Nuclear fuel pellets, manufacturing method and nuclear reactor

Abstract

The invention relates to a nuclear fuel pellet and a manufacturing method thereof, and a nuclear reactor. The nuclear fuel pellet at least comprises a first fuel zone and a second fuel zone which are arranged from inside to outside, wherein the thickness of the second fuel zone is much smaller than that of the first fuel zone; and the reactivity of a nuclear fuel material of the first fuel zone is higher than that of a nuclear fuel material of the second fuel zone. The nuclear fuel material with lower reactivity is arranged on the periphery of the nuclear fuel pellet with higher reactivity to perform the function of lowering initial reactivity margin, so that burnable poisons and / or boric acid in the reactor core are correspondingly reduced, thereby being beneficial to reactor core nuclear design and reactivity control; or more fissionable materials can be loaded to implement longer fuel cycle. More neutrons can be effectively absorbed, thereby enhancing the conversion ratio of the fuel. Besides, the nuclear fuel material with lower reactivity is arranged at the innermost ring of the nuclear fuel pellet to have the function of reducing fissible material residues, thereby enhancing the utilization ratio of nuclear fuels.

Description

technical field [0001] The present invention relates to fuel for nuclear power plants, and more particularly, to a nuclear fuel pellet that can be used in nuclear power plants. Background technique [0002] There are three kinds of fissile materials U233, U235 and Pu239. But only U235 exists naturally, and U233 and Pu239 need to be transformed by Th232 and U238 after absorbing a neutron. [0003] Each fission releases about 200 MeV energy and 2-3 neutrons, and the core power determines the number of fissions per unit time. The 2-3 neutrons released by each fission, except one for the continuous chain reaction, the rest of a multi-neutron is absorbed by the core structure material, leaked, poisoned (including fission products, combustible poisons, dissolved in water boric acid and control rods), or by Th232 or / and U238. The amount of U233 or / and Pu239 produced by consuming one fissile material is called the conversion ratio, and when the conversion ratio is greater than 1,...

AI Technical Summary

Problems solved by technology

[0005] For small reactors with long cycle lengths, control rods, burnable poisons, and / or boric acid are used to control excess reactivity. When the concentration of boric acid is too high, the temperature coefficient of the moderator is positive, and the insertion of the control rods is too deep. have a large negative impact on the power distribution of the core

However, for some special small reactors that need to achieve ultra-long cycle lengths, the consumption of combustible poisons is too fast and the addition of too much affects the loading capacity of fissile materials, making the long-term effective suppression of reactivity a difficult problem

Images