Asymmetric loading method for square component nuclear power plant reactor core

Abstract

The present invention relates to an asymmetric loading method for a square-component nuclear power plant reactor core. The asymmetric loading method for a square-component nuclear power plant reactor core provided by the present invention is used to design an asymmetric loading scheme by using the keff equivalence and combustible poison content equivalence methods, which is used to improve the quadrant power tilt caused by asymmetric loading and the quadrant power tilt caused by asymmetric combustible poisons, provide assistance for asymmetric loading from a numerical calculation perspective, and more systematically solve the problem of asymmetric loading. When the method provided by the present invention is used for asymmetric core loading, when a fuel assembly is damaged, it is not necessary to discard the assembly in the symmetrical position of the damaged assembly, which can improve the fuel economy of the core while ensuring the safe operation of the core.

Description

Technical Field

[0001] The invention belongs to the technical field of reactor design and relates to an asymmetric loading method for a square component nuclear power plant reactor core. Background Art

[0002] In a nuclear reactor, the core power quadrant tilt must be less than 2%. When a fuel assembly is damaged, in order to ensure the symmetry of power distribution, the damaged assembly is discarded and the assembly at the symmetrical position of the damaged assembly is also discarded to ensure the symmetry of core power distribution, which will lead to the waste of nuclear fuel assemblies. If other fuel assemblies are used to replace the damaged fuel assembly, the new fuel assembly may have a difference in system effective neutron multiplication factor (keff) with the original symmetrical position assembly, resulting in the power distribution symmetry not meeting the requirements.

[0003] At present, the existing related technologies include a Chinese patent application (application number CN201310270683.8, publication date November 20, 2013) disclosed in a method for asymmetric loading of a VVER nuclear power plant reactor core, submitted by Xu Min, one of the inventors of the present invention, which is a method for adjusting the arrangement of core components through experience.

[0004] In order to enable asymmetric loading methods for nuclear power plant reactor cores to be applied more systematically, the inventors of the present invention, based on a method for asymmetric loading of a VVER nuclear power plant reactor core, provide a method for designing an asymmetric loading scheme based on system effective neutron multiplication factor (keff) equivalence and combustible poison content equivalence, thereby providing assistance for asymmetric loading from the perspective of numerical calculation and solving the problem of asymmetric loading in a more systematic manner. Summary of the invention

[0005] In view of the defects existing in the prior art, the purpose of the present invention is to provide a method for asymmetric loading of the reactor core of a square component nuclear power plant, to design an asymmetric loading scheme by using the method of system effective neutron multiplication factor equivalence, to provide assistance for asymmetric loading from the perspective of numerical calculation, to more systematically solve the problem of asymmetric loading and to improve the fuel economy of the core.

[0006] To achieve this object, the present invention provides a method for asymmetric loading of a square assembly nuclear power plant reactor core, the method comprising the following steps:

[0007] S1. When at least one fuel assembly is damaged, a new fuel assembly is used to replace the damaged fuel assembly at the beginning of a new cycle, and the remaining fuel assemblies continue to be used;

[0008] S2, with the goal of keff equivalence, the fuel assemblies are grouped and rearranged;

[0009] S3. Reposition the fuel assemblies throughout the core to maintain the core quadrant power tilt at a safe operating level.

[0010] Furthermore, the grouping and rearranging of the fuel assemblies refers to dividing the new fuel assemblies and the remaining fuel assemblies that continue to be used into four fuel assembly combinations, corresponding to the four quadrants of the core respectively.

[0011] Furthermore, the keff equivalence means that the difference between the sum of the keffs of the fuel assembly combinations is minimized to improve the quadrant power tilt caused by asymmetric loading.

[0012] Furthermore, the step S2 also includes the following steps: grouping and rearranging the fuel assemblies with the goal of achieving equivalent combustible poison content.

[0013] Furthermore, the re-adjustment of the position of the fuel assemblies within the entire core range refers to placing the four fuel assembly combinations into four quadrants of the core layout diagram respectively, and calculating the corresponding enthalpy rise factor and core quadrant power tilt of each fuel assembly in the core, and adjusting the position of the placed fuel assemblies within each quadrant to keep the core quadrant power tilt at a safe operating level.

[0014] Furthermore, the equivalent burnable poison content means that the difference between the sum of gadolinium contents of each fuel assembly combination is minimized to improve the quadrant power tilt caused by burnable poison asymmetry.

[0015] Furthermore, the weights of the keff equivalent and the combustible poison content equivalent are each 0.5.

[0016] The beneficial effect of the present invention is that the square assembly nuclear power plant reactor core asymmetric loading method provided by the present invention is adopted, and the asymmetric loading scheme is designed by the method of keff equivalence and burnable poison content equivalence, which is used to improve the quadrant power tilt caused by asymmetric loading and the quadrant power tilt caused by burnable poison asymmetry, and provide assistance for asymmetric loading from the perspective of numerical calculation, and can more systematically solve the problem of asymmetric loading. When the method provided by the present invention is used for asymmetric core loading, when the fuel assembly is damaged, it is not necessary to abandon the assembly in the symmetrical position of the damaged assembly, and the fuel economy of the core can be improved under the premise of ensuring the safe operation of the core. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of the asymmetric loading method for the square assembly nuclear power plant reactor core according to the present invention.

[0018] Figure 2 It is a schematic diagram of an asymmetric loading scheme for a nuclear power plant reactor core with square components when one component is damaged according to an embodiment of the present invention.

[0019] Figure 3 This is a diagram of the enthalpy rise factors of each component in the adjusted asymmetric loading scheme of the nuclear power plant reactor core with square components in an embodiment of the present invention.

[0020] Figure 4 It is a quadrant power tilt diagram of the asymmetric loading scheme of the reactor core of a nuclear power plant with square components after adjustment in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0022] like Figures 1 to 4 As shown, this embodiment provides a method for asymmetric loading of a square assembly nuclear power plant reactor core, comprising the following steps:

[0023] S1. When at least one fuel assembly is damaged, a new fuel assembly is used to replace the damaged fuel assembly at the beginning of a new cycle, and the remaining fuel assemblies continue to be used;

[0024] In this embodiment, taking the M310 unit as an example, the reactor type has a total of 157 fuel assemblies, and the number of new fuel assemblies for the next cycle is 68. Assuming that a certain assembly is damaged in the previous cycle, the damaged assembly has a large reactivity and is originally planned to be put into the next cycle. New fuel assemblies are used to replace the damaged assemblies in the previous cycle. In this way, the assemblies put into the core include 88 irradiated fuel assemblies, one new fuel assembly for replacement, and 68 new fuel assemblies.

[0025] Since the position of the new fuel assembly in the core is always 1 / 4 symmetrical, the assembly placed in the symmetrical position of the core center has no effect on the symmetry of the core. Therefore, it is necessary to arrange and combine 87 groups of irradiated fuel assemblies and 88 groups of fuel assemblies consisting of one group of new fuel assemblies so that the core loading scheme meets the requirements. In the scheme provided in this embodiment, the enrichment of the new fuel assembly replacing the damaged fuel assembly is 3.2%.

[0026] S2. Rearrange the fuel assemblies in groups with the goal of achieving equivalent system effective neutron multiplication factor (keff) and / or equivalent burnable poison content;

[0027] Taking the keff and gadolinium content of the above 88 fuel assemblies at full power and zero xenon state, and taking the total keff equivalence and / or the nuclear equivalence of the burnable poison content of each fuel assembly combination as the goal, the 88 fuel assemblies are divided into 4 fuel assembly combinations with equal numbers of fuel assemblies.

[0028] The keff equivalence means that the difference between the sum of the keffs of the various fuel assembly combinations is minimized, and is used to improve the quadrant power tilt caused by asymmetric loading.

[0029] The burnable poison content equivalence means that the difference between the sum of the gadolinium contents of the various fuel assembly combinations is minimal, which is used to improve the quadrant power tilt caused by the burnable poison asymmetry.

[0030] In this embodiment, with the goal of minimizing the difference between the sums of keff of each fuel assembly combination and the sums of gadolinium contents of each fuel assembly combination, 88 fuel assemblies are grouped and rearranged between 4 fuel assembly combinations to improve quadrant power tilt caused by asymmetric loading and asymmetric burnable poisons.

[0031] The grouping rearrangement process involves multi-objective optimization. In the optimization process, this embodiment adopts a linear weighted model, and sets the weights of minimizing the difference between the sum of keff of each fuel assembly combination and minimizing the difference between the sum of gadolinium content of each fuel assembly combination to 0.5, respectively, to obtain four rearranged fuel assembly combinations.

[0032] S3. Reposition the fuel assemblies throughout the core to maintain the core quadrant power tilt at a safe operating level.

[0033] The four fuel assembly combinations are placed in four quadrants of the core layout diagram respectively, and the corresponding enthalpy rise factor and core quadrant power tilt of each fuel assembly in the core are calculated, and the position of the fuel assemblies in the corresponding fuel assembly combination placed in each quadrant is adjusted, that is, the position of the placed fuel assemblies is adjusted within each quadrant, so that the core quadrant power tilt is maintained at a safe operating level.

[0034] Among them, when adjusting the enthalpy rise factor, the fuel assemblies arranged at symmetrical positions in each quadrant are adjusted using a symmetrical enthalpy rise factor mode, and the fuel assemblies arranged at symmetrical positions in each quadrant are adjusted with the goal of symmetrical equivalence of enthalpy rise factors, that is, the adjustment is made with the goal of minimizing the difference in enthalpy rise factors of the fuel assemblies in symmetrical positions in each quadrant.

[0035] When adjusting the core quadrant power tilt, the fuel assemblies arranged in each quadrant of the core layout diagram are adjusted asymmetrically until the optimal fuel management solution that meets the safety operation level requirements is reached.

[0036] When one assembly formed by the method provided in this embodiment is damaged, the schematic diagram of the asymmetric loading scheme of the square assembly nuclear power plant reactor core is as follows: Figure 2As shown in the figure, the new fuel assembly is loaded at position R08 to replace the damaged fuel assembly. The enthalpy rise factors of each assembly in the asymmetric loading scheme of the reactor core of the square assembly nuclear power plant after adjustment are as follows: Figure 3 The quadrant power tilt of the asymmetric loading scheme of the reactor core of a square component nuclear power plant after adjustment is shown in Figure 4 shown.

[0037] The above embodiments are merely examples of the present invention, and those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for asymmetric loading of a square-assembly nuclear power plant reactor core, characterized in that: The method comprises the following steps: S1. When at least one fuel assembly is damaged, a new fuel assembly is used to replace the damaged fuel assembly at the beginning of a new cycle, and the remaining fuel assemblies continue to be used; S2, keff With equivalence as the goal, fuel assemblies are grouped and rearranged; Said keff Equivalence refers to the combination of each of the fuel assemblies keff The gap between the sums is minimal to improve quadrant power tilt due to asymmetric loading; The step S2 further includes the following steps: grouping and rearranging the fuel assemblies with the goal of equivalent burnable poison content; the equivalent burnable poison content means that the difference between the sum of the gadolinium contents of each fuel assembly combination is the smallest, so as to improve the quadrant power tilt caused by the asymmetry of the burnable poison; The grouping and rearranging of the fuel assemblies refers to dividing the new fuel assemblies and the remaining fuel assemblies that continue to be used into 4 fuel assembly combinations, corresponding to the four quadrants of the core respectively; S3, readjusting the positions of the fuel assemblies within the entire core range to keep the core quadrant power tilt at a safe operating level; the readjusting the positions of the fuel assemblies within the entire core range refers to placing the 4 fuel assembly combinations into the four quadrants of the core layout diagram respectively, and calculating the corresponding enthalpy rise factor and core quadrant power tilt of each fuel assembly in the core, and adjusting the positions of the placed fuel assemblies within each quadrant to keep the core quadrant power tilt at a safe operating level.

2. The asymmetric loading method for a square-assembly nuclear power plant reactor core according to claim 1, characterized in that: Said keff The weights equivalent to the combustible poison content are each 0.5.

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