Heat pipe micro-reactor sodium fire hot gas layer simulation calculation method and device and safety analysis system

Abstract

The invention discloses a heat pipe micro-reactor sodium fire hot gas layer simulation calculation method. Firstly, the heat release rate of sodium fire is calculated according to the number of broken heat pipes and the sodium leakage rate; the working state of the heat pipe micro-stack is determined; when the heat pipe micro-stack is in a natural convection state, temperature and pressure rise caused by the sodium fire heat release rate is calculated; when the heat pipe micro-stack is in the forced heat exchange state, temperature and pressure rise caused by the sum of the sodium fire heat release rate and the heat transfer power of the heat pipe micro-stack heat exchanger is calculated. According to the method, the simulation calculation of the heat pipe micro-reactor sodium fire accident can be quickly, simply and conveniently realized, and guidance can be provided for the safety design and structure optimization of the heat pipe micro-reactor. The invention further provides a heat pipe micro-reactor sodium fire hot gas layer simulation calculation device and a safety analysis system.

Description

Technical Field

[0001] The present invention belongs to the field of nuclear power, and in particular relates to a heat pipe micro-pile nanofire hot gas layer simulation calculation method, device and safety analysis system. Background Art

[0002] Heat pipe micro reactor is a new type of miniaturized nuclear reactor, whose power is usually less than 20MWt or electric power is less than 10MWe. Heat pipe micro reactor does not need main pump during operation, and adopts solid core and passive heat pipe to transfer heat. Heat generated by fuel rod is led out through heat pipe for power generation. The heat transfer medium inside the heat pipe is usually sodium vapor. One end of the heat pipe is the evaporation end of sodium, and the other end is the condensation end. The circulation of sodium in the heat pipe realizes efficient heat conduction. However, the active nature of sodium is very active. Once it leaks into the high-temperature air environment, a sodium fire phenomenon will occur, causing the pressure and temperature in the heat pipe heat exchanger to change, interfering with the normal operation of the secondary circuit, and causing safety hazards to the reactor. At present, there is a lack of research on the distribution of temperature layers in the heat pipe heat exchanger after the sodium fire accident, which restricts the structural design optimization and safety assessment of heat pipe micro reactor. Therefore, it is of high practical value to provide a simulation calculation method for the hot gas layer of sodium fire in heat pipe micro reactor. Summary of the invention

[0003] The purpose of the present invention is to provide a heat pipe micro-reactor sodium fire hot gas layer simulation calculation method, and to predict and calculate the temperature and pressure state in the heat exchanger in the sodium fire accident. The present invention also provides a calculation device and a safety analysis system.

[0004] According to an embodiment of one aspect of the present invention, a method for simulating and calculating the hot gas layer of a heat pipe micro-reactor sodium fire is provided, comprising the following steps: calculating the heat release rate Q of a heat pipe micro-reactor sodium fire s , Q s =k s nm / t, where n is the number of broken heat pipes, m is the mass of sodium contained in a single heat pipe, t is the leakage time, k s is the heat released by the combustion of unit mass of sodium in a sodium fire accident; determine the working state of the heat pipe micro-reactor when a sodium fire accident occurs, and calculate the maximum temperature of the hot gas layer T g , when a sodium fire accident occurs in a natural convection state, Among them, T a is the initial temperature in the heat pipe heat exchanger, d1 is the exhaust air inlet and outlet diameter of the heat pipe heat exchanger, l is the exhaust air inlet and outlet height of the heat pipe heat exchanger, D is the inner diameter of the heat pipe heat exchanger, H is the length of the heat pipe heat exchanger, h k is the heat transfer coefficient of the heat pipe heat exchanger shell surface; when the sodium fire accident occurs in the forced heat exchange state, Among them, Q s ' is the sum of the heat release rate of sodium fire combustion and the heat transfer power of the heat pipe micro-reactor heat exchanger, ms is the air flow rate of the heat pipe heat exchanger, c p is the specific heat capacity of the air inside the heat pipe heat exchanger, d2 is the diameter of the compressed air inlet and outlet of the heat pipe heat exchanger; according to the maximum temperature inside the heat pipe heat exchanger, calculate the maximum pressure P of the hot gas layer g .

[0005] The above method can quickly and easily calculate the temperature and pressure state of the hot gas layer of the heat pipe micro-reactor after a sodium fire accident occurs during shutdown or operation based on the structural characteristics of the heat pipe micro-reactor combined with the calculation formula obtained by experimental verification and engineering experience, providing guidance for the safety design and structural optimization of the heat pipe micro-reactor.

[0006] Furthermore, in some embodiments, in the step of calculating the heat release rate of the heat pipe micro-pile sodium fire, t≤1s is taken. In order to leave safety redundancy for the safety design of the heat pipe micro-pile, the simulation estimate of the leakage rate of sodium vapor in the calculation process is that it leaks completely within no more than 1s.

[0007] Furthermore, in some embodiments, k s The value is calculated by weighted average based on the ratio of Na2O to Na2O2 generated by Na combustion.

[0008] Further, in some embodiments, the Where k is the heat transfer coefficient of the heat exchanger shell, ρ is the density of the heat exchanger shell, and c is the specific heat capacity of the heat pipe of the heat exchanger. k The calculation can be simplified.

[0009] Further, in some embodiments, when calculating the maximum pressure P in the hot gas layer, g When the gas in the heat pipe heat exchanger is calculated as an ideal gas, P g =(T g / T a ) a , where P a is the normal pressure in the heat pipe heat exchanger.

[0010] According to an embodiment of another aspect of the present invention, there is provided a heat pipe micro-reactor sodium fire hot gas layer simulation calculation device, the device comprising a memory and a processor, the memory storing program instructions, and when the program instructions are executed by the processor, the heat pipe micro-reactor sodium fire hot gas layer simulation calculation method provided in any of the aforementioned embodiments is implemented.

[0011] According to an embodiment of yet another aspect of the present invention, there is provided a safety analysis system for performing a probabilistic safety analysis on a heat pipe micro-reactor, the safety analysis system comprising the heat pipe micro-reactor sodium fire hot gas layer simulation calculation device of the aforementioned embodiment, the heat pipe micro-reactor sodium fire hot gas layer simulation calculation device being used to provide input for the probabilistic safety analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the structure of a heat pipe micro-stack heat exchanger in one embodiment;

[0013] Figure 2 Flow chart of a method for calculating the temperature and pressure of the hot gas layer of a heat pipe micro-stack in one embodiment.

[0014] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. For the sake of simplicity, the above drawings only schematically illustrate the structures related to the technical features of the present invention, and do not strictly follow the actual scale to draw the complete structure and all details. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0016] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. Those skilled in the art should be able to understand that the embodiments herein may be combined with other embodiments without causing structural conflicts.

[0017] In the description of this article, unless otherwise clearly specified and limited, the technical terms "install", "connect", "connect", etc. should be understood in a broad sense. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0018] In the description of this document, terms indicating orientation or positional relationships, such as "up", "down", "left", "right", "horizontal", "vertical", "height", "length", and "width", are intended to accurately describe the embodiments and simplify the description, but are not intended to limit the parts or structures involved to have a specific orientation, be installed or operate in a specific orientation, and should not be construed as a limitation on the embodiments in this document.

[0019] In the description of this article, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the quantity, specific order or primary and secondary relationship of the described technical features. In the description of this article, the meaning of "plurality" is at least two.

[0020] An embodiment of the present invention provides a heat pipe micro-reactor sodium fire hot gas layer simulation calculation method, which is used to simulate and calculate the temperature and pressure state of the sodium fire hot gas layer inside the heat exchanger shell when a sodium fire accident occurs in a heat pipe micro-reactor, and provide guidance for the heat pipe micro-reactor sodium fire PSA (probabilistic safety assessment) PSA.

[0021] Heat pipe micro stack heat exchanger structure Figure 1 As shown, it includes a heat pipe 1 and a heat exchanger shell 2. One end of the heat pipe 1 extends into the heat exchanger shell for heat exchange, and the other end is inserted into the reactor of the heat pipe micro-pile. The heat conduction from the reactor to the heat exchanger is realized through the sodium vapor in the heat pipe micro-pile. The heat exchanger shell 2 is provided with a residual air inlet and outlet 3 and a compressed air inlet and outlet 4. The residual air inlet and outlet are used to discharge the residual heat in the heat exchanger shell 2 through natural air convection when the heat pipe micro-pile is shut down (such as during transportation), and the compressed air inlet and outlet 4 is used to input compressed air to reduce the temperature of the heat pipe 1 by forced convection when the reactor is operating normally.

[0022] When simulating the hot gas layer generated by a sodium fire accident in a heat pipe micro reactor, the process is as follows: Figure 2 First, determine the heat release efficiency Q of the heat pipe micro-reactor sodium fire s , which is calculated as follows: Q s =ksnm / t, where n is the number of broken heat pipes, in units of roots; m is the mass of sodium contained in a single heat pipe, in units of kg / root; t is the leakage time, in units of seconds; k s It is the heat released by the combustion of unit mass of sodium in a sodium fire accident, measured in kJ / kg.

[0023] When sodium burns in air, it produces two products, sodium oxide and sodium peroxide, and releases heat.

[0024] 4Na+O2→2Na2O+9460kJ / kg

[0025] 2Na+O2→Na2O2+11279kJ / kg

[0026] The k under the corresponding conditions can be calculated by taking the weighted average of the reaction heat and the ratio of sodium oxide to peroxide generated in the sodium fire accident under the preset simulation conditions or the test measurement results. s In a preferred embodiment, assuming that the total amount of sodium oxide in the sodium fire accident caused by the heat pipe micro-pile sodium leakage is a, then k s =11279-1819a kJ / kg.

[0027] Next, determine the maximum temperature of the hot gas layer in the heat pipe heat exchanger shell. Depending on whether the heat pipe micro-reactor is still in operation, the accident situation is divided into two categories: the maximum temperature under natural convection through the residual air inlet and outlet 3, and the maximum temperature under forced heat exchange through the compressed air inlet and outlet 4.

[0028] In the shutdown state, such as when the heat pipe micro-stack is being transported, the exhaust air inlet and outlet 3 on the heat exchanger shell 2 is in an open state, and the residual heat of the heat pipe micro-stack is discharged by passive natural convection. At this time, if the heat pipe leaks and a sodium fire occurs, it can be considered that the space connected to the outside world exchanges heat through natural convection, and the maximum temperature of the hot gas layer T g It can be calculated as

[0029]

[0030] Among them, T a is the initial temperature inside the heat pipe heat exchanger shell 2, d1 is the diameter of the exhaust air inlet and outlet 3 of the heat pipe heat exchanger, l is the height of the exhaust air inlet and outlet 3 of the heat pipe heat exchanger, D is the inner diameter of the heat pipe heat exchanger shell 2, H is the length of the heat pipe heat exchanger shell 2, h k is the heat transfer coefficient of the heat pipe heat exchanger shell 2. Since the sodium fire burns for a short time, h k Can be Calculate, where k is the heat transfer coefficient of the heat exchanger shell 2, ρ is the density of the heat exchanger shell 2, and c is the specific heat capacity of the heat exchanger heat pipe.

[0031] When the heat pipe micro-reactor is running, the fan continuously blows the air at the turbine outlet into the heat pipe heat exchanger, taking away the heat of the reactor core derived from the heat pipe. At this time, the sodium fire phenomenon occurs, and it can be considered that the heat exchanger is in a forced heat exchange state. Since the heat pipe micro-reactor is in operation at this time, the maximum temperature of the hot gas layer T g The heat conducted by the heat pipe micro-UI itself must be considered during calculation.

[0032]

[0033] Among them, Q s ' is the sum of the heat release rate of sodium fire combustion and the heat transfer power of the heat pipe micro-reactor heat exchanger, m s is the air flow rate of the heat pipe heat exchanger, c p is the specific heat capacity of the air inside the heat pipe heat exchanger shell 2, and d2 is the diameter of the compressed air inlet and outlet 4 on the heat pipe heat exchanger shell 2.

[0034] The highest temperature T of the sodium fire hot gas layer is calculated. g Finally, the maximum pressure P of the hot gas layer is calculated. g : Under normal conditions, the gas in the heat pipe heat exchanger can be regarded as an ideal gas P g =(Tg / T a ) a , where P a is the normal pressure in the heat pipe heat exchanger. In other embodiments, the maximum pressure of the hot gas layer can also be corrected by the non-ideal gas state equation.

[0035] In the above process, the specific calculation formula is obtained according to the structural characteristics of the heat pipe micro-reactor combined with a large number of experimental verifications and engineering experience optimization by the inventor. It has the advantages of small calculation amount and high simulation accuracy, and is convenient for rapid analysis and simulation of sodium fire accidents in heat pipe micro-reactors.

[0036] In a preferred embodiment, the simulation calculates the accident state in which the number of broken heat pipes 1 is one, and the heat release rate of sodium fire combustion is calculated to be 2213.4kW according to the mass of sodium contained in a single heat pipe 1 and the proportion of oxygen in the heat pipe heat exchanger shell 2 under the simulation state. When the heat pipe heat exchanger is in the natural convection state, the initial temperature is 473.15K, the initial pressure is 0.1MPa, and after substituting the relevant parameters of the heat pipe heat exchanger, the simulation calculates that the maximum temperature inside the heat pipe heat exchanger shell 2 is 483.78K and the maximum pressure is 0.103MPa; when the heat pipe micro-pile is in operation, the initial temperature and pressure are higher than the natural convection state, the initial temperature is 500K, the initial pressure is 0.3MPa, and after taking into account the heat transfer power of the heat pipe micro-pile heat exchanger, the maximum temperature inside the heat pipe heat exchanger is calculated to reach 957.34K and the maximum pressure is 0.39MPa.

[0037] The above process is converted into a program language and stored as a program instruction in the memory of the heat pipe micro-pile sodium fire hot gas layer simulation computing device. When the processor of the computing device executes the program instruction, the heat pipe micro-pile sodium fire hot gas layer simulation computing process provided in the above embodiment can be completed, thereby improving the analysis speed of the sodium fire PSA. When simulating and calculating different accident conditions, only the initial accident parameters need to be adjusted to achieve rapid analysis and simulation of sodium fire accidents.

[0038] Another embodiment of the present invention provides a safety analysis system for performing PSA analysis of a heat pipe micro-reactor. The safety analysis system includes the heat pipe micro-reactor sodium fire hot gas layer simulation calculation device provided in the aforementioned embodiment. The heat pipe micro-reactor sodium fire hot gas layer simulation calculation device provides information input for PSA analysis.

[0039] The purpose of the above embodiments is to further explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the disclosure of the present invention, the optimization or equivalent replacement of the method steps involved, and the combination of the implementation methods in different embodiments without conflict of principle, all fall within the protection scope of the present invention.

Claims

1. A heat pipe micro-pile heat pipe sodium fire hot gas layer simulation calculation method, characterized in that: The following steps are involved: Calculation of heat release rate Q of sodium fire in heat pipe micro reactor s , Q s =k s nm / t, where n is the number of broken heat pipes, m is the mass of sodium contained in a single heat pipe, t is the leakage time, k s It is the heat released by the combustion of unit mass of sodium in a sodium fire accident; Determine the working state of the heat pipe micro-reactor when a sodium fire accident occurs and calculate the maximum temperature T of the hot gas layer g , when a sodium fire accident occurs in a natural convection state, Among them, T a is the initial temperature in the heat pipe heat exchanger, d1 is the exhaust air inlet and outlet diameter of the heat pipe heat exchanger, l is the exhaust air inlet and outlet height of the heat pipe heat exchanger, D is the inner diameter of the heat pipe heat exchanger, H is the length of the heat pipe heat exchanger, h k is the heat transfer coefficient of the heat pipe heat exchanger shell surface; When a sodium fire accident occurs during forced heat exchange, Among them, Q s ' is the sum of the heat release rate of sodium fire combustion and the heat transfer power of the heat pipe micro-reactor heat exchanger, m s is the air flow rate of the heat pipe heat exchanger, c p is the specific heat capacity of the air inside the heat pipe heat exchanger, d2 is the diameter of the compressed air inlet and outlet of the heat pipe heat exchanger; According to the maximum temperature in the heat pipe heat exchanger, the maximum pressure P of the hot gas layer is calculated. g .

2. The heat pipe micro-reactor sodium fire hot gas layer simulation calculation method according to claim 1 is characterized in that: In the step of calculating the heat release rate of the heat pipe micro-pile sodium fire, t≤1s.

3. The heat pipe micro-reactor sodium fire hot gas layer simulation calculation method according to claim 1 or 2 is characterized in that: The k s The value is calculated by weighted average based on the ratio of Na2O to Na2O2 generated by the combustion of Na.

4. The heat pipe micro-reactor sodium fire hot gas layer simulation calculation method according to claim 1 or 2, characterized in that: Said Wherein k is the heat transfer coefficient of the heat exchanger shell, ρ is the density of the heat exchanger shell, and c is the specific heat capacity of the heat pipe of the heat exchanger.

5. The heat pipe micro-reactor sodium fire hot gas layer simulation calculation method according to claim 1 or 2, characterized in that: In calculating the maximum pressure P in the hot gas layer g When the gas in the heat pipe heat exchanger is calculated as an ideal gas, P g =(T g / T a ) a , where P a is the normal pressure in the heat pipe heat exchanger.

6. A heat pipe micro-reactor sodium fire hot gas layer simulation calculation device, characterized in that: It comprises a memory and a processor, wherein the memory stores program instructions, and when the program instructions are executed by the processor, the heat pipe micro-reactor sodium fire hot gas layer simulation calculation method as claimed in any one of claims 1 to 5 is implemented.

7. A safety analysis system for probabilistic safety evaluation of a heat pipe micro-reactor, characterized in that: The safety analysis system includes the heat pipe micro-reactor sodium fire hot gas layer simulation calculation device as described in claim 6, and the heat pipe micro-reactor sodium fire hot gas layer simulation calculation device provides input for the probabilistic safety evaluation.

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