CN113506646B - Method and device for judging geometric structure of reactor core node in reactor core melting process - Google Patents

Abstract

The application relates to a method and a device for judging a core node geometric structure in a core fusion process, wherein the method comprises the following steps: obtaining initial porosity and critical porosity; the initial porosity is a calculated value of the porosity of the reactor core node in a complete state; acquiring the current porosity and the current melting share of each reactor core node; comparing the current porosity with the initial porosity and the critical porosity; and judging the geometric structure of the corresponding reactor core node according to the comparison result and the current melting share value. According to the scheme, the judgment criterion is established for the geometric structure of the reactor core nodes through the reactor core geometric parameters, so that the mass energy transfer between the reactor core nodes and the mass energy transfer between the reactor core nodes can be accurately calculated, and an analysis basis is provided for the numerical analysis of the reactor core melting process of the plate-shaped fuel element reactor.

Description

Method and device for judging the geometric structure of core nodes in the process of core fusion

technical field

The application relates to the technical field of safety analysis of nuclear reactors, and in particular to a method and device for judging the geometric structure of core nodes in the process of core melting.

Background technique

Since the beginning of the development of nuclear energy, nuclear safety has been the focus of public attention, and safety analysis has always been the focus of nuclear energy scientific research. Nuclear reactors are the core of nuclear energy utilization. After the reactor core loses cooling, under the superposition of a series of risks such as human error and equipment failure, it may lead to the melting of core materials, resulting in serious accidents, resulting in the leakage of radioactive fission products. Fuel elements are the main components of the reactor core. Currently, the fuel elements of light water reactors mainly include rod-shaped fuel elements and plate-shaped fuel elements. Rod fuel elements are mainly used in commercial light water reactors and boiling water reactors, and plate fuel elements are mainly used in research reactors, test reactors, nuclear powered submarines, nuclear powered aircraft carriers and other special nuclear power devices. The melting behavior of fuel elements in severe accidents has an important impact on the melting process of the reactor core. The melting behavior of fuel elements with different geometric forms and material types is significantly different. The melting process of a typical rod-shaped fuel element reactor core is shown in Figure 1. Carrying out numerical research on the core melting process under severe reactor accidents has certain significance for the analysis of severe reactor accidents and the formulation of mitigation measures.

Many institutions have developed severe accident analysis programs to simulate the core melting process. Typical examples include the SCDAP/RELAP5 program of the National Engineering and Environmental Laboratory in Idaho, the French Institute for Radiation Protection and Nuclear Safety, and the German Association for Nuclear Equipment and Reactor Safety. The ASTEC program of the American Electric Power Research Association, the MAAP program of the American Electric Power Research Association, the MELCOR program of the Sandia National Laboratory, the CATHARE/ICARE program of the French Institute of Radiation Protection and Nuclear Safety, the ATHLET-CD program of the German Association for Nuclear Equipment and Reactor Safety, etc. System analyzer. The above severe accident analysis programs all have good simulation capabilities for the core melting process of rod-shaped element reactors. Only the SCDAP/RELAP5 program can perform simple numerical analysis on the core melting process of plate-shaped fuel element reactors. At present, when the SCDAP/RELAP5 program numerically analyzes the core melting process of the plate fuel element reactor, it does not judge the core node geometry.

In the numerical study of the core melting process under severe accident, the core is divided into axial and radial nodes, as shown in Fig. 2, the core node geometry has an important influence on the conservation of mass and energy between the core nodes and within the nodes, which in turn affects the entire core node. The core melting process and accurate determination of the core node geometry are the keys to numerical research on the core melting process. When carrying out the numerical analysis of the core melting process of the plate fuel element, it is necessary to judge the geometric structure of the core node, which is of great significance for the accurate numerical analysis of the core melting process of the plate fuel element.

In the related art, in the numerical analysis of the core melting process of the plate-shaped fuel element reactor, the geometric structure of the core node is not divided in detail.

SUMMARY OF THE INVENTION

In order to overcome the problems existing in the related art at least to a certain extent, the present application provides a method and apparatus for judging the geometric structure of a core node during a core fusion process.

According to a first aspect of the embodiments of the present application, a method for judging the geometric structure of a core node during a core fusion process is provided, including:

Obtain the initial porosity and critical porosity; the initial porosity is the calculated value of the porosity in the intact state of the core node;

Obtain the current porosity and current melting share of each core node;

Compare the current porosity with the initial porosity and critical porosity;

Determine the geometry of the corresponding core node according to the comparison result and the value of the current melting share.

Further, the porosity is the ratio of the flow cross-sectional area of the core node to the total cross-sectional area; the melting share is the ratio of the mass of the melted material of the core node to the total mass of the material.

Further, the obtaining the current porosity and the current melting share of each core node includes:

According to the preset time step, the current porosity and current melting share of each core node are obtained at different times.

Further, the types of the geometric structures of the core nodes include at least: intact fuel elements, thickened fuel elements, core monocoques, and core molten pools.

Further, judging the geometric structure of the corresponding core node according to the comparison result and the value of the current melting share includes:

If the porosity of the core node is greater than the preset critical porosity and greater than or equal to the initial porosity, the type of the geometric structure of the core node is a complete fuel element;

If the porosity of the core node is greater than the preset critical porosity and less than the initial porosity, the type of the geometry of the core node is a thickened fuel element.

Further, judging the geometric structure of the corresponding core node according to the comparison result and the value of the current melting share includes:

If the porosity of the core node is less than the preset critical porosity, the geometry is judged according to the value of the current melt fraction.

Further, judging the geometric structure according to the value of the current melting share includes:

If the value of the current melt share is greater than 99%, the type of core node geometry is core melt pool;

Otherwise the core node geometry is of the core monocoque type.

According to a second aspect of the embodiments of the present application, there is provided a device for judging the geometric structure of a core node during a core fusion process, including:

The initialization module is used to obtain the initial porosity and the critical porosity; the initial porosity is the calculated value of the porosity in the intact state of the core node;

The monitoring module is used to obtain the current porosity and current melting share of each core node;

The judgment module is used to compare the current porosity with the initial porosity and the critical porosity, and judge the geometric structure of the corresponding core node according to the comparison result and the value of the current melting share.

According to a third aspect of the embodiments of the present application, a computer device is provided, including:

memory for storing computer programs;

The processor is configured to execute the computer program in the memory to implement the operation steps of the method described in any one of the above embodiments.

According to a fourth aspect of the embodiments of the present application, there is provided a computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, implements the operation steps of the method described in any one of the above embodiments.

The technical solutions provided by the embodiments of the present application have the following beneficial effects:

The solution of the present application establishes a judgment criterion for the geometric structure of the core node through the core geometric parameters, which is beneficial to accurately calculate the mass energy transfer within the core node and between the nodes, and provides an analysis basis for the numerical analysis of the core melting process of the plate fuel element reactor.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not limiting of the present application.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description serve to explain the principles of the application.

Figure 1 is a schematic diagram of the core melting process.

Figures 2(a)-(b) are schematic diagrams of division of radial nodes and axial nodes of core nodes, respectively.

FIG. 3 is a flow chart of a method for judging a core node geometry in a core fusion process according to an exemplary embodiment.

Figures 4(a)-(d) are schematic diagrams of the geometrical structure types of the four core nodes, respectively.

FIG. 5 shows a core node geometry distribution according to an exemplary embodiment.

FIG. 6 shows a criterion for determining a core node geometry according to an exemplary embodiment.

Figure 7(a) is a schematic diagram of the distribution of the core node geometry before the center channel repositioning in the SPERT experimental reactor example.

Figure 7(b) is a schematic diagram of the core node geometry distribution before the side channel repositioning in the SPERT experimental reactor example.

Detailed ways

Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. Where the following description refers to the drawings, the same numerals in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the illustrative examples below are not intended to represent all implementations consistent with this application. Rather, they are merely examples of methods and apparatus consistent with some aspects of the present application as recited in the appended claims.

FIG. 3 is a flow chart of a method for judging a core node geometry in a core fusion process according to an exemplary embodiment. The method may include the following steps:

Step S1: obtaining the initial porosity and the critical porosity; the initial porosity is the calculated value of the porosity in the intact state of the core node;

Step S2: obtaining the current porosity and current melting share of each core node;

Step S3: comparing the current porosity with the initial porosity and the critical porosity;

Step S4: Determine the geometric structure of the corresponding core node according to the comparison result and the value of the current melting share.

The solution of the present application establishes a judgment criterion for the geometric structure of the core node through the core geometric parameters, which is beneficial to accurately calculate the mass energy transfer within the core node and between the nodes, and provides an analysis basis for the numerical analysis of the core melting process of the plate fuel element reactor.

It should be understood that although the various steps in the flowchart of FIG. 3 are shown in sequence according to the arrows, these steps are not necessarily executed in the sequence shown by the arrows. Unless explicitly stated herein, the execution of these steps is not strictly limited to the order, and these steps may be performed in other orders. Moreover, at least a part of the steps in FIG. 3 may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but may be executed at different times. The execution of these sub-steps or stages The sequence is also not necessarily sequential, but may be performed alternately or alternately with other steps or sub-steps of other steps or at least a portion of a phase.

In order to further describe the technical solution of the present application, firstly, the basis for dividing the node geometry in the process of reactor core fusion is explained in detail.

As shown in Fig. 4, in the core melting process of the plate-shaped fuel element reactor, according to the characteristics of the plate-shaped fuel element with different geometric structures and material types, this scheme divides the node geometry in the core melting process of the plate-shaped fuel element reactor. There are five structural types: complete fuel element a, thickened fuel element b, core hard shell c, core melting pool d, and empty node e.

When the fuel plate remains intact, it is defined as geometric structure a; when the fuel cladding is damaged, the core melt flows out along the crack, or the upper node melt migrates to the current node, resulting in an increase in the thickness of the fuel plate at the current node, which is defined as geometric structure b; Downward migration of the resolidified melt and downward migration of oxides forms a core hard shell structure in the lower region of the core, which seriously blocks the flow channel, which is defined as geometric structure c; The core hard shell in the lower region supports the core structural material , forming the core melting pool, which is defined as geometric structure d; when there is no core material in the node, it is defined as geometric structure e. Figure 5 shows a schematic diagram of the distribution of the core node geometry composed of each node geometry. The core molten pool is adjacent to the core hard shell, thickened fuel elements, and complete fuel elements in sequence.

The node geometry is closely related to the porosity, and the specific judgment process is shown in Figure 6. In the figure: POR is the nodal porosity, POR0 is the initial porosity of the core, PORC is the set critical porosity, and _fmelt is the melting fraction of the nodal material. Among them, the porosity is the ratio of the flow cross-sectional area of the core node to the total cross-sectional area; the melting share is the ratio of the mass of the molten material at the core node to the total mass of the material. The initial porosity is the calculated value when the core nodes are complete. The critical porosity is a preset value, which is set according to the actual situation of the reactor, and may be 0.1 in some embodiments.

In some embodiments, in the step S2, obtaining the current porosity and the current melting share of each core node specifically includes: according to a preset time step, respectively obtaining the current porosity, Current melt share. That is, at each time step, the current porosity and melt fraction for each node is calculated.

After obtaining the above several core geometric parameters, the node geometry is judged by the relationship between the porosity, the set critical porosity, and the initial porosity: if the porosity is greater than the set critical porosity and greater than or equal to the initial porosity, it means that the fuel The element maintains the plate-like structure a; if the porosity is greater than the set critical porosity and less than the initial porosity, it means that the upper node melt migrates down to the current node, and the fuel element has a thickened structure b; if the porosity is less than the set critical porosity For the porosity, it is necessary to judge the melting share of the node material. When the melting share of the node material exceeds 99%, it is the core melting pool structure d, otherwise it is the core hard shell structure c.

During the core melting process, the evolution process of the node geometry is affected by the adjacent nodes and the current node geometry. .

In the following, the solution of the present application will be expanded and explained in conjunction with the specific reactor experiment scenario.

The D-12/25 plate-shaped fuel element in the SPERT-I reactor uses aluminum alloy cladding and U-Al alloy core. A large number of studies have been carried out and have a detailed research basis. The SPERT-ID-12/25 experiment is used as the research object. Numerical analysis of the core melting process under severe accident is carried out, and the technical effect of the method for judging the core node geometry during the core melting process is shown.

The core geometry distribution before the core material is relocated to the lower head is shown in Figure 7: the core material undergoes extensive migration and repositioning before being repositioned to the lower head. In the figure, channel is the central channel, and channel2 is the side channel.

Before the core material in the central channel is relocated to the lower head, the nodes in the upper region of the core maintain a complete plate-like geometry, and the lower nodes transition to a thickened geometry. The porosity of the bottom node of the central channel is lower than the critical porosity of 0.1 , forming a hard shell structure, the core temperature does not exceed the melting point of alumina, all alumina remains solid, and no core node transitions to the core melting pool structure. The core material in the side channel is relocated to the lower head, and there is no core material in the central channel. The nodes in the upper region of the core maintain a complete plate-like geometry, and the lower nodes transition to a thickened geometry. The core material is the most and the nodal porosity is the lowest.

The application also provides the following examples:

A device for judging the geometric structure of a core node in a core melting process, comprising:

The initialization module is used to obtain the initial porosity and the critical porosity; the initial porosity is the calculated value of the porosity in the intact state of the core node;

The monitoring module is used to obtain the current porosity and current melting share of each core node;

The judgment module is used to compare the current porosity with the initial porosity and the critical porosity, and judge the geometric structure of the corresponding core node according to the comparison result and the value of the current melting share.

Regarding the device, the specific steps in which each module performs operations have been described in detail in the embodiments of the method, and will not be described in detail here. All or part of each module in the above judgment device can be implemented by software, hardware and combinations thereof. The above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or stored in the memory in the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

The application also provides the following examples:

A computer device comprising:

memory for storing computer programs;

The processor is used for executing the computer program in the memory, so as to realize a method for judging the geometric structure of the core node during the core melting process: obtaining the initial porosity and the critical porosity; the initial porosity is the core node Calculated value of porosity in the complete state; obtain the current porosity and current melting share of each core node; compare the current porosity with the initial porosity and critical porosity; judge the corresponding Core node geometry.

The application also provides the following examples:

A computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, realizes a method for judging the geometric structure of a core node in a core melting process: obtaining an initial porosity and a critical porosity; The initial porosity is the calculated value of the porosity in the complete state of the core node; the current porosity and the current melting share of each core node are obtained; the current porosity is compared with the initial porosity and the critical porosity; according to the comparison result and the value of the current melting share to determine the corresponding core node geometry.

It can be understood that, the same or similar parts in the above embodiments may refer to each other, and the content not described in detail in some embodiments may refer to the same or similar content in other embodiments.

It should be noted that, in the description of the present application, the terms "first", "second" and the like are only used for the purpose of description, and should not be construed as indicating or implying relative importance. Also, in the description of this application, unless otherwise specified, the meaning of "plurality" means at least two.

Any description of a process or method in the flowcharts or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing a specified logical function or step of the process , and the scope of the preferred embodiments of the present application includes alternative implementations in which the functions may be performed out of the order shown or discussed, including performing the functions substantially concurrently or in the reverse order depending upon the functions involved, which should It is understood by those skilled in the art to which the embodiments of the present application belong.

It should be understood that various parts of this application may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or a combination of the following techniques known in the art: Discrete logic circuits, application specific integrated circuits with suitable combinational logic gates, Programmable Gate Arrays (PGA), Field Programmable Gate Arrays (FPGA), etc.

Those skilled in the art can understand that all or part of the steps carried by the methods of the above embodiments can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, and the program can be stored in a computer-readable storage medium. When executed, one or a combination of the steps of the method embodiment is included.

In addition, each functional unit in each embodiment of the present application may be integrated into one processing module, or each unit may exist physically alone, or two or more units may be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware, and can also be implemented in the form of software function modules. If the integrated modules are implemented in the form of software functional modules and sold or used as independent products, they may also be stored in a computer-readable storage medium.

The above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, and the like.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limitations to the present application. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (6)

1. A method for judging the geometric structure of a core node in a core fusion process, characterized in that, comprising: Obtain the initial porosity and critical porosity; the initial porosity is the calculated value of the porosity in the intact state of the core node; Obtain the current porosity and current melting share of each core node; Compare the current porosity with the initial porosity and critical porosity; Determine the geometric structure of the corresponding core node according to the comparison result and the value of the current melting share. The step includes: if the porosity of the core node is greater than a preset critical porosity and greater than or equal to the initial porosity, then the The type of the geometry is the intact fuel element; if the porosity of the core node is greater than the preset critical porosity and less than the initial porosity, the type of the geometry of the core node is the thickened fuel element; If the porosity of the node is less than the preset critical porosity, the geometry is judged according to the value of the current melting share; if the value of the current melting share is greater than 99%, the type of the geometry of the core node is the core melting pool; otherwise, the The type of core node geometry is core hard shell; Wherein, the porosity is the ratio of the flow cross-sectional area of the core node to the total cross-sectional area; the melting fraction is the ratio of the mass of the melted material of the core node to the total mass of the material. 2 . The method according to claim 1 , wherein the acquiring the current porosity and the current melting share of each core node comprises: 2 . According to the preset time step, the current porosity and current melting share of each core node are obtained at different times. 3. The method according to claim 1 or 2, wherein the types of the geometry of the core nodes include at least: integral fuel elements, thickened fuel elements, core monocoque, and core molten pool. 4. A device for judging the geometric structure of a core node in the process of core fusion, which is applied to the method for judging the geometric structure of a core node in the process of core fusion according to any one of claims 1-3, wherein the The judging device includes: The initialization module is used to obtain the initial porosity and the critical porosity; the initial porosity is the calculated value of the porosity in the intact state of the core node; The monitoring module is used to obtain the current porosity and current melting share of each core node; The judgment module is used to compare the current porosity with the initial porosity and the critical porosity, and judge the geometric structure of the corresponding core node according to the comparison result and the value of the current melting share. 5. A computer equipment, characterized in that, comprising: memory for storing computer programs; A processor for executing the computer program in the memory to implement the operation steps of the method of any one of claims 1-3. 6. A computer-readable storage medium on which a computer program is stored, characterized in that, when the computer program is executed by a processor, the operation steps of the method of any one of claims 1-3 are implemented.

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