Heat Capacity Measurements of U1-yGdyO2(y=0-0.27)from 325 to 1,673 K

• Published in: Journal of nuclear science and technology Vol. 41; no. 2; pp. 108 - 115
• Main Authors: AMAYA, Masaki, UNE, Katsumi, HIRAI, Mutsumi
• Format: Journal Article
• Language: English
• Published: Tokyo Taylor & Francis Group 01.02.2004; Atomic Energy Society of Japan
• Subjects: (U, Gd)O; Applied sciences; differential scanning calorimetry; Energy; Exact sciences and technology; Fuels; heat capacity; high temperature; nuclear fuel; Nuclear fuels; oxide fuels; Preparation and processing of nuclear fuels; thermal functions; uranium dioxide; Measurement; Differential scanning calorimetry; thermal functions; Heat capacity; Nuclear fuel; High temperature; uranium dioxide; Gadolinium oxides; U; Radiation effect; Gd)O2; Uranium oxide; oxide fuels
• ISSN: 0022-3131; 1881-1248
• DOI: 10.1080/18811248.2004.9715466

Molar heat capacities were measured for U 1-y Gd y O 2 (y=0-0.27) by differential scanning calorimetry (DSC) in the temperature region from 325 to 1,673 K. The molar heat capacities of U 1-y Gd y O 2 (0<y lt;0.27) were close to, or slightly lower than, the values calculated by using the summation rule, and anomalous increases of heat capacities were not clearly observed at temperatures above 1,000 K. The heat capacity analysis for (U, Gd)O 2 showed that the excess heat capacities of (U, Gd)O 2 tended to decrease with increasing cation concentration excluding U 4+ ions in crystals. This suggested that the Schottky term contribution to the heat capacity, which was mainly caused by the excitation of f electrons in the 5f 2 configuration in U 4+ ions, decreased in (U, Gd)O 2 , compared to that in undoped UO 2 due to the formation of U 5+ and Gd 3+ ions in (U, Gd)O 2 by addition of Gd 2 O 3 . Thermal functions of (U, Gd)O 2 were also evaluated.