Book Description

Safety analyses of nuclear reactors require knowledge of the evaporation behavior of UO2 at temperatures well above the melting point of 3140 K. In this study, rapid transient heating of a small spot on a UO2 specimen was accomplished by a laser pulse, which generates a surface temperature excursion. This in turn vaporizes the target surface and the gas expands into vacuum. The surface temperature transient was monitored by a fast-response automatic optical pyrometer. The maximum surface temperatures investigated range from approx. 3700 K to approx. 4300 K.A computer program was developed to simulate the laser heating process and calculate the surface temperature evolution. The effect of the uncertainties of the high temperature material properties on the calculation was included in a sensitivity study for UO2 vaporization. The measured surface temperatures were in satisfactory agreements.