Fuel pellets and preparation method thereof

Abstract

The invention discloses a fuel pellet and a preparation method thereof. The fuel pellet comprises a first fissible part and a second fissible part filling the inner side of the first fissible part, wherein raw materials of the second fissible part comprise a fissible material and additives, and a high-thermal-conductivity area is formed by the second fissible part. Under the condition that life cycle of nuclear fuel is not influenced obviously, the high-thermal-conductivity area is formed by the second fissible part by the aid of the additives, and the center temperature of the pellet can be reduced under the condition of the same heating power; the loading quantity of the fissible material in the pellet area can be properly reduced in the presence of the additives, then the fission density is reduced, the center temperature of the pellet can be reduced finally, and the thermal margin of a reactor is increased. The second fissible part is arranged in the first fissible part, so that the whole fuel pellet is enabled to be in a solid structure, the strength of the fuel pellet is higher than that of a fuel pellet with a hollow structure, and the pellet is prevented from cracking after bearing high stress; an inner passage with smaller MDNBR (minimum departure from nucleate boiling ratio) does not exist, and DNB is avoided more easily.

Description

technical field [0001] The invention relates to the technical field of nuclear reactors, in particular to a fuel pellet and a preparation method thereof. Background technique [0002] At present, fuel pellets used in nuclear power plants include pellets with a hollow structure, and the structure includes an inner cladding tube and an outer cladding tube arranged inside and outside, both of which are hollow cylindrical. However, the existing hollow fuel pellets bring the following problems: [0003] 1. Due to the hollow area in the center of the fuel pellets, the uranium loading of the core will be significantly reduced, thereby reducing the reactivity of the core, shortening the cycle length, and ultimately leading to a decline in the reactor economy. [0004] 2. The hollow fuel pellets have low strength, and the pellets are prone to fragmentation when subjected to high stress, which affects the safety of the reactor. [0005] 3. Due to the limited internal flow rate, the ...

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Problems solved by technology

[0003] 1. Due to the hollow area in the center of the fuel pellets, the uranium loading of the core will be significantly reduced, thereby reducing the reactivity of the core, shortening the cycle length, and ultimately leading to a decline in the reactor economy

[0004] 2. The hollow fuel pellets have low strength, and the pellets are prone to fragmentation when subjected to high stress, which affects the safety of the reactor.

[0005] 3. Due to the limited internal flow rate, the MDNBR (minimum deviation from nucleate boiling ratio) of the internal cladding is often small, and DNB (deviation from nucleate boiling) is prone to occur, which affects the thermal margin of the core

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