Thermophysical Properties and Radiation Damage of NdCrO3 and NdAlO3

Abstract

Nuclear power is a popular and sustainable method to generate electricity. In order to increase the economic efficiency, it is possible to add dopants into nuclear fuel to increase the fuel burn-up. PuCrO3 and PuAlO3 have been demonstrated to be formed in UO2 fuel because of the interaction of additives (Cr2O3 and Al2O3) and Pu that is produced by neutron capture reactions. The formation of these phases will have impact on the properties of the waste form generated from the used fuel. Here, the thermophysical properties and radiation tolerance of these chromates and aluminates have been examined using Nd as a surrogate for Pu. In this project, two kinds of perovskite-type ceramic materials (NdCrO3 and NdAlO3) were investigated to simulate PuCrO3 and PuAlO3. They were prepared using co-precipitation followed by cold isostatic or uniaxial pressing and conventional sintering. Thereafter, heat capacity, thermal expansion and thermal diffusivity were measured to calculate the thermal conductivity of neodymium chromate and neodymium aluminate. Neodymium aluminate showed higher thermal conductivity than that of neodymium chromate. Ion beam irradiation using Au-ions and He-ions has been utilized to simulate the consequences of α-decay and the effects of irradiation on the structural and macroscopic properties have been investigated. Irradiation by Au-ions resulted in volume swelling, a loss in long-range order, a reduction in hardness for neodymium aluminate and an increase in hardness for neodymium chromate at fluences above 1014 Au-ions/cm2. On the contrary, little effect on the materials properties was observed for samples irradiated with He-ions up to a fluence of 1017 ions/cm2. In summary, the thermal conductivity of neodymium chromate and neodymium aluminate were investigated. The radiation tolerance of these two kinds of ceramic materials were also studied. The results indicated that the presence of plutonium chromate and plutonium aluminate may have significant impact on the properties of used uranium dioxide fuel.