Tritium in Nitride Fuel of Fast Reactors

The formation of tritium in reactors, its behavior in nitride fuel and possibility of bonding with fission products, and the characteristics of migration out of the fuel-element cladding are examined. It is shown by a computational method that owing to diffusion through the steel cladding the stationary content of tritium in a fuel element is established over several hours of operation and most of the formed tritium escapes through the cladding, some being retained in it. The presence of hydrogen (tritium) in structural reactor materials in the course of operation of the reactor and thermal vibrations of the structure can significantly degrade the strength of steel structural materials. In this connection, in the BREST facility, the emphasis on the problem of catching tritium is shifted from reprocessing of spent nuclear fuel to handling the lead coolant and the gas medium in the interior of the reactor.