Hydrogen retention in high-Z materials with various contents of carbon

In order to estimate hydrogen retention and recycling in high-Z plasma faci ng components, bulk hydrogen retention in molybdenum and tungsten cct-exist ing with carbon has been studied. Hydrogen retention in powdered specimens of molybdenum and tungsten is considerably higher than that in sheet specim ens due to surface impurities and defects. When molybdenum and tungsten are well carbonized, bulk hydrogen retention is drastically reduced. Coexistin g carbon strongly suppresses hydrogen diffusion to reduce absorption rate i nto the specimen. Ion and neutron irradiation may produce Free carbon to en hance the hydrogen retention in molybdenum and tungsten. (C) 1998 Elsevier Science B.V. All rights reserved.