Thermomigration of tritium in V-4Cr-4Ti alloy

In order to obtain heat of transport, Q*, of tritium in V-4Cr-4Ti alloy (NIFS-HEAT-2), thermomigration experiments have been carried out at a temperature ranging from 333 to 471 K. Tritium homogeneously distributed in the specimen bar was forced to migrate by an applied temperature gradient. The resulting tritium profile was visualized by an imaging plate technique and Q* was determined from the profile according to a thermomigration theory. The obtained value of Q* was about +20 kJ/mol for the initial hydrogen concentration of 0.008 at.%, and no appreciable temperature dependence was observed. In order to examine the effect of thermomigration on tritium retentions in pure V and the alloy used as cooling tubes or first walls of the blanket, a simple model calculation was made under designed temperature gradients in fusion reactors. The result showed that tritium retention could be enhanced about 10-20% compared with the case without thermomigration.