TRITIUM RETENTION CHARACTERISTICS OF SEVERAL LOW-Z MATERIALS

The conditions that exist in a fusion reactor often require very specialized materials. In locations where there is interaction with the plasma, it is desirable to have the material composed of low-Z elements to minimize radiative cooling of the plasma. While graphite and beryllium are low-Z and satisfy many of the requirements for plasma-facing components, there are problems associated with their use that leads the fusion designer to search for alternative materials. As part of this search, the tritium retention characteristics of boron doped graphites, boron nitride, and silicon carbide have been measured in laboratory experiments. Experiments performed with USB-15, a boron-doped graphite, show boron-doping to suppress the retention of tritium in graphite. The silicon carbide results reveal a very low apparent solubility for tritium. The behavior of tritium in boron nitride was more like that for a metal than the other two materials tested as the diffusion of the tritium into boron nitride was seen at much lower temperatures.