Experimental measurements of fission product release from reactor fuel materials

Measurements of fission product emission from uranium dioxide during irradiation are presented. The emission of 85Kr from single crystal U02 has been studied to yield information on the migration rates of a long-lived gaseous fission product species through the oxide lattice as a function of temperature and burnup. Studies on polycrystalline U02 have given an insight into the rates and mechanisms of stable gas build-up and subsequent release from grain boundaries. The release behaviour of short-lived fission product species has been investigated to determine the effect of half-life upon emission. The release of daughter and parent nuclides within the same mass chain is considered against some experimental evidence. The observations made are reviewed against existing knowledge and theories of gas release processes. (author)