas, were irradiated with thermal neutrons in a fission reactor. Radiolysis products hydrogen and oxygen (from hydrogen peroxide) as well as tritium were measured after irradiation. Tritium served as an internal dosimeter. The experimental results with LiNO3 , Li2SO4 and LiOH solutions indicate that the radiolytic gas production in an ASCB is proportional to the absorbed radiation energy. The observed radiation chemical yields allow the preliminary estimation of the radiolysis effects for a specific ASCB design. Contrary to the theoretical predictions, the use of hydrogen as a cover gas at up to 1 MPa had no measurable effect on the radiolytic gas production. Probably it will thus not be possible to suppress the radiolytic decomposition of a low-pressure ASCB by the addition of H2. Catalytic recombination will be required