Codeposition of deuterium with ITER materials

Abstract

Abstract:The levels of retention in codeposited layers of each of the three ITER materials (C, Be and W) are compared.Scaling laws, based on the conditions during the codeposition process (surface temperature, incident particle energy and ratio of the depositing fluxes), are presented to allow prediction of expected retention under ITER conditions. Retention in carbon codeposits scales inversely with incident particle energy, whereas in the metallic codeposits the retention level scales proportional to increasing particle energy. The differing scaling of retention with incident particle energy provides insight into which material may impact the global retention in ITER depending on where it may form codeposits. In addition to the amount of retention, the release behavior of tritium from codeposits will influence the tritium accumulation rate within ITER. The thermal release behavior of T (or D) from codeposits can be used to evaluate the effectiveness of baking at different temperatures as a means of tritium removal. Finally, the desorption kinetics from Be and W codeposits are contrasted. In the case of W codeposits, the duration of the baking cycle is important in determining the removal efficiency, whereas with Be codeposited layers, the maximum achievable bake temperature plays the leading role in determining removal efficiency.

Multi machine scaling of fuel retention in 4 carbon dominated tokamaks

“…The scaling described in section 3 uses the D/C ratio estimated from [17] with the local surface temperature calculated for the PFC substrate. However, codeposition will lead to C layers deposited either in areas in view of the plasma conductive or radiative heat loads, in which case they will be hotter than the surrounding PFC substrate due to their bad thermal conductivity, or in remote areas hidden from heat fluxes, in which case they will be colder (typically the local cooling temperature of the PFC).…”

“…• Step 4 : estimate of the D retention rate using D/C ratio scalings as a function of incident energy and wall temperature [17], which can play a prominent role in the D content of the deposited layers.…”

“…The same procedure is applied to the 4 tokamaks involved for comparison with experimental retention rates, except that a fixed value is used for the D/C ratio instead of the scaling of [17]. Two options were considered : D/C=0.1 corresponding to redeposited layers found in areas exposed to the plasma (TEXTOR, TS), or D/C=1, corresponding to soft layers found in remote areas (JET, AUG) [2].…”

Recent analysis of key plasma wall interactions issues for ITER

“…Co-deposition is the incorporation of hydrogen in deposited layers where impurity For deuterium co-deposition in W few data exist and the values are often close or below the detection limit of the measurements [80,75]. These low values combined with the very low erosion yields of W lead to the conclusion that co-deposition with W or WC will not be a critical process for ITER.…”

Some Thoughts About Beryllium Resources, Impurities in It and Necessity of Its Detritiation After Irradiation

“…Здесь уместно заметить, что 3 H, соосаждённый с Be, при взаимодействии плазмы с поверхностью вакуумной камеры удаляется при существенно более низкой температуре (около 350 ºС) [38,39].…”