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The prediction of erosion and co-deposition processes for ITER is necessary information for the design and material choice of the first wall. A model has been developed that describes this coupling of local erosion to the global impurity transport and re-deposition processes in a self-consistent way. The erosion and deposition on each surface element of first wall is described by an ordinary differential equation (ODE). The resulting system of ODEs is coupled via the impurity influx, which is derived from the re-distribution of the erosion fluxes through the global impurity transport as calculated by DIVIMP. As a test case, the model is applied to a standard ITER reference discharge calculating the re-distribution of Be, C and W inside the ITER vessel with time.

Numerous experiments have been performed in the past few years on solid hydride deposition under berylliumseeded plasma action or on energetic hydrogen implantation into metallic beryllium. This article reports on calculations carried out using first-principles density functional theory (DFT) and discusses the results with respect to thermal desorption experiments. The structures of amorphous beryllium hydride were investigated for various H/Be ratios. They were compared to the structure of the organized BeH 2 crystal as a test for the validity of this model. The formation and reactivity of atomic vacancies were also investigated, together with atomic hydrogen trapping. Hints are proposed for hydrogen detrapping mechanisms.

In this contribution we present results from the first N 2 seeding experiments in JET performed after installation of the ITER-like Wall. Gas balance measurements for seeded L-mode 2 possible influence of ammonia production on this apparent retention is discussed. Plasma parameters and impurity content were monitored throughout the seeded discharges as well as during subsequent clean-up discharges. These experiments give first insight into phenomena related to the use of nitrogen as seeding gas in JET with the ITER-like Wall, such as ammonia production and nitrogen legacy.

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