Fuel rod and crud behavior under long-term dry fuel storage conditions

Conference · Sun Jan 01 04:00:00 EST 1984

OSTI ID:6287763

Olsen, C S

Eight commercial PWR and BWR spent fuel rods were tested to determine their long-term stability under a variety of possible dry storage conditions. The two-year test was comprised of three interim nondestructive examinations. This paper presents the results of the third examination conducted to determine any degradation in all eight fuel rods after being subjected to 13,168 h at temperatures between 502 K and 490 K. The PWR fuel rods showed no measurable change from the pretest condition. A BWR fuel rod replaced one that breached after the second interim examination, and a 1.9-cm crack developed in this rod at the bottom defect. About 17% cladding deformation was observed at the defect. Minute amounts of crud consisting of the /sup 60/Co isotope fell into the fuel rod capsules. A small amount of fuel (0.1 g) from the breached BWR fuel rod was found in the capsules. The BWR fuel rod removed after the second interim examination was destructively examined. The fuel was oxidized to U/sub 3/O/sub 8/ in the area of the cladding defect. The extensive fuel oxidation may result from diffusion of oxygen through the open porosity. The results of the testing with the BWR fuel would indicate that dry storage above 490 K to 502 K is not acceptable for this particular fuel used. This fuel may be atypical of current fuel design and fabrication techniques. The BWR results may not be applicable to PWR fuel because of the wide differences observed between PWR and BWR fuel rod behavior. The PWR fuel rods are being destructively examined to determine the extent of oxidation, but additional effort is required to determine oxidation mechanisms and identify the causes of the differences in behavior between PWR and BWR UO/sub 2/ fuel. Oxidation studies of other BWR fuel should be done to determine if the current observed behavior is unique to the BWR fuel before any generic licensing rules are established.

• Research Organization: EG and G Idaho, Inc., Idaho Falls (USA)
• DOE Contract Number: AC07-76ID01570
• OSTI ID: 6287763
• Report Number(s): EGG-M-23184; CONF-841094-2; ON: DE85003261
• Country of Publication: United States
• Language: English

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