CN115116630A - Reactor core reactivity control method for small direct circulation reactor - Google Patents

Reactor core reactivity control method for small direct circulation reactor Download PDF

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Publication number
CN115116630A
CN115116630A CN202210794282.1A CN202210794282A CN115116630A CN 115116630 A CN115116630 A CN 115116630A CN 202210794282 A CN202210794282 A CN 202210794282A CN 115116630 A CN115116630 A CN 115116630A
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control
reactor
rods
poison
reactivity
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Inventor
王诗倩
李庆
陈长
刘琨
王连杰
秦冬
娄磊
李满仓
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Nuclear Power Institute of China
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Nuclear Power Institute of China
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    • GPHYSICS
    • G21NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21CNUCLEAR REACTORS
    • G21C7/00Control of nuclear reaction
    • G21C7/06Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section
    • G21C7/08Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section by displacement of solid control elements, e.g. control rods
    • G21C7/12Means for moving control elements to desired position
    • GPHYSICS
    • G21NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21CNUCLEAR REACTORS
    • G21C7/00Control of nuclear reaction
    • G21C7/06Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section
    • G21C7/08Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section by displacement of solid control elements, e.g. control rods
    • G21C7/10Construction of control elements
    • G21C7/103Control assemblies containing one or more absorbants as well as other elements, e.g. fuel or moderator elements
    • GPHYSICS
    • G21NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21CNUCLEAR REACTORS
    • G21C7/00Control of nuclear reaction
    • G21C7/06Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section
    • G21C7/08Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section by displacement of solid control elements, e.g. control rods
    • G21C7/10Construction of control elements
    • G21C7/117Clusters of control rods; Spider construction
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00Energy generation of nuclear origin
    • Y02E30/30Nuclear fission reactors

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Monitoring And Testing Of Nuclear Reactors (AREA)

Abstract

The invention discloses a method for controlling the reactor core reactivity of a small direct circulation reactor, which does not use soluble boron poison and only controls the reactor core reactivity by matching control rods with burnable poison. The reactivity control method provided by the invention only depends on the control rods and the burnable poison rods to carry out reactivity control, so that the residual reactivity of the reactor core in the whole service life is not too high, and enough cycle length needs to be ensured.

Description

Reactor core reactivity control method for small direct circulation reactor
Technical Field
The invention belongs to the technical field of nuclear reactor core design, and particularly relates to a method for controlling the reactor core reactivity of a small direct circulation reactor.
Background
The reactivity control is very important for the safety of the reactor, the control difficulty of the reactor is increased along with the improvement of the service life and the power index of the reactor, and the contradiction is particularly obvious for a pure rod-controlled small reactor with the service life.
Control of the reactivity of long-life, high-safety small direct cycle reactors is particularly difficult, mainly due to the following reasons:
(1) early k of life eff The method is as follows: the reactor core adopts full ceramic coated Fuel (FCM) fuel which has higher safety and can effectively prevent the release of fission products, but the uranium content is less, and one of the negative effects brought by the fuel is k at the beginning of the life eff Relatively common UO 2 The ceramic core block is large, and the reactor core is required to operate at long term power without material change, so that the two effects are superposed to cause the k at the beginning of the service life eff Is much higher than the core of the traditional pressurized water reactor;
(2) the control means of the inverse reaction is less: because the reactor is a direct circulation boiling water reactor, the reactor cannot carry soluble poison to operate, and the reactivity control only depends on a control rod and solid combustible poison, thereby bringing two difficulties:
(a) more control rod arrangements: the reactor is a direct circulation reactor, the degree of under-moderation of the reactor is high, the energy spectrum is hard, the value of corresponding control rods is low, meanwhile, excessive residual reactivity in the early life can require more control rods to be arranged, the value of the control rods is high, more fuel element positions are occupied by the control rods in an extruding mode, the uranium loading of a reactor core is reduced, high enrichment fuel is needed to achieve the same life, and then the k in the early life is increased eff
(b) The poison is more, and it is difficult to match: excessive residual reactivity inevitably requires the addition of more poisons, increases the poison punishment at the end of the service life, influences neutron economy and also can reduce fuel uranium loading, and direct circulation reactor moderator axial density changes greatly simultaneously, influences the axial moderating ability of reactor core, makes fuel axial power distribution difference great then, leads to the poison to match harder.
Disclosure of Invention
In order to realize reliable control of the reactor core reactivity of the small direct circulation reactor with long service life, pure rod control and high safety, the invention provides a reactor core reactivity control method of the small direct circulation reactor, which does not depend on soluble boron control, completes the loading measurement research of control rods and burnable poisons and realizes the reactivity control target.
The invention is realized by the following technical scheme:
a method for controlling the reactivity of reactor core of small-sized direct circulation reactor features that the control rods are matched with combustible poison without using soluble boron poison.
In a preferred embodiment, the core of the invention uses FCM fuel elements, the pellets of the FCM fuel elements are loaded by mixing TRISO particles and QUADRISO particles, and the ratio of the two particle loads is adjusted according to the requirements of life and reactivity control.
As a preferred embodiment, the intra-pellet loading of the FCM fuel element of the present invention is 40% PF TRISO + 4% PF quadurio, where PF is the loading ratio.
In a preferred embodiment, the burnable poison materials and the loading of the burnable poison material are axially and radially partitioned according to the axial segmentation and the power distribution of the coolant of the small direct circulation reactor, and different poison materials and different poison loadings are adopted in different partitions.
As a preferred embodiment, the control rod arrangement of the core of the present invention employs reserved control rod locations.
In a preferred embodiment, all the control rods of the present invention are inserted from the bottom of the core, and the control rods are partially long control rods.
As a preferred embodiment, the control rods of the present invention are zoned according to small direct cycle reactor coolant phase change and fuel axial power distribution, with different control rod materials being arranged in different zones to meet reactivity control requirements.
In a preferred embodiment, the control rods of the invention are divided into a regulating rod group and a shutdown rod group;
each adjusting rod in the adjusting rod group is provided with an independent control rod driving mechanism;
the shutdown rod group is provided with two groups of driving mechanisms.
In a preferred embodiment, the control material used in the control rod of the present invention is hafnium hydride, hafnium boride or Eu 2 O 3
In a preferred embodiment, the burnable poison material of the present invention is B, Gd, Hf, Er, Eu, Dy or Sm.
The invention has the following advantages and beneficial effects:
the reactivity control method provided by the invention only depends on the control rods and the burnable poison rods to carry out reactivity control, so that the residual reactivity of the reactor core in the whole service life is not too high, and enough cycle length needs to be ensured.
The control method provided by the invention effectively flattens the axial power of the reactor core according to the axial segmentation of the poison, reduces the poison punishment as far as possible, and is matched with the reasonable arrangement of the control rods, so that the safety of the reactor core is improved, and the economy of the reactor core is improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a schematic view of the axial placement of toxins within an FCM fuel element in accordance with an embodiment of the present invention.
FIG. 2 is a schematic view of the radial placement of toxins within an FCM fuel element in accordance with an embodiment of the present invention.
FIG. 3 is an axial zoning schematic view of a burnable poison containing fuel element according to an embodiment of the present invention.
FIG. 4 is a schematic illustration of a core radial control rod arrangement according to an embodiment of the present invention.
FIG. 5 is a schematic illustration of core axial control rod arrangement according to an embodiment of the present invention.
Reference numbers and corresponding part names in the drawings:
1-pellets, 11-QUADRISO poison fuel particles, 12-TRISO fuel particles, 2-cladding, 3-liquid segment, 4-two-phase segment, 5-vapor segment, 6-regulating rod group, 7-shutdown rod group.
Detailed Description
Hereinafter, the term "comprising" or "may include" used in various embodiments of the present invention indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. Furthermore, as used in various embodiments of the present invention, the terms "comprises," "comprising," "includes," "including," "has," "having" and their derivatives are intended to mean that the specified features, numbers, steps, operations, elements, components, or combinations of the foregoing, are only meant to indicate that a particular feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as first excluding the existence of, or adding to the possibility of, one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.
In various embodiments of the invention, the expression "or" at least one of a or/and B "includes any or all combinations of the words listed simultaneously. For example, the expression "a or B" or "at least one of a or/and B" may include a, may include B, or may include both a and B.
Expressions (such as "first", "second", and the like) used in various embodiments of the present invention may modify various constituent elements in various embodiments, but may not limit the respective constituent elements. For example, the above description does not limit the order and/or importance of the elements described. The foregoing description is for the purpose of distinguishing one element from another. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of various embodiments of the present invention.
It should be noted that: if it is described that one constituent element is "connected" to another constituent element, the first constituent element may be directly connected to the second constituent element, and a third constituent element may be "connected" between the first constituent element and the second constituent element. In contrast, when one constituent element is "directly connected" to another constituent element, it is understood that there is no third constituent element between the first constituent element and the second constituent element.
The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the various embodiments of the invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the present invention belong. The terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning that is consistent with their contextual meaning in the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in various embodiments of the present invention.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Examples
The embodiment provides a method for controlling the reactivity of a core of a small direct circulation reactor aiming at a pure rod control and long-life high-safety small direct circulation reactor, wherein partial long control rods and burnable poison are reasonably configured, so that the residual reactivity of the core in the whole long-life period can be effectively controlled, the control requirement of the core reactivity in the long-life period is met, the requirements of shutdown allowance and rod clamping criterion are met, and the improvement of the core economy is facilitated while the core safety is improved through the reasonable arrangement of the burnable poison and the control rods.
The control method of the embodiment specifically includes:
(1) the poison loading form adopts four layers of concentric coating (QUADRISO) particles, which is a peculiar poison loading form of FCM fuel, a combustible poison layer is added in a fuel core and a buffer layer of TRISO particles, and the thickness of the combustible poison layer can be controlled to be between 0.003 and 0.03mm according to reactivity. The poison layer varies according to reactivity control requirements, and common burnable poison materials such as B, Gd, Hf, Er, Eu, Dy and Sm are used.
(2) The FCM fuel pellets are loaded with TRISO particles mixed with QUADRISO particles, and the ratio of the two particle loadings (PF) can be adjusted according to the lifetime and reactivity control requirements, for example 40% PF TRISO + 4% PF QUADRISO. Meanwhile, the fuel enrichment degree in the QUADRISO fuel core can be adjusted, so that the aims of completely burning the poisons and improving the neutron economy of the reactor core are fulfilled.
(3) The poison material and the content can be matched in an axial and radial partition mode according to the axial partition of the cooling agent, the power distribution of the fuel and the like, and different poison materials and different poison loading amounts can be adopted in different partitions.
(4) The control rod arrangement mode adopts the reserved control rod position, namely, part of the fuel element positions are replaced by the control rod positions, and no water squeezing rod or flow blocking plug is added, so that the positions where the control rods are not inserted in the power operation period such as the shutdown rod position can be used as the water rods to additionally increase the direct circulation reactor core moderation, and the neutron economy is improved.
(5) To prevent localized fuel element overheating due to over-slowing near the control rod position for extended core withdrawal, control rods of this type should be selected from control materials having a large absorption cross-section to increase control rod value and reduce control rod placement, such as hafnium hydride (HfH) x X represents the atomic ratio of H/Hf), hafnium boride (HfB) 2 ) And Eu 2 O 3 And the like.
(6) The control rod bundles are divided into regulating rod groups and shutdown rod groups according to functions, the regulating rod groups have independent control rod driving mechanisms for flexible control of the reactor core; the shutdown rod group is provided with two groups of driving mechanisms in consideration of properly improving the economy of the reactor core, 6 groups of shutdown rods in the inner ring share one driving mechanism, and 12 groups of shutdown rods in the outer ring share the other driving mechanism.
(7) Because the reactor type is a direct circulation boiling water reactor, the control rods are inserted from the bottom, and simultaneously, because the moderation capacity is very low after the coolant is completely vaporized, the under-moderation degree of a steam section is high, the fuel power is low, the control rods are designed to be only inserted into a liquid section and a two-phase section, namely, part of long control rods, the control capacity of the control rods is ensured, the cost is saved, and the economy of a reactor core is improved.
(8) The control rods can be partitioned according to direct circulation reactor coolant phase change and fuel axial power distribution, and different control rod materials are arranged in different partitions to meet reactivity control requirements.
The reactor core of the small direct circulation reactor proposed by the embodiment has the height of 280cm, 2971 fuel elements are arranged, the reactor core is arranged in a hexagonal shape, the axial height of the core active area is totally wrapped by a slowing layer (such as a BeO layer), the core life reaches 4000EFPD, and the control rods and burnable poison share the reactivity control task.
As shown in fig. 1-2, the fuel element of the core of this embodiment is FCM fuel element, which includes fuel pellets 1 and cladding 2, and the fuel pellets 1 are loaded with mixture of TRISO fuel particles 12 and quadurio poison fuel particles 11.
The fuel element is axially segmented according to direct circulating reactor coolant and fuel axial power, poison arrangement in the fuel element is divided into a liquid section 3, a two-phase section 4 and a steam section 5, and a specific axial segmentation schematic diagram is shown in fig. 3. The liquid section has higher power and faster consumption, poisons with larger neutron absorption cross sections and faster consumption are adopted to match the characteristics, the adding amount of the poisons is also larger, considering poison punishment, B is finally selected as a poison material, and TRISO PF/QUADRISO PF is 19/25. The initial power of the two-phase section in the service life is smaller, the later power of the two-phase section in the service life is larger, the total power is smaller compared with that of the liquid section, so that the initial section of the service life is smaller, but the poison which can better suppress the power of the two-phase section when the power is reduced due to faster uranium consumption in the later water section in the service life is matched with the characteristics of the poison, Er is more suitable, and TRISO PF/QUADRISO PF is 29/15. Specific poison-containing fuel element parameters are shown in table 1.
TABLE 1 poison-containing Fuel element parameters
Figure BDA0003735034080000071
Figure BDA0003735034080000081
As shown in fig. 4-5, the control clusters are divided into groups of conditioning bars 6 and groups of shutdown bars 7 by function.
The reactor core comprises 6 regulating rod groups, 18 regulating rod groups in total, and Hf is selected as a regulating rod material to ensure that the regulating rods can keep the stable control of the reactivity for a long time and have excellent mechanical property and corrosion resistance; 3 shutdown rods are bundled into 21 bundles, and Eu is selected 2 O 3 As a material for regulating rods to ensure that local fuel elements are not overheated due to over-slowing in the vicinity of the position where the shutdown rods are proposed when the reactor is operated at power, two groups of driving mechanisms are arranged in a total manner, 6 groups of shutdown rods on the inner ring share one driving mechanism, and 12 groups of shutdown rods on the outer ring share the other driving mechanism in consideration of properly improving the economy of the reactor core.
The control rods are all inserted from the bottom of the reactor core, all the control rods are partial long control rods, namely, the control rods are only inserted into the liquid section and the two-phase section when being fully inserted, the coolant complete vaporization section has lower power due to poor power moderation, and the control rods are not inserted.
The reactor core of the small direct circulation reactor of the embodiment adopts the control method, and only depends on the control rods and burnable poison to carry out reactivity control, so that the residual reactivity of the reactor core in the whole service life is effectively controlled while the 4000EFPD operation is kept and the refueling is not carried out, and the rapid shutdown can be realized and enough shutdown allowance can be provided by depending on the control rods at any time. The key parameters relevant for reactivity control are shown in table 2. Meanwhile, the reactivity control strategy meets the rod clamping criterion in the whole service life of the reactor core.
TABLE 2 high safety direct cycle reactor reactivity control related Key parameters
Figure BDA0003735034080000082
Figure BDA0003735034080000091
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A reactor core reactivity control method of a small direct circulation reactor is characterized in that soluble boron poison is not used in the control method, and the reactor core reactivity control is carried out only by matching control rods with burnable poison.
2. The method as claimed in claim 1, wherein the reactor core is FCM fuel element, and the pellet of FCM fuel element is loaded with mixture of TRISO particles and QUADRISO particles, and the ratio of loading the two particles is adjusted according to the requirement of life and reactivity control.
3. The method of claim 2, wherein the FCM fuel elements are mixed with 40% PF TRISO + 4% PF QUADRISO in the core, where PF is the loading ratio.
4. The method of claim 1, wherein the burnable poison materials and loadings are axially and radially partitioned according to coolant axial segmentation and power distribution of the small direct cycle reactor, and different poison materials and different poison loadings are used for different partitions.
5. The method of claims 1-4 wherein the core control rod arrangement is in the form of reserved control rod locations.
6. The method as claimed in any one of claims 1 to 4, wherein all the control rods are inserted from the bottom of the core, and the control rods are partially long control rods.
7. The method as claimed in any one of claims 1 to 4, wherein the control rods are zoned according to coolant phase change and fuel axial power distribution of the small direct cycle reactor, and different control rod materials are arranged in different zones to meet reactivity control requirements.
8. The method as claimed in any one of claims 1 to 4, wherein the control rods are divided into a group of adjusting rods and a group of shutdown rods;
each group of adjusting rods in the adjusting rod group is provided with an independent control rod driving mechanism;
the shutdown rod group is provided with two groups of driving mechanisms.
9. The method as claimed in any one of claims 1 to 4, wherein the control material used for the control rods is hafnium hydride, hafnium boride or Eu 2 O 3
10. The method of any one of claims 1-4, wherein the burnable poison material is B, Gd, Hf, Er, Eu, Dy, or Sm.
CN202210794282.1A 2022-07-07 2022-07-07 Reactor core reactivity control method for small direct circulation reactor Withdrawn CN115116630A (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120314831A1 (en) * 2011-06-10 2012-12-13 Ut-Battelle, Llc Light Water Reactor TRISO Particle-Metal-Matrix Composite Fuel
CN108320820A (en) * 2018-02-13 2018-07-24 中国核动力研究设计院 A kind of 100,000 kilowatts of order reaction heap Nuclear design methods

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120314831A1 (en) * 2011-06-10 2012-12-13 Ut-Battelle, Llc Light Water Reactor TRISO Particle-Metal-Matrix Composite Fuel
CN108320820A (en) * 2018-02-13 2018-07-24 中国核动力研究设计院 A kind of 100,000 kilowatts of order reaction heap Nuclear design methods

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Application publication date: 20220927