Coated granular YHx-based moderator

Abstract

The invention discloses a coated granular YHx-based moderator, and relates to the technical field of nuclear reactor materials, the coated granular YHx-based moderator comprises YHx particles and a coating layer, the chemical formula of the YHx particles is YHx, x ranges from 1.5 to 2, the coating layer sequentially comprises a loose pyrolytic carbon layer, an inner compact isotropic pyrolytic carbon layer, a silicon carbide layer and an outer compact isotropic pyrolytic carbon layer from inside to outside, and the thickness of the coating layer is 10 to 100 microns. The preparation method of the YHx particles comprises the step that high-purity metal yttrium particles directly react with high-purity hydrogen in a high-temperature vacuum environment to prepare the YHx particles. The preparation method of the coating layer is chemical vapor deposition. The coated granular YHx-based moderator is subjected to heat treatment, the heat treatment temperature is 1200-1500 DEG C, the heat treatment time is 1-2 hours, and the coated granular YHx-based moderator is suitable for being used as a moderator material in a nuclear reactor. The YHx particles are protected by the coating layer, so that the stability of the YHx particles in high-temperature and irradiation environments is improved, and the service life of the YHx particles is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear reactor materials, and particularly relates to a coated granular YHx-based moderator. Background Art

[0002] In a nuclear reactor, a moderator is a key material used to slow down fast neutrons to thermal neutrons, thereby improving the efficiency of nuclear fission reactions. Traditional moderator materials include graphite, heavy water, and light water, etc., but these materials have certain limitations in some specific application scenarios. For example, graphite is prone to oxidation at high temperatures, and the thermal stability of heavy water and light water is relatively poor. Therefore, developing a new type of moderator material has important practical significance.

[0003] As a potential moderator material, yttrium hydride (YHx) has a high hydrogen density and good thermal stability. However, YHx is prone to hydrogen release and structural damage under high temperature and irradiation environments, which limits its use in practical applications. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies existing in the prior art, and provide a coated granular YHx-based moderator, which protects the YHx particles through a coating layer, improves their stability under high temperature and irradiation environments, and extends the service life.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] A coated granular YHx-based moderator, comprising YHx particles and a coating layer. The chemical formula of the YHx particles is YHx, where x is from 1.5 to 2. The coating layer sequentially includes a porous pyrolytic carbon layer, an inner dense isotropic pyrolytic carbon layer, a silicon carbide layer, and an outer dense isotropic pyrolytic carbon layer from the inside out. The thickness of the coating layer is from 10 to 100 microns.

[0007] Further, the preparation method of the YHx particles is to directly react yttrium powder with hydrogen in a high-temperature and high-vacuum environment.

[0008] Further, the preparation method of the coating layer is chemical vapor deposition (CVD).

[0009] Further, the coated granular YHx-based moderator is heat-treated, and the heat treatment temperature is from 1200 to 1500 °C, and the time is from 1 to 2 hours.

[0010] Further, the coated granular YHx-based moderator is suitable for use as a moderator material in a nuclear reactor.

[0011] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0012] 1. Solved the problems of easy oxidation and cracking of metal hydrides, and greatly extended the service life of the moderator.

[0013] 2. Achieved stable operation in high-temperature environments, providing a reliable moderator material for high-temperature microreactors.

[0014] 3. Improved the neutron moderation efficiency, thereby reducing the fuel demand and lowering the reactor operation cost and core volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the composition structure of the present invention.

[0016] Names of components and reference numerals in the drawings:

[0017] 1 - YHx particles, 2 - loose pyrolytic carbon layer, 3 - inner dense isotropic pyrolytic carbon layer, 4 - silicon carbide layer, 5 - outer dense isotropic pyrolytic carbon layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The present invention will be further described in detail below in conjunction with test examples and specific embodiments. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments. All technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0019] In this embodiment, a coated particulate YHx-based moderator is provided, as Figure 1 shown, including YHx particles 1 and a coating layer. The chemical formula of the YHx particles 1 is YHx, where x is 1.5 to 2. The coating layer sequentially includes a loose pyrolytic carbon layer 2, an inner dense isotropic pyrolytic carbon layer 3, a silicon carbide layer 4, and an outer dense isotropic pyrolytic carbon layer 5 from the inside out. The thickness of the coating layer is 10 to 100 microns.

[0020] Further, the YHx particles are prepared by directly reacting yttrium powder with hydrogen in a high-temperature and high-vacuum environment.

[0021] Further, the coating layer is prepared by chemical vapor deposition (CVD).

[0022] Further, the coated particulate YHx-based moderator is heat-treated at a temperature of 1200 to 1500 °C for 1 to 2 hours.

[0023] Further, the coated particulate YHx-based moderator is suitable as a moderator material in nuclear reactors.

[0024] Specifically:

[0025] 1. Preparation of YHx particles:

[0026] o Put yttrium powder with a purity of ≥99.9% into the reaction furnace. After pumping to a vacuum of 10 -5 Pa, heat up to the required preparation temperature (800 - 900 °C), and introduce high-purity hydrogen with a controllable flow rate until the pressure in the reaction furnace stabilizes at the target equilibrium pressure, then generate YHx particles.

[0027] 2. Preparation of the coating layer:

[0028] Adopt the CVD method, use trichloromethylsilane (CH3SiCl3) as the precursor and hydrogen as the carrier gas to deposit a coating layer on the surface of the YHx particles. The deposition temperature is 1000 to 1200 °C, and the deposition time is 1 to 3 hours.

[0029] o Put the coated particles into the heat treatment furnace and conduct heat treatment in an argon atmosphere at a temperature of 1200 to 1500 °C for 1 to 2 hours.

[0030] Examples:

[0031] Example 1:

[0032] o Preparation of YHx particles: React yttrium powder with hydrogen at 840 °C and 1 MPa for 4 hours to generate YH2 particles.

[0033] o Preparation of the coating layer: Adopt the CVD method to deposit a SiC coating layer on the surface of the YH2 particles with a thickness of 50 microns.

[0034] o Heat treatment: Conduct heat treatment at 1300 °C for 1.5 hours in an argon atmosphere.

[0035] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A coated granular YHx-based moderator, characterized in that, It includes YHx particles and a coating layer. The chemical formula of the YHx particles is YHx, where x is from 1.5 to 2. The coating layer sequentially includes a loose pyrolytic carbon layer, an inner dense isotropic pyrolytic carbon layer, a silicon carbide layer, and an outer dense isotropic pyrolytic carbon layer from inside to outside. The thickness of the coating layer is 10 to 100 microns.

2. The encapsulated granular YHx-based moderator according to claim 1, characterized in that, The preparation method of the YHx particles is to directly react yttrium powder with hydrogen in a high-temperature and high-vacuum environment.

3. The coated granular YHx-based moderator according to claim 1, wherein, The preparation method of the coating layer is chemical vapor deposition (CVD).

4. The coated granular YHx-based moderator according to claim 1, wherein The coated particulate YHx-based moderator is heat-treated at a temperature of 1200 to 1500 °C for 1 to 2 hours.

5. The encapsulated granular YHx-based moderator according to claim 1, wherein The coated particulate YHx-based moderator is suitable for use as a moderator material in a nuclear reactor.

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