Behavior of short-lived fission products in UO2 fuel elements during steady power operation

An irradiation test at a linear power range of 20-55 kW/m has been carried out by using the sweep gas technique in order to evaluate the behaviour of short-lived fission products within an intact fuel element. Experimental procedure and the corrections applied to measured release rates are presented and the experimental data obtained are discussed. It is found that release rates decrease in time during steady power irradiation periods and the that the release rates were power-dependent from 20-55 kW/m. The lines of R/B against decay constance had slopes of -0.4 to -0.7 emphasizing that lattice diffusion is a most important release mechanism. During longer constant power irradiation periods, the release of stored inventory may have some contribution to the overall fission gas release. (authors)