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Method for reducing volume of radioactive contaminated graphite

A graphite and additive technology, applied in radioactive purification, nuclear engineering, etc., can solve the problems of high gas flow rate, large disturbance, high reaction temperature, etc., and achieve the effects of inhibiting diffusion, reducing ignition point, and improving safety

Pending Publication Date: 2018-01-19
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

[0005] Although the above method can achieve a large volume reduction of graphite, there are obvious problems, such as high reaction temperature (>1000 ℃), high gas flow rate, and large disturbance
In the process of processing radioactive pollutants, the high reaction temperature will lead to a decrease in the matching ability between the connecting parts of the equipment, and the sealing ability of the equipment against radioactive aerosols will be reduced, which will pose a great threat to the health of operators and the surrounding environment.
The high gas flow rate will also cause the radionuclide to be in a disturbed state with the gas flow, which is unfavorable for the sealed interception and recovery of radionuclide

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] will have a U 3 o 8 Graphite with a particle size of less than 2 mm (the mass content of U is less than 5 w%) and molybdenum trioxide are placed in a ball mill jar at a mass ratio of 1:4, and are ground for 5 hours at a revolution speed of 350 rpm by a planetary ball mill. Get 2 grams of the obtained powder and place it in a heating furnace, feed air into the furnace at a flow rate of 150 ml / min, and keep the temperature at 650° C. for 1 hour.

[0022] The off-gas of the furnace was monitored using gas chromatography to obtain the time required for complete oxidation of the graphite. The gasification rate of graphite, the average oxidation rate and the retention rate of U can be obtained by the following formula:

[0023] Graphite gasification rate = (1- organic carbon content in the sample before constant temperature / organic carbon content in the sample after constant temperature) × 100%;

[0024] The average oxidation rate of graphite = the amount of graphite add...

Embodiment 2

[0031] will have a U 3 o 8 Graphite with a particle size of less than 2 mm (the mass content of U is less than 5 w%) and molybdenum trioxide are placed in a ball mill jar at a mass ratio of 1:0.25, and are ground for 3 hours at a revolution speed of 500 rpm by a planetary ball mill. Take 2 grams of the obtained powder and place it in a heating furnace, feed air into the furnace at a flow rate of 100 ml / min, and keep the temperature at 750° C. for 1 hour. It has been determined that the ignition point of graphite is 590 °C, the gasification rate of graphite is 99.9%, the average oxidation rate of graphite is 162 g / h, and the retention rate of U is 99.0%.

Embodiment 3

[0033] will have a U 3 o 8 Graphite with a particle size of less than 2 mm (mass content of U is less than 5 w%) and molybdenum trioxide are placed in a ball mill jar at a mass ratio of 1:16, and are ground for 1 hour at a revolution speed of 500 r / min by a planetary ball mill. 2 g of the obtained powder was placed in a heating furnace, air was introduced into the furnace at a flow rate of 500 ml / min, and the temperature was kept at 500° C. for 1 hour. It has been determined that the ignition point of graphite is 438 °C, the gasification rate of graphite is 99.3%, the average oxidation rate of graphite is 112 g / h, and the retention rate of U is 99.2%.

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Abstract

The invention discloses a method for reducing volume of radioactive contaminated graphite. The method comprises the steps that radioactive graphite is broken into particles with an average particle size less than 2 mm, the graphite particles are placed into a ball grinding mill for ball milling together with an additive according to a certain quality ratio, and a required first class solid powderis obtained; the obtained first class solid powder is put into a heating furnace, then reaction gas is passed in, the first class solid powder with reaction gas is heated at a constant temperature, and a second class solid powder is obtained. According to the method for reducing volume of radioactive contaminated graphite, the ignition point of graphite is significantly reduced, the static state and complete oxidation of graphite can be achieved at low gas flow rate, the diffusion of radioactive aerosol can be effectively suppressed, the safety of the treatment process is greatly improved, favorable conditions are provided for subsequent recovery of valuable radionuclides, and the method is suitable for eliminating the radioactive contamination of graphite which has been stockpiled for a long time in the nuclear industry.

Description

technical field [0001] The invention relates to the technical field of radioactive waste treatment, in particular to a method for reducing the volume of radioactively contaminated graphite. Background technique [0002] The nuclear industry produces large quantities of radioactively contaminated graphite. Due to the large volume, it is unacceptable in terms of cost and implementation to directly implement deep geological disposal without volume reduction treatment. Therefore, effective volume reduction treatment of radioactively contaminated graphite is extremely important for the final disposal of waste graphite. The following introduces two kinds of volume reduction technology researches carried out internationally on radioactively contaminated graphite. [0003] Incineration method: France has developed a circulating fluidized bed incineration technology for the radioactively contaminated graphite produced by the decommissioning of its nuclear power plants. The graphit...

Claims

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Application Information

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IPC IPC(8): G21F9/32
Inventor 庞敏潘社奇王永鹏
Owner MATERIAL INST OF CHINA ACADEMY OF ENG PHYSICS