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Directional high thermal conductivity uranium dioxide pellet and preparation method thereof

A technology of uranium dioxide and high thermal conductivity, which is applied in the manufacture of reactors, reactor fuel elements, nuclear power generation, etc., can solve problems such as safety accidents, low radial thermal conductivity, and low thermal conductivity, so as to improve safety and improve Radial thermal conductivity, the effect of simple methods

Active Publication Date: 2019-01-18
MATERIAL INST OF CHINA ACADEMY OF ENG PHYSICS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to provide a directional high thermal conductivity uranium dioxide pellet to solve the problem of low thermal conductivity of uranium dioxide in the prior art, especially low radial thermal conductivity, which easily leads to safety accidents

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  • Directional high thermal conductivity uranium dioxide pellet and preparation method thereof

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Embodiment 1

[0025] This embodiment provides the preparation method of the directional high thermal conductivity uranium dioxide pellet of the present invention, which can increase the radial thermal conductivity of the uranium dioxide pellet by more than 5%, and the axial thermal conductivity is almost unchanged. Specifically:

[0026] Raw material: uranium dioxide powder 235 The U enrichment degree is 1%, the oxygen-uranium ratio is 1.95, and the particle size is about 1 μm; the diameter of the flake graphite sheet is about 3 μm, and the thickness is about 1 μm.

[0027] Step 1. Put 98% volume fraction of uranium dioxide powder and 2% volume fraction of flake graphite into a mixing tank and mix for 24 hours at a speed of 200r / min.

[0028] Step 2. Carry out sintering as follows:

[0029] Put the mixed powder obtained in step 1 into a forming mold, vibrate on a vibrator for 0.1 h, and then mold it under a pressure of 100 MPa to obtain a green body. The green body is placed in a molybde...

Embodiment 2

[0032] This embodiment provides a method for preparing directional high thermal conductivity uranium dioxide pellets of the present invention, which can increase the radial thermal conductivity of the uranium dioxide pellets by more than 300%, and the axial thermal conductivity by more than 30%. Specifically:

[0033] Raw material: uranium dioxide powder 235 The U enrichment degree is 19%, the oxygen-uranium ratio is 2.15, and the particle size is about 50 μm; the diameter of the flake graphite sheet is about 200 μm, and the thickness is about 20 μm.

[0034] Step 1. Proportion the raw materials as follows:

[0035] Put 50% volume fraction of uranium dioxide powder and 50% volume fraction of flake graphite into a mixing tank and mix for 12 hours at a speed of 300r / min.

[0036] Step 2. Carry out sintering as follows:

[0037] Put the mixed powder obtained in step 1 into a forming mold, vibrate on a vibrator for 2 hours, and then mold it under a pressure of 500 MPa to obtain...

Embodiment 3

[0040] This embodiment provides the preparation method of the directional high thermal conductivity uranium dioxide pellet of the present invention, the method can increase the radial thermal conductivity of the uranium dioxide pellet by more than 60%, and the axial thermal conductivity by more than 10%. Specifically:

[0041] Raw material: uranium dioxide powder 235 The U enrichment degree is 10%, the oxygen-uranium ratio is 2.05, and the particle size is about 5 μm; the diameter of the flake graphite sheet is about 100 μm, and the thickness is about 5 μm.

[0042] Step 1. Proportion the raw materials as follows:

[0043] Put 90% volume fraction of uranium dioxide powder and 10% volume fraction of flake graphite into a mixing tank and mix for 4 hours at a speed of 300r / min.

[0044] Step 2. Carry out sintering as follows:

[0045] Put the mixed powder obtained in step 1 into a graphite mold, vibrate on an oscillator for 2 hours, and then carry out hot-press sintering. The...

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Abstract

The invention discloses a directional high thermal conductivity uranium dioxide pellet and a preparation method thereof, and solves the problem of low thermal conductivity of uranium dioxide in the prior art, especially low radial thermal conductivity which easily leads to safety accidents. The directional high thermal conductivity uranium dioxide pellet disclosed by the invention is prepared fromuranium dioxide powder and flake graphite which serve as raw materials, and the flake graphite is aligned in a horizontal direction in a uranium dioxide pellet. The preparation method disclosed by the invention comprises the following steps: uniformly mixing the uranium dioxide powder with the flake graphite serving as the raw materials, oscillating the mixed powder to enable the flake graphite to be aligned in the horizontal direction in the mixed powder, and then performing high temperature sintering to obtain the directional high thermal conductivity uranium dioxide pellet. The directionalhigh thermal conductivity uranium dioxide pellet is scientific in design, and the method is simple; the radial thermal conductivity of the uranium dioxide pellet can be obviously improved, and the safety of a fuel assembly is improved.

Description

technical field [0001] The invention relates to the technical field of nuclear fuel, in particular to a directional high thermal conductivity uranium dioxide pellet and a preparation method thereof. Background technique [0002] The Fukushima nuclear accident in Japan in 2011 revealed that the commercially available uranium dioxide pellets still have great safety risks in the accident state. This is mainly due to the low thermal conductivity of uranium dioxide, which cannot dissipate the internal heat in time under accident conditions, and the temperature of the fuel rises rapidly or even melts, causing serious consequences. Even under normal operating conditions, uranium dioxide pellets have large internal temperature gradients due to their low thermal conductivity, increasing the risk of pellet cracking and failure. Therefore, improving the thermal conductivity of uranium dioxide pellets is an effective way to improve the safety of nuclear fuel, and it is also a research ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G21C3/62G21C21/02
CPCG21C3/623G21C21/02Y02E30/30
Inventor 李冰清杨振亮高瑞黄奇奇王志毅刘徐徐钟毅段丽美褚明福
Owner MATERIAL INST OF CHINA ACADEMY OF ENG PHYSICS
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