Fission gas release and grain growth in THO/sub 2/-UO/sub 2/ fuel irradiated at high temperature

Technical Report · Sun Jul 01 04:00:00 EDT 1979

OSTI ID:5801120

Goldberg, I; Waldman, L A; Giovengo, J F; Campbell, W R

Data are presented on fission gas release and grain growth in ThO/sub 2/-UO/sub 2/ fuels irradiated as part of the LWBR fuel element development program. These data were obtained from three fuel rods that experienced peak linear power outputs ranging from 15 to 22 KW/ft and supplement fission gas release data previously reported for 51 rods containing ThO/sub 2/ and ThO/sub 2/-UO/sub 2/ fuel irradiated at peak linear powers predominantly below 14 KW/ft. Fission gas release was relatively high (up to 15.0 percent) for the rods operated at high power in contrast to the relatively low fission gas release (0.1 to 5.2 percent) measured for the rods operated at lower power. Metallographic examination revealed extensive equiaxed grain growth in the fuel at the high power axial locations of the three rods. The amount of fission gas released was correlated with both the magnitude and extent of grain growth in the fuel. Operation at a decreasing power rating through life results in much lower fission gas release than operation at a constant power. Calculational models for grain growth and fission gas release are presented. Based on these calculations, it is concluded that about 90% of the fission gas produced is released from the fuel region experiencing grain growth (fuel temperature above about 3400/sup 0/F) and about 5% of the fission gas produced is released in fuel regions experiencing temperatures between about 2700/sup 0/F and 3400/sup 0/F. Below 2700/sup 0/F, fission gas release is low (about 1 percent or less) depending on fuel density and burnup.

• Research Organization: Bettis Atomic Power Lab., West Mifflin, PA (USA)
• DOE Contract Number: EY-76-C-11-0014
• OSTI ID: 5801120
• Report Number(s): WAPD-1350(Add.)
• Country of Publication: United States
• Language: English

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