Preparation method of monocrystalline high-heat-conductivity uranium dioxide nuclear fuel core block

Abstract

The invention discloses a preparation method of a monocrystal high-heat-conductivity uranium dioxide nuclear fuel core block. The preparation method comprises the following steps: mixing and wrappinga monocrystal growth aid and a heat conductivity enhancing phase with UO2 particles, carrying out the high-temperature sintering in an active atmosphere, liquedifying the monocrystal growth aid, mutually diffusing the liquefied monocrystal growth aid and UO2 to form UO2 monocrystals, continuously distributing the heat conductivity enhancing phase on the periphery of each monocrystal UO2 particle,and forming the monocrystal high-heat-conductivity UO2 fuel core block with an inter-penetrating network structure with the monocrystal UO2 particles. The heat conductivity of the fuel core block is greatly improved, so that the operation safety of a reactor can be apparently improved, and the economic benefit of a nuclear station can be increased.

Description

technical field [0001] The invention relates to the preparation of nuclear fuel elements, in particular to a method for preparing single crystal high thermal conductivity uranium dioxide nuclear fuel pellets. Background technique [0002] Uranium dioxide (UO 2 ) is currently the most commonly used nuclear fuel for commercial nuclear reactors. It has high melting point, good high temperature stability, good chemical compatibility with cladding materials and coolants, strong radiation resistance, and thermal neutron capture of oxygen as a non-fission combination element Significant advantages such as low cross-section. But UO 2 There is still a significant problem of low thermal conductivity, which is only 2.8 W / m K at 1000 °C, which leads to UO 2 There is a large temperature gradient in the fuel pellets, resulting in high core temperature and severe thermal stress, which will lead to large-scale cracking of the fuel pellets, and these cracks will significantly increase the...

AI Technical Summary

Problems solved by technology

But UO 2 There is still a significant problem of low thermal conductivity, which is only 2.8 W / m K at 1000 °C, which leads to UO 2 There is a large temperature gradient in the fuel pellets, resulting in high core temperature and severe thermal stress, which will lead to large-scale cracking of the fuel pellets, and these cracks will significantly increase the release of fission gases under high burnup conditions, The increase of the operating temperature of the reactor will further accelerate the release of fission gas and form bubbles, which will cause the swelling of the fuel pellets. Therefore, the UO in the reactor 2 Fuel life is significantly limited

[0003] In addition, the high temperature at the center of the fuel pellet and the large temperature gradient will lead to the existence of a large amount of waste heat, which will significantly increase the cladding temperature in the event of a coolant failure accident

For example, the uranium dioxide fuel pellets with zirconium alloy cladding, because the reaction rate between zirconium alloy cladding and water will be greatly increased above 1200 ° C, a large amount of ZrO will be generated on the surface 2 , thereby reducing the thermal conductivity of the cladding, which eventually leads to the rupture of the zirconium alloy cladding layer, causing safety hazards (R.O.Meyer, Nucl.Technol., 2006,155:293)

Images