Testing fuel elements in conditions of reactivity insertion

Irradiation tests are carried out to obtain experimental data regarding the nuclear fuel behavior in accident regime, used for validation and calibration of computational codes. These are done with a capsule (C-6) containing the fuel element immersed in steady water at ambient pressure and temperature. It is placed in dry cavity of the TRIGA ACPR reactor core, operated in pulsing regime. Although reactivity insertion accident are not specific to CANDU type fuel, these tests give information concerning the thermal-mechanical behavior of the fuel and can in RIA type accident conditions. The following irradiation conditions were fulfilled: - capsule pressure, 1atm; - coolant temperature, ambient temperature; - maximal temperature in the fuel element at the pulse peak, about 2,800 deg.C; - maximal external temperature at the fuel element can during the pulse, 1,700 deg.C. The main objectives of the tests were: - analysis of thermal-mechanical behavior of the CANDU fuel element in case of RIA type event. Fuel-can mechanical interaction; - analysis of mechanisms and limits of failure of fuel element in case of RIA accident; - establishing the threshold energy for failure as a function of the geometrical and microstructural characteristics of fuel elements; - developing an experimental data base necessary for calibration and validation of the computer codes used in the analyses required by the Safety Final Report of Cernavoda NPP. A number a 34 fuel elements were irradiated in 50 pulses. Procedures of measurements of temperature and pressure during tests and pulses are presented. During experiments, it was observed the possibility of can failure due to the pressure increase in the fuel elements. Tests with pre-irradiated fuel with high burnup are in progress