CN108511092A - A kind of integral structure that nuclear fuel element is nested with circuit parallel type cooling heat pipe - Google Patents

Abstract

The invention discloses the integral structures that a kind of nuclear fuel element is nested with circuit parallel type cooling heat pipe, including circuit parallel type to cool down heat pipe, the rectangular parallelepiped structure that bottom surface is square or bottom surface as the nuclear fuel element of the hexagonal prisms structure of regular hexagon；Circuit parallel type cooling heat pipe is connected by two straight pipes and two U-shaped elbows, the evaporator section of two straight pipes is respectively placed in the core bore in the middle part of two adjacent nuclear fuel elements, the central steam area of cooling heat pipe includes evaporator section, adiabatic section, condensation segment successively from bottom to top in the axial direction, and the length of evaporator section is consistent with the length of nuclear fuel element；It is fuel pellet inside nuclear fuel element, outside is involucrum, and the tube wall of center cooling heat pipe is integrated with the involucrum design on the inside of nuclear fuel element centre bore.Overall structure is simple, compact in design, safe, good heat-transfer, adaptability are good, especially suitable for nuclear reactor for space and other small-sized nuclear reactors.

Description

A nested integrated structure of nuclear fuel elements and loop parallel cooling heat pipes

technical field

The invention relates to the technical field of nuclear power generation, in particular to an integrated structure in which nuclear fuel elements and loop parallel cooling heat pipes are nested.

Background technique

With the continuous development and maturity of space exploration technology and the expansion of space exploration application requirements, human beings have set their sights on planets far away from the earth or even the solar system, and hope to build space bases on the planets to conduct related scientific research. In the future, the construction of space bases on the surface of other planets (such as the moon, Mars, etc.) will have very important scientific, military and political values. The construction of space bases is faced with a complex and severe space environment, and the stable supply and management of energy has become an important guarantee for the normal operation of space bases. Due to their own inherent defects, solar power and chemical energy power cannot overcome the influence of some factors such as day and night changes and fuel reserves, so their application on space bases is greatly limited. The space nuclear reactor power supply is not affected by the environment, has high power, long life, safety and reliability, and strong energy supply sustainability. Therefore, it is considered to be an ideal and reliable energy supply solution for space bases and other deep space exploration missions.

Because space nuclear reactors have many irreplaceable advantages in space bases and other deep space exploration missions, the United States, Russia, Japan, France and other countries have conducted many in-depth studies on space nuclear reactors and proposed dozens of space nuclear reactor solutions. Cooling methods include gas cooling, liquid metal cooling, heat pipe cooling, etc. Due to the complexity of the space base environment, passive cooling technology is the first choice for space nuclear reactors, and heat pipe cooling technology is a passive cooling technology with advantages such as high thermal conductivity, high transient feedback performance, high reliability, and low maintenance requirements. Therefore, At present, space nuclear reactor designs are mostly cooled by heat pipes.

In the existing space nuclear reactor design, a single cooling heat pipe is arranged in the fuel element. In the radial arrangement of the core, some of the existing arrangements will cause a gap between the fuel element and the heat pipe, resulting in a low fuel filling rate. low, and the gap between the fuel element and the heat pipe is filled with structural materials, resulting in an increase in the critical mass of the nuclear reactor and the total mass of the core; some will place high requirements on the reliability of a single heat pipe, once a If the heat pipe fails, the heat generated by the nuclear fuel element at the heat pipe is difficult to be taken away by the surrounding heat pipes, which may cause damage to the nuclear fuel element.

Contents of the invention

The object of the present invention is to address the deficiencies of the prior art and provide an integrated structure in which nuclear fuel elements and circuit parallel cooling heat pipes are nested with high safety, good reliability and compact layout.

The purpose of the present invention can be achieved through the following technical solutions:

An integrated structure in which nuclear fuel elements and loop parallel cooling heat pipes are nested, including nuclear fuel elements and cooling heat pipes, the cooling heat pipes are placed in the center of the nuclear fuel elements, and the two ends of the cooling heat pipes at the center of the adjacent two nuclear fuel elements are U-shaped Elbow connection to form a loop parallel.

Further, the cooling heat pipe includes a central steam area, a porous liquid-absorbing core, a liquid annular cavity, and a pipe wall from inside to outside, wherein the pipe wall and the inner cladding of the nuclear fuel element are designed as one.

Further, the porosity of the porous liquid-absorbent core is 0.5 to 0.7.

Further, the central steam area of the cooling heat pipe includes an evaporation section, an adiabatic section and a condensation section in the axial direction from the bottom to the top, and the bottom of the evaporation section of the central steam area of two adjacent cooling heat pipes adopts a U-shaped bend of the evaporation section The top of the condensation section is connected by a U-shaped elbow in the condensation section.

Further, the inside of the nuclear fuel element is a fuel pellet, and the outside is a cladding, and the length of the evaporation section of the cooling heat pipe is consistent with the height of the nuclear fuel element.

Further, there is a gap of 0.1 to 0.3 mm between the fuel pellet and the cladding.

Further, the nuclear fuel element is a cuboid structure with a square base, or a hexagonal prism structure with a regular hexagon base.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The present invention provides an integrated structure in which nuclear fuel elements and loop parallel cooling heat pipes are nested. Due to the use of loop parallel heat pipes, when the heat flux density in the heating section or condensation section is unbalanced, the working liquid inside the tube is in the channel. The overall form of circulation is generated, and the steam pressure generated on the side with high heat flux density in the evaporation section is relatively high, pushing the steam to the side with low heat flux density and low pressure, and the whole loop finally reaches a state of self-excited balance. The loop-type parallel heat pipe structure, The heat exchange capacity can be automatically adjusted in a wide range, with high safety and reliability.

2. The integrated structure of the nuclear fuel element and the loop parallel cooling heat pipe nested by the present invention nests the loop parallel cooling heat pipe and the nuclear fuel element together. The nuclear fuel element is a rectangular parallelepiped structure with a square bottom, or a bottom surface of The regular hexagonal hexagonal prism structure can be closely arranged in the core, thereby increasing the nuclear fuel filling rate, reducing the core volume, and reducing the critical mass. This structure has high safety, good reliability, and compact layout, and is especially suitable for space nuclear reactors and other small nuclear reactors.

Description of drawings

Fig. 1 is a schematic diagram of a radial cross-section of a nested integrated structure of a nuclear fuel element and a circuit parallel cooling heat pipe according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of an axial cross-sectional structure of a nested integrated structure of a nuclear fuel element and a circuit parallel cooling heat pipe according to an embodiment of the present invention.

Fig. 3 (a) is a radial cross-sectional layout diagram of a nuclear fuel element and a loop parallel cooling heat pipe nesting integrated structure applied to a reactor core in an embodiment of the present invention; Fig. 3 (b) is a schematic diagram of a nuclear fuel element and a loop in parallel in an embodiment of the present invention Schematic diagram of the axial cross-sectional layout of the integrated cooling and heat pipe nesting structure applied to the reactor core.

Fig. 4 is a structural schematic view of a single cooling heat pipe arranged in a fuel element in the prior art.

Fig. 5 is a schematic diagram of a core radial arrangement in which a single cooling heat pipe is arranged in a fuel element in the prior art.

Fig. 6 is a schematic diagram of another core radial arrangement in which a single cooling heat pipe is arranged in a fuel element in the prior art.

Among them, 1- fuel pellets, 2- cladding, 3- liquid ring cavity, 4- porous liquid-absorbing core, 5- evaporation section, 6- adiabatic section, 7- condensation section, 8- U-shaped elbow in evaporation section, 9-U-shaped elbow in the condensation section, 10-nuclear fuel element, 11-cooling heat pipe.

Detailed ways

The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example:

This embodiment is applied to the core design of a space nuclear reactor as an example. The design life of the nuclear fuel element and the cooling heat pipe is consistent with the core life, and there is no need to replace it during the core life. A parallel cooling heat pipe for the nuclear fuel element and the circuit is provided. A nested integrated structure, the radial section and axial section of the structure are shown in Figure 1 and Figure 2 respectively, including a nuclear fuel element (10) and a cooling heat pipe (11), and the cooling heat pipe (11) is placed on the nuclear fuel element (10) center, and the two ends of the cooling heat pipes (11) in the center of two adjacent nuclear fuel elements (10) are connected by U-shaped elbows to form a parallel loop, compared to the prior art shown in Figure 4 The structure in which a single cooling heat pipe is arranged in the fuel element, and the loop-type parallel heat pipe structure can automatically adjust the heat exchange capacity in a wide range, with high safety and reliability.

Wherein, the cooling heat pipe (11) is sequentially composed of a central steam region, a porous liquid-absorbing core (4), a liquid annular cavity (3) and a pipe wall from the inside to the outside, wherein the pipe wall and the inner cladding of the nuclear fuel element (10) are designed As a whole, the porosity of the porous liquid-absorbent core (4) is 0.5 to 0.7.

Specifically, the central vapor zone of the cooling heat pipe (11) includes an evaporation section (5), an adiabatic section (6) and a condensation section (7) in the axial direction from the bottom to the top, and two adjacent cooling heat pipes ( 11) The bottom of the evaporation section in the central steam zone is connected by a U-shaped elbow (8) in the evaporation section, and the top of the condensation section is connected by a U-shaped elbow (9) in the condensation section.

The inside of the nuclear fuel element (10) is a fuel pellet (1), and the outside is a cladding (2), and the length of the evaporation section (5) of the cooling heat pipe (11) is consistent with the height of the nuclear fuel element (10), so A gap of 0.1 to 0.3 mm is left between the fuel pellet (1) and the cladding (2). The evaporating section (5) in the central steam area of the cooling heat pipe (11) absorbs the heat generated by the fuel pellets (1), and after passing through the adiabatic section (6), transfers the heat to other working media in the condensation section (7), and the fuel pellets The gap between (1) and the cladding (2) is used to accommodate the expansion of the pellet and to accommodate the fission gas.

Specifically, the nuclear fuel element (10) is a cuboid structure with a square bottom surface, or a hexagonal prism structure with a regular hexagon bottom surface.

The schematic diagram of this embodiment applied to the core design of a space nuclear reactor is shown in Figure 3 (a) and Figure 3 (b). Compared with the core layout shown in Figure 5 and Figure 6 in the prior art, the entire core The layout is compact and can be closely arranged in the core, thereby increasing the filling rate of nuclear fuel, reducing the volume of the core, and reducing the critical mass. The cooling heat pipe is placed in the center of the nuclear fuel element, and the two ends of the cooling heat pipe in the center of the two adjacent fuel elements are connected by a U-shaped elbow to form a parallel circuit, which can automatically adjust the heat exchange capacity in a wide range, and can effectively avoid The problem caused by the failure of a single heat pipe has high reliability.

The above is only a preferred embodiment of the patent of the present invention, but the scope of protection of the patent of the present invention is not limited thereto. The equivalent replacement or change of the technical solution and its invention patent concept all belong to the protection scope of the invention patent.

Claims (7)

1. A nested integrated structure of nuclear fuel elements and circuit parallel cooling heat pipes, characterized in that: it includes nuclear fuel elements and cooling heat pipes, the cooling heat pipes are placed in the center of the nuclear fuel elements, and the cooling heat pipes at the centers of the adjacent two nuclear fuel elements The two ends are connected by U-shaped elbows to form a parallel circuit. 2. The integrated structure of nested nuclear fuel elements and circuit parallel cooling heat pipes according to claim 1, characterized in that: the cooling heat pipes are sequentially composed of a central steam area, a porous liquid-absorbing core, and a liquid ring from the inside to the outside. The cavity and the tube wall, wherein the tube wall and the inner cladding of the nuclear fuel element are designed as one. 3 . The integrated structure of nested nuclear fuel elements and circuit parallel cooling heat pipes according to claim 2 , characterized in that: the porosity of the porous liquid-absorbing core is 0.5 to 0.7. 4. The integrated structure of nested nuclear fuel elements and circuit parallel cooling heat pipes according to claim 2, characterized in that: the central steam area of the cooling heat pipes includes evaporation sections in the axial direction from the bottom to the top , adiabatic section and condensing section, and the bottom of the evaporating section in the central steam area of two adjacent cooling heat pipes is connected by a U-shaped elbow of the evaporating section, and the top of the condensing section is connected by a U-shaped elbow of the condensing section. 5. A nested integrated structure of nuclear fuel elements and circuit parallel cooling heat pipes according to claim 4, characterized in that: the inside of the nuclear fuel element is a fuel pellet, the outside is a cladding, and the cooling heat pipe The length of the evaporation section is consistent with the height of the nuclear fuel element. 6 . The integrated structure of nuclear fuel elements nested with loop parallel cooling heat pipes according to claim 5 , wherein a gap of 0.1 to 0.3 mm is left between the fuel pellets and the cladding . 7. According to any one of claims 1 to 6, a nested integrated structure of nuclear fuel elements and circuit parallel cooling heat pipes is characterized in that: the nuclear fuel elements are rectangular parallelepiped structures with a square bottom, or a regular hexagonal bottom surface. Hexagonal prism structure.