Water radiolysis in fusion neutron environments

Cooling loop water chemistry is important for it dictates corrosion, and key safety and environmental issues. Martensitic and austenitic steels with plasma facing components (first wall, divertor), blankets, and vacuum vessel, have been used in the design of PPCS (power plant conceptual studies), DEMO and ITER. Under radiolysis, a rise in oxidation potential enhances material corrosion, with a corresponding increase in build-up of gamma field from transport of activated corrosion products to the heat-exchanger/boiler units. The cooling system requires scheduled maintenance that involves component checking and changing. Workers could potentially be exposed to an unusual ORE (occupational radiological exposure) due to deposits of active corroded material around the cooling loop. The activation transport and deposition code transport of activation (TRACT) uses approximate concentrations (based on empirical data) of injected hydrogen for suppression of radiolysis in fusion power plant cooling channels. While it is possible to measure at some point outside the radiation-zone the concentrations of the stable end-products, their concentrations inside the radiation-zone, along with the concentrations of the short-lived intermediates, can only be estimated through computer simulation. This paper presents the time–dependent transport code water radiolysis H2ORAD with example calculations, based on ITER and generic Power Plant studies. H2ORAD will be used to replace the empirical data of injected hydrogen for suppression of radiolysis in TRACT.