Experimental determination of the surface rate constants of protium and deuterium in Eurofer97

The EUROFER reduced activation ferritic-martensitic (RAFM) steel is meant to be a firm candidate as structural material to be part of future fusion reactors. The correct definition of the transport parameters of hydrogen isotopes in these materials turns out to be a key issue in this field, as long as it can affect the operation of the reactor itself when quantifying the fuel inventory as well as the radiological safety of the whole facility.Traditionally the diffusion limited regime (DLR) of these kind of RAFM steels has been experimentally tested and values for the permeability and diffusivity have been published, showing some differences depending on the specific composition of the steel, the thermal treatment during the manufacturing processes, etc. However, these RAFM steels will have to operate also under conditions of pressure and temperature that will lead to surface limited regimes (SLR). In this case, there is much less information available and data for the adsorption and recombination constants is not so extensive.This work shows the results for a new set of experimental permeation measurements carried out within the EUROfusion program in order to determine the SLR. The surface rate constants of protium and deuterium were experimentally obtained for Eurofer97-3 at two different facilities (PermRIG at UPV/EHU and Thermoperm at CIEMAT), with consistent results that show a good agreement.