CN110531635A - One kind being based on the fast reactor main pump circulation passage Modeling Calculation method of " virtual valve " - Google Patents

Abstract

The invention discloses a "virtual valve"-based fast reactor main pump circulation channel modeling calculation method, which belongs to the technical field of electric stack three-dimensional numerical simulation. Based on the pool-type sodium-cooled fast reactor, the reactor container and internal components are reasonably simplified, and a three-dimensional pool-type fast reactor model is established; using one model, the three-dimensional thermal fluid transient in the fast reactor under various working conditions can be carried out. State calculation, by changing the properties of each surface of the connection coupling module between the main pump and the pressure pipe, and partially changing the surface properties of the connection coupling module of the main pump of the primary circuit, the transient state of the flow process in the reactor can be accurately simulated Operating conditions: Perform system analysis of fast reactor primary circuit accidents and 3D thermal transient calculations of fluids in the reactor under various operating conditions, including normal operation, expected operating events and accident conditions. The invention greatly reduces the workload of modeling and calculation. Realize the calculation of multiple working conditions by using a set of grid files, and provide support and basis for fast reactor design and safety analysis.

Description

A Modeling and Calculation Method for Fast Reactor Main Pump Flow Channel Based on "Virtual Valve"

technical field

The invention belongs to the technical field of three-dimensional numerical simulation of fast reactors, and in particular relates to a modeling and calculation method of a main pump circulation channel of a fast reactor based on a "virtual valve". Specifically, it is a method that can be used for system analysis of fast reactor primary circuit accidents and 3D thermal transient calculation of fluid in the reactor under various operating conditions, including normal operation, expected operating events and accident conditions.

Background technique

Fast reactors are an important direction of the fourth generation reactors. Fast reactors can consume the nuclear waste produced by thermal neutron reactors, use the non-fissile nuclides that exist widely in nature that thermal neutron reactors cannot use, and generate heat energy. Taking the pool-type sodium-cooled fast reactor as an example, the system includes primary and secondary sodium loops and sodium-water (steam) heat exchangers. The core, the primary loop coolant pump and its outlet pipeline, and the intermediate heat exchanger are arranged in In a sodium pool, an integrated structure is formed. Liquid metal sodium is used as a coolant in the primary circuit and a heat carrier in the secondary circuit. The stack body is arranged in one piece. The upper part of the main container is an argon cavity, which isolates the primary loop of sodium and the external atmosphere. A primary circuit has two parallel circuits. There is one main circulation pump and two intermediate heat exchangers on each loop. The internal structure of the reactor is very complex, and the structural dimensions of different internal components vary greatly, which poses a great challenge to the numerical simulation calculation.

Many one-dimensional and two-dimensional system software analyzes have been carried out on the primary loop system in the reactor at home and abroad, such as the FASYS program developed by the China Institute of Atomic Energy for pool type sodium-cooled fast reactor accident analysis, and the THPCS and THACS programs developed by Xi'an Jiaotong University. , and some foreign accident analysis software such as SSC-L, SSC-K, SIMMER, etc., all get one-dimensional or two-dimensional system analysis results. However, the thermal fluid characteristics in the pool fast reactor have obvious three-dimensional characteristics, and detailed three-dimensional transient characteristics simulation is required. At present, the three-dimensional calculations of fast reactors at home and abroad are mostly local single components. For example, Zhang Xiaolong et al. studied the influence of different arrangements of tube bundles in the intermediate heat exchanger on its internal temperature and flow field temperature distribution. Faruk et al. studied the internal blockage of a box of components. The impact of different positions and shapes on the temperature field and flow field in the box, as well as the three-dimensional and two-dimensional calculations of the main vessel cooling system of the pool-type fast reactor, and the simple establishment of the primary loop of the fast reactor by Brendan et al. The model is used to analyze the thermal stratification phenomenon in the primary circuit. For the coupling simulation of the whole pool fast reactor, A.Toti et al. used RELAP5 and FLUENT to conduct three-dimensional calculations in the transient state of water loss for the research reactor MYRRHA. U.Parthasarathy et al. used commercial software and two-loop one-dimensional software Combined method to calculate the effect of waste heat removal system of PHENIX reactor, Xu Yijun et al. modeled and calculated the cold and hot sodium pool of CEFR, but the model is relatively simplified and cannot be accurately calculated Simulate the flow characteristics of the fluid in the reactor under various working conditions. At present, there is no precedent for full-stack and detailed three-dimensional transient numerical simulation of fast reactors at home and abroad.

The invention provides a "virtual valve"-based fast reactor main pump circulation channel modeling calculation method, taking the pool type sodium-cooled fast reactor as an example, through different processing of boundary conditions under different accidents, a set of grids can be established The three-dimensional thermal transient calculation of the pool-type sodium-cooled fast reactor under various accident conditions can greatly reduce the workload of grid modification and modeling. For example, when a water loss accident occurs, the two main pumps of the primary circuit can operate normally, but at this time the core must be shut down. In order to match the changes in the reactor, the flow rate of the main pumps of the primary circuit also changes accordingly. At this time, for the model For example, the inlet of the main pump is the constant flow inlet boundary condition. When a pump shaft stuck accident occurs, the boundary conditions of one of the main pumps remain unchanged, and the thermal parameters of the fluid passing through the other main pump are no longer known boundary conditions, and can only be obtained by calculation. In the event of a plant-wide power outage, the two main pumps in the primary circuit run idly. After the idling ends, there are no inlets and outlets in the reactor, and a natural circulation in the reactor is established. The thermal parameters of the fluid passing through the two pumps are unknown. None of the pumps can be calculated as boundary conditions. The research results can provide support and basis for the design of fast reactors.

Contents of the invention

The object of the present invention is to provide a kind of fast reactor main pump circulation channel modeling calculation method based on "virtual valve", it is characterized in that, a circuit in the described fast reactor vessel is composed of two main pumps 7, a communication coupling module 13, The primary circuit of the pool-type sodium-cooled fast reactor formed by connecting the pressure tube 5, the grid header 3 and the core 2 is a closed system, and the b-side and d-side of the connecting coupling modules 13 on both sides are set as internal surfaces, and the Surface a and surface c are set as solid surfaces; surface e is the channel through which the fluid enters the pump from the cold pool; the calculation of the transient state of the three-dimensional thermal fluid in the primary circuit includes the following steps:

Step 1. At the connection between the two main pumps of the primary circuit and the pressure pipe, set up a connection coupling module for boundary condition conversion. The connection coupling module is connected to the overall fast reactor model through the interface in fluent, and through the Adjust the surface type of the interface in fluent, change the flow inlet of the fast reactor model or close the flow inlet, simplify the grid model, so that a set of grid models can be used for calculation of various working conditions;

Step 2. In the pool-type sodium-cooled fast reactor, rationally simplify the reactor vessel and reactor internals, and establish a system including the central measurement column 1, the core 2, the grid header 3, the main vessel 4, the pressure tube 5, and the reactor Support 6, two primary circuit main pumps 7, overflow window 8, biological shielding column 9, intermediate heat exchanger 10, external biological shielding column 11, core shielding 12, communication coupling module 13, core melting collector The detailed three-dimensional pool-type sodium-cooled fast reactor model of the sodium squeezer; this model can accurately simulate the transient working conditions of the flow process in the reactor, and obtain detailed three-dimensional thermal and hydraulic parameters of the fluid in the reactor. temperature, pressure, speed;

Step 3, determine the physical parameters of the sodium fluid, the physical parameters of sodium are the density, viscosity, and specific heat capacity of the liquid sodium input before the calculation, and then after the calculation, the three-dimensional thermal hydraulic parameters of the fluids in the stack obtained include the temperature of the fluid , speed, pressure; and the physical parameters of the materials of each component: in fluent, the density, specific heat capacity, and viscosity of sodium change with temperature; the body cooling source of the intermediate heat exchanger IHX and the waste heat exhaust heat exchanger DHX, and the body heat source of the core It is controlled by writing the Users-defined function program that comes with fluent, so as to control the power of each component of the pool-type sodium-cooled fast reactor under different working conditions to change with time.

The boundary conditions of the fast reactor model: the inlet fluid is given at the inlet of the pressure tube, and the pressure outlet is given above the pressure tube and inside the pump.

When calculating the steady state, it is necessary to artificially set the inlet and outlet to simulate the primary loop sodium flow in the stack. The inlet is set at the outlet of the impeller of the main pump, that is, the c-plane where the main pump and the pressure pipe are connected in the model, and the outlet Set the impeller inlet a surface of the main pump in the actual model and set it as the pressure outlet to balance the flow of the primary circuit; under different accident conditions, by changing the properties of each surface of the transition section and the external udf to the inlet flow and temperature control to change the boundary conditions for different cases.

The beneficial effect of the present invention is that a single model can be used for the transient calculation of the three-dimensional thermal fluid in the fast reactor under various operating conditions, by changing the attributes of each surface of the communication coupling module between the main pump and the pressure pipe, for The three-dimensional calculation under this working condition can be realized by simply changing the surface properties of the connection coupling module of the main pump of the primary circuit, which greatly reduces the workload of modeling and calculation. Different boundary conditions can be given under different working conditions, and the calculation of multiple working conditions can be completed using a set of grid files, which provides support and basis for fast reactor design and safety analysis.

Description of drawings

Figure 1 is a schematic diagram of the established pool-type fast reactor model.

Figure 2 is a schematic diagram of the coolant flow path in the primary circuit.

The flow situation of the internal fluid at the communication coupling module between the main pump and the pressure pipe of Fig. 3, wherein (a) transition communication coupling module setting strategy 1; (b) transition communication coupling module setting strategy 2;

Detailed ways

The present invention provides a "virtual valve"-based fast reactor main pump circulation channel modeling calculation method, which will be described below in conjunction with the accompanying drawings.

Figure 1 shows a schematic diagram of a pool-type fast reactor model. The pool-type fast reactor established includes central measuring column 1, core 2, grid header 3, main container 4, pressure pipe 5, reactor support 6, two primary circuit main pumps 7, overflow window 8, biological shielding The detailed three-dimensional pool-type sodium-cooled fast reactor model of column 9, intermediate heat exchanger 10, extra-core biological shielding column 11, core shielding 12, communication coupling module 13, core melting collector and sodium squeezer; In the built three-dimensional pool-type fast reactor model, the fluid enters the grid header 3 through the main pump 7 and the pressure tube 5, and the flow is distributed. Most of the fluid enters the core 2 to be heated, and flows out of the core 2 through the The overflow window 8 on the biological shielding column 9 enters the hot pool area, and then enters the intermediate heat exchanger 10 to be cooled and sent back to the cold pool, and then driven into the core 2 by the main pump 7. The fluid flow route is shown by the arrow in Figure 1 Show.

Fig. 2 is a schematic diagram of the flow route of the coolant in the primary circuit. The primary circuit in the fast reactor vessel is a pool-type sodium-cooled fast reactor primary circuit composed of two main pumps 7, connection coupling modules 13, pressure pipes 5, grid header 3 and core 2. It is a closed system and Set the b and d faces of the connecting coupling modules 13 on both sides as internal faces, and set the a and c faces as solid faces; the e face is the passage for fluid to enter the pump from the cold pool; the three-dimensional thermal fluid of the first circuit is instantaneous The calculation of the state includes the following steps:

Step 1, at the junction of the two main pumps of the primary circuit and the pressure pipe, each set up a communication coupling module 13 for boundary condition conversion, and the communication coupling module 13 is connected to the overall fast reactor model through an interface in fluent ( As shown in Figures 1 and 2), by adjusting the surface type of the interface in fluent, the b and d surfaces of the connected coupling modules 13 on both sides are set as internal surfaces, and the a and c surfaces are set as solid surfaces; The flow inlet or closed flow inlet of the stack model simplifies the grid model, so that a set of grid models can be used for the calculation of various working conditions;

Step 2. In the pool-type sodium-cooled fast reactor, the reactor vessel and internal components are reasonably simplified. This model can accurately simulate the transient conditions of the flow process in the reactor, and the detailed three-dimensional thermal-hydraulic parameters of the reactor fluid are obtained as Fluid temperature, pressure, and velocity throughout the reactor; under normal operating conditions of the reactor, the temperature and flow rate of the fluid delivered by the main pump of the primary circuit to the core are given. At this time, the top of the pressure tube is shown in Figure 2 The annular c-surface shown is set as the flow boundary inlet of the model, and the a-surface is set as the outlet of the model. The flow entering the system through surface c is controlled by an external udf program, and the temperature obtained through surface a is assigned to the fluid flowing through surface c. Although the entrance and exit are artificially given in the model, the entrance is the obtained exit , and setting the outlet as a pressure boundary outlet, balances the flow in the system so the flow and temperature in the system match.

Step 3, determine the physical parameters of the sodium fluid, the physical parameters of sodium are the density, viscosity, and specific heat capacity of the liquid sodium input before the calculation, and then after the calculation, the three-dimensional thermal hydraulic parameters of the fluids in the stack obtained include the temperature of the fluid , speed, pressure; and the physical parameters of the materials of each component: in fluent, the density, specific heat capacity, and viscosity of sodium change with temperature; the body cooling source of the intermediate heat exchanger IHX and the waste heat exhaust heat exchanger DHX, and the body heat source of the core It is controlled by writing the Users-defined function program that comes with fluent, so as to control the power of each component of the pool-type sodium-cooled fast reactor under different working conditions to change with time. As shown in Figure 3, the power of IHX and core changes with time under accident conditions. In this calculation strategy, it is also controlled by an external udf program. There is no need to modify the cas file, only need to change the udf program The corresponding function can satisfy the power of IHX and core to change according to the law required by the corresponding working conditions.

Example

By adjusting the properties of each surface of the T-shaped connection coupling module 13 between the main pump 7 and the pressure pipe 5, it is possible to set different boundary conditions and perform calculations for different working conditions without changing the grid. Specific operation:

1) Steady-state working condition: when performing steady-state calculations, surface c is set as the inlet boundary of constant flow and constant temperature, surface a is the pressure outlet boundary, and other surfaces connected to the coupling module are set as wall;

2) Transient working condition 1, water loss accident on the secondary side of the steam generator: When this accident occurs, the steam generator cannot take away the heat of the intermediate heat exchanger 10 of the secondary circuit, and accordingly, the hot sodium in the primary circuit cannot be effectively The cooling power of the primary loop intermediate heat exchanger 10 drops rapidly. Within a few seconds of receiving the water loss signal from the steam generator, the control rods were inserted, and the reactor core 2 began to shut down. In order to match the power change in the reactor, the flow rate of the main pump 7 of the primary circuit gradually decreased, and the fluid temperature also increased with the temperature in the cold pool. The temperature changes, so in this transient condition, the flow and temperature of the inlet change with time. In the udf program, the surface a and surface b are set as the boundary conditions of the flow inlet that the flow changes with time, and the average value of surface a is taken The temperature is given to the fluid entering the system through the c-plane, the settings of the two main pumps 7 and the pressure pipe 5 are the same, and the fluid flow direction is shown in Figure 3 (a).

3) Transient working condition 2, one main pump shaft stuck accident in the primary circuit: When this accident occurs, it is assumed that the second main pump 7 of the primary circuit (on the right side of Figure 2) is stuck and cannot provide kinetic energy to the fluid. The pump 7 becomes a channel with a certain resistance that can accommodate the passage of fluid. At this time, the a surface of the second main pump 7 is set as a solid surface, and the b surface and d surface that will communicate with the coupling module 13 are turned into internal surfaces, allowing fluid to pass through the e surface, so that the communication between the second main pump 7 In the coupling module, a channel is formed, and the direction of fluid flow in it is shown by the arrow in Fig. 3(b). Another intact first main pump 7 is then given the inlet flow boundary according to the setting mode shown in (a) in Fig. 3 .

4) Transient working condition 3, the whole field power failure accident: when this accident takes place, the whole power plant loses power supply, and two main pumps 7 all can lose power, begin to run idly. During the idling time of the main pump 7, the connection and coupling modules 13 of the two main pumps 7 are set as shown in Fig. 3 (a), and the inlet flow is given according to the flow idling curve; The module 13 adopts the setting shown in (b) in Fig. 3, and the b-side and d-side of the connecting and coupling modules on both sides are set as internal surfaces, and the a-side and c-side are set as solid surfaces, so that the fluid can be allowed to flow in the main pump 7 The internal flow satisfies the setting of natural circulation in the heap.

Claims (3)

1. A fast reactor main pump circulation channel modeling calculation method based on "virtual valve", it is characterized in that, a loop in the described fast reactor vessel is composed of two main pumps (7), a communication coupling module (13), The primary circuit of the pool type sodium-cooled fast reactor formed by connecting the pressure tube (5), the grid header (3) and the core (2) is a closed system, and the b-side, The surface d is set as the internal surface, and the surfaces a and c are set as solid surfaces; the surface e is the channel through which the fluid enters the pump from the cold pool; the calculation of the transient state of the three-dimensional thermal fluid in the primary circuit includes the following steps: Step 1. At the connection between the two main pumps of the primary circuit and the pressure pipe, set up a connection coupling module for boundary condition conversion. The connection coupling module is connected to the overall fast reactor model through the interface in fluent, and through the Adjust the surface type of the interface in fluent, change the flow inlet of the fast reactor model or close the flow inlet, simplify the grid model, so that a set of grid models can be used for calculation of various working conditions; Step 2, in the pool-type sodium-cooled fast reactor, rationally simplify the reactor vessel and the reactor internals, and establish a structure including the central measuring column (1), the core (2), the grid header (3), the main vessel (4 ), pressure pipe (5), support in the reactor (6), two primary circuit main pumps (7), overflow window (8), biological shielding column (9), intermediate heat exchanger (10), external core A detailed three-dimensional pool-type sodium-cooled fast reactor model of the biological shielding column (11), core shielding (12), communication coupling module (13), core melting collector and sodium squeezer; this model can accurately simulate the Transient working conditions of the flow process, to obtain detailed three-dimensional thermal hydraulic parameters of the fluid in the reactor, which are fluid temperature, pressure, and velocity in various places in the reactor; Step 3. Determine the physical parameters of the sodium fluid. The physical parameters of sodium are the density, viscosity, and specific heat capacity of the liquid sodium input before the calculation. After the calculation, the three-dimensional thermal-hydraulic parameters of the fluids in the stack are obtained, including the temperature of the fluid. , speed, pressure; and the physical parameters of each component material: the density, specific heat capacity, and viscosity of sodium are used in fluent to change with temperature; the body cooling source of the intermediate heat exchanger IHX and the waste heat exhaust heat exchanger DHX, and the body heat source of the core It is controlled by writing the Users-defined function program that comes with fluent, so as to control the power of each component of the pool-type sodium-cooled fast reactor under different working conditions to change with time. 2. according to claim 1, based on the fast reactor main pump circulation channel modeling calculation method of "virtual valve", it is characterized in that, the boundary condition of described fast reactor model: give inlet fluid at the inlet of pressure tube, in pressure tube Above, inside the pump to give the pressure outlet. 3. According to the "virtual valve" based fast reactor main pump circulation channel modeling calculation method according to claim 1, it is characterized in that, when calculating the steady state of the three-dimensional thermal fluid of the primary circuit, it is necessary to artificially set the inlet and outlet to simulate The primary loop of sodium flow in the stack, the inlet is set at the outlet of the impeller of the main pump, that is, the surface c where the main pump and the pressure pipe are connected in the model, and the outlet is set at the surface a of the impeller inlet of the main pump in the actual model, and set as The pressure outlet balances the primary circuit flow; under different accident conditions, the boundary conditions of different working conditions are changed by changing the properties of each surface of the transition section and the control of the inlet flow and temperature by the external udf.