A Method to Optimize the Thermal Stability of Uranium-Gadolinium Fuel
Thermal stability (resintering) of uranium-gadolinium fuel depends largely on porosity, the size-based distribution of pores and grains, the ratio between open and closed pores, etc. In turn, porosity and size-based distribution of pores depend on the characteristics of the initial uranium dioxide powder and the fuel pellet fabrication technology. The existing nuclear fuel fabrication technology securely provides for the required properties, which make it possible to operate nuclear fuel reliably and safely to a burn-up level of up to ~ 60 MW day/kg of uranium . Meanwhile, recent trends have been towards increasing the burn-up depth and the duration of the irradiation cycle to refueling, and achieving a zero failure level [2 – 4], this requiring integrated studies to be conducted at all nuclear fuel manufacturing stages, including determination of the technology-structure-property dependences. In 2008, as shown in , the results obtained after the resintering test complied with the radiation-induced densification of fuel achievable at a relatively low burn-up of 10 MW·day/kg. This was also confirmed in [6, 7] and in a work by A.S. Shcheglov and V.N. Proselkov on the peculiarities of the VVER U-Gd fuel rod BOL behavior , where the calculated results met the measured values. The paper shows the effects of the pore agent quantity introduced in the fuel pellet fabrication process, and a method has been proposed to achieve the required porosity for stabilizing the uranium-gadolinium fuel resintering.
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