阅读说明：本技术 一种核电站反应堆堆芯 (Reactor core of nuclear power station reactor ) 是由 马兹容 宿健 周胜 于 2020-04-03 设计创作，主要内容包括：本发明提供一种核电站反应堆堆芯,包括压力容器、燃料组件和反射层,所述燃料组件与所述反射层均设置于压力容器内部,且所述反射层包裹所述燃料组件；所述燃料组件包括多组第一燃料组件、多组第二燃料组件和多组第三燃料组件,所述多组第一燃料组件围绕压力容器的中心设置,形成内边界；所述多组第三燃料组件围绕所述第一燃料组件设置,形成外边界；所述第二燃料组件设置于内边界与外边界之间。所述第一燃料组件和第二燃料组件中均包括含钆燃料棒,且第一燃料组件含钆燃料棒中三氧化二钆的重量百分比小于所述第二燃料组件含钆燃料棒中三氧化二钆的重量百分比。本发明实施例降低了堆芯轴向功率偏移的最大值,提升了核电站的安全性和运行灵活性。(The invention provides a reactor core of a nuclear power station reactor, which comprises a pressure vessel, a fuel assembly and a reflecting layer, wherein the fuel assembly and the reflecting layer are both arranged in the pressure vessel, and the reflecting layer wraps the fuel assembly; the fuel assemblies comprise a plurality of groups of first fuel assemblies, a plurality of groups of second fuel assemblies and a plurality of groups of third fuel assemblies, wherein the plurality of groups of first fuel assemblies are arranged around the center of the pressure vessel to form an inner boundary; the plurality of sets of third fuel assemblies are arranged around the first fuel assembly to form an outer boundary; the second fuel assembly is disposed between the inner boundary and the outer boundary. The first fuel assembly and the second fuel assembly respectively comprise gadolinium-containing fuel rods, and the weight percentage of gadolinium trioxide in the gadolinium-containing fuel rods of the first fuel assembly is smaller than that of gadolinium trioxide in the gadolinium-containing fuel rods of the second fuel assembly. The embodiment of the invention reduces the maximum value of axial power deviation of the reactor core and improves the safety and the operation flexibility of the nuclear power station.)

1. A nuclear power plant reactor core comprising a pressure vessel, a fuel assembly and a reflective layer, both disposed inside the pressure vessel, and the reflective layer encasing the fuel assembly; it is characterized in that the preparation method is characterized in that,

the fuel assemblies comprise a plurality of groups of first fuel assemblies, a plurality of groups of second fuel assemblies and a plurality of groups of third fuel assemblies, the plurality of groups of first fuel assemblies are arranged around the center of the pressure vessel, and the first fuel assemblies close to the center of the pressure vessel are arranged in a surrounding mode to form an inner boundary; the plurality of groups of third fuel assemblies are arranged around the plurality of groups of first fuel assemblies, and the third fuel assemblies far away from the center of the pressure vessel are arranged in an enclosing mode to form an outer boundary;

the second fuel assembly is disposed between the inner boundary and the outer boundary;

each group of the first fuel assemblies, each group of the second fuel assemblies and each group of the third fuel assemblies comprise a plurality of first fuel rods, each group of the first fuel assemblies further comprises a plurality of second fuel rods, each group of the second fuel assemblies further comprises a plurality of third fuel rods, and the second fuel rods and the third fuel rods are gadolinium-containing fuel rods;

wherein the weight percentage of the gadolinium oxide in the second fuel rod is less than the weight percentage of the gadolinium oxide in the third fuel rod.

2. The nuclear power plant reactor core of claim 1, wherein the plurality of groups of first fuel assemblies, the plurality of groups of second fuel assemblies, and the plurality of groups of third fuel assemblies are divided by U235 enrichment, the U235 enrichment of the plurality of groups of first fuel assemblies being the same, the U235 enrichment of the plurality of groups of second fuel assemblies being the same, and the U235 enrichment of the plurality of groups of third fuel assemblies being the same;

the first, second, and third fuel assemblies each have a different U235 enrichment.

3. The nuclear power plant reactor core of claim 1, wherein the first, second, and third fuel assemblies are less than 5% U235 enrichment.

4. The nuclear power plant reactor core of claim 1, wherein each set of the third fuel assemblies further comprises a plurality of fourth fuel rods, the fourth fuel rods being gadolinium-containing fuel rods, the weight percentage of gadolinium trioxide in the fourth fuel rods being greater than the weight percentage of gadolinium trioxide in the third fuel rods.

5. The nuclear power plant reactor core of claim 4, wherein the gadolinium oxide is present in the second, third and fourth fuel rods in an amount of 2 to 12% by weight.

6. The nuclear power plant reactor core according to claim 4, wherein the second, third and fourth fuel rods are each arranged in an axially asymmetric segmented arrangement, comprising uranium pellets and gadolinium pellets, the distance from the uranium pellets to the pressure vessel tip being less than the distance from the gadolinium pellets to the pressure vessel tip.

7. The nuclear power plant reactor core of claim 1, wherein the number of the first fuel assemblies is 73-137 groups, the number of the second fuel assemblies is 48-80 groups, and the number of the third fuel assemblies is 28-48 groups.

8. The nuclear power plant reactor core of claim 1, wherein the first, second, and third fuel assemblies each further comprise a plurality of guide tubes and an instrumentation tube;

in each of the first fuel assemblies, the plurality of first fuel rods, the plurality of second fuel rods, the plurality of guide tubes and the one instrumentation tube are arranged in a 17 x 17 lattice pattern;

in each of the second fuel assemblies, the plurality of first fuel rods, the plurality of third fuel rods, the plurality of guide tubes and the one instrumentation tube are arranged in a 17 x 17 lattice pattern;

in each set of the third fuel assemblies, the first fuel rods, the guide tubes and the instrumentation tubes are arranged in a 17 x 17 grid.

9. The nuclear power plant reactor core of claim 8, wherein one of the instrumentation tubes of the first, second and third fuel assemblies is replaced by one fuel rod disposed in the 17 x 17 grid in place of the one instrumentation tube.

Technical Field

The invention relates to the technical field of nuclear power, in particular to a reactor core of a nuclear power station reactor.

Background

Fuel assemblies are an important component of a nuclear power plant reactor core, and in the fuel management of the reactor core, the arrangement of the fuel assemblies is not only concerned with the economic efficiency of the nuclear power plant, but also with the safety and operational flexibility of the nuclear power plant.

At present, in a reactor core composed of multiple groups of fuel assemblies, because a reactivity inflection point exists in the service life of each fuel assembly containing gadolinium, and at the reactivity inflection point, the power difference of the upper half part and the lower half part of the reactor core is increased, the axial power deviation of the reactor core in the service life is increased steeply, so that the maximum value of the power deviation is large, in order to ensure the safety of the reactor core in the first cycle, partial functions in a nuclear power station are limited, and the operation flexibility of the nuclear power station is influenced. Therefore, the problem of low operation flexibility of the nuclear power plant exists in the prior art.

Disclosure of Invention

The embodiment of the invention provides a reactor core of a nuclear power station, which aims to solve the problem of low operation flexibility of the nuclear power station in the prior art.

The embodiment of the invention provides a reactor core of a nuclear power station reactor, which comprises a pressure vessel, a fuel assembly and a reflecting layer, wherein the fuel assembly and the reflecting layer are both arranged in the pressure vessel, and the reflecting layer wraps the fuel assembly;

the fuel assemblies comprise a plurality of groups of first fuel assemblies, a plurality of groups of second fuel assemblies and a plurality of groups of third fuel assemblies, the plurality of groups of first fuel assemblies are arranged around the center of the pressure vessel, and the first fuel assemblies close to the center of the pressure vessel are arranged in a surrounding mode to form an inner boundary; the plurality of groups of third fuel assemblies are arranged around the plurality of groups of first fuel assemblies, and the third fuel assemblies far away from the center of the pressure vessel are arranged in an enclosing mode to form an outer boundary;

the second fuel assembly is disposed between the inner boundary and the outer boundary;

each group of the first fuel assemblies, each group of the second fuel assemblies and each group of the third fuel assemblies comprise a plurality of first fuel rods, each group of the first fuel assemblies further comprises a plurality of second fuel rods, each group of the second fuel assemblies further comprises a plurality of third fuel rods, and the second fuel rods and the third fuel rods are gadolinium-containing fuel rods;

wherein the weight percentage of the gadolinium oxide in the second fuel rod is less than the weight percentage of the gadolinium oxide in the third fuel rod.

Optionally, the plurality of groups of first fuel assemblies, the plurality of groups of second fuel assemblies, and the plurality of groups of third fuel assemblies are divided according to U235 enrichment degrees, the U235 enrichment degrees of the plurality of groups of first fuel assemblies are the same, the U235 enrichment degrees of the plurality of groups of second fuel assemblies are the same, and the U235 enrichment degrees of the plurality of groups of third fuel assemblies are the same;

the first, second, and third fuel assemblies each have a different U235 enrichment.

Optionally, the first, second and third fuel assemblies have a U235 enrichment of less than 5%.

Optionally, each group of the third fuel assemblies further includes a plurality of fourth fuel rods, each of the fourth fuel rods is a gadolinium-containing fuel rod, and a weight percentage of gadolinium trioxide in each of the fourth fuel rods is greater than a weight percentage of gadolinium trioxide in each of the third fuel rods.

Optionally, the second fuel rod, the third fuel rod and the fourth fuel rod are all arranged in an axially asymmetric partition mode and comprise uranium pellets and gadolinium pellets, and the distance from the uranium pellets to the top end of the pressure vessel is smaller than the distance from the gadolinium pellets to the top end of the pressure vessel.

Optionally, the weight percentage of gadolinium oxide in the second fuel rod, the third fuel rod and the fourth fuel rod is 2% -12%.

Optionally, the second fuel rod, the third fuel rod and the fourth fuel rod are all arranged in an axially asymmetric partition mode and comprise uranium pellets and gadolinium pellets, and the distance from the uranium pellets to the top end of the pressure vessel is smaller than the distance from the gadolinium pellets to the top end of the pressure vessel.

Optionally, the number of the first fuel assemblies is 73-137 groups, the number of the second fuel assemblies is 48-80 groups, and the number of the third fuel assemblies is 28-48 groups.

Optionally, the first fuel assembly, the second fuel assembly and the third fuel assembly each further comprise a plurality of guide tubes and an instrument tube;

in each of the first fuel assemblies, the plurality of first fuel rods, the plurality of second fuel rods, the plurality of guide tubes and the one instrumentation tube are arranged in a 17 x 17 lattice pattern;

in each of the second fuel assemblies, the plurality of first fuel rods, the plurality of third fuel rods, the plurality of guide tubes and the one instrumentation tube are arranged in a 17 x 17 lattice pattern;

in each set of the third fuel assemblies, the first fuel rods, the guide tubes and the instrumentation tubes are arranged in a 17 x 17 grid.

Optionally, one instrument tube in each of the first fuel assembly, the second fuel assembly and the third fuel assembly is replaced by one fuel rod, and the one fuel rod is arranged in the 17 × 17 grid instead of the one instrument tube.

In an embodiment of the present invention, a fuel assembly including a fuel rod containing gadolinium has a reactivity inflection point during a lifetime, which causes a sharp increase in Axial Offset (AO), and the higher the weight percentage of gadolinium oxide is, the later the reactivity inflection point comes. Meanwhile, due to the difference of the burning-up speed of the inner ring and the outer ring of the reactor core, the reactivity inflection point of the fuel assembly of the inner ring is prior to the reactivity inflection point of the fuel assembly of the outer ring. According to the embodiment of the invention, the weight percentage of the gadolinium contained in the second fuel rod of gadolinium-containing second fuel rod in the first fuel assembly positioned in the inner ring is lower than the weight percentage of the gadolinium contained in the gadolinium-containing third fuel rod of second fuel assembly positioned in the second outer ring, so that the interval between the reactivity inflection points of the inner ring and the second outer ring of fuel assemblies is enlarged, the total axial power offset amplitude of a reactor core passing through the reactivity inflection points is reduced, the maximum value of the axial power offset is reduced, the safety of the reactor core is ensured, and the operation flexibility of a nuclear power station is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments of the present invention will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is a schematic 1/4 fuel assembly distribution diagram of a nuclear power plant core provided by an embodiment of the present invention;

FIG. 2 is a 1/4 core loading schematic diagram of a nuclear power plant provided by an embodiment of the present invention;

FIG. 3 is a graphical representation of axial power excursions as a function of burnup for a comparative example of the invention;

FIG. 4 is a graphical representation of axial power offset as a function of burnup for an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships are changed accordingly.

Referring to fig. 1, fig. 1 is a schematic diagram illustrating 1/4 fuel assemblies 10 distribution in a nuclear power plant core according to an embodiment of the present invention. The embodiment of the invention provides a reactor core of a nuclear power station reactor, which comprises a pressure vessel, a fuel assembly 10 and a reflecting layer, wherein the fuel assembly 10 and the reflecting layer are both arranged in the pressure vessel, and the reflecting layer wraps the fuel assembly 10;

the fuel assemblies 10 include a plurality of first fuel assemblies 11, a plurality of second fuel assemblies 12, and a plurality of third fuel assemblies 13, the plurality of first fuel assemblies 11 are disposed around the center of the pressure vessel, and the first fuel assemblies 11 near the center of the pressure vessel are disposed around the inner boundary; the plurality of sets of third fuel assemblies 13 are arranged around the first fuel assembly 11, and the third fuel assemblies 13 far away from the center of the pressure vessel are arranged around to form an outer boundary;

the second fuel assembly 12 is disposed between the inner boundary and the outer boundary;

each of the first fuel assemblies 11, each of the second fuel assemblies 12, and each of the third fuel assemblies 13 includes a plurality of first fuel rods, each of the first fuel assemblies 11 further includes a plurality of second fuel rods, each of the second fuel assemblies 12 further includes a plurality of third fuel rods, and each of the second fuel rods and the third fuel rods is a gadolinium-containing fuel rod;

wherein, the weight percentage of the gadolinium oxide in the second fuel rod is less than the weight percentage of the gadolinium oxide in the third fuel rod.

Specifically, the arrangement of the first fuel assembly 11, the second fuel assembly 12 and the third fuel assembly 13 may be set according to actual requirements. In the embodiment of the present invention, as shown in fig. 1, a planar rectangular coordinate system is established with the core center as the origin, the positive direction of the X axis is the direction from H to a in the figure, and the positive direction of the Y axis is the direction from 15 to 8 in the figure. It is to be understood that fig. 1 is a schematic view of the distribution of the fuel assemblies 10 in the core in the fourth quadrant. The distribution of the fuel assemblies 10 in the first, second and third quadrants is shown in rotational symmetry with respect to the origin in fig. 1.

The plurality of first fuel assemblies 11, the plurality of second fuel assemblies 12, and the plurality of third fuel assemblies 13 are substantially enclosed into a circle, the plurality of first fuel assemblies 11 are located at an inner circle, the second fuel assemblies 12 are located at a next outer circle, and the third fuel assemblies 13 are located at an outer circle.

The first fuel rods may be uranium rods, wherein the U235 enrichment of the uranium rods in each group of fuel assemblies 10 is approximately the same, and the U235 enrichment of the uranium rods in different groups of fuel assemblies 10 may be different.

The number of the second fuel rods in each group of the first fuel assemblies 11 can be set according to actual needs, and specifically can be 4-24. Meanwhile, in order to flatten the power peak factor of the core, the number of the second fuel rods in the first fuel assemblies 11 located at the positions where the power peak factor is higher may be greater than the number of the second fuel rods in the remaining sets of the first fuel assemblies 11. Accordingly, the data of the second fuel rods in each set of the second fuel assemblies 12 can be set according to actual needs, and specifically, the number of the second fuel rods can be 4-24.

Since the gadolinium-containing fuel assembly 10 has a inflection point of reactivity, it is necessary to use as little gadolinium as possible while satisfying the requirement of the temperature coefficient of the moderator, and therefore the gadolinium-containing fuel rod may not be included in the third fuel assembly 13.

In an embodiment of the invention, the axial power excursion is increased dramatically due to the presence of a reactivity inflection point in the life of the fuel assembly 10 comprising the gadolinium-containing fuel rod, with the reactivity inflection point coming later the greater the weight percentage of gadolinium oxide. While the reactivity inflection point of the fuel assembly 10 of the inner circle comes before the reactivity inflection point of the fuel assembly 10 of the outer circle due to the difference in the burnup speed of the inner and outer circles of the reactor core. According to the embodiment of the invention, the weight percentage of the gadolinium contained in the second fuel rod gadolinium trioxide of the first fuel assembly 11 is lower than that of the gadolinium contained in the third fuel rod gadolinium trioxide of the second fuel assembly 12, so that the interval between the reactive inflection points of the inner ring fuel assembly 10 and the outer ring fuel assembly 10 is increased, the total axial power offset amplitude of a reactor core in the service life is reduced, the maximum value of the axial power offset is reduced, the safety of the reactor core is ensured, and the operation flexibility of a nuclear power plant is improved.

Further, to simplify assembly manufacturing, the above-described groups of first fuel assemblies 11, second fuel assemblies 12, and third fuel assemblies 13 may be divided by the U235 enrichment. I.e., the U235 enrichment of each of said first fuel assemblies 11 is the same, the U235 enrichment of each of said second fuel assemblies 12 is the same, and the U235 enrichment of each of said third fuel assemblies 13 is the same;

the first fuel assembly 11, the second fuel assembly 12 and the third fuel assembly 13 have different U235 enrichment degrees. The specific U235 enrichment can be set according to actual needs, and in the embodiment of the present invention, the U235 enrichment of the first fuel assembly 11, the second fuel assembly 12, and the third fuel assembly 13 is less than 5%, and can be 2.4%, 3.1%, and 1.8%, respectively.

It is understood that, when the core circulation length is longer, in order to meet the requirement of the moderator temperature coefficient, each set of the third fuel assemblies 13 may further include a plurality of fourth fuel rods, where the fourth fuel rods are gadolinium-containing fuel rods, and the weight percentage of gadolinium oxide in the fourth fuel rods is greater than the weight percentage of gadolinium oxide in the third fuel rods.

Due to the temperature difference between the upper and lower halves of the core, the axial power excursion of the core at the beginning of the first cycle life is relatively negative. In order to reduce the absolute value of the axial power deviation at the beginning of the core life, the second fuel rod, the third fuel rod and the fourth fuel rod can adopt an axially asymmetric partition arrangement, and comprise uranium pellets and gadolinium pellets.

Specifically, the distance from the uranium pellet to the top end of the pressure vessel is smaller than the distance from the gadolinium pellet to the top end of the pressure vessel, in other words, the uranium pellet is disposed at the top end of the active region, so that the power of the upper half part of the core in the initial cycle life is increased, and further the axial power deviation of the core in the initial cycle life approaches 0.

Wherein the U235 enrichment of uranium pellets is consistent with the U235 enrichment of the first fuel rod in the same fuel assembly 10 group. The specific length and weight ratio of the uranium pellets to the gadolinium pellets can be set according to actual needs.

Further, the weight percentage of the gadolinium oxide in the second fuel rod, the third fuel rod and the fourth fuel rod may be set according to actual needs. On the premise of satisfying the size relationship among the three, the ratio can be specifically 2% -12%. For example, in one embodiment, the percentage by weight of the gadolinium oxide in the second fuel rod, the third fuel rod and the fourth fuel rod may be 8%, 9% and 10%, respectively.

Further, the number of the above-mentioned sets of first fuel assemblies 11, second fuel assemblies 12 and third fuel assemblies 13 can be set according to actual needs. In an embodiment of the present invention, the number of the first fuel assemblies 11 may be 73 to 137, the number of the second fuel assemblies 12 may be 48 to 80, and the number of the third fuel assemblies 13 may be 28 to 48.

Further, each of the first fuel assembly 11, the second fuel assembly 12 and the third fuel assembly 13 may further include a plurality of guide pipes and an instrument pipe;

in each of the first fuel assemblies 11, the plurality of first fuel rods, the plurality of second fuel rods, the plurality of guide tubes, and the one instrumentation tube may be arranged in a lattice pattern of 17 × 17;

in each of the second fuel assemblies 12, the plurality of first fuel rods, the plurality of third fuel rods, the plurality of guide tubes, and the one instrumentation tube may be arranged in a 17 × 17 lattice pattern;

in each of the third fuel assemblies 13, the first fuel rods, the guide tubes, and the instrumentation tubes may be arranged in a 17 × 17 lattice pattern.

Note that, since the function of the instrument tube may be implemented by a guide tube provided in a fuel assembly, one instrument tube in each of the first fuel assembly 11, the second fuel assembly 12, and the third fuel assembly 13 may be replaced by one fuel rod provided in the lattice of 17 × 17 instead of the one instrument tube.

Wherein, the specific number of the fuel rods can be set according to actual conditions. In an embodiment of the present invention, the sum of the number of the first fuel rods and the number of the second fuel rods in the first fuel assembly 11 may be 264, and the first fuel rods and the second fuel rods are respectively disposed in 264 grids. Each of the remaining 25 cells is used to provide an instrumentation tube, or a guide tube. Accordingly, the sum of the number of the first fuel rods and the number of the third fuel rods in the second fuel assembly 12 may be 264. The number of the first fuel rods in the third fuel assembly 13 may be 264.

In order to better understand the present invention, a specific implementation process of the present invention will be described in detail below by taking a specific embodiment as an example.

Referring to FIG. 2, in an embodiment of the invention, the reactor core is comprised of 177 groups of fuel assemblies having an active area length of 3657.6mm, with an enrichment of 1.8% for the 32 groups, 2.4% for the 73 groups, and 3.1% for the 72 groups.

The layout of the reactor core fuel assemblies is as shown in FIG. 2, wherein the fuel assemblies with the enrichment degree of 2.4% are positioned in the inner ring of the reactor core; in order to reduce the power peak factor of the reactor core, a small amount of fuel assemblies with the enrichment degree of 3.1% can be positioned in the inner ring of the reactor core, a small amount of fuel assemblies are positioned in the outer ring of the reactor core, and the rest fuel assemblies are positioned in the secondary outer ring of the reactor core; the fuel assemblies with the enrichment degree of 1.8% are positioned on the outer ring of the reactor core.

Wherein the fuel assembly with the enrichment degree of 2.4%, the fuel assembly with the enrichment degree of 3.1% and the fuel assembly with the enrichment degree of 1.8% comprise a plurality of fuel rods without gadolinium. Meanwhile, the fuel assembly with the enrichment degree of 2.4% and the fuel assembly with the enrichment degree of 3.1% also comprise a plurality of gadolinium-containing fuel rods, and the specific number can be set to be 4-24.

In order to simplify the assembly manufacture, the gadolinium oxide content of the gadolinium-containing fuel rods in the fuel assembly with enrichment degrees of 2.4% and 3.1% is set to be 8% and 9% respectively. Of course, in other embodiments, the gadolinium oxide in the gadolinium-containing fuel rod in the inner ring and the fuel rod in the next outer ring may be 8% and 9% by weight, respectively.

Meanwhile, the gadolinium-containing fuel rod adopts an axial partition design, and 304.8mm of the top of the gadolinium-containing fuel rod in the fuel assembly with the enrichment degrees of 2.4% and 3.1% is 2.4% and 3.1% of uranium pellet respectively.

A comparative example is provided, wherein the enrichment degrees of gadolinium oxide of gadolinium-containing fuel rods in the fuel assembly of the comparative example are 2.4% and 3.1%, the weight percentages of gadolinium oxide in the fuel assembly are the same and are both 8%, and the gadolinium-containing fuel rods are axially arranged in a non-partitioned manner.

Fig. 3 is a schematic diagram of the change of the axial power deviation of the nuclear power plant core with the fuel consumption in the comparative example, and it can be seen from fig. 3 that the axial power deviation AO in the comparative example increases sharply in the life period, which affects the effectiveness of the setting of the fixed value of the axial power deviation reference value (Δ Iref, Δ I ═ AO × Pr) related to the axial power deviation, and the number of the periodic tests and the number of the parameter fixed value setting need to be increased. Meanwhile, the maximum value after the steep increase is larger, so that the safety and the operation flexibility of the nuclear power station can be reduced.

FIG. 4 is a schematic diagram of the axial power deviation of the nuclear power plant core as a function of the fuel consumption in the embodiment, and it can be seen from FIG. 4 that the axial power deviation at the beginning of life in the embodiment of the present invention is adjusted to be about 0 in comparison with the comparative example of the prior art; the axial power deviation changes smoothly in the service life, the change speed and the change amplitude are equivalent to those of other stages, and the problem that the axial power deviation amplitude of the comparative example increases steeply in the service life is solved.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.