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A kind of preparation method of max phase improved uranium dioxide pellet

A uranium dioxide and improved technology, which is applied in the field of preparation of MAX phase modified uranium dioxide pellets, can solve the problems of inability to dissipate heat in time, low thermal conductivity of uranium dioxide, and cracking of pellets, and achieve excellent performance. The effect of anti-radiation performance, good anti-radiation performance and safety performance improvement

Active Publication Date: 2020-05-12
MATERIAL INST OF CHINA ACADEMY OF ENG PHYSICS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the thermal conductivity of uranium dioxide is low, and it is easy to cause the temperature gradient inside the pellet to be too large, which will lead to problems such as cracking, failure, and even contact reaction of the pellet.
In an accident state, this effect is further amplified, the heat in the reactor cannot be dissipated in time, the temperature of the fuel rises rapidly or even melts, and the cladding material reacts with water vapor to release hydrogen gas, causing an explosion and causing a serious safety accident

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0020] Raw material: UO 2 in powder 235 The U enrichment degree is 1%, the oxygen-uranium ratio is 1.95, and the particle size is about 1 μm; the MAX phase adopts the 312 series compound Ti 3 SiC 2 , the particle size is about 50nm;

[0021] Step 1, mix and match raw materials as follows:

[0022] Put 98% volume fraction of uranium dioxide powder and 2% volume fraction of MAX phase powder into a ball mill and mix for 12 hours at a speed of 100 r / min.

[0023] Step 2, carry out sintering as follows:

[0024] The mixed powder obtained in step 1 is molded under a pressure of 100MPa to obtain UO 2 -MAX phase biscuit, put the biscuit in an atmosphere sintering furnace for sintering, the temperature process is as follows: firstly raise the temperature to 1500°C at a rate of 5°C / min, then raise the temperature to 1600°C at a rate of 1°C / min, and keep it for 7 hours ; After that, the furnace is cooled to below 100°C and the furnace is started; the sintering process and the cooli...

Embodiment 2

[0028] Raw material: UO 2 in powder 235 The U enrichment degree is 19%, the oxygen-uranium ratio is 2.15, and the particle size is about 50 μm; the MAX phase adopts the 312 series compound Ti 3 AlC 2 , the particle size is about 40 μm;

[0029] Step 1, mix and match raw materials as follows:

[0030] Put 50% volume fraction of uranium dioxide powder and 50% volume fraction of MAX phase powder into a ball mill and mix for 24 hours at a speed of 300 r / min.

[0031] Step 2, carry out sintering as follows:

[0032] The mixed powder obtained in step 1 is molded under a pressure of 300MPa to obtain UO 2 -MAX phase biscuit. The green body is placed in an atmosphere sintering furnace for sintering. The temperature process is as follows: firstly, the temperature is raised to 1500°C at a rate of 10°C / min, then to 1800°C at a rate of 5°C / min, and kept for 1 hour; then the furnace is cooled to below 100°C and started. The sintering process and the cooling process are connected by ...

Embodiment 3

[0036] Raw material: UO 2 in powder 235 The U enrichment degree is 4.95%, the oxygen-uranium ratio is 2.02, and the particle size is about 5 μm; the MAX phase adopts the 211 series compound Ti 2 AlC, the particle size is about 5μm;

[0037] Step 1, mix and match raw materials as follows:

[0038] The uranium dioxide powder was molded at 200MPa, passed through a 50-mesh sieve, and self-grinding and spheroidized in a ball mill tank for 6 hours at a speed of 100r / min. Mix in a ball mill tank for 0.5h at a speed of 50r / min, so that the MAX phase powder is coated on the surface of the uranium dioxide pellets.

[0039] Step 2, carry out sintering as follows:

[0040]Put the mixed powder obtained in step 1 into a graphite mold for hot-press sintering. The sintering process is as follows: first, the temperature is raised to 1450°C at a heating rate of 5°C / min, and then to 1500°C at a heating rate of 2°C / min; after holding for 2 hours, the furnace is cooled to below 100°C and open...

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Abstract

The invention discloses a method for preparing an MAX phase improved uranium dioxide pellet. The method comprises the following steps: performing direct mixing or granulation mixing on uranium dioxidepowder and MAX phase powder according to a volume ratio of (49-1):1, performing atmosphere sintering, hot pressing sintering or discharge plasma sintering on the obtained mixture, and taking out, processing and molding the sintered mixture to obtain the pellet. The enrichment degree of <235>U in the uranium dioxide powder 1-19%, a ratio of uranium to uranium ratio of 1.95-2.15, and the particle size of 1-50 [mu]m. The particle diameter of the MAX phase is 50 nm to 40 [mu]m, and the MAX phase is a 312 series compound, a 211 series compound or a 413 series compound; and the 312 series compoundis Ti3SiC2 or Ti3AlC2. The method has the advantages of reasonable design and simplicity in operation, and the prepared uranium dioxide pellet can further improve the thermal conductivity on the basisof keeping the original advantages of uranium dioxide, improve the safety performance of a fuel and enhance the accident condition resistance of a reactor.

Description

technical field [0001] The invention relates to a preparation method of MAX phase improved uranium dioxide pellets. Background technique [0002] Uranium dioxide pellets have many advantages, such as high melting point, anti-oxidation, good neutron economy, water vapor corrosion resistance, good radiation stability, good compatibility with cladding, and good tolerance of fission gas. Currently, they are widely used as nuclear fuels. Commercial nuclear reactors. However, the thermal conductivity of uranium dioxide is low, and it is easy to cause the temperature gradient inside the pellet to be too large, which will lead to problems such as cracking, failure of the pellet, and even contact reaction with the cladding. In the accident state, this effect is further amplified, the heat in the reactor cannot be dissipated in time, the temperature of the fuel rises rapidly and even melts, and the cladding material reacts with water vapor to release hydrogen, causing an explosion an...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G21C21/02
CPCG21C21/02Y02E30/30
Inventor 李冰清杨振亮高瑞张鹏程褚明福唐浩钟毅刘徐徐段丽美黄奇奇王志毅
Owner MATERIAL INST OF CHINA ACADEMY OF ENG PHYSICS