Progress in establishing the influence of intense magnetic fields and other fusion-specific factors on high temperature water corrosion

Chemistry regimes for coolant circuits of commercial LWR plant have been developed over several decades to optimise corrosion control, radiation fields and performance, based on the technical drivers for different plant types. Future power stations using high temperature irradiated water as a heat transfer medium will need to undertake similar chemistry programme development with consideration of their own characteristics, requirements and constraints. For the EU DEMO prototype fusion power station, this is an ongoing process which requires underpinning of some comparatively unusual factors specific to this heat production technology, in particular magnetic fields and tritiated coolant. Intense magnetic fields are present to confine the fusion plasmas, and extend to coolant circuit locations, with peak field strengths in the region of 4-10 T, depending on location. The possible impact of magnetic fields on corrosion in this context has been reviewed recently and some initial experimental trials undertaken, which indicated that there is the potential for an effect. Further work is reported here aimed at identifying the nature and extent of any impact on corrosion behaviour of the main circuit materials, Eurofer-97 and AISI 316LN in high temperature water (330°C at 155 bar). In addition to magnetic fields, the DEMO deuterium-tritium fuel cycle requires the breeding of tritium which results in a high level of coolant tritiation. This has also been suggested as a possible influence on corrosion and further examination of relevant literature and experimental approaches is outlined.