Post irradiation examination of the fuel discharged from the Trino Vercellese reactor after the 2nd irradiation cycle

The post-irradiation analysis of the fuel discharged from the Trino Vercellese reactor after the 2nd irradiation cycle was carried out in the Ispra and Karlsruhe Establishments of the Joint Research Centre. The main objective of the post-irradiation examination programme was the measurement of the burn-up and isotopic composition of selected fuel samples in order to obtain a set of data to be used for checking the accuracy of nuclear code calculations. The other objective of the programme was the metallographic analysis of the UO2 fuel and the stainless steel cladding. The fuel assembly selected for the analysis (No 509-069) was dismantled at Ispra, in the pool of the ESSOR reactor. The removed fuel rods were subjected to the following examinations: optical inspection, metrology, mechanical tests on the fuel cladding and metallography. Gamma scanning measurements on the fuel rods and gamma spectrometry measurements on selected rod positions were also carried out. Fuel samples to be subjected to radiochemical analyses were cut from the rods at selected positions. The fuel samples were dissolved and aliquots of the solutions were subjected to radiochemical processes and to gamma, mass and alpha-spectrometry determinations. Gamma spectrometry was used mainly to determine the 137Cs activity, from which the burn-up was derived. Mass-spectrometry, combined in some cases with isotope dilution techniques, was used to determine the concentrations and/or isotopic compositions of the heavy isotopes uranium, plutonium, americium of 148Nd and of the krypton and xenon fission gases. Alpha-spectrometry was used to determine the concentrations of some nuclides of plutonium, americium and curium. The concentrations of the heavy isotopes and 148Nd were then used for separate evaluation of the burn-up