A device and method for water and oxygen removal from a base graphite

Abstract

The application discloses a device and method for removing water and oxygen from base graphite, which comprises a heating cabin, a vacuum system, an inert gas supply air path system, a trace water and oxygen test system and a storage box. The heating cabin is internally provided with a heating element and at least one tray for placing base graphite. The vacuum system is used for extracting gas in the heating cabin to promote the removal of water and oxygen. The inert gas supply air path system is used for continuously supplying air to purge the heating cabin and remove water and oxygen through a cold trap and a carrier tape. The trace water and oxygen test system is used for continuously sampling and measuring water and oxygen content. The storage box is arranged adjacent to the heating cabin and used for storing the processed base graphite, preventing the base graphite from being contaminated during storage and keeping the water and oxygen content in a target range. The method provided by the application can effectively remove water and oxygen in the base graphite without damaging the structure of the base graphite, guarantee the stability and safety of fuel elements in a high-temperature environment, and is particularly suitable for the manufacture of fuel elements in a fourth-generation nuclear reactor, such as a solid fuel molten salt reactor.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of reactor technology, in particular to a device and method for removing water and oxygen from matrix graphite material. BACKGROUND

[0002] The dispersed coated fuel particles are uniformly dispersed in the matrix graphite, pressed into fuel compacts, and loaded into graphite cladding to form fuel elements of different shapes, which have the characteristics of high temperature resistance and effective prevention of release of fission products, and have wide application prospects in fourth-generation reactors such as solid fuel molten salt reactors.

[0003] As an important component of dispersed fuel, matrix graphite is the external wrapper of coated particles. Graphite itself has a porous structure and is prone to adsorb O2 and H2O and other oxidizing gases. When the fuel enters the molten salt reactor, the matrix graphite is in direct contact with the primary coolant, and at high temperatures (600-700℃), the oxidizing impurity gases in the matrix graphite, such as O2 and H2O, are oxidized, which in turn causes corrosion damage. The consequences of corrosion not only reduce the strength, Young's modulus, toughness, and electrical conductivity of the graphite, but also cause abnormal temperature rise in the reactor and accumulation of flammable gases (CO and H2) in the reactor. Therefore, the adsorption of water and oxygen on the surface or inside of the matrix graphite during the production and manufacturing stage will have an important impact on the safety of the molten salt reactor. At the same time, to ensure the safe operation of the reactor, the integrity of the fuel during the production and manufacturing stage should be ensured as much as possible during the fuel loading process.

[0004] The Oak Ridge National Laboratory (ORNL) in the United States once conducted a study on the removal of water from the graphite moderator in the molten salt reactor (MRER) using liquid fuel. In the experiment, 6-12 inch graphite moderator samples were placed in a metal box and heated in a heating furnace and circulated with helium gas, and then the water content was tested by flowing through a cold trap. The experimental results showed that the adsorbed water content in the graphite moderator was quite low, and the graphite moderator was almost not contaminated by humid air during the maintenance operation of the reactor core. Therefore, the graphite moderator was acceptable for the operation of the MSRE. However, during the reactor startup operation, the empty reactor was heated and purged with helium gas, and the empty molten salt without nuclear fuel was used to clean the core before the fuel was loaded into the core, which was a supplementary means to remove water and oxygen from the moderator. Since the MSRE is a liquid fuel reactor, this method only targets the large amount of graphite moderator arranged in the reactor, and does not involve the matrix graphite as fuel. Moreover, the process is carried out in the reactor, which has high operation difficulty and complexity.

[0005] Therefore, if the water and oxygen content of the fuel matrix graphite can be reduced to a certain extent before the nuclear fuel is loaded into the reactor, and the integrity of the matrix graphite is maintained during the water and oxygen removal process, the safety of the reactor can be better ensured. SUMMARY

[0006] The present application aims to provide a device and method for removing water and oxygen from base graphite, so as to solve the problem that the prior art lacks a method for removing water and oxygen from fuel base graphite while maintaining the integrity of the base graphite during the water and oxygen removal process.

[0007] To solve the above problems, the present application adopts the following technical solutions:

[0008] According to a first aspect of the present application, a device for removing water and oxygen from base graphite is provided, comprising: a heating cabin, which is internally provided with a heating element and at least one tray for placing base graphite to be treated; a vacuum system for extracting gas in the heating cabin, reducing pressure, and facilitating the removal of water and oxygen; an inert gas supply gas path system for continuously purging inert gas and connecting a cold trap for condensing and removing water carried out during the purging process; a trace water and oxygen testing system for continuously sampling and measuring water and oxygen content during the inert gas purging process; and a storage box arranged adjacent to the heating cabin for storing the treated base graphite, preventing the base graphite from being contaminated during storage, and keeping the water and oxygen content within a target range.

[0009] Preferably, the heating cabin is designed to withstand high temperature and negative pressure, and has a certain volume to ensure the stability of a large amount of base graphite during the treatment process.

[0010] Preferably, the front side of the heating cabin is provided with a first door body, and the rear side of the heating cabin is provided with a second door body at the connection with the storage box.

[0011] Preferably, the vacuum system and the inert gas supply system are connected with the storage box at the same time to adjust the atmosphere in the storage box.

[0012] Preferably, the outer wall of the storage box is provided with gloves extending into the internal cavity to facilitate the transfer of the treated base graphite from the heating cabin to the storage box by hand.

[0013] Preferably, the bottom of the heating cabin is provided with a guide rail, and the bottom of the tray is provided with a roller to facilitate the movement of the tray in the heating cabin.

[0014] According to a second aspect of the present invention, a method for removing water and oxygen from a matrix graphite material using the device is provided, comprising the following steps: S1, placing the matrix graphite on a tray and ensuring that the heating chamber is sealed; S2, gradually heating the matrix graphite to a set temperature in the sealed heating chamber and keeping the temperature constant to remove water and oxygen from the matrix graphite; S3, starting a vacuum system to continuously reduce the pressure in the heating chamber; S4, continuously purging the matrix graphite in the heating chamber through an inert gas supply gas system to carry the released water and oxygen; S5, using a cold trap to remove the purged graphite. The process of removing moisture carried out; S6, using a trace water and oxygen testing system to continuously sample and measure the inert gas in the heating chamber to monitor the water and oxygen content therein; S7, when the water and oxygen content reaches the target range and remains stable at a predetermined equilibrium stable value, stop heating and cool to room temperature; S8, turn off the vacuum system, keep the inert gas supply environment in the heating chamber and keep it in balance with the inert gas environment pressure in the storage box; S9, open the door connecting the heating chamber and the storage box, and transfer the matrix graphite from the heating chamber to the storage box to prevent the matrix graphite from re-adsorbing moisture and oxygen during storage.

[0015] Preferably, the pressure in the heating chamber is reduced to less than 5 Pa by the vacuum system to further promote the removal of moisture and oxygen.

[0016] Preferably, the gas flow rate of the inert gas supply gas system is set to 0-10 L / min.

[0017] Preferably, after the matrix graphite is transferred from the heating chamber to the storage box, all doors are closed to ensure that the matrix graphite is not contaminated during storage.

[0018] This invention provides, for the first time, an apparatus and method for non-destructive dehydration and deoxygenation of graphite matrix. The key aspect of this invention lies in the design of a rationally constructed apparatus for dehydration and deoxygenation of graphite matrix, which uses a combination of vacuum, heating, and inert gas purging to reduce the water and oxygen content in the graphite matrix while maintaining the integrity of the graphite matrix material. The connection method and equipment layout employed by this apparatus can be directly applied or scaled up for large-scale, non-destructive treatment of water and oxygen content in graphite matrix. It is suitable for the mass production of large-scale graphite matrix fuels, meeting the fuel element requirements of fourth-generation nuclear reactors, such as solid-fuel molten salt reactors.

[0019] The device and method for dehydrating and deoxygenating matrix graphite provided by the present invention have the following beneficial effects compared with the prior art:

[0020] The present invention removes water and oxygen from the matrix graphite by vacuum heating and inert gas purging the carrier.

[0021] The treated matrix graphite is stored in a storage box to avoid water and oxygen contamination of the matrix graphite again;

[0022] Through real-time monitoring of the trace water and oxygen test system, it is ensured that the treated base graphite meets the strict water and oxygen content requirements in the storage device;

[0023] During the entire water and oxygen removal process, the base graphite is not damaged and remains intact, and the water and oxygen can be effectively removed without damaging the structure of the base graphite. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a structural schematic diagram of a water and oxygen removal device according to a preferred embodiment of the present application;

[0025] In the drawings, the meanings of the reference numerals are as follows:

[0026] 1, graphite ball; 2, tray; 3, heating cabin; 4, first door body; 5, second door body; 6, storage box; 7, vacuum system; 8, cold trap; 9, trace water and oxygen test system; 10, inert gas supply gas path system; 11, glove. DETAILED DESCRIPTION

[0027] The present application will be further described in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the present application and are not intended to limit the scope of the present application. Unless otherwise specified, the technical means used in the examples are conventional operations in the art, or according to the experimental methods recommended by the instrument and equipment manufacturers. The reagents and materials used in the examples are commercially available unless otherwise specified.

[0028] As shown in Figure 1 , a water and oxygen removal device according to a preferred embodiment of the present application, which comprises a tray 2, a heating cabin 3, a storage box 6, a vacuum system 7, a cold trap 8, a trace water and oxygen test system 9, and an inert gas supply gas path system 10.

[0029] The front side and the rear side of the heating cabin 3 are respectively provided with a first door body 4 and a second door body 5, and a heating element is arranged inside. The heating cabin is designed to withstand high temperature and negative pressure to ensure the stability of the base graphite during the treatment process. A plurality of trays 2 are arranged inside in a stacked manner from bottom to top for placing the base graphite 1 to be treated. A guide rail is arranged inside the heating cabin, and the bottom of the tray 2 is designed with a roller to facilitate manual loading and unloading of the graphite. The heating element is used to provide heat to make the graphite reach a certain temperature, thereby promoting the release of water and oxygen. The heating temperature can be adjusted according to the type of graphite.

[0030] The vacuum system 7 is used to extract the gas in the heating cabin 3 to reduce the pressure and further promote the removal of water and oxygen. The design of the vacuum system should ensure that the required negative pressure level can be quickly reached. The vacuum system 7 is arranged outside the heating cabin 3 and communicates with the heating cabin 3 to realize vacuum extraction in the heating cabin.

[0031] An inert gas supply system 10 is located outside and connected to the heating chamber 3, continuously supplying air to purge the chamber. Released moisture is removed and discharged through a cold trap 8. A cold trap is a device that prevents vapor or liquid from entering the measuring instrument, or vice versa. It provides a very low-temperature surface on which molecules can condense, increasing the vacuum level by one to two orders of magnitude. The trace water and oxygen testing system 9 continuously samples and measures during the inert gas purge until the water and oxygen content decreases and reaches a stable equilibrium.

[0032] Storage box 6 is located adjacent to heating chamber 3. A vacuum system 7 and an inert gas supply system 10 are connected to storage box 6 to regulate the atmosphere within. Gloves 11 are also provided on the outer wall of storage box 6, extending into the internal cavity. This facilitates manual transfer of processed graphite matrix from heating chamber 3 to storage box 6, preventing contamination during storage and maintaining the water and oxygen content within the target range.

[0033] According to a preferred embodiment of the present invention, a method for dehydrating and deoxygenating matrix graphite using the above-mentioned device is also provided, and the method specifically comprises the following steps:

[0034] 1) Open the first door 4, place a certain amount of matrix graphite 1 on the tray 2, manually place it on the guide rail in the heating chamber and ensure that the first door 4 is sealed. Ensure that the vacuum system 7, inert gas supply system 10, cold trap 8 and trace water and oxygen testing system 9 are all connected and in working condition.

[0035] 2) The heating chamber 3 is sealed and gradually heats the graphite to a set temperature, usually between 100°C and 600°C, and keeps the temperature to remove moisture and oxygen from the graphite.

[0036] 3) Start the vacuum system 7 to continuously reduce the pressure in the heating chamber 3 until the vacuum drops below several Pa, further promoting the removal of moisture and oxygen.

[0037] 4) The vacuum system 7 is closed, and the graphite in the heating chamber 3 is continuously purged through the inert gas supply system 10 to help remove the released moisture and oxygen.

[0038] 5) The inert gas supply gas system 10 purges the inert gas and is connected to the cold trap 8 to condense and remove the moisture carried out during the purge process.

[0039] 6) The trace water and oxygen testing system 9 continuously samples and measures the inert gas purged in the heating chamber 3 to monitor the water and oxygen content therein.

[0040] Continue the above steps 3)-6), and if necessary, steps 3) and 4) can be performed alternately to remove water and oxygen from the matrix graphite.

[0041] 7) When the water and oxygen content reaches the target interval range and remains stable at a predetermined equilibrium stable value (e.g. water and oxygen < 30 ppm), stop heating and cool to room temperature.

[0042] 8) The vacuum system 7 is closed, maintaining the inert gas supply environment in the heating chamber 3 and balancing the inert gas environment pressure with the storage tank 6.

[0043] 9) The second door 5 connecting the heating chamber 3 and the storage tank 6 is opened, and the substrate graphite is transferred to the storage tank 6 for storage. The second door 5 is closed to prevent the substrate graphite from re-adsorbing moisture and oxygen during storage.

[0044] Example 1

[0045] 60mm graphite mock fuel element water and oxygen removal, the specific steps are as follows:

[0046] Substrate graphite loading: Place the 60mm diameter spherical graphite elements into the tray, with 50 graphite balls per layer of tray, for a total of 250 graphite balls.

[0047] Vacuum heating: Open the first door 4, place the graphite balls together with the tray into the heating chamber 3, and close the first door 4. The heating chamber 3 is heated from room temperature to 200°C, with a 1h holding time, and the temperature rise rate is set to 60°C / hr. Then open the vacuum system 7, and vacuum to 5Pa, and close the vacuum system. The heating chamber 3 is heated to 400°C, with a temperature rise rate set to 60°C / hr, and the holding time is set.

[0048] Gas purging: Start the inert gas (Ar) supply gas path system 10 to continuously purge the graphite in the heating chamber 3, with a gas flow rate set to 5L / min. Observe the cold trap 8, and find that the cold trap 8 has cooling water condensation. Continue gas purging, and when the cold trap 8 has no cooling water condensation, measure the water and oxygen content in the purging gas. The process time is related to the substrate graphite manufacturing process.

[0049] Water and oxygen measurement: After 8h, when the water analyzer drops to 30ppm and the oxygen analyzer drops to 30ppm or below, and for 1 hour, the test value tends to be a constant value, i.e. the conditions for graphite water and oxygen treatment are met.

[0050] Transfer storage: Close the heating elements of the heating chamber 3, and naturally cool to room temperature. When the storage tank 6 and the heating chamber 3 are two-stage gas balanced, and the target water and oxygen is reached, open the second door 5, and use the glove 11 to transfer the graphite to the storage tank 6 for storage, and close the second door 5.

[0051] The above merely describes preferred embodiments of the present application, and is not intended to limit the scope of the present application. The above-described embodiments of the present application can be variously changed. Any simple, equivalent changes and modifications made according to the content of the claims and the specification of the present application are intended to fall within the scope of the present application. The present application is not limited by the above-described embodiments.

Claims

1. A method for water and oxygen removal from a base graphite material, characterized by, The method uses a device for removing water and oxygen from the substrate graphite, which comprises: a heating cabin with a heating element and at least one tray for placing the substrate graphite to be treated inside; a vacuum system for pumping out the gas in the heating cabin, reducing the pressure to facilitate the removal of water and oxygen; an inert gas supply system for continuous inert gas purging and connecting a cold trap to condense and remove the water carried out during purging; a trace water and oxygen test system for continuous sampling and measuring the water and oxygen content during inert gas purging; and a storage box adjacent to the heating cabin for storing the treated substrate graphite to prevent contamination of the substrate graphite during storage and maintain the water and oxygen content within the target range; the method comprises the following steps: S1, place the substrate graphite on the tray and ensure that the heating cabin is sealed; S2, the heating cabin gradually heats the substrate graphite to the set temperature by the heating element in a sealed state, and keeps warm to remove the water and oxygen in the substrate graphite; S3, start the vacuum system to continuously reduce the pressure in the heating cabin; S4, continuously purge the substrate graphite in the heating cabin by the inert gas supply system to carry and transfer the released water and oxygen; S5, use the cold trap to remove the water carried out during purging; S6, use the trace water and oxygen test system to continuously sample and measure the inert gas in the heating cabin to monitor the water and oxygen content therein; S7, when the water and oxygen content reaches the target range and remains stable at the predetermined equilibrium value, stop heating and cool to room temperature; S8, turn off the vacuum system, maintain the inert gas supply environment in the heating cabin and balance the inert gas environment pressure in the storage box; S9, open the door body connecting the heating cabin and the storage box, and transfer the substrate graphite from the heating cabin to the storage box to prevent the substrate graphite from re-adsorbing water and oxygen during storage.

2. The method of claim 1, wherein, The heating cabin is designed to withstand high temperature and negative pressure, and has a certain volume to ensure the stability of a large amount of substrate graphite during treatment.

3. The method of claim 1, wherein, The front side of the heating cabin is provided with a first door body, and the rear side of the heating cabin is provided with a second door body at the connection with the storage box.

4. The method of claim 1, wherein, The vacuum system and the inert gas supply system are connected with the storage box at the same time to adjust the atmosphere in the storage box.

5. The method of claim 1, wherein, A glove is provided on the outer wall of the storage box to extend into the internal cavity, so as to facilitate the manual operation of transferring the treated substrate graphite from the heating cabin to the storage box.

6. The method of claim 1, wherein, The bottom of the heating cabin is provided with a guide rail, and the bottom of the tray is provided with a roller to facilitate the movement of the tray in the heating cabin.

7. The method of claim 1, wherein, The pressure in the heating cabin is reduced to within 5 Pa by the vacuum system to further facilitate the removal of water and oxygen.

8. The method of claim 1, wherein, The gas flow of the inert gas supply system is set to 0-10 L / min.

9. The method of claim 1, wherein, After the substrate graphite is transferred from the heating cabin to the storage box, all the door bodies are closed to ensure that the substrate graphite is not contaminated during storage.

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