[en] The fracture strength of uranium oxide pellets was measured in vacuum in a temperature range from room temperature to 1,300⁰C by diametral compression. Two kinds of pellets with different pore size were tested. The basic compression rate was set to 1.0 mm/min, but the rates of 20 mm/min, 100 mm/min, and 500 mm/min were also adopted to investigate the relationship between the fracture stress and the compression rate. The experimental procedures are illustrated together with the specifications of the test specimens and the test apparatus. The experimental results are summarized in a figure representing the effect of temperature and compression rate on the fracture stress. An electron micrograph showing the cracks in a fractured pellet is also given. To investigate the validity of the fracture stress thus obtained, elastic analysis was also made on the stress distribution in a compressed disk pellet by the finite element method (FEM). They agreed with the precision of about 90%. The results of FEM analysis and the comparison with measured values are illustrated. Typical conclusions drawn from this experimental analysis were that the fracture strength is independent of the temperature within the range from room temperature to 800⁰C, and that the tensile fracture strength is greatly affected by the size of pores. (Aoki, K.)