The low-temperature heat capacity of (U1-yAmy)O 2−x for y = 0.08 and 0.20

The low-temperature heat capacity of (U 1-y,Amy)O 2−x solid solution with y = 0.0811 and 0.2005 and x = 0.01-0.03 was determined from a minimum of 12.52 K up to 297.1 K and from 9.77 K up to 302.3 K, respectively, using hybrid adiabatic relaxation calorimtry. The low temperature heat capacity results of the investigated system revealed the absence of the magnetic transition specific for UO2 in the temperature region of 30 K. Since there are no experimental data available for AmO2 in this temperature region, the results obtained for the intermediate compositions are validated based on the experimental data of UO2 end-member and the low-temperature heat capacity computation of AmO2. In the measured temperature interval, excess heat capacity was observed for the two investigated intermediate compositions, which is concluded to be dominated by self-radiation effects at very low temperature.