Diffusion of Tritium In V, Nb and Ta Under Concentration, Temperature and Electric Potential Gradients

Abstract

The diffusion data of hydrogen isotopes, especially tritium, are essential to evaluate the hydrogen recycling rate, hydrogen retention and tritium inventory in the reactor core materials. Such data, however, have not necessarily been provided for candidate materials of plasma facing components. In the cases in which the tritium data are not provided, the data of protium or deuterium is usually used in place of tritium, or certain kind of extrapolation from the data of protium and deuterium is made. Therefore, it is important to know a limit of the validity of such treatment. In addition, it should be noted that the severe thermal gradient and the electric potential gradient may be imposed to the plasma facing components. Then, it is also important to evaluate the influence of such potential gradients on the diffusion flux. From such viewpoints, we have accumulated the diffusion data of hydrogen isotopes under concentration, temperature and electric potential gradient in some materials which have a potential for the plasma facing component.