Neutron absorption material, use thereof, and control rod for nuclear reactor core

Abstract

The present application relates to a neutron absorption material, the use thereof, and a control rod for a nuclear reactor core. The neutron absorption material provided by the present application comprises ytterbium element and holmium element in a mass ratio of (0.7-0.95):1.

Description

Neutron absorbing materials and their applications, control rods for nuclear reactor cores

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 2023115286068, filed on November 16, 2023, entitled “Neutron Absorbing Materials and Their Applications, Control Rods for Nuclear Reactor Cores,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the technical field of neutron absorbing materials for nuclear reactors, and in particular to a neutron absorbing material and its application, and a control rod for a nuclear reactor core. Background Art

[0004] Nuclear power plants typically control reactor power levels and average primary circuit temperature by adjusting control rod positions or boric acid concentration. While chemical compensation, which involves varying boric acid concentration, provides relatively stable and uniform reactivity control, boron adjustment is slow and produces significant amounts of boron-containing wastewater. Therefore, rapid core reactivity control is currently achieved by inserting and withdrawing control rods.

[0005] Neutron absorbers in control rods are crucial components for controlling power levels and primary circuit average temperature in nuclear reactors. These materials must be permanently inserted into the active region of the reactor core to control changes in burnup reactivity, xenon-induced reactivity, and temperature reactivity within the reactor core. Consequently, these materials are susceptible to irradiation at high neutron flux rates within the active region. Currently, Ag-In-Cd is the most widely used neutron absorber. However, the reactivity of Ag-In-Cd decreases rapidly with burnup, making it difficult to guarantee a sufficient service life for the absorber under the conditions within the active region.

[0006] Summary of the Invention

[0007] The present application provides a neutron absorbing material and its application, as well as a control rod for a nuclear reactor core. The neutron absorbing material provided in the present application can maintain its neutron absorption properties and reactivity value at high burnup depths, thereby extending the service life of the control rod for a nuclear reactor core.

[0008] In a first aspect of the present application, a neutron absorbing material is provided, the components of which include ytterbium and holmium in a mass ratio of (0.7-0.95):1.

[0009] A second aspect of the present application provides a control rod for a nuclear reactor core, comprising a cladding and a neutron absorbing material filled inside the cladding, wherein the neutron absorbing material is the neutron absorbing material described in any one of the embodiments of the first aspect of the present application.

[0010] The third aspect of the present application provides a use of the neutron absorption material described in any embodiment of the first aspect of the present application as a control rod or shielding ceramic material for a high-temperature gas-cooled reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG1 is a graph showing the neutron absorption characteristics of the neutron absorption materials of Examples 1 to 4 and Comparative Example 1 of the present application at a burnup depth of 0 GWd / tU to 70 GWd / tU. DETAILED DESCRIPTION

[0012] The following provides a more complete and clear description of neutron absorbing materials, their applications, and control rods for nuclear reactor cores, using specific examples. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to facilitate a more thorough and comprehensive understanding of the disclosure herein.

[0013] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0014] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. Unless otherwise specified or there is a contradiction, the terms or phrases used herein have the following meanings:

[0015] In this application, "plurality", "multiple", "multiple times", "multiples", etc., unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0016] In this application, the terms "first," "second," "third," "fourth," etc., in the "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the indicated technical features. Furthermore, "first," "second," "third," "fourth," etc., are only used for non-exhaustive enumeration and description purposes, and should be understood not to constitute a closed-ended limitation on quantity.

[0017] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0018] In this application, the terms "preferred", "better", "more preferred" and "suitable" are only used to describe implementation methods or examples with better effects. It should be understood that they do not constitute limitations on the scope of protection of this application.

[0019] In this application, the terms “further”, “further”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0020] In this application, the terms "optionally," "optional," and "optional" refer to options that are optional and may or may not be present, i.e., to the selection of either option from the two parallel options of "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or constraints, each "option" is independent.

[0021] In this application, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval and includes the two numerical endpoints of the numerical range (i.e., the minimum and maximum values), as well as each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1 to 10, indicating that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges included therein.

[0022] Unless otherwise specified, the temperature parameters in this application allow for both constant temperature treatment and temperature fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows for temperature fluctuations within the accuracy range of instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0023] In this application, references to percentage concentrations, unless otherwise specified, refer to final concentrations, which are the percentage of an added component in the system after the addition of that component.

[0024] In this application, "neutron absorption characteristic" refers to the ratio of the reactivity value of the neutron absorber material when burnup is considered to the reactivity value calculated without burnup. This ratio provides a visual representation of the neutron absorption characteristics of the control rod neutron absorber. A ratio closer to 1 indicates that the control rod reactivity value remains nearly constant as burnup increases.

[0025] Control rods are made of neutron-absorbing material. When inserted into a fuel assembly for control and regulation, they absorb a large number of neutrons, preventing the fission chain reaction in a nuclear reactor. However, as the control rod's neutron-absorbing material remains inserted into the fuel assembly for a longer period, the neutron-absorbing material itself begins to absorb neutrons and burn up. This burnup causes the neutron-absorbing material to become a weak neutron absorber, reducing its neutron absorption properties.

[0026] Based on this, in a first aspect of the present application, a neutron absorbing material is provided, comprising ytterbium and holmium in a mass ratio of (0.7-0.95):1.

[0027] It can be understood that the mass ratio of the ytterbium element to the holmium element in the present application can be selected from any value between (0.7 and 0.95): 1. Specifically, the mass ratio of the ytterbium element to the holmium element includes but is not limited to 0.7: 1, 0.71: 1, 0.72: 1, 0.73: 1, 0.75: 1, 0.78: 1, 0.8: 1, 0.81: 1, 0.82: 1, 0.83: 1, 0.85: 1, 0.88: 1, 0.89: 1, 0.9: 1, 0.91: 1, 0.92: 1, 0.93: 1, 0.94: 1 or 0.95: 1; or within the range formed by any two of the above point values ​​as end values.

[0028] The neutron absorption material provided in the present application combines ytterbium and holmium in a mass ratio of (0.7 to 0.95):1, which can effectively exert the high neutron capture cross-section characteristics of ytterbium and holmium, thereby effectively absorbing thermal neutrons, ensuring good chemical and thermal stability, and thus being able to maintain its structural and performance stability for a long time in a high-irradiation environment, effectively preventing the material from converting into a weak neutron absorption material after absorbing neutrons, thereby avoiding affecting the neutron absorption characteristics of the material.

[0029] Furthermore, the neutron absorption material provided in the present application can still maintain its neutron absorption characteristics and reactivity value at a high burnup depth, thereby extending the service life of the neutron absorber.

[0030] In one example, the components of the neutron absorbing material include a first component, a second component, and a third component, and the mass ratio of the first component, the second component, and the third component is (0.7-0.95):1:(0.4-4);

[0031] Wherein, the first component includes ytterbium element and / or ytterbium oxide;

[0032] The second component includes holmium element and / or holmium oxide;

[0033] The third component includes one or more of molybdenum element, molybdenum oxide, AlN, yttrium element, yttrium oxide and calcium oxide.

[0034] It is understandable that in the present application, the mass ratio of ytterbium element and / or ytterbium oxide, holmium element and / or holmium oxide, and the third component can be selected from any value between (0.7-0.95):1:(0.4-4). Specifically, the ratio of ytterbium element and / or ytterbium oxide, holmium element and / or holmium oxide, and the third component includes but is not limited to 0.7:1:0.4, 0.71:1:0.8, 0.72:1:1, 0.76:1:1, 0.8:1:2, 0.85:1:2.5, 0.9:1:3, 0.9:1:3.5 or 0.95:1:4, or is within the range formed by any two of the above point values ​​as end values.

[0035] The elements and compounds in the third component absorb neutrons less strongly than ytterbium and holmium, thereby avoiding affecting the stable absorption characteristics of the Yb / Ho ratio. Furthermore, the addition of the third component effectively adjusts the mass fraction of ytterbium in the neutron absorber, imparting excellent radiation resistance to the material. This effectively reduces or inhibits radiation-induced material damage and degradation, improves the material's reliability under high radiation conditions, and extends the service life of control rods used in nuclear reactors.

[0036] In addition, the third component includes molybdenum element, molybdenum oxide, AlN, yttrium element, and yttrium oxide, wherein molybdenum oxide includes but is not limited to MoO2 and MoO3; yttrium oxide includes but is not limited to Y2O3.

[0037] In one example, the mass percentage of the ytterbium element in the neutron absorbing material is 7% to 15%. It is understandable that the mass percentage of the ytterbium element in the neutron absorbing material can be selected from any value between 7% and 15%. Specifically, the mass percentage of the ytterbium element in the neutron absorbing material includes but is not limited to 7%, 8%, 10%, 12%, 14% or 15%, or is within a range consisting of any two of the above point values ​​as end values. By definition, the mass percentage of the ytterbium element in the neutron absorbing material can optimize the burnup depth of the neutron absorbing material, so that it can still maintain a high neutron absorption characteristic after use, thereby extending the service life of the neutron absorbing material and improving its utilization efficiency.

[0038] Preferably, the mass ratio of the first component, the second component, and the third component is (0.7-0.95):1:(0.4-1). By further adjusting the weight ratio of the first component, the second component, and the third component, it is possible to further prevent the material from converting into a weak neutron absorber after absorbing neutrons, control its neutron absorption properties, and further improve its neutron absorption properties at high burnup depths, effectively maintaining reactivity value and extending service life.

[0039] Preferably, the ytterbium content of the neutron absorber is 10% to 15% by mass. This preferred range of ytterbium content can further optimize the burnup depth of the neutron absorber, extending its service life and achieving higher burnup efficiency, reducing material decay losses, and ensuring a neutron absorption characteristic of ≥97%, thereby extending the reliable service life of the neutron absorber.

[0040] In one example, the ytterbium oxide includes Yb2O3. Ytterbium oxide has a strong resistance to ionizing radiation and can withstand the radiation environment in a nuclear reactor while maintaining its performance and stability. It should be understood that the chemical formula of "ytterbium oxide" referred to in this application is Yb2O3.

[0041] In one example, the holmium oxide includes Ho 2 O 3. It should be understood that the chemical formula of "holmium oxide" mentioned in this application is Ho 2 O 3.

[0042] More preferably, the neutron absorber material described herein comprises ytterbium and / or its oxide, holmium and / or its oxide, and a third component in a mass ratio of (0.7-0.95):1:(0.4-1); and the mass percentage of ytterbium in the neutron absorber is 10%-15%. Neutron absorbers meeting these two mass ratios can adjust the function and performance of the neutron absorber, causing its neutron absorption characteristics to decrease slowly with increasing burnup depth, effectively ensuring a neutron absorption characteristic of ≥97%, and extending the reliable service life of the neutron absorber.

[0043] In one example, the mass percentage of the holmium element in the neutron absorbing material is 7% to 21%. The mass percentage of the holmium element in the neutron absorbing material includes, but is not limited to, 7%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, or 21%, or a range formed by any two of the above values.

[0044] In one example, under the condition of a burnup depth of 70 GWd / tU, the neutron absorption characteristic of the neutron absorbing material is ≥90%.

[0045] A nuclear reactor, also known as an atomic reactor or reactor, is a device capable of maintaining a controlled, self-sustaining chain nuclear fission reaction to achieve nuclear energy utilization. By rationally arranging the nuclear fuel, a nuclear reactor can sustain a self-sustaining chain nuclear fission process without the need for additional neutron sources. Nuclear reactors include pressurized water reactors (PWRs), boiling water reactors (BWRs), heavy water reactors (HWRs), and fast reactors. The control rods of different reactors vary in shape and size. Heavy water reactors use thick rods or sleeves, boiling water reactors use cross-shaped control rods, and PWRs use bundled rods, typically consisting of 24 very thin rods.

[0046] Based on this, the second aspect of this application provides a control rod for a nuclear reactor core, comprising a cladding and a neutron-absorbing material filled within the cladding. The neutron-absorbing material is the neutron-absorbing material described in any example of the second aspect of this application. It will be understood that this application primarily considers the composition of the control rod for a nuclear reactor core and does not limit the specific shape of the control rod for a nuclear reactor core.

[0047] The control rod for the nuclear reactor core provided by the present application can still ensure its neutron characteristics at a high burnup depth, maintain the reactivity value, and extend the service life of the neutron absorber. In addition, it can be understood that the control rod for the nuclear reactor core in the present application has all the advantages of the neutron absorption material described in any example of the first aspect of the present application, and no further details will be given here. The control rod for the nuclear reactor core in the present application is made of the neutron absorption material described in any example of the first aspect. There is a set of mechanical devices outside the nuclear reaction pressure vessel to operate the control rod. When the control rod is fully inserted into the center of the reactor, it can absorb a large number of neutrons to weaken the progress of the fission chain reaction; if the control rod is pulled out a little, the speed of the chain reaction gradually reaches a certain stable value; if you want to increase the energy released by the reactor, you only need to pull out the control rod a little more, so that the absorbed neutrons are reduced and more neutrons participate in the fission reaction; inserting the control rod fully into the center of the nuclear reaction to absorb most of the neutrons can stop the chain reaction. Furthermore, the control rods for nuclear reactor cores provided in the present application can effectively avoid conversion into weak neutron absorbing materials after absorbing neutrons, thereby being able to control the neutron characteristics of the control rods so that they can still maintain their neutron characteristics at high burnup depths and maintain their reactivity value, thereby extending the service life of the neutron absorber.

[0048] The following specific examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples. Unless otherwise specified, the raw materials used in the examples are all commercially available products.

[0049] Example 1

[0050] Example 1 of the present application provides a neutron absorbing material comprising Yb2O3, Ho2O3, and MoO3. In particular, by weight, the Yb2O3 comprises 9.44 parts, the Ho2O3 comprises 10 parts, and the MoO3 comprises 8.2 parts. The mass ratio of Yb2O3 to Ho2O3 is 0.944:1, and the mass ratio of ytterbium to holmium is 0.95:1. In the neutron absorbing material of Example 1, the mass percentage of Yb2O3 is 34.2%, and the mass percentage of ytterbium in the neutron absorbing material is 15%.

[0051] Example 2

[0052] Example 2 of the present application provides a neutron absorbing material comprising Yb2O3, Ho2O3, and MoO3. In particular, by weight, the Yb2O3 comprises 7.36 parts, the Ho2O3 comprises 10 parts, and the MoO3 comprises 4.18 parts. The mass ratio of Yb2O3 to Ho2O3 is 0.736:1, and the mass ratio of ytterbium to holmium is 0.74:1. In the neutron absorbing material of Example 2, the mass percentage of Yb2O3 is 34.2%, and the mass percentage of ytterbium in the neutron absorbing material is 15%.

[0053] Example 3

[0054] Example 3 of the present application provides a neutron absorbing material comprising Yb2O3, Ho2O3, and MoO3. In particular, by weight, the Yb2O3 comprises 9.44 parts, the Ho2O3 comprises 10 parts, and the MoO3 comprises 39.8 parts. The mass ratio of Yb2O3 to Ho2O3 is 0.944:1, and the mass ratio of ytterbium to holmium is 0.95:1. In the neutron absorbing material of Example 3, the mass percentage of Yb2O3 is 16%, and the mass percentage of ytterbium in the neutron absorbing material is 7%.

[0055] Example 4

[0056] Example 4 of the present application provides a neutron absorbing material comprising Yb2O3, Ho2O3, and MoO3. In particular, by weight, the Yb2O3 comprises 7.36 parts, the Ho2O3 comprises 10 parts, and the MoO3 comprises 28.8 parts. The mass ratio of Yb2O3 to Ho2O3 is 0.736:1, and the mass ratio of ytterbium to holmium is 0.74:1. In the neutron absorbing material of Example 4, the mass percentage of Yb2O3 is 16%, and the mass percentage of ytterbium in the neutron absorbing material is 7%.

[0057] Comparative Example 1

[0058] Comparative Example 1 of the present application provides a neutron absorbing material comprising metal Ag, metal In and metal Cd, wherein the mass ratio of the metal Ag, metal In and metal Cd is 80:15:5.

[0059] The mass ratios of the contents of the components in Examples 1 to 4 and Comparative Example 1 are shown in Table 1.

[0060] Table 1

[0061] Test method: The neutron absorbing materials in Examples 1 to 4 and Comparative Example 1 were modeled using the Monte Carlo program according to the mass ratio, and the fuel consumption calculation can be calculated using the Chebyshev rational approximation method, as shown in the paper (Calculation and analysis of the value loss of gray body control rods using the RMC program, Modern Applied Physics, 2020, 11(01)).

[0062] The neutron absorption characteristics test results of the neutron absorber materials in Examples 1 to 4 and Comparative Example 1 at burnup depths of 0 GWd / tU to 70 GWd / tU are shown in Figure 1. In Figure 1, the y-axis represents the ratio of the reactivity value of the control rod absorber material calculated with burnup taken into account to the reactivity value calculated without burnup. This ratio intuitively demonstrates the neutron absorption characteristics of the control rod neutron absorber. The closer the ratio is to 1, the closer the reactivity value remains to a constant level during burnup. The neutron absorption characteristics of the Ag-In-Cd neutron absorber in Comparative Example 1 are 85% at a burnup depth of 70 GWd / tU, indicating that their reactivity value remains at 85% of their original value. However, the neutron absorption characteristics of the neutron absorber materials provided in Examples 1 to 4 of the present application at a burnup depth of 70 GWd / tU are ≥95%, indicating that their neutron absorption characteristics, i.e., their reactivity value, remain essentially unchanged, thereby extending the service life of the control rod neutron absorber.

[0063] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The embodiments described above only express several implementation methods of the present application, which are convenient for understanding the technical solutions of the present application in a specific and detailed manner, but they cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all fall within the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the content of the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A neutron absorbing material, comprising ytterbium and holmium in a mass ratio of about (0.7-0.95):

1.

2. The neutron absorbing material according to claim 1, characterized in that: The components of the neutron absorbing material include: a first component, a second component and a third component; The mass ratio of the first component, the second component and the third component is approximately (0.7-0.95): 1: (0.4～4)； wherein the first component comprises one or more of ytterbium element and ytterbium oxide; The second component includes one or more of holmium simple substance and holmium oxide.

3. The neutron absorbing material according to claim 2, characterized in that: The third component includes one or more of molybdenum element, molybdenum oxide, AlN, yttrium element, yttrium oxide and calcium oxide.

4. The neutron absorbing material according to claim 3, characterized in that: The molybdenum oxide includes one or more of MoO2 and MoO3.

5. The neutron absorbing material according to claim 3, characterized in that: The yttrium oxide includes Y2O3.

6. The neutron absorbing material according to any one of claims 1 to 5, characterized in that: In the neutron absorbing material, the mass percentage of the ytterbium element is about 7% to 15%.

7. The neutron absorbing material according to any one of claims 2 to 6, characterized in that: The mass ratio of the first component, the second component and the third component is approximately (0.7-0.95):1:(0.4-1).

8. The neutron absorbing material according to any one of claims 1 to 7, characterized in that: In the neutron absorbing material, the mass percentage of the ytterbium element is about 10% to 15%.

9. The neutron absorbing material according to any one of claims 2 to 8, characterized in that: The ytterbium oxide includes Yb2O3.

10. The neutron absorbing material according to any one of claims 2 to 9, characterized in that: The holmium oxide includes Ho2O3.

11. The neutron absorbing material according to any one of claims 1 to 10, characterized in that: In the neutron absorbing material, the mass percentage of the holmium element is about 7% to 21%.

12. The neutron absorbing material according to any one of claims 1 to 11, characterized in that: Under the condition of a burnup depth of 70 GWd / tU, the neutron absorption characteristic of the neutron absorption material is approximately ≥90%.

13. The neutron absorbing material according to any one of claims 1 to 12, characterized in that: The neutron absorbing material includes Yb2O3, Ho2O3 and MoO3; Among them, by weight, Yb2O3 is about 7.36 parts, Ho2O3 is about 10 parts, and MoO3 is about 4.18 parts; The mass ratio of Yb2O3 to Ho2O3 is about 0.736:1, and the mass ratio of ytterbium to holmium is about 0.74:1; In the neutron absorbing material, the mass percentage of Yb2O3 is about 34.2%, and the mass percentage of the ytterbium element in the neutron absorbing material is about 15%.

14. A control rod for a nuclear reactor core, comprising: Encapsulation; A neutron absorbing material is filled in the cladding, and the neutron absorbing material is the neutron absorbing material according to any one of claims 1 to 13.

15. A shielding ceramic material comprising the neutron absorbing material according to any one of claims 1 to 13.

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