Behavior of Nb_2O_5 Doped/Unpressurized UO_2 Fuel under Transient
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This paper describes the results of reactivity initiated accident (RIA) experiments using unpressurized UO<SUB>2</SUB> fuel pellets containing 0.30 wt% Nb<SUB>2</SUB>O<SUB>5</SUB> additive. From the result of postpulse-irradiation examination (PIE) such as visual inspection, dimensional measurement and metallo/ceramography, fuel failure threshold and failure mechanism were explored. The results obtained were: (1) Failure threshold of the Nb<SUB>2</SUB>O<SUB>5</SUB> doped fuel was almost equal to that of NSRR standard fuel rod data, which were adopted in the Licensing Guideline for RIA, Japan. (2) Failure mechanism of the Nb<SUB>2</SUB>O<SUB>5</SUB> doped fuel under unpressurized condition was cladding melt followed by enbrittlement of thinned cladding wall. No significant difference in the failure mechanism existed between the doped and undoped fuels. Bonding is not peculiar to the doped fuel, namely occurred at lower value of deposited energy (276cal/g•fuel) in the doped fuel than that (341cal/gfuel) in the undoped fuel. (3) No measurable difference in the threshold for mechanical energy release existed between Nb<SUB>2</SUB>O<SUB>5</SUB> doped fuel rod and NSRR standard fuel rods. (4) Axial elongation in the unpressurized doped fuels was significantly greater than that in prepressurized doped ones.
- Journal of Nuclear Science and Technology
Journal of Nuclear Science and Technology 32(2), 111-117, 1995-02-25
Atomic Energy Society of Japan