Revised scaling equation for the prediction of tritium retention in beryllium co-deposited layers

The prediction of tritium retention in ITER relies on the extrapolation from present data. An empirical equation was proposed in (De Temmerman G. et al 2008 Nucl. Fusion 48 075008) to account for the influence of the beryllium deposition rate, the substrate temperature and the average energy of the deuterium neutrals on the deuterium retention. However, the beryllium deposition rate observed in PISCES-B is much lower than that expected in the ITER divertor. On the other hand, the flux ratios of deuterium and beryllium are comparable in magnitude. Therefore, a revised scaling equation is proposed here to take into account the flux ratio of deuterium to beryllium arriving at the co-depositing surface and to match the validity range of the scaling equation with the ITER parameters. (letter)