阅读说明：本技术 一种基于复合式燃料元件的超临界水冷堆 (Supercritical water-cooled reactor based on combined type fuel element ) 是由 夏榜样 姚磊 卢迪 王连杰 李庆 李翔 肖鹏 甯忠豪 李司南 于 2019-11-21 设计创作，主要内容包括：本发明公开了一种应用于超临界水冷堆的复合式燃料芯块,沿径向包括实心内区燃料芯块和包围实心内区燃料芯块的连续环状外区燃料芯块,以外区燃料芯块为UO<Sub>2</Sub>、内区燃料芯块为BeO形成UO<Sub>2</Sub>/BeO复合芯块；或者以外区燃料芯块为UO<Sub>2</Sub>、内区燃料芯块为ThO<Sub>2</Sub>形成UO<Sub>2</Sub>/ThO<Sub>2</Sub>复合芯块；一种复合燃料元件,在燃料元件沿轴向方向上,UO<Sub>2</Sub>/BeO复合芯块与UO<Sub>2</Sub>/ThO<Sub>2</Sub>复合芯块交替布置；一种燃料组件,导向管和所述燃料元件按照正方形或正三角形栅格规则排列,构成正方形或正六角形燃料组件；一种临界水冷堆,由若干上述燃料组件构成超临界水冷堆堆芯。本发明利于提升超临界水冷堆的堆芯安全性及其燃料经济性,并简化燃料组件及堆芯方案,大幅提高超临界水冷堆的可靠性及工程可实现性。(The invention discloses a composite fuel pellet applied to a supercritical water-cooled reactor, which comprises a solid inner-zone fuel pellet and a continuous annular outer-zone fuel pellet surrounding the solid inner-zone fuel pellet along the radial direction, wherein the outer-zone fuel pellet is UO 2 Inner zone fuel pellet to form UO for BeO 2 a/BeO composite core block; or the outer zone fuel pellet is UO 2 Inner zone fuel pellet ThO 2 Formation of UO 2 /ThO 2 Compounding the core block; composite fuelElement, in the axial direction of the fuel element, UO 2 BeO composite pellet and UO 2 /ThO 2 The composite core blocks are alternately arranged; a fuel assembly, the guide tube and the fuel element are arranged according to a square or regular triangle grid rule to form a square or regular hexagon fuel assembly; a critical water-cooled reactor is characterized in that a supercritical water-cooled reactor core is formed by a plurality of fuel assemblies. The invention is beneficial to improving the reactor core safety and the fuel economy of the supercritical water-cooled reactor, simplifying the fuel assembly and the reactor core scheme, and greatly improving the reliability and the engineering realizability of the supercritical water-cooled reactor.)

1. Be applied to supercritical water coolingA stack of composite fuel pellets, characterized in that the composite fuel pellets radially comprise a solid inner zone fuel pellet and a continuous annular outer zone fuel pellet surrounding the solid inner zone fuel pellet, the outer zone fuel pellet being UO₂Inner zone fuel pellet to form UO for BeO₂a/BeO composite core block; or the outer zone fuel pellet is UO₂Inner zone fuel pellet ThO₂Formation of UO₂/ThO₂And (3) compounding the core blocks.

2. The composite fuel pellet applied to supercritical water-cooled reactor of claim 1, wherein the UO is used for fuel pellet₂The enrichment degree of the fuel pellet is lower than 6.0 percent, and the BeO pellet is a high-temperature resistant neutron moderating material ThO₂The core block is a high-temperature resistant proliferation conversion material.

3. Composite fuel element of composite fuel pellets for supercritical water-cooled reactor, based on claim 1 or 2, characterized by UO in the axial direction of the fuel element₂BeO composite pellet and UO₂/ThO₂The composite core blocks are alternately arranged.

4. A composite fuel element according to claim 3, characterised in that the axially upper region of the fuel element is the UO₂a/BeO composite pellet, the axially lower region of the fuel element being UO₂/ThO₂And (3) compounding the core blocks.

5. A composite fuel element according to claim 3, characterised in that the fuel element has axially opposite end regions of UO₂BeO composite pellet with fuel element axial middle region of UO₂/ThO₂And (3) compounding the core blocks.

6. A composite fuel element in accordance with claim 3, wherein said fuel element cladding is of SiC material.

7. A fuel assembly applied to a supercritical water-cooled reactor, which is characterized by comprising guide pipes and the fuel elements as defined in any one of claims 3 to 6, wherein the guide pipes and the fuel elements are regularly arranged according to a square or regular triangular grid to form a square or regular hexagonal fuel assembly, and a square or regular hexagonal assembly box is arranged at the periphery of the fuel assembly.

8. The fuel assembly applied to the supercritical water-cooled reactor of claim 7, wherein the assembly box and the guide tube cladding are made of SiC material.

9. The supercritical water cooled reactor of fuel assemblies as claimed in claim 7 or 8, wherein the supercritical water cooled reactor core is formed by a plurality of square or hexagonal fuel assemblies, and the coolant in the guide pipe flows in the direction opposite to the coolant flow direction between the fuel elements.

Technical Field

The invention relates to the technical field of nuclear reactors, in particular to a supercritical water-cooled reactor based on a composite fuel element.

Background

Supercritical water cooled reactor (SCWR) is one of six nuclear energy systems screened by International Forum for nuclear energy (GIF) generation IV with the most development prospect. The SCWR nuclear power unit has the outstanding advantages of high thermal efficiency, simplified system and the like. In order to improve the thermal efficiency of the system, the pressure of the SCWR system reaches more than 25MPa, and the outlet temperature reaches more than 500 ℃, so that the design requirement of the reactor fuel element is greatly improved, and particularly, the fuel element cladding not only resists irradiation, but also resists high-temperature and high-pressure coolant. In addition, due to the low density of the SCWR coolant, the neutron moderation of the reactor core is insufficient, and a 'water rod' (low-temperature coolant flow channel) design technology needs to be introduced, so that the fuel assembly and the reactor core are very complicated in structure, and the engineering realizability is greatly reduced.

At present, the technical scheme of the main supercritical water-cooled reactor at home and abroad is as follows: the European Union HPLWR scheme, the Japanese SCLWR-H scheme, the American SCWR scheme, etc.,stainless steel is adopted as a cladding material, and a fuel core is UO₂The ceramic utilizes "water bar" structure to strengthen neutron moderation ability, and fuel element can satisfy supercritical water-cooled reactor high temperature high pressure operating environment basically, but has seriously influenced fuel economy, fuel assembly and reactor core structure reliability for the reason as follows:

(1) the strong neutron absorption capacity of the stainless steel cladding material directly leads to the reduction of fuel economy;

(2) by limiting the average linear power density and the bulk power density of the fuel rods, the fuel core temperature and the cladding temperature are ensured to meet the design criteria, the increase of the reactor core coolant outlet temperature and the fuel economy are seriously influenced, and the system thermal efficiency cannot be further improved;

(3) in order to fully and uniformly slow the fuel rods, a plurality of 'water rod' structures are arranged in the SCWR fuel assembly and are mixed with the fuel elements to be used as low-temperature coolant channels, and the low-temperature coolant in the 'water rod' and the high-temperature coolant outside the 'water rod' for cooling the fuel elements are divided and insulated, so that the fuel assemblies and the reactor core are very complicated in structure, and the performance index and the economical efficiency of the existing reactor design scheme are seriously influenced.

Therefore, it is necessary to reconsider the structural form of the supercritical water-cooled reactor fuel element and the fuel assembly, simplify the structure of the fuel element and the fuel assembly, and improve the fuel economy and the overall performance index of the SCWR.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the invention provides a supercritical water-cooled reactor based on a composite fuel element, which solves the problems and adopts a fuel pellet as UO₂BeO and UO₂/ThO₂The composite fuel element with SiC as cladding material replaces the prior stainless steel cladding and UO₂A pellet fuel rod. Due to the improvement of the design limit values of the temperature of the cladding and the core of the fuel element and the enhancement of the neutron moderating capacity, the linear power density and the bulk power density of the fuel element can be obviously increased, and the outlet temperature of the coolant of the reactor core is improved, so that the linear power density and the bulk power density of the fuel element are obviously increased, and the outlet temperature of the coolant of the reactor coreThe reactor core safety and the fuel economy of the supercritical water-cooled reactor are improved, the design of a water rod is cancelled, the fuel assembly and the reactor core arrangement scheme are simplified, and the reliability and the engineering realizability of the supercritical water-cooled reactor are greatly improved.

The invention is realized by the following technical scheme:

the composite fuel pellet for supercritical water-cooled reactor includes one solid inner fuel pellet and one continuous annular outer fuel pellet surrounding the solid inner fuel pellet and with UO as the outer fuel pellet₂Inner zone fuel pellet to form UO for BeO₂a/BeO composite core block; or the outer zone fuel pellet is UO₂Inner zone fuel pellet ThO₂Formation of UO₂/ThO₂And (3) compounding the core blocks.

Further, the UO₂The enrichment degree of the fuel pellet is lower than 6.0 percent, the BeO pellet is a high-temperature resistant neutron moderating material, ThO₂The core block is a high-temperature resistant proliferation conversion material.

Based on the composite fuel element of the composite fuel pellet applied to the supercritical water-cooled reactor, the UO is arranged on the fuel element along the axial direction₂BeO composite pellet and UO₂/ThO₂The composite core blocks are alternately arranged.

Further, the fuel element axially upper region is UO₂a/BeO composite pellet, the axially lower region of the fuel element being UO₂/ThO₂And (3) compounding the core blocks.

Further, the axial two end regions of the fuel element are UO₂BeO composite pellet with fuel element axial middle region of UO₂/ThO₂And (3) compounding the core blocks.

Further, the cladding of the fuel element is made of SiC material.

A fuel assembly applied to a supercritical water-cooled reactor, which comprises guide pipes and fuel elements as defined in any one of claims 3 to 6, wherein the guide pipes and the fuel elements are regularly arranged according to a square or regular triangular grid to form a square or regular hexagonal fuel assembly, and a square or regular hexagonal assembly box is arranged at the periphery of the fuel assembly.

Further, the component box and the guide tube cladding are made of SiC materials.

The supercritical water-cooled reactor based on the fuel assemblies is characterized in that the supercritical water-cooled reactor core is formed by a plurality of square or regular hexagonal fuel assemblies, and the flow direction of the coolant in the guide pipe is opposite to the flow direction of the coolant between the fuel elements.

The invention has the following advantages and beneficial effects:

the invention provides a composite fuel pellet applied to a supercritical water-cooled reactor, which comprises a solid inner fuel pellet and a continuous annular outer fuel pellet surrounding the solid inner fuel pellet along the radial direction, wherein the outer fuel pellet is a UO with low enrichment degree₂The inner fuel pellet forms UO for BeO with strong neutron moderating capability and high temperature resistance₂a/BeO composite core block; or UO with low enrichment of foreign fuel pellets₂The fuel pellet in the inner zone is ThO with high temperature resistance and strong multiplication capacity₂Formation of UO₂/ThO₂And (3) compounding the core blocks. Further, the invention provides a fuel pellet which adopts the fuel pellet as UO₂BeO composite pellet and UO₂/ThO₂The composite fuel element with SiC as composite pellet and cladding material replaces the prior stainless steel cladding and UO₂A pellet fuel rod. Because the design limit values of the temperatures of the fuel element cladding and the fuel core are improved, the neutron moderating capability is enhanced, the linear power density and the bulk power density of the fuel element can be obviously increased to the level of the traditional large pressurized water reactor, the outlet temperature of the reactor core coolant is increased to more than 550 ℃, the structural design scheme of the fuel assembly and the reactor core is simplified under the condition of ensuring the reactor core safety and the fuel economy of the supercritical water-cooled reactor, and the reliability and the engineering realizability of the supercritical water-cooled reactor are greatly improved.

UO₂the/BeO composite pellets are arranged on the upper part of the fuel rod, so that the problem of insufficient neutron moderation caused by high-temperature low-density coolant on the upper part of the reactor core can be effectively solved, the central temperature of the fuel pellets can be reduced, the water rod (low-temperature coolant runner) structure of a fuel assembly can be eliminated, and the fuel assembly can be greatly reducedSimplifying the fuel assembly scheme; UO₂/ThO₂The pellets are arranged in the middle or lower part of the fuel rod, so that the power share of the middle or lower part of the reactor core and the central temperature of the pellets can be effectively reduced, and ThO is fully utilized₂The multiplication conversion characteristic increases the multiplication conversion ratio of the reactor core, thereby improving the fuel economy of the reactor.

In conclusion, the invention overcomes the defects of the existing supercritical water-cooled reactor fuel assembly and reactor core design, increases the linear power density of the fuel rods and the power density of the reactor core body, improves the maximum temperature limit value of the fuel element cladding and the fuel pellet, cancels the complex structures such as the slowing water rods in the fuel assembly and the like, simplifies the design scheme of the fuel assembly and the reactor core, and improves the safety and the fuel economy of the supercritical water-cooled reactor core.

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 a composite fuel pellet construction of the present invention;

FIG. 2 is a schematic view of the composite fuel element of the present invention;

FIG. 3 is a schematic diagram of a supercritical water-cooled reactor fuel assembly according to the present invention;

FIG. 4 is a schematic diagram of the flow structure of a supercritical water-cooled reactor core coolant of the present invention;

FIG. 5 is a schematic diagram of a supercritical water-cooled reactor core arrangement according to the present invention.

Reference numbers and corresponding part names in the drawings: 1-inner zone fuel pellet, 2-outer zone fuel pellet, 3-cladding, 4-UO₂BeO composite pellet, 5-UO₂/ThO₂Composite pellets, 6-fuel elements, 7-guide tubes, 8-spacer grids, 9-module boxes, 10-fuel modules, 11-pressure vessels.

Detailed Description

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.

1-inner zone fuel pellet, 2-outer zone fuel pellet, 3-cladding, 4-UO₂BeO composite pellet, 5-UO₂/ThO₂Composite pellets, 6-fuel elements, 7-guide tubes, 8-spacer grids, 9-module boxes, 10-fuel modules, 11-pressure vessels.