Heating device and method for graphite corrosion under steam admission of pebble-bed reactor

Abstract

The invention discloses a method for graphite corrosion under steam admission of a pebble-bed reactor, and relates to the technical field of accident experiment research of pebble-bed high-temperature gas cooled reactors. Comprising a mounting unit which comprises a graphite cavity, and graphite nodules are placed in the graphite cavity; and the heating unit comprises a stainless steel sleeve on the outer wall of the graphite cavity, a cover plate on the graphite cavity, a flange connection between the stainless steel sleeve and the cover plate, and an air outlet at the bottom of the graphite cavity. The experimental device can simulate different steam admission accident working conditions, research oxidation corrosion behaviors of graphite nodules and provide data support for high-temperature gas cooled reactor steam admission accident safety assessment and accident analysis program verification, has innovativeness, and is simple in structure, convenient to operate and high in practicability. The graphite corrosion behavior under the steam admission accident of the high-temperature gas cooled reactor can be effectively researched, practicability is achieved, research results of the experimental device can provide important reference for safety design and operation of the high-temperature gas cooled reactor, and the experimental device has important significance.

Description

Technical Field

[0001] The invention relates to the technical field of accident experimental research of a pebble bed type high temperature gas-cooled reactor, and in particular to a heating device and a method for graphite corrosion under steam inlet of a pebble bed reactor. Background Art

[0002] As one of the fourth generation advanced reactor types, the high temperature gas-cooled reactor (HTGR) has the characteristics and advantages of inherent safety, high power generation efficiency, simple system, wide application, and modular construction. The pebble bed type high temperature gas-cooled reactor refers to a nuclear reactor that uses helium as a coolant and graphite as a neutron moderator. The core of the pebble bed type high temperature gas-cooled reactor is composed of spherical fuel elements stacked in the reactor pressure vessel.

[0003] The oxidation corrosion behavior of graphite balls involves complex thermochemical reactions, and the relevant test conditions are demanding. As a result, there is a serious lack of graphite oxidation corrosion data under steam inlet accident conditions in high-temperature gas-cooled reactors. Due to the lack of experimental data, the safety margin of high-temperature gas-cooled reactors under steam inlet accident conditions is difficult to establish, and there are difficulties in verifying the core safety assessment and accident analysis procedures. Summary of the invention

[0004] In view of the problems existing in the above-mentioned existing method of graphite etching in pebble bed under steam, the present invention is proposed.

[0005] Therefore, the present invention provides a method for graphite corrosion under steam inlet in a pebble bed reactor, the purpose of which is that high temperature gas-cooled reactor steam inlet accident experimental data are urgently needed in core safety assessment and related accident analysis program verification, so as to provide experimental benchmarks and data support for establishing the safety boundary of steam inlet accidents.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a heating device, comprising an installation unit, comprising a graphite cavity, in which graphite balls are placed; a heating unit, comprising a stainless steel sleeve arranged on the outer wall of the graphite cavity, a cover plate arranged on the graphite cavity, a flange connection between the stainless steel sleeve and the cover plate, and an air outlet arranged at the bottom of the graphite cavity.

[0007] As a preferred solution of the heating device of the present invention, the cooling chamber is arranged between the stainless steel sleeve and the graphite cavity, and the water outlet and water inlet are arranged on the outer wall of the stainless steel sleeve.

[0008] As a preferred solution of the heating device described in the present invention, it includes: a heating rod arranged on the cover plate, temperature and pressure measuring points arranged at the upper and lower ends of the graphite cavity, a steam inlet arranged on the cover plate, and an air inlet arranged on the cover plate.

[0009] The beneficial effects of this device are as follows: by arranging a heating rod in the graphite cavity, the graphite balls can be quickly heated to achieve vaporization temperature regulation; at the same time, by arranging a water outlet and a water inlet, water circulation is achieved to avoid damage to the graphite cavity due to excessive temperature.

[0010] Another object of the present invention is to provide a method for graphite corrosion in a pebble bed pile under steam inlet conditions, the purpose of which is to provide test benchmarks and data support for establishing a safe boundary for a steam inlet accident.

[0011] In order to solve the above technical problems, the present invention provides the following technical solutions: the graphite balls to be tested are piled up in a graphite cavity, and the graphite cavity is filled with helium; cooling water is introduced to protect the graphite cavity, and heating is performed, and when the temperature reaches the set value, steam is introduced to simulate a steam inlet accident; the gas generated in the experiment is collected and analyzed by a gas-liquid separation tank to evaluate the graphite corrosion.

[0012] As a preferred solution of the method for graphite corrosion under steam injection in a ball bed of the present invention, after the graphite balls to be tested are accumulated in the graphite cavity, the valve of the helium bottle is opened, and the graphite cavity is filled with helium through the air inlet, the liquid level of the water tank is checked, and after ensuring that there is sufficient cooling water, the water pump is turned on to fill the cooling cavity through the water inlet to protect the graphite cavity, and the heating power is turned on.

[0013] As a preferred solution of the method for graphite corrosion under steam in a pebble bed according to the present invention, the heating power supply includes starting a heating rod, reading the temperature and pressure of the graphite cavity through temperature and pressure measuring points, and opening the steam tank after reaching the set value to generate steam under specified working conditions.

[0014] As a preferred solution of the method for graphite corrosion under steam injection in a pebble bed pile of the present invention, the steam injection experiment starts after the steam tank produces steam that meets the setting, the manual control valve at the air inlet of the helium bottle is closed, the helium source is closed, the electric control valve and the electromagnetic regulating valve are opened to control the flow rate of the steam, so that the steam enters the graphite cavity according to the flow rate set in the experiment and reacts with the graphite balls.

[0015] As a preferred solution of the method for graphite corrosion under steam in a ball bed stack described in the present invention, the electric control valve is opened after the experimental set time is reached, so that the gas and liquid generated by the reaction in the graphite cavity are discharged through the gas outlet and enter the gas-liquid separation tank, and the liquid will enter the collection water tank.

[0016] As a preferred solution of the method for graphite corrosion under steam in a pebble bed according to the present invention, the manual control valve and the manual control valve are opened respectively to allow the separated gas to enter the gas sampling device for sampling, and at the same time, liquid is sampled from the collection water tank.

[0017] As a preferred scheme of the method for graphite corrosion under steam injection in the ball bed of the present invention, the sampling gas is analyzed by gas chromatograph to obtain the relationship between the generation rate of gases such as hydrogen and carbon monoxide and the time, and the graphite corrosion situation is evaluated. At the same time, the graphite cavity is dismantled, and the surface morphology, microstructure, etc. of the graphite balls are analyzed to further determine the corrosion situation.

[0018] The beneficial effects of the present invention are as follows: the experimental device can simulate different steam inlet accident conditions, study the oxidation corrosion behavior of graphite balls, and provide data support for the safety assessment of high-temperature gas-cooled reactor steam inlet accidents and the verification of accident analysis procedures. The experimental device is innovative, has a simple structure, and is easy to operate. It can effectively study the graphite corrosion behavior under high-temperature gas-cooled reactor steam inlet accidents and is practical. The research results of the experimental device can provide important reference for the safe design and operation of high-temperature gas-cooled reactors, and are of great significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 It is an overall schematic diagram of the heating device of the present invention.

[0021] Figure 2 It is an overall schematic diagram of the method for graphite etching under steam in a pebble bed according to the present invention. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0023] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0024] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0025] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0026] Example 1, reference Figure 1 , which is the first embodiment of the present invention, provides a heating device, including a stainless steel sleeve 201 surrounding a graphite cavity 101, a cooling cavity 201a is arranged in the stainless steel sleeve 201, the cooling cavity 201a is used for circulating cooling water, and a water inlet 201c and a water outlet 201b are respectively arranged near both ends of the outer wall of the stainless steel sleeve 201. The cooling water enters the cooling cavity 201a through the water inlet 201c and starts to circulate. The cooling water flows out of the cooling cavity 201a through the water outlet 201b and returns to the water tank for cooling again, taking away the heat and preventing the graphite cavity 101 from overheating.

[0027] Furthermore, the cover plate 202 and the stainless steel sleeve 201 are connected by flanges to provide a stable connection method, enclosing the graphite cavity 101, and the cover plate 202 carries components such as the heating rod 202a, the temperature and pressure measuring point 202b, the steam inlet 202c and the air inlet 202d. The heating rod 202a is arranged on the cover plate 202, and the heating body of the heating rod 202a extends through the cover plate 202 to the bottom of the graphite cavity 101, providing heat for the graphite cavity 101, simulating the operating temperature of the high temperature gas-cooled reactor.

[0028] Among them, the temperature and pressure measuring point 202b is used to monitor the temperature and pressure inside the graphite cavity 101. During the steam intake accident, there is a pressure gradient inside the graphite cavity 101, and there is a difference in pressure at both ends. Installing the temperature and pressure measuring points 202b at both ends can more accurately measure the pressure changes and study the stress conditions of the graphite ball 102 to ensure that the experimental conditions meet the requirements.

[0029] Furthermore, the steam inlet 202c is used to introduce steam into the graphite cavity 101 to simulate a steam inlet accident condition, and the gas inlet 202d is used to introduce helium into the graphite cavity 101 to protect the graphite ball 102 and prevent dry burning.

[0030] Example 2, reference Figure 2 , which is the second embodiment of the present invention, and this embodiment is different from the first embodiment in that it includes: the test circuit system mainly consists of a cooling water circuit system, a steam circuit system, a test body, i.e., embodiment 1, an outlet auxiliary system, and a data acquisition system. In this test system, the oxidation corrosion test of the graphite ball 102 under various different steam inlet accident conditions can be completed to study the oxidation corrosion behavior of the graphite ball 102 bed under different temperatures and different steam pressures.

[0031] The test body is a cylindrical graphite cavity 101, in which a bed is stacked to simulate the graphite fuel pebble bed of a pebble bed high temperature gas-cooled reactor. A stainless steel sleeve 201 is provided outside the graphite cavity 101 to protect the test body.

[0032] The cooling water circuit system mainly includes a deionized water tank, a shielded pump, an electric regulating valve, a mass flow meter, and a solenoid valve, etc. The cooling water from the deionized water tank enters the stainless steel sleeve 201 outside the graphite chamber 101 after passing through the shielded pump and the mass flow meter. The steam circuit system mainly includes a steam tank, an electric regulating valve, a mass flow meter, and a solenoid valve, etc.

[0033] Before the experiment, all valves were closed, and only the valve for connecting helium to the gas inlet 202d of the graphite chamber 101 and the helium valve of the helium bottle were opened. Helium was continuously introduced during the heating process to protect the test heating device, and at the same time, damage due to dry burning during the heating of the body could be prevented. Before steam injection, cooling water would first circulate in the water circuit and be adjusted to the flow rate required for the experiment. When the temperature of the ball bed reached the required experimental temperature, the helium inlet and outlet valves were quickly closed, and the solenoid valve connected to the steam circuit above the experimental body was opened to simulate the steam inlet accident process. The temperature, flow rate, and pressure difference in the graphite ball 102 bed during the steam inlet process were recorded by the data acquisition system. The outlet gas of the experimental body was connected to the gas-liquid separation tank of the outlet auxiliary system through a pipeline. A copper coil was set in the gas-liquid separation tank, which was connected to the chiller and passed circulating cooling water, so that the steam condensed during the flow and gathered at the bottom of the tank, and the remaining non-condensable gas entered the exhaust gas collection tank through the top outlet and the gas sampling device. During the steam inlet process, the outlet gas is sampled regularly, and the sampled gas is input into the gas chromatograph to analyze the volume fraction of each gas component, and the relationship between the generation rate of hydrogen, carbon monoxide, etc. and time is obtained. Parameters such as temperature, flow, pressure, and gas component concentration during the experiment are recorded, stored, and analyzed by the data acquisition system. In each set of test conditions, two special graphite balls 102 (inner diameter 50mm, non-fuel graphite cladding layer thickness 5mm) are placed near the steam inlet nozzle to study whether the graphite cladding shell is broken or cracked. At the same time, after each set of test conditions, it is necessary to monitor the corrosion conditions at different positions inside the graphite cylinder.

[0034] The remaining structures are the same as those of Example 1.

[0035] Example 3, reference Figure 2, which is the third embodiment of the present invention, and this embodiment is different from the second embodiment in that it includes: weighing the graphite balls 102 to be tested and stacking them in the test body to simulate the graphite fuel ball bed of the ball bed type high temperature gas-cooled reactor, turning on the helium source, filling the test body with helium, protecting the test body and avoiding dry burning damage. Turning on the cooling water circuit, adjusting the flow, and protecting the test body. Turning on the test body heating power supply, heating the body, ensuring the flow of helium, avoiding dry burning damage, monitoring the temperature and pressure of the test body through the temperature and pressure measuring point 202b, and turning on the steam generator after reaching the set value to generate steam under the specified working condition.

[0036] Furthermore, when the steam that meets the setting is generated, the helium inlet and outlet valves are closed, and the electric control valve and the electromagnetic regulating valve are opened to control the steam flow so that it enters the test body and reacts with the graphite ball 102. During the steam inlet process, the temperature, flow, pressure difference and other parameters in the graphite ball 102 bed are recorded by the data acquisition system. After the experimental setting time is reached, the electric control valve is opened to discharge the gas and liquid generated by the reaction in the body and enter the gas-liquid separation tank.

[0037] The manual control valve is opened to allow the separated gas to enter the gas sampling device. The gas is sampled in the gas sampling device and the collection water tank, and the gas can be analyzed by a gas chromatograph to obtain the relationship between the generation rate of gases such as hydrogen and carbon monoxide and the time. The parameters such as temperature, flow, pressure, and gas component concentration recorded during the experiment are stored and analyzed to study the oxidation corrosion behavior of the graphite ball 102 at different temperatures and different steam pressures.

[0038] Finally, the experimental body is dismantled, and the test graphite ball 102 is weighed and analyzed to determine the corrosion condition.

[0039] The experimental data were compared and analyzed with the theoretical model to verify the accuracy of the theoretical model and provide data support for the establishment of the safety boundary of the high-temperature gas-cooled reactor steam inlet accident.

[0040] The remaining structure is the same as that of Example 2.

[0041] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​such as temperature, pressure, etc., installation arrangements, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to several modifications still falling within the scope of the appended claims.

[0042] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0043] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A heating device, characterized in that: include, The mounting unit (100) comprises a graphite cavity (101), and a graphite ball (102) is placed in the graphite cavity (101); The heating unit (200) comprises a stainless steel sleeve (201) arranged on the outer wall of the graphite cavity (101), a cover plate (202) arranged on the graphite cavity (101), a flange connection between the stainless steel sleeve (201) and the cover plate (202), and an air outlet (203) arranged at the bottom of the graphite cavity (101).

2. The heating device according to claim 1, characterized in that: A cooling chamber (201a) between the stainless steel sleeve (201) and the graphite cavity (101), and a water outlet (201b) and a water inlet (201c) arranged on the outer wall of the stainless steel sleeve (201).

3. The heating device according to claim 2, characterized in that: A heating rod (202a) arranged on the cover plate (202), temperature and pressure measurement points (202b) arranged at the upper and lower ends of the graphite cavity (101), a steam inlet (202c) arranged on the cover plate (202), and an air inlet (202d) arranged on the cover plate (202).

4. A method for graphite corrosion under steam in a pebble bed, characterized in that: Applicable to the heating device as claimed in any one of claims 1 to 3, the method comprises: The graphite balls (102) to be tested are stacked in a graphite cavity (101), and the graphite cavity (101) is filled with helium gas; Cooling water is introduced into the graphite cavity (101) for protection and heating, and when the temperature reaches a set value, steam is introduced to simulate a steam inlet accident; The gas produced in the experiment was collected and analyzed by a gas-liquid separation tank to evaluate the graphite corrosion.

5. The method for graphite etching in a pebble bed under steam injection according to claim 4, characterized in that: After the graphite balls (102) to be tested are accumulated in the graphite cavity (101), the valve of the helium bottle is opened to fill the graphite cavity (101) with helium through the gas inlet (202d), the liquid level of the water tank is checked, and after ensuring that there is sufficient cooling water, the water pump is turned on to fill the cooling cavity (201a) through the water inlet (201c) to protect the graphite cavity (101), and the heating power is turned on.

6. The method for graphite etching in a pebble bed under steam injection according to claim 5, characterized in that: The heating power supply starts the heating rod (202a), reads the temperature and pressure of the graphite cavity (101) through the temperature and pressure measuring point (202b), opens the steam tank after reaching the set value, and generates steam of the specified working condition.

7. The method for graphite etching in a pebble bed under steam injection according to claim 6, characterized in that: After the steam tank produces steam that meets the setting, the steam inlet experiment begins, the manual control valve of the helium bottle inlet (202d) is closed, the helium source is turned off, and the electric control valve and the electromagnetic regulating valve are opened to control the flow rate of the steam, so that the steam enters the graphite cavity (101) according to the flow rate set in the experiment and reacts with the graphite ball (102).

8. The method for graphite etching in a pebble bed under steam injection according to any one of claims 5 to 7, characterized in that: After the experimental set time is reached, the electric control valve is opened to allow the gas and liquid generated by the reaction in the graphite cavity (101) to be discharged through the gas outlet (203) and enter the gas-liquid separation tank, and the liquid will enter the collection water tank.

9. The method for graphite etching in a pebble bed under steam injection according to claim 8, characterized in that: Open the manual control valve and the manual control valve respectively to allow the separated gas to enter the gas sampling device and be sampled. At the same time, sample the liquid from the collection tank.

10. The method for graphite etching in a pebble bed under steam injection according to claim 9, characterized in that: The sampled gas is analyzed by a gas chromatograph to obtain the relationship between the generation rate of hydrogen and carbon monoxide and time, and the corrosion of the graphite is evaluated. At the same time, the graphite cavity (101) is removed, and the surface morphology and microstructure of the graphite ball (102) are analyzed to further determine the corrosion condition.

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