The influence of irradiation test parameters on changes in microhardness of the components of dispersion fuel elements with uranium--molybdenum fuel

Full-scale fuel elements (FE) with a U-Mo fuel of a low enrichment of ∼ 36.3% 235U dispersed in an aluminium matrix with an average uranium content of 5.4 g/cm3 were tested in-pile of the IVV-2M reactor. The fuel is the U-9% Mo alloy particles of a ball-shape produced by the atomization method. Two series of the tests were performed with two FE irradiated in each to reach an average equivalent 235U burn up of ∼ 40% and ∼ 80%, respectively. In the first series the test parameters were changing as follows: an initial fission rate, φBOL, along the FE length from 1.8.1014 to 4.2·1014 fiss/(cm3·s), a temperature of fuel cladding, ΤBOL, from 38 to ∼ 70 deg. C and a density of thermal flux, qBOL, from 40 to 85 W/cm2. In the second series they were changing along the fuel length within the following values: φBOL (2.7-5.7)·1014 fiss/(cm3·s), ΤBOL = 41 to ∼ 86 deg. C, qBOL 60-120 W/cm2. This paper presents the data on the influence of in-pile test parameters (a fuel cladding temperature, a fission rate, a total amount of fission number and neutron fluence) on changes in the microhardness of the FE components such as a fuel cladding material (SAV-1 alloy), an aluminium matrix of a fuel meat, a fuel particle material (U-9 % Mo alloy) and an interaction (U,Mo)Alx layer between the fuel particles and the aluminium matrix. (author)