A review of the oxidation of uranium dioxide at temperatures below 400°C

Low cost, proliferation resistant, uranium–thorium dioxide fuels for light water reactors

A conceptual model for the fuel oxidation of defective fuel

A review of kinetic data on the rate of U3O7 formation on UO2

The early stages of U3O8 formation on unirradiated CANDU UO2 fuel oxidized in air at 200–300°c

Irradiated UO2 fuel elements with and without deliberately induced 0.8-mm-diam defects were heated in air at 220, 230, and 250°C for times up to 685 h. Pretest burnup was typically 190 MW·h/kg U (7600 MW·d/TeU) at a maximum linear power of 45 kW/m; cooling times were 1 to 3 yr. In fuel elements with six defects, diametral increases in excess of 5% and sheath splitting occurred after ∼200 h at 250°C, consistent with oxidation to U3O8. There was a maximum 2% increase in elements with one defect at 250°C, but no change in an irradiated but undefected control. Dimensional increases in defected elements at 220 and 230°C were typically <1% for times in excess of 600 h, consistent with oxidation primarily to nonswelling U3O7.The rate of weight change at 230 and 250°C was up to 50 times greater in defected irradiated elements, compared with that for defected unirradiated elements. There was no significant effect of power history or cooling time in the elements studied.

Postirradiation behavior of UO2 fuel I: elements at 220 to 250°C in air

Fragments of UO2 fuel pellets extracted from irradiated elements were heated in air at 175 to 275 °C for times up to 800 h. Unirradiated pellets and fragments were studied for comparison. Pretest burnup of the irradiated fuel was typically 190 MW-h/kgU (7900 MWd per tonne of uranium) at a maximum linear power of 45 kW/m. The fuel had been discharged for 1 to 3 yr. The maximum weight gain was at 275 °C, ∼4% in 70 h, indicating 100% conversion to U3O8. The activation energy for the oxidation process at 175 to 275 °C was 130 ± 10 kJ/mol. There was a strong effect of prior irradiation on oxidation rate; the weight gain at 250 °C was about a factor of 6 greater in irradiated compared with unirradiated fuel. There was also an effect of fragment size on oxidation rate. Also, weight gains of fragments from a naturally defected element were less than those for fragments from intact fuel, consistent with prior oxidation in the defected state.

Postirradiation Behavior of UO2 Fuel II: Fragments at 175 to 275°C in Air

Irradiated UO/sub 2/ fuel elements with and without deliberately induced 0.8-mm-diam defects were heated in air at 220, 230, and 250/sup 0/C for times up to 685 h. Pretest burnup was typically 190 MW X h/kg U (7600 MW X d/TeU) at a maximum linear power of 45 kW/m; cooling times were 1 to 3 yr. In fuel elements with six defects, diametral increases in excess of 5% and sheath splitting occurred after about200 h at 250/sup 0/C, consistent with oxidation to U/sub 3/O/sub 8/. There was a maximum 2% increase in elements with one defect at 250/sup 0/C, but no change in an irradiated but undefected control. Dimensional increases in defected elements at 220 and 230/sup 0/C were typically <1% for times in excess of 600 h, consistent with oxidation primarily to nonswelling U/sub 3/O/sub 7/. The rate of weight change at 230 and 250/sup 0/C was up to 50 times greater in defected irradiated elements, compared with that for defected unirradiated elements. There was no significant effect of power history or cooling time in the elements studied.

Real J. Chenier

Papers

Postirradiation behavior of UO2 fuel I: elements at 220 to 250°C in air

Postirradiation Behavior of UO2 Fuel II: Fragments at 175 to 275°C in Air

Post-irradiation behavior of UO/sub 2/ fuel 1: Elements at 220 to 250/sup 0/C in air