Irradiation-Induced Creep and Re-Sintering of Large Grain Sized UO.sub.2 Fuel

A study of irradiation-induced creep and re-sintering of large grain sized fuel of the VVER type was carried out using the developed procedures and experimental facilities under irradiation with fission rates of 1.0 x 10.sup.13 and 1.2 x 10.sup.13 1/(cm.sup.3 s). Strain diagrams generated during creep studies within the strain range of 10-40 MPa were obtained at effective sample temperatures of 943, 1020, 1200 and 1301 K. It was demonstrated that strain is controlled by irradiation-induced creep within the temperature range of up to 1123 K. This was confirmed by its linear dependency on stress. At higher temperatures, the effect of radiation-thermal creep grows, and its contribution to the total strain increases with the growth of stress. Creep rate values obtained at temperatures of 1200 and 1301 K are higher than those of uranium dioxide with standard grain size. Strain diagram produced during the studies of re-sintering of an 88.32 mm high fuel column was obtained at the effective sample temperature of 960 K. In terms of height, re-sintering amounted to 0.070-0.095%. It was demonstrated that irradiation-induced re-sintering did not affect the irradiation-induced creep rate within the experimental accuracy range.