WO2014187339A1

WO2014187339A1 - Image reconstruction method，image reconstruction device and monitoring system for monitoring core debris state

Info

Publication number: WO2014187339A1
Application number: PCT/CN2014/078148
Authority: WO
Inventors: Yuanyuan Liu; Jianping Cheng; Chunming Zhang; Peng Zheng; Huiguo YUE; Haifeng Yang
Original assignee: Nuclear And Radiation Safety Center
Priority date: 2013-05-23
Filing date: 2014-05-22
Publication date: 2014-11-27
Also published as: CN104183286B; CN104183286A

Abstract

The present invention discloses an image reconstruction method, an image reconstruction device and a monitoring system for monitoring core debris state. The method comprises the steps of: establishing a system model of a monitored object, and obtaining a system matrix between the projection data and an image of cosmic ray muons that penetrate through the monitored object; initializing the image; obtaining the real projection data of the cosmic ray muons that penetrate through the monitored object; performing an algebraic iteration on the image based on the initialized image, the real projection data and the system matrix; and obtaining a final image by combining the reconstructed image of the core debris state obtained by algebraic iteration with the system model of the monitored object. According to the technical solution of the invention, the core state can be monitored rapidly and accurately, so that an emergency commander can accurately know the accident process in time according to the reconstruction result of the invention, thereby a more effective accident mitigation measures can be proposed.

Description

IMAGE RECONSTRUCTION METHOD, IMAGE RECONSTRUCTION DEVICE AND MONITORING SYSTEM FOR MONITORING CORE DEBRIS

STATE

BACKGROUND

[0001] The present invention relates to the field of nuclear power plant safety, and in particular, to an image reconstruction method, an image reconstruction device and a monitoring system for monitoring core debris state in a severe accident.

[0002] The fantasy that core melting, which is a severe accident with a very small probability, is impossible to occur is broken down by the occurrence of the accident of USA Three Mile Island Nuclear Power Plant on Mar 28, 1979 and the accident of the former USSR Chernobyl Nuclear Power Plant on Apr 26, 1986. Thereafter, a 3G nuclear power concept represented by API 000 is put forward, which contributes to the lowering of the probability of severe accidents. However, people are indolent in the propelling of the 3G nuclear power; instead, people are engrossed in prolonging the life of the existing nuclear power plant. This shows that the Three Mile Island nuclear accident and the Chernobyl nuclear accident are gradually fading from people's memory. Finally, on Mar 11, 2011, the occurrence of Fukushinia severe accident again tolls an alarm bell that severe accidents are nonnegligible.

[0003] Therefore, in view of nuclear safety, every tried and true preventing and mitigation measures should be employed to ensure the integrality of the reactor pressure vessel and the containment vessel of the reactor in a nuclear power plant and to ensure that no radioactive substance leaks out from the nuclear power plant, thereby to ensure that the public and the environment will not be harmed by an accident, because once a severe accident occurs, the consequence thereof will be unevaluable. [0004] The hallmark event of a severe accident is the severe damage of a reactor core; the cooling of the core is insufficient, the core is exposed and heated up, and it causes the melt of the fuel element, and finally the core debris enters the lower chamber of the pressure vessel, which severely threatens the integral construction of the pressure vessel. When a severe accident occurs, the state of the core debris is particularly important for tracking the accident process, thereby determining an emergency plan.

[0005] However, at present, the core state cannot be accurately monitored in the prior art under the severe conditions of ultra-high temperature, intense radiation and strong corrosivity, etc., during core melting.

SUMMARY

[0006] Therefore, it is a main object of the present invention to provide a method and a system for monitoring core debris state in a severe accident, thereby solving the problem of the prior art that the core state cannot be accurately monitored.

[0007] According to the first aspect of the invention, there provides an image reconstruction method for monitoring core debris state in a severe accident, comprising the steps of: establishing a system model of a monitored object, and obtaining a system matrix between the projection data and an image of cosmic ray muons that penetrate through the monitored object; initializing the image; obtaining the real projection data of the cosmic ray muons that penetrate through the monitored object; performing an algebraic iteration on the image based on the initialized image, the real projection data and the system matrix; and obtaining a final image by combining the reconstructed image of the core debris state obtained by algebraic iteration with the system model of the monitored object. [0008] According to the second aspect of the invention, there provides an image reconstruction device for monitoring core debris state in a severe accident, comprising: a module for establishing a system model of a monitored object and obtaining a system matrix between the projection data and an image of cosmic ray muons that penetrate through the monitored object; a module for initializing the image; a module for obtaining the real projection data of the cosmic ray muons that penetrate through the monitored object; a module for performing an algebraic iteration on the image based on the initialized image, the real projection data and the system matrix; and module for obtaining a final image by combining the reconstructed image of the core debris state obtained by algebraic iteration with the system model of the monitored object.

[0009] According to the third aspect of the invention, there provides a monitoring system for monitoring core debris state in a severe accident, comprising: a data collecting device, for collecting the angle data and the displacement data of cosmic ray muons from a monitored region; a data processing device, for pre-processing the data returned by the data collecting device so as to make preparation for image reconstruction; and the image reconstruction device according to the second aspect of the invention, wherein the data pre-processed by the data processing device are the real projection data of the cosmic ray muons that penetrate through the monitored object.

[0010] In comparison with the prior art, according to the technical solution of the invention, the core state can be monitored rapidly and accurately, so that an emergency commander can accurately know the accident process in time according to the reconstruction result of the invention, thereby a more effective accident mitigation measures can be proposed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS [0011] The drawings illustrated here, which construct a part of the application, are provided for further understanding of the invention; the exemplary embodiments of the invention and the illustration thereof are used for explaining the invention, rather than inappropriately limiting the invention. In the drawings:

[0012] Fig. 1 schematically shows a flow chart of a method for monitoring core debris state in a severe accident according to an embodiment of the invention;

[0013] Fig. 2 schematically shows a system model of a monitored object according to an embodiment of the invention;

[0014] Fig. 3 shows a principle-level schematic diagram of multiple coulomb scatterings between a muon and a matter;

[0015] Fig. 4 shows a schematic diagram of the relation between the scattering density {

) and the atomic number (Z); and

[0016] Fig. 5 schematically shows a structural block diagram of a monitoring system for monitoring core debris state in a severe accident according to a preferred embodiment of the invention.

[0017] In the drawings, the same or a similar part is represented by the same reference label.

DETAILED DESCRIPTION

[0018] In order to make the objects, the technical solutions and advantages of the invention more apparent, the invention will be further illustrated below in detail in conjunction with the drawings and specific embodiments. [0019] In the description below, the quotation of "an embodiment", "the embodiment", "an example" and "the example", etc., indicates that the embodiment or example thus described may include a specific characteristic, structure, feature, property, element or limitation, but each embodiment or example does not necessarily include the specific characteristic, structure, feature, property, element or limitation. Additionally, although the phrase "in an embodiment" that is used repeatedly may represent the same embodiment, but the phrase does not necessarily represent the same embodiment.

[0020] For simplicity, certain technical characteristics well-known to those skilled in the art are omitted in the description below.

[0021] Cosmic ray muon imaging monitoring technology has the characteristics of being sensitive to a matter with a high atomic number and having a high penetrability, etc. In 2003, it was first proposed by Los Alamos National Laboratory (LANL) of USA that cosmic ray muon imaging monitoring technology could be applied to the monitoring and imaging of a nuclear matter, and the achievement was published on a world-famous science and technology journal, Nature.

[0022] Due to its unique advantages, the muon imaging monitoring technology has been successfully applied to other fields, for example, monitoring the internal state of a large object.

[0023] In 1960s, the American winner of Nobel Prize in physics, Luis Alvarez, had tried to take a perspective picture, which is similar to an X-ray picture, on a pyramid so as to verify whether more graves and galleries exist inside a pyramid. Alvarez drew the first perspective view of a pyramid in the world according to the data detected, and his experiment created much of a stir in the physical world and the archaeological world at that time. [0024] Additionally, in Japan, the study group of Kanetada Nagamine from KEK muon scientific laboratory detects the premonition of a possible volcanic eruption via cosmic ray muons. By using muons that move horizontally after reaching the surface of the earth, the shape of the mountain may be measured and a channel through which the internal lava may well up may be searched for by placing several detectors around the volcano, and the welling up of lava is a premonition of a possible volcanic eruption. At present, the study group has studied on several volcanoes in Japan, including an evaluation on the lava amount on an active volcano, Asama.

[0025] Although the muon imaging monitoring technology proposed by LANL has been successfully applied to the imaging of a nuclear matter with a high atomic number and the internal imaging of a large object such as a pyramid, a volcano and the like, the application of the muon imaging monitoring technology to the detection of the core debris state in a nuclear island containment vessel during a severe accident is still a novel topic.

[0026] The invention proposes a novel method and a novel system for monitoring core debris state in a severe accident. The main concept of the invention lies in that the core debris in a severe accident is monitored and a corresponding system model is established based on the cosmic ray muon imaging technology. The invention has an important meaning on the mitigation of a severe accident and the provision of a basis for accident emergency response.

[0027] The principle of muon imaging monitoring according to the invention will be illustrated in detail below from two aspects.

[0028] On one hand, the muon imaging monitoring technology has a super-high penetrability. The muons on the earth mainly derive from the cosmic ray. After the cosmic ray acts with the atmosphere, a large amount of nuclear mesons will be generated. However, the lifetime of a nuclear meson is very short, and it will be rapidly attenuated to a muon. The lifetime of a muon is long, and the muon mainly interacts with a matter in the form of a weak coulomb scattering, thus little energy is attenuated. Therefore, the number of muons that reach the ground is much larger than that of other particles, and the muons have a strong penetrating power usually with energy of 3GeV-4GeV.

[0029] On the other hand, the muon imaging monitoring technology has a feature of being sensitive to a matter with a high atomic number. It may be know from a preliminary analysis that a muon mainly interacts with a matter in the form of multiple coulomb scatterings, as shown in Fig. 3. Fig. 3 shows a principle-level schematic diagram of multiple coulomb scatterings between a muon and a matter. Wherein, L_rad represents the radiation length of an object to be detected. A new physical quantity, scattering density _Lrad, is hypothesized based on L_rad, and _Lrad represents an average value of the squares of the deflected radian of a muon with a momentum of p₀ after passing through a material with a unit thickness of L_rad. Fig. 4 shows a schematic diagram of the relation between the scattering density ._Lrad) and the atomic number (Z). It is indicated by a large amount of experiments that Z†— > X_Lrad T , that is, a monitored matter may be reconstructed by computing the scattering density of a monitored object.

[0030] Therefore, it is found by the inventors that the muon imaging monitoring technology may be used for monitoring a nuclear matter with a high atomic number.

[0031] Referring to Fig. 1 below, it schematically shows a flow chart of a method 100 for monitoring core debris state in a severe accident according to an embodiment of the invention.

[0032] The method 100 begins from step 110: establishing a system model of a monitored object, and obtaining a system matrix between the projection data and an image of cosmic ray muons that penetrate through the monitored object. [0033] According to an embodiment of the invention, the "monitored object" mentioned here may be a nuclear island system that comprises the core debris. First of all, by fully investigating and analyzing the design information of a nuclear island system of the existing nuclear reactor type, a critical component inside a nuclear island may be reasonably simplified and modularized, the geometric dimensions and the material compositions thereof may be determined, and a system model of a nuclear island may be established.

[0034] Fig. 2 schematically shows a system model of a monitored object according to an embodiment of the invention.

[0035] As shown in the figure, the "monitored object" mentioned here may be a nuclear island system. It should be noted that, although the invention is illustrated by taking a nuclear island system as an example, the invention is not limited to the application to a nuclear island system; instead, it may also be applied to other similar monitored objects.

[0036] According to an embodiment of the invention, the system model of the nuclear island may comprise a containment vessel 210, a pressure vessel 220 and a core debris 230. Wherein, the containment vessel 210 may be a concrete and/or steel housing.

[0037] According to an embodiment of the invention, the system model of the nuclear island may also comprise other critical components in the primary circuit, for example, a steam generator 240, a pressurizer 250, a coolant pump 260 and a tube 270 that is a metal equipment filled with a coolant, etc.

[0038] According to an embodiment of the invention, it may further determine the detailed geometric dimensions and material compositions of each part of the nuclear island, so as to determine a final solution for the system model of the nuclear island.

[0039] A certain correspondence exists between the projection data and the image of cosmic ray muons that penetrate through the monitored object, and this correspondence may be referred to as a system matrix. The system matrix is a transmission matrix, which is hypothesized as H, thus P_reai⁼Hf_reai, wherein P_reai represents the real projection data, and f_reai represents the real image of the real core debris state.

[0040] Next, in step 120: initializing the image.

[0041] According to an embodiment of the invention, the system model of the monitored object comprises a nuclear island system and a core (Intact). The initialized image mentioned here refers to the core (Intact). Therefore, the core part in the system model of the monitored object is the initialized image.

[0042] According to an embodiment of the invention, if the requirement of the convergence rate is not strict, the initialized image may be taken as zero, that is, the existence of the core is not considered in initialization.

[0043] In step 130: obtaining the real projection data of the cosmic ray muons that penetrate through the monitored object.

[0044] According to an embodiment of the invention, the angle data and the displacement data of cosmic ray muons may be collected from a monitored region by a data collecting device 510 in Fig. 5. Then, the angle data and the displacement data of the cosmic ray muons may be processed by a data processing device 520 in Fig. 5, and the real projection data to be used for image reconstruction is formed. [0045] In step 140: performing an algebraic iteration on the image based on the initialized image, the real projection data and the system matrix.

[0046] At present, there are mainly two types of muon imaging and reconstructing methods: a track reconstruction method based on an analytic method, and an expectation maximization method based on an iteration method. When the track reconstruction method based on an analytic method is employed, the reconstruction time is very short, but the reconstruction quality is poor. The expectation maximization method based on an iteration method is on the contrary.

[0047] According to an embodiment of the invention, algebraic iteration may be realized by the formul low:

[0048] Wherein, f^^RT represents a reconstructed image after the m^th iteration, f₀ ^ART is the initialized image, H represents a system matrix, P represents the real projection data, i.e., the angle data and the displacement data of the cosmic ray muons. [pl - Hf ART

m-l represents the difference between the real projection data and the data obtained by projecting the image (f^^T) obtained via the (m-l)^th iteration, which is an original basis for each iteration. Being divided by [H]_{m >} represents normalization, and [H]^ represents the direction of the step size of iteration.

[0049] According to an embodiment of the invention, after algebraic iteration, a minimization total variation (TV) denoising process may also be performed on the image. The minimization total variation may be realized by the formula below:

4v , ||Λ _ν = min [|/_{ij (}|_Tv ] (2) [0050] Wherein, f_{Sj t} represents the pixel value of the image, and wherein s and t respectively represent the lateral and vertical labels of a two-dimensional image.

[0051] Then, the above steps are repeated, until a termination condition is met. The termination condition may be whether the quality of the reconstructed image meets a certain requirement. According to an embodiment of the invention, termination condition may be that the norm of the difference between the images obtained in two adjacent iterations is less than a certain fixed value.

[0052] During an emission imaging process and a penetration imaging process, the projection data will be incomplete due to various reasons; if it still employs the traditional analytic method, an image artifact will be generated on the image reconstructed; however, if an iteration method is employed, the image quality will be improved greatly.

[0053] According to an embodiment of the invention, a novel, rapid and accurate incomplete data muon imaging iteration method may be utilized, and it may be realized by programming. Incomplete data refers to that the data volume is insufficient and it cannot meet the sampling law, and accurate reconstruction cannot be realized mathematically by the traditional method.

[0054] The incomplete data muon imaging method is a preferred way of implementing the debris muon imaging monitoring system (DMMS) of the invention, and the quality of the imaging method will directly influence the monitoring effect of the DMMS on the core debris.

[0055] First of all, in the muon imaging iteration method according to the invention, the monitored object, i.e., a system model of a nuclear island, may be regarded as the iteration initial value. Thus, the convergence rate can be improved effectively, thereby the reconstruction rate can be improved. [0056] Next, the muon imaging iteration method according to the invention may be based on an Algebraic Reconstruction Technique - Total Variation (ART-TV) that employs the theory of compressed sensing, so that accurate reconstruction may be realized by using a small amount of incomplete projection data. Thus, a high-quality reconstructed image may be obtained by using only a small amount of projection data.

[0057] The method of the invention is a rapid and accurate method, and relative to the traditional muon imaging expectation maximization method, the reconstruction quality can be effectively improved.

[0058] The method 100 ends at step 150: obtaining a final image of the core debris state by combining the reconstructed image of the core debris state obtained by algebraic iteration with the system model of the monitored object.

[0059] Based on the reconstructed image obtained in step 140, the core debris state may be obtained; but at this time, the relative position of the core debris in the nuclear island system cannot be known accurately.

[0060] According to an embodiment of the invention, the reconstruction result may be combined with the system model of the monitored object established in step 110, and a final image may be obtained by which emergency personnel can observe the position of the core debris in the overall nuclear island. For example, the specific position of the debris in the nuclear island system may be known by mapping this image and the image of the monitored object (the nuclear island system) to one image, so that it is convenient for working personnel to observe. Thus, it has an advantage that the utilization rate of the reconstructed image can be improved effectively. [0061] Fig. 5 schematically shows a structural block diagram of a system 500 for monitoring core debris state in a severe accident according to a preferred embodiment of the invention.

[0062] According to an embodiment of the invention, the system 500 may comprise a data collecting device 510, a data processing device 520 and an image reconstruction device 530.

[0063] The data collecting device 510 may be used for collecting the angle data and the displacement data of cosmic ray muons from a monitored region.

[0064] The monitored region mentioned here refers to a maximum effective region in which cosmic ray muons may be collected.

[0065] According to an embodiment of the invention, the data collecting device 510 may comprise two groups of resistive plate detectors 511. Each group of resistive plate detectors may comprise three position-sensitive detectors for obtaining the angle data and the displacement data of the muons.

[0066] It should be noted that, although the invention has been illustrated by taking two groups of resistive plate detectors as an example, the invention is not limited to employing two groups of resistive plate detectors; instead, more than two groups of resistive plate detectors may be employed. For example, totally six groups of resistive plate detectors, i.e., front and rear, right and left, and upper and lower, may be employed in the invention.

[0067] According to the invention, it is not limited that three position-sensitive detectors are employed in one group; instead, more than three position-sensitive detectors may also be employed. The larger the number of the detectors is, the more accurate the computation will be; because the detectors have a certain error, one gauss or a trace of other subdivision needs to be added to each coordinate, and then the muon track is determined by three points, thus it will be more accurate; therefore, the more the detectors are, the more accurately the muon track will be determined.

[0068] According to an embodiment of the invention, the data collecting device 510 may also comprise a read-out circuit for the data on the resistive plate detector, a logic control unit and a data transmission device, etc.

[0069] According to an embodiment of the invention, the data processing device 520 may be adapted to pre-process the data returned by the data collecting device 510 and make preparation for image reconstruction.

[0070] According to an embodiment of the invention, the data processing device 520 may also be used for the master control during the operating process of the monitoring system 500, for example, electric control, data collection control, data transmission control and safety linkage control, etc.

[0071] It should be noted that, here, it is only exemplary, rather than being limitative, that the master control during the operating process of the monitoring system 500 is performed by the data processing device 520. It is not necessary that the master control during the operating process of the monitoring system 500 should be performed by the data processing device 520, instead, it may be performed by another device.

[0072] According to an embodiment of the invention, the image reconstruction device 530 may be used for image reconstruction.

[0073] According to an embodiment of the invention, the image reconstruction device 530 may also be adapted to report and display the reconstruction monitoring result of the core debris state in a severe accident for emergency personnel who works in an emergency control center. [0074] It should be noted that, here, it is only exemplary, rather than being limitative, that the monitoring result is reported and displayed by the image reconstruction device 530. It is not necessary that the report and display of the monitoring result is performed by the image reconstruction device 530; instead, it may be performed by another device. Further, it is not necessary that the report and display of the monitoring result should be performed by one and the same device; instead, the report and display of the monitoring result may be performed by different devices respectively. For example, one device performs the report of the monitoring result, and the other device performs the display of the monitoring result.

[0075] The invention further provides a method for verifying the image reconstruction method according to the invention.

[0076] According to an embodiment of the invention, it may be verified whether a core debris state image consistent with the core debris state can be obtained by the image reconstruction method according to the invention via a numerical model of the core debris.

[0077] According to an embodiment of the invention, for the core debris of a local interested region in the monitored object, multiple typical severe accidents are selected for hypothesizing the operating conditions based on the debris generation mechanism, and the geometric parameters (for example, the stratification situation of the debris inside the core) and the material parameter (for example, the compositions of the debris) of the debris are determined in detail, and a corresponding numerical model is established.

[0078] According to an embodiment of the invention, the numerical model of the core debris may comprise the shape, size and compositions of the core debris. [0079] The formation process of the debris is very complex, and the knowledge on a severe accident process is being updated and deepened continuously. For example, some scholars consider that the debris has a two-layer structure, and some scholars consider that the debris has a three-layer structure. The basis of the former conclusion lies in that when a severe accident occurs, the core debris shifts to the lower end plate of the pressure vessel and is mixed and recombined again to form a stable melt bath, wherein, the components of the melt bath may be divided, according to material characteristics, into metal and uranium oxide, the metal layer and the uranium oxide layer will be separated to form a two-layer melt bath structure.

[0080] According to the invention, in view of nuclear safety, uranium is employed to represent the material component of the core debris so as to ensure safety profile. For the determination of the geometric dimension of the core debris, multiple typical severe accidents may be selected for hypothesizing the operating condition, for example, total core melting and half core melting, so as to determine the corresponding geometric parameters of the core debris respectively. Finally, a final solution for the numerical model of the core debris is established. Here, as determined by the geometry of the debris, the geometric parameters may be ordinary geometric parameters; if it is a rectangle, the geometric parameters may refer to the length, the width and the height, and if it is a spherical cap, the geometric parameters may refer to the radius and the height, and the like.

[0081] According to the invention, during the stage of verifying the image reconstruction method according to the invention, the angle data and the displacement data of the cosmic ray muons is obtained by simulation.

[0082] According to an embodiment of the invention, by simulating the projection data of cosmic ray muons that penetrate through the system model of the monitored object, the muon transport simulation projection data may be obtained, and the simulation projection data may be utilized to verify whether a core debris state image consistent with the core debris state can be obtained by the image reconstruction method according to the invention.

[0083] According to an embodiment of the invention, a transport simulation process of muons that penetrate through the monitored object may be realized via Geant4 programming of the Monte Carlo method based on the system model of the monitored object established in step 110, and the simulation projection data required for verifying the image reconstruction method may be obtained.

[0084] At present, in the two most typical programs of the Monte Carlo method, i.e., Geant4 and MC P, the programming of Geant4 is more suitable for high-energy physical simulation, and Geant4 is a "programming" Monte Carlo program, but MCNP is a "card-type" Monte Carlo program, that is, Geant4 has a better flexibility. Therefore, according to an embodiment of the invention, the muon transport simulation projection data is obtained by Geant4 programming.

[0085] It should be noted that, although the invention is illustrated by taking Geant4 as an example, the invention is not limited to Geant4; instead, other methods that can realize the object of the invention may be employed. For example, the invention may also be realized by employing MCNP, but the effect will be better when Geant4 is employed.

[0086] Additionally, when a Geant4 program is employed to generate the projection data, because the primary shields of the external surfaces of the containment vessel 210 and the pressure vessel 220 in the system model of the nuclear island are both consisted of a thick concrete, a deep penetration problem may appear, that is, during the process in which the particles penetrate through a very thick material, the number of particles obtained via transmission will be too small due to the reasons such as scattering and absorbing, so that the variance will be too large, thereby the result will be inaccurate. Therefore, in order to obtain more accurate simulation projection data, during the computation process, the problem of too large resultant variance caused by "deep penetration problem" may be reduced as much as possible by using a variance-reduction technique and the like.

[0087] The image reconstruction algorithm proposed by the invention can be verified according to the above verifying method, thus it may be proved that high-quality image reconstruction can be realized rapidly by the present invention, so that the core debris state in a severe accident can be monitored accurately.

[0088] It should be understood by one skilled in the art that the embodiments of the invention may be provided as a method, a system or a computer program product. Therefore, the invention may take the form of total hardware embodiments, total software embodiments or embodiments that combine software and hardware. Moreover, the invention may take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM and optical storage, etc.) that contain computer-usable program codes.

[0089] The above description only shows some embodiments of the invention, rather than limiting the scope of the invention. Various modifications and variations may be made by one skilled in the art. All the modifications, equivalent substitutions and improvements made without departing from the spirit and scope of the invention should be encompassed by the scope of the claims of the invention.

Claims

1. An image reconstruction method for monitoring core debris state in a severe accident, comprising the steps of:

establishing a system model of a monitored object, and obtaining a system matrix between the projection data and an image of cosmic ray muons that penetrate through the monitored object;

initializing the image;

obtaining the real projection data of the cosmic ray muons that penetrate through the monitored object;

performing an algebraic iteration on the image based on the initialized image, the real projection data and the system matrix; and

obtaining a final image of the core debris state by combining the reconstructed image of the core debris state obtained by algebraic iteration with the system model of the monitored object.

2. The image reconstruction method according to claim 1, wherein, the step of performing an algebraic iteration on the image based on the initialized image, the real projection data and the system matrix further comprises: performing a minimization total variation denoising process on the image after each iteration.

3. The image reconstruction method according to claim 1, wherein, the algebraic iteration is a compressed sensing algebraic iteration based on incomplete projection data.

4. The image reconstruction method according to claim 1, wherein, the step of initializing the image further comprises: taking the intact core as the initial image.

5. An image reconstruction device for monitoring core debris state in a severe accident, comprising: a module for establishing a system model of a monitored object and obtaining a system matrix between the projection data and an image of cosmic ray muons that penetrate through the monitored object;

a module for initializing the image;

a module for obtaining the real projection data of the cosmic ray muons that penetrate through the monitored object;

a module for performing an algebraic iteration on the image based on the initialized image, the real projection data and the system matrix; and

a module for obtaining a final image of the core debris state by combining the reconstructed image of the core debris state obtained by algebraic iteration with the system model of the monitored object.

6. The image reconstruction device according to claim 5, wherein, the module for performing an algebraic iteration on the image based on the initialized image, the real projection data and the system matrix further comprises a module for performing a minimization total variation denoising process on the image after each iteration.

7. The image reconstruction device according to claim 5, wherein, the algebraic iteration is a compressed sensing algebraic iteration based on incomplete projection data.

8. The image reconstruction device according to claim 5, wherein, the module for initializing the image is further used for taking the intact core as the initial image.

9. A monitoring system for monitoring core debris state in a severe accident, comprising:

a data collecting device, for collecting the angle data and the displacement data of cosmic ray muons from a monitored region; a data processing device, for pre-processing the data returned by the data collecting device so as to make preparation for image reconstruction; and

the image reconstruction device according to any one of claims 5-8, wherein the data pre-processed by the data processing device are the real projection data of the cosmic ray muons that penetrate through the monitored object.

10. The monitoring system according to claim 9, wherein, the data collecting device is further used for the master control during the operating process of the monitoring system.