CN110531635B - A "virtual valve"-based modeling and calculation method for the flow channel of the main pump of the fast reactor - Google Patents

Abstract

The invention discloses a "virtual valve"-based modeling calculation method for the flow channel of a main pump of a fast reactor, which belongs to the technical field of three-dimensional numerical simulation of electric stacks. Based on the pool-type sodium-cooled fast reactor, the reactor vessel 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 transients in the fast reactor under various operating conditions can be carried out. By changing the properties of each surface of the communication coupling module between the main pump and the pressure pipe, and making some simple changes to the surface properties of the communication coupling module of the primary circuit main pump, the transient state of the flow process in the reactor can be accurately simulated. Under various operating conditions, the accident system analysis of the primary circuit of the fast reactor and the three-dimensional thermal transient calculation of the fluid in the reactor are carried out, including normal operation, predicted operating events and accident conditions. The present invention greatly reduces the workload of modeling and calculation. It is realized that a set of grid files can be used to complete the calculation of multiple operating conditions, providing support and basis for fast reactor design and safety analysis.

Description

A "virtual valve"-based modeling and calculation method for the flow channel of the main pump of the fast reactor

technical field

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

Background technique

Fast reactor is an important direction of the fourth generation reactor. Fast reactor can consume the nuclear waste produced by thermal neutron reactor, utilize the non-fissionable nuclides widely existing in nature that thermal neutron reactor cannot use, and generate thermal energy. Taking the pool-type sodium-cooled fast reactor as an example, the system includes primary and secondary sodium circuits and sodium-water (steam) heat exchangers. The core, the primary circuit coolant pump and its outlet pipes, and the intermediate heat exchanger are arranged in In a sodium pool, an integrated structure is formed. Liquid sodium metal is used as primary circuit coolant and secondary circuit heat carrier. The reactor body is integrally arranged. The upper part of the main container is an argon gas chamber, which isolates the primary circuit sodium and the external atmosphere. A loop has two loops in parallel. 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.

At home and abroad, many one-dimensional and two-dimensional system software analysis has been carried out on the primary circuit system in the reactor, such as the FASYS program developed by China Institute of Atomic Energy for accident analysis of pool-type sodium-cooled fast reactor, THPCS and THACS developed by Xi'an Jiaotong University , and some foreign accident analysis software such as SSC-L, SSC-K, SIMMER, etc., all obtain one-dimensional or two-dimensional system analysis results. However, the characteristics of thermal fluid in the fast pool reactor have obvious three-dimensional characteristics, and detailed three-dimensional transient characteristics simulation is required. At present, most of the three-dimensional calculations of fast reactors at home and abroad are local single components. For example, Zhang Xiaolong et al. studied the influence of different arrangements of the internal tube bundles of the intermediate heat exchanger on the internal temperature and flow field temperature distribution, and Faruk et al. studied the internal blockage of a box of components The influence 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 cooling system of the main container of the pool 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 coupled simulation of the full reactor of the pool-type fast reactor, A.Toti et al. used RELAP5 and FLUENT for the MYRRHA research reactor to perform 3D calculations under the water loss transient state, and U.Parthasarathy et al. used commercial software and secondary loop 1D software. The combined method is used to calculate the effect of the waste heat removal system of the PHENIX reactor. Xu Yijun et al. modeled the cold and hot sodium pool of CEFR and calculated it in a transient state, but the model is relatively simplified and cannot be accurate. Simulate the flow characteristics of the fluid in the reactor under various operating conditions. At present, there is no precedent for full-reactor and detailed three-dimensional transient numerical simulation of fast reactors at home and abroad.

The present invention provides a "virtual valve"-based modeling calculation method for the main pump flow channel of a fast reactor. Taking a 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 3D thermal transient calculation of the pooled sodium-cooled fast reactor under various accident conditions can greatly reduce the workload of modifying the mesh and modeling. For example, in the event of a water loss accident, the two primary circuit main pumps can operate normally, but the reactor core must be shut down at this time. In order to match the changes in the reactor, the flow rate of the primary circuit main pump also changes accordingly. In other words, the inlet of the main pump is the constant flow inlet boundary condition. When a pump shaft jam accident occurs, the boundary conditions of one main pump 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 power outage in the whole plant, the two main pumps in the primary circuit are idling. After the idling is over, there is no inlet and outlet 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. No pump can be calculated as a boundary condition. The research results can provide support and basis for the design of fast reactors.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a "virtual valve" based method for modeling and calculating the flow channel of the main pump of the fast reactor, characterized in that the primary circuit in the 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 the connection of the pressure pipe 5, the grid header 3 and the core 2 is a closed system, and the b and d surfaces of the communication 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 transient calculation of the three-dimensional thermal fluid in the primary circuit includes the following steps:

Step 1: At the junction of the two main pumps in the first circuit and the pressure pipe, each set up a connected coupling module for boundary condition conversion. The connected coupling module is connected with the overall fast reactor model through the interface in fluent. Adjust the surface type of the interface in fluent, change the flow inlet of the fast reactor model or close the flow inlet, which 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, reasonably simplify the reactor vessel and internal components, and establish a central measuring column 1, the core 2, the grid header 3, the main vessel 4, the pressure tube 5, the inner Support 6, two primary circuit main pumps 7, overflow window 8, biological shielding column 9, intermediate heat exchanger 10, extra-core biological shielding column 11, core shielding 12, communication coupling module 13, core melting collector A detailed three-dimensional pool-type sodium-cooled fast reactor model with a sodium extruder; this model can accurately simulate the transient conditions of the flow process in the reactor, and obtain the detailed three-dimensional thermal-hydraulic parameters of the reactor fluid. temperature, pressure, speed;

Step 3: Determine the physical property parameters of the sodium fluid. The physical property parameters of the sodium are the density, viscosity, and specific heat capacity of the liquid sodium input before the calculation, and then after the calculation, the obtained three-dimensional thermal-hydraulic parameters of the fluid in the reactor include 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 heat 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 fuction program that comes with fluent, thereby controlling the power change of each component of the pool-type sodium-cooled fast reactor under different working conditions.

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

When calculating the steady state, artificially given inlet and outlet are needed to simulate the sodium flow in the primary circuit of the reactor. 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. 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. Controls to change the boundary conditions for different cases.

The beneficial effect of the present invention is that one model can be used to carry out the three-dimensional thermal fluid transient calculation in the fast reactor under various working conditions. By changing the properties of each surface of the communication coupling module between the main pump and the pressure pipe, By simply changing the surface properties of the connected coupling module of the primary circuit main pump, the three-dimensional calculation under this working condition can be realized, and the workload of modeling and calculation can be greatly reduced. Different boundary conditions can be given under different working conditions, and the calculation of multiple working conditions can be completed by 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 pooled fast reactor model established.

FIG. 2 is a schematic diagram of the flow route of the primary circuit coolant.

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

Detailed ways

The present invention provides a "virtual valve" based method for modeling and calculating the flow channel of a main pump of a fast reactor. The present invention will be described below with reference to the accompanying drawings.

Figure 1 shows a schematic diagram of the pooled fast reactor model. The established pool-type fast reactor includes a central measuring column 1, a core 2, a grid header 3, a main vessel 4, a pressure pipe 5, an inner support 6, two primary circuit main pumps 7, an overflow window 8, and a biological shield. Detailed three-dimensional pool-type sodium-cooled fast reactor model of column 9, intermediate heat exchanger 10, ex-core bioshield column 11, core shield 12, on-coupling module 13, core melt collector and sodium squeezer; in In the built three-dimensional pool type fast reactor model, after the fluid enters the grid header 3 through the main pump 7 and the pressure pipe 5, the flow is distributed, and most of the fluid enters the core 2 to be heated, and flows out of the core 2 through 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 then 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 showing the flow route of the primary circuit coolant. The primary circuit in the fast reactor vessel is a pool-type sodium-cooled fast reactor primary circuit composed of two main pumps 7, a communication coupling module 13, a pressure pipe 5, a grid header 3 and the core 2. It is a closed system. The b and d surfaces of the communication coupling modules 13 on both sides are set as internal surfaces, and the a and c surfaces are set as solid surfaces; the e surface is the channel through which the fluid enters the pump from the cold pool; The calculation of the state includes the following steps:

Step 1, at the junction of the two main pumps of the first circuit and the pressure pipe, each is provided with a communication coupling module 13 for boundary condition conversion, and the communication coupling module 13 is connected with the overall fast reactor model through the interface in fluent ( As shown in Figures 1 and 2), by adjusting the surface type of the interface in fluent, set the b and d surfaces of the connected coupling modules 13 on both sides as internal surfaces, and set the a and c surfaces as solid surfaces; The flow inlet of the stack model or the closed flow inlet 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. The 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 follows: The temperature, pressure and velocity of the fluid everywhere in the reactor; under the normal operating conditions of the reactor, the temperature and flow rate of the fluid delivered to the core by the main pump of the primary circuit are all given. The annular c-plane shown is set as the flow boundary inlet of the model, and the a-plane is set as the outlet of the model. The flow into the system through the c-surface is controlled by an external udf program, and the temperature is assigned to the fluid flowing through the c-surface through the temperature obtained by the a-surface. Although the model is artificially given the entrance and exit, but the entrance is the obtained outlet. temperature, and set the outlet as a pressure boundary outlet to balance the flow in the system, so the flow and temperature in the system are matched.

Step 3: Determine the physical property parameters of the sodium fluid. The physical property parameters of the sodium are the density, viscosity, and specific heat capacity of the liquid sodium input before the calculation, and then after the calculation, the obtained three-dimensional thermal-hydraulic parameters of the fluid in the reactor include 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 heat 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 fuction program that comes with fluent, thereby controlling the power change of each component of the pool-type sodium-cooled fast reactor under different working conditions. As shown in (a) and (b) of 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, and no modification of cas is required. file, only need to change the corresponding function in the udf program, the power of the IHX and core can be changed according to the law required by the corresponding working conditions.

Example

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

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

2) Transient 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 secondary circuit intermediate heat exchanger 10, and accordingly, the hot sodium in the primary circuit cannot be effectively obtained. The cooling power of the primary circuit intermediate heat exchanger 10 drops rapidly. Within a few seconds of receiving the water loss signal from the steam generator, the control rods are inserted, and the reactor core 2 starts to shut down. In order to match the power change in the reactor, the flow rate of the primary circuit main pump 7 gradually decreases, and the fluid temperature also increases with the temperature in the cold pool. The temperature changes, so in this transient condition, the inlet flow and temperature change with time. In the udf program, the a and b surfaces are set as the flow inlet boundary conditions where the flow changes with time, and the average of the a surface is taken. The temperature is imparted to the fluid entering the system through the c-plane, and the two main pumps 7 and the pressure pipe 5 are set like this, and the fluid flow direction is shown in Fig. 3(a).

3) Transient condition 2, one main pump in the primary circuit gets stuck: when this accident occurs, suppose the second main pump 7 (on the right in Figure 2) of the primary circuit is stuck and cannot provide kinetic energy to the fluid, the second main pump The pump 7 becomes a resistance channel through which the fluid can be accommodated. At this time, the a surface of the second main pump 7 is set as a solid surface, and the b and d surfaces of the communication coupling module 13 are changed into internal surfaces, allowing the 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). The other intact first main pump 7 gives the inlet flow boundary according to the arrangement shown in (a) of FIG. 3 .

4) Transient working condition 3, full-scale power failure accident: When this accident occurs, the entire power plant loses power, and the two main pumps 7 will lose power and start idling. During the idle time of the main pumps 7, the communication coupling modules 13 of the two main pumps 7 are set as shown in (a) in Figure 3, and the inlet flow is given according to the flow idle curve; The module 13 adopts the setting shown in (b) of FIG. 3 . The b and d surfaces of the communication coupling modules on both sides are set as internal surfaces, and the a and c surfaces are set as solid surfaces, so that the fluid can be allowed to flow in the main pump 7 . Internal flow, which satisfies the setting of natural circulation in the heap.

Claims (3)

1. a fast reactor main pump flow channel modeling calculation method based on "virtual valve" is characterized in that, the primary circuit in the fast reactor container is composed of two main pumps (7), a communication coupling module (13), a pressure pipe (5) The primary circuit of the pool-type sodium-cooled fast reactor formed by connecting the grid header (3) and the core (2) is a closed system, and connects the b and d surfaces of the communication coupling modules (13) on both sides. It is set as an internal surface, and the a and c surfaces are set as solid surfaces; the e surface is the channel for the fluid to enter the pump from the cold pool; the transient calculation of the three-dimensional thermal fluid in the primary circuit includes the following steps: Step 1: At the junction of the two main pumps in the first circuit and the pressure pipe, each set up a connected coupling module for boundary condition conversion. The connected coupling module is connected with the overall fast reactor model through the interface in fluent. By adjusting the surface type of the interface in fluent, the flow inlet or outlet of the fast reactor model can be changed without changing the grid, 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, reasonably simplify the fast reactor vessel and reactor internals, and establish a central measuring column (1), core (2), grid header (3), main vessel ( 4), pressure pipe (5), inner support (6), two main pumps (7), overflow window (8), biological shielding column (9), intermediate heat exchanger (10), extra-core biological Detailed three-dimensional pooled sodium-cooled fast reactor model of shield column (11), core shield (12), on-coupling module (13), core melt collector and sodium squeezer; the model can accurately simulate the flow in the reactor The transient working conditions of the process are obtained, and the detailed three-dimensional thermal-hydraulic parameters of the fluid in the reactor are obtained as the temperature, pressure, and velocity of the fluid everywhere in the reactor; Step 3: Determine the physical property parameters of the sodium fluid. The physical property parameters of the sodium fluid are the density, viscosity, and specific heat capacity of the liquid sodium input before the calculation; , 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 heat 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 fuction program that comes with fluent, thereby controlling the power change of each component of the pool-type sodium-cooled fast reactor under different working conditions. 2. The method for modeling and calculating the flow channel of the main pump of a fast reactor based on the "virtual valve" according to claim 1, wherein the boundary conditions of the fast reactor model are as follows: the inlet of the pressure pipe is given to the inlet fluid, and the pressure pipe is Above, the inside of the pump gives the pressure outlet. 3. The fast reactor main pump flow channel modeling calculation method based on "virtual valve" according to claim 1, is characterized in that, when calculating the steady state of the three-dimensional thermal fluid of the primary circuit, artificial given entrances and exits are required to simulate In the primary circuit of sodium flow in the reactor, the inlet is set at the impeller outlet of the main pump, that is, the c-surface where the main pump and the pressure pipe are connected in the model, and the outlet is set at the a-surface of the impeller inlet of the main pump in the actual model, and is set as The pressure outlet balances the flow of the primary circuit; 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.

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