Chemistry and Corrosion in the irradiated cooling circuits of a prototype fusion power station

Irradiated water cooling circuits in the EU DEMO fusion reactor will experience a combination of conditions which has the potential to influence the performance of coolant-facing structural materials. In common with LWR primary circuits, heat transfer plant in the Breeding Blanket, Divertor and First Wall locations will be exposed to high temperature, high pressure water within an intense neutron and beta/gamma irradiation field. The neutron energy of 14 MeV is significantly higher than thermal fission plant and components will experience significant fluences over their expected plant lives. In addition, the influence of strong magnetic fields and highly tritiated water (due to tritium fuel breeding) are possible exacerbating factors which are less well understood. In order to ensure that the possible effects of these parameters are adequately controlled, a conceptual water chemistry programme has previously been proposed and is now under development.

This paper outlines several strands of work that are ongoing to address these challenges within a wider technology development programme under the EUROfusion framework, and their implications to the further chemistry programme development:

• Review of relevant operating experience from fission LWR plant
• Radiolysis modelling to assess options for suppression of oxidising species under high energy neutron irradiation
• High temperature water corrosion testing for chemistry optimisation
• Influence of intense magnetic fields and tritium on high temperature corrosion
• Approaches for assessing environmental degradation of highly irradiated new materials

The project aims to further transfer experience from the worldwide fission power station fleet as well as being a strategic theme for capability development in the UK with relevance to near term new build and small modular reactor designs.