JP2022091259A - Reactor core structure and nuclear reactor - Google Patents

Abstract

To increase fuel loading capacity.SOLUTION: A reactor core structure provided herein has all fuel rods 8 independently arranged in a triangular grid pattern in a reactor core 7.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a core structure and a nuclear reactor.

For example, Patent Document 1 discloses a configuration in which a plurality of fuel rods are arranged in a triangular lattice pattern as a fuel assembly constituting the core, and the distance between the fuel rods is maintained by a spacer. In this fuel assembly, a region for inserting the control element assembly having a plurality of thin plate-shaped control elements radially is provided along the axial direction inside the array of fuel rods.

Japanese Unexamined Patent Publication No. 2-228591

A fuel assembly is composed of a plurality of fuel rods bundled together, and the plurality of fuel rods are arranged in a forest to form a core. Increasing the fuel load can extend the life of the core. However, when a fuel assembly is used, the gap between the core and the core tank is an area where nuclear fuel cannot be placed. Therefore, the fuel load cannot be increased or maximized in a predetermined core range.

The present disclosure is to solve the above-mentioned problems, and an object of the present invention is to provide a core structure and a nuclear reactor capable of increasing the fuel load.

In order to achieve the above object, in the core structure according to one aspect of the present disclosure, all the fuel rods of the core are independently arranged in a triangular lattice pattern.

In order to achieve the above-mentioned object, the reactor according to one aspect of the present disclosure includes a reactor vessel, a core having the above-mentioned core structure and arranged inside the reactor vessel, and the reactor vessel. A steam generator, which is arranged inside the reactor vessel and the secondary coolant is supplied from the outside of the reactor vessel while the steam of the secondary coolant is discharged to the outside of the reactor vessel, and the reactor vessel. A primary cooling material pump that is arranged inside and circulates a primary cooling material that exchanges heat with the secondary cooling material between the core and the steam generator, and a control member that is placed inside the reactor vessel and inserted and removed from the core. The control member drive mechanism is provided.

The present disclosure can increase the fuel load.

FIG. 1 is a schematic diagram of a nuclear reactor according to an embodiment. FIG. 2 is a schematic view of the inside of the furnace according to the embodiment. FIG. 3 is a partially enlarged sectional schematic view of the core according to the embodiment. FIG. 4 is a partially enlarged sectional schematic view of the core according to the embodiment. FIG. 5 is a schematic cross-sectional view of the core according to the embodiment. FIG. 6 is a partially cut schematic diagram of a control member in the core according to the embodiment. FIG. 7 is an enlarged schematic view of the core according to the embodiment. FIG. 8 is an enlarged bottom view of the fuel rods in the core according to the embodiment. FIG. 9 is an enlarged bottom view of the fuel rods in the core according to the embodiment. FIG. 10 is an enlarged bottom view of fuel rods in the core according to the embodiment. FIG. 11 is a schematic cross-sectional view of another example of the core according to the embodiment.

Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components in the following embodiments include those that can be easily replaced by those skilled in the art, or those that are substantially the same.

FIG. 1 is a schematic diagram of a nuclear reactor according to an embodiment.

The reactor 1 of the embodiment includes a reactor vessel 2, a core support structure 3, a control member drive mechanism 4, a steam generator 5, and a primary coolant pump 6.

The reactor vessel 2 includes a core support structure 3, a control member drive mechanism 4, a steam generator 5, and a primary coolant pump 6. The reactor vessel 2 is a pressure vessel, and is composed of a vessel body 2A having an opening at the top and a vessel lid 2B having an opening at the top of the vessel body 2A. The container lid 2B is detachably provided with respect to the container body 2A. The container body 2A is formed in a cylindrical shape with the lower part closed. The inside of the reactor vessel 2 is filled with a primary coolant. The primary coolant consists of, for example, light water.

The core support structure 3 has a core tank 3A, an upper core support plate 3B, and a lower core support plate 3C in order to support the core 7. The core tank 3A is formed in a cylindrical shape extending in the vertical direction. The upper core support plate 3B is provided at the lower part of the core tank 3A and is arranged above the core 7. The lower core support plate 3C is provided at the lower end of the core tank 3A and is arranged below the core 7. The upper core plate may be used instead of the upper core support plate 3B. Further, the lower core plate may be used instead of the lower core support plate 3C. The core support structure 3 is arranged in the center of the reactor vessel 2.

The control member drive mechanism 4 inserts and removes the control member 10 described later with respect to the core 7. The control member 10 of the present embodiment is inserted into a plurality of positions of the core 7 from above. Therefore, the control member drive mechanism 4 corresponds to each control member 10 and is arranged above the core 7 and reaches the uppermost portion inside the reactor vessel 2. The control member drive mechanism 4 is provided with an urging device that urges the control member 10 in the direction of insertion into the core 7, and is automatically driven when the drive with the control member 10 is cut off by a clutch mechanism or the like. Is inserted into the core 7. Therefore, for example, in an emergency when the core temperature of the core 7 becomes equal to or higher than the set temperature, the control member 10 can be automatically inserted into the core 7 to reduce the reactivity of the fuel rods 8 of the core 7.

The steam generator 5 is arranged inside the reactor vessel 2, and the heat transfer tube is configured in a helical shape so as to surround the core tank 3A, for example. In the steam generator 5, the secondary coolant is supplied to the inside of the heat transfer tube from the outside of the reactor vessel 2. The steam generator 5 exchanges heat with the primary coolant to evaporate the secondary cooling water to generate steam. The secondary coolant is, for example, pure water. Although not explicitly shown in the figure, the steam generator 5 is connected to the outside of the reactor vessel 2 via a pedestal. The pedestal includes one that sends the steam generated by the steam generator 5 to the outside of the reactor vessel 2 and one that supplies the secondary coolant to the steam generator 5 from the outside of the reactor vessel 2. The pedestal that sends steam to the outside of the reactor vessel 2 is connected to the steam turbine. The steam turbine is driven by the steam generated by the steam generator 5, and the generator generates electricity. In addition, the steam turbine has a condenser, and cools and condenses the secondary cooling water used for driving, and returns it to a low-pressure saturated liquid. This condenser is connected to a conduit that supplies a secondary coolant to the steam generator 5.

The primary coolant pump 6 guides the primary coolant from the core tank 3A to the steam generator 5. As shown in FIG. 1, the primary coolant pump 6 sends the primary coolant from the inside of the core tank 3A to the outside above the core tank 3A, and sends it downward outside the core tank 3A, and lowers the core tank 3A. It is circulated so as to pass from the lower side to the upper side through the core support plate 3C and the upper core support plate 3B. The primary coolant is heated in the process of passing through the core tank 3A from the bottom to the top, exchanges heat with the secondary coolant of the steam generator 5 outside the core tank 3A, and moves the core tank 3A from the bottom to the top again. pass. In the core tank 3A, a through hole 3Aa is formed in order to send the primary coolant to the outside above (see FIG. 2).

FIG. 2 is a schematic view showing the inside of the furnace according to the embodiment. FIG. 3 is a partially enlarged sectional schematic view of the core according to the embodiment. FIG. 4 is a partially enlarged sectional schematic view of the core according to the embodiment. FIG. 5 is a schematic cross-sectional view of the core according to the embodiment. FIG. 6 is a partially cut schematic diagram of a control member in the core according to the embodiment.

As shown in FIG. 2, the core 7 applied to the above-mentioned reactor 1 includes a fuel rod 8, a grid 9, a control member 10, a control member guide tube 11, and a neutron reflector 12.

The fuel rod 8 is configured in the shape of a rod extending in the vertical direction, which will be described in detail later. As shown in FIG. 2, a plurality of fuel rods 8 are provided inside the core tank 3A in a form extending in the vertical direction between the upper core support plate 3B and the lower core support plate 3C to form the core 7. .. Further, as shown in FIG. 3, the fuel rods 8 are independent of each other and are arranged in a triangular lattice pattern in a plan view viewed from above. The triangular grid is a grid of 60 degrees in a plan view, and the fuel rods 8 are located at the intersections of the triangular grid. The fuel rods 8 are provided inside the core tank 3A, and all of the fuel rods 7 constituting the core 7 are individually and independently arranged in a triangular lattice pattern. The fuel rods 8 of the embodiment are provided inside the core tank 3A, and all of the fuel rods 8 constituting the core 7 are individually arranged independently in a triangular lattice pattern, but are provided inside the core tank 3A. It does not exclude that all the constituents of the core 7 are individually arranged independently in a grid pattern.

As shown in FIG. 2, the grid 9 is provided at a plurality of locations in the vertical direction (two locations in the vertical direction in the embodiment). As shown in FIG. 4, the grid 9 has a cell 9A into which individual fuel rods 8 can be inserted from above. The cell 9A is provided with a gap 9Aa between the inserted fuel rods 8 so that the primary coolant passing through the core tank 3A from the lower side to the upper side can pass through the gap 9Aa. The grid 9 does not have a configuration for holding the fuel rods 8 in the cell 9A, but merely inserts the fuel rods 8 into the cell 9A in a free form. The cells 9A are formed in a hexagonal shape in a plan view viewed from above, and a plurality of the hexagonal cells 9A are adjacently combined to form the entire grid 9 in a honeycomb structure. Therefore, the grid 9 can be provided with a gap 9Aa between the individual fuel rods 8 arranged in a triangular grid pattern.

The control member 10 is provided inside the core tank 3A so as to be vertically insertable or retractable along the fuel rod 8. The control member 10 is inserted along the fuel rods 8 and is arranged between the upper core support plate 3B and the lower core support plate 3C according to the length of the fuel rods 8. As shown in FIGS. 2 to 5, the fuel rod 8 is not arranged at the place where the control member 10 is arranged in the core 7. The control member 10 is inserted into and removed from the core 7 by the control member drive mechanism 4 described above. The control member 10 is formed by a neutron absorber. As the neutron absorber, for example, boron carbide (boron carbide: B _4C ) can be used. The control member 10 made of a neutron absorber can control the reactivity of the fuel rods 8 constituting the core 7 by approaching the fuel rods 8 by inserting and separating from the fuel rods 8 by pulling out, and the core 7 can be controlled. The core temperature of the can be controlled.

As shown in FIGS. 3 and 5, the control member 10 is formed as a plate body 10A along the triangular lattice pattern of the fuel rods 8. The control member 10 is formed in the shape of an isotropically arranged plate in which the plate bodies 10A are combined in a plan view viewed from the insertion direction. That is, the control member 10 is formed in an isotropic arrangement plate shape in which three plate bodies 10A are combined at 120 ° intervals in a plan view, and each plate body 10A is arranged along the triangular lattice pattern of the fuel rods 8. To. The control member 10 formed in the shape of an isotropic arrangement plate is arranged between the predetermined fuel rods 8. As shown in FIG. 5, a plurality of control members 10 are evenly arranged at equal intervals in a core 7 composed of fuel rods 8, so that the reactivity of each fuel rod 8 can be controlled to be constant. Although not explicitly shown in the figure, for example, when the fuel rods 8 are arranged in a grid pattern, the control member 10 is formed as a plate body 10A along the grid pattern of the fuel rods 8 and is viewed in a plan view from the insertion direction. The plate bodies 10A are combined to form a cross shape. Further, the control member 10 is not limited to the shape of the isotropically arranged plate or the cross shape, but is formed in a single character shape only by the configuration of the plate body 10A and is provided so as to be able to be inserted or removed in the vertical direction along the fuel rod 8. You may.

As shown in FIGS. 3 and 6, the control member 10 has a plate body 10A having a control material 10Aa and a covering material 10Ab that covers the control material 10Aa. The control material 10Aa is formed by a neutron absorber. The control material 10Aa is formed by dividing it into a plurality of blocks as rectangular blocks, and the control materials 10Aa are arranged side by side so as to form a plate body 10A by a grid 10Ac. The control material 10Aa is composed of a plurality of blocks. Therefore, it can be easily manufactured. The covering material 10Ab covers each control material 10Aa together with the grid 10Ac. That is, the covering material 10Ab forms the outer shell of the plate body 10A (control member 10). The covering material 10Ab is made of, for example, pure iron or stainless steel.

The control member guide pipe 11 guides the movement of the control member 10 into and out of the core 7. As shown in FIGS. 2 and 3, the control member guide tube 11 is formed in a cylindrical shape according to the outer shape of the control member 10 in a plan view. The control member guide pipe 11 is arranged between the upper core support plate 3B and the lower core support plate 3C. As shown in FIG. 4, the control member guide pipe 11 is joined to the grid 9 by welding or the like. The control member guide tube 11 is added with flammable toxic substances such as erbium oxide (Er ₂ O ₃ ), gadolinium oxide (Gd ₂ O ₃ ), and boron carbide (B ₄ C).

The neutron reflector 12 is arranged on the outer periphery of the core 7 and is provided in a cylindrical shape so as to surround each fuel rod 8. The neutron reflector 12 includes a reflector 12A and a reinforcing material 12B. The reflector 12A is configured as an inner cylinder arranged inside the cylinder of the neutron reflector 12. The reflective material 12A is beryllium oxide (BeO), which is a compound containing beryllium (Be), aluminum oxide (Al ₂ O ₃ ), which is a compound containing aluminum, and oxidation, which is a compound containing magnesium (Mg). Contains magnesium (MgO). The reinforcing material 12B is provided on the outer periphery of the reflective material 12A and is configured as an outer cylinder arranged on the outer side of the tubular shape of the neutron reflector 12. The neutron reflector 12 may be composed of only the reflector 12A.

FIG. 7 is an enlarged schematic view of the core according to the embodiment. FIG. 8 is an enlarged bottom view of the fuel rods in the core according to the embodiment. FIG. 9 is an enlarged bottom view of the fuel rods in the core according to the embodiment. FIG. 10 is an enlarged bottom view of fuel rods in the core according to the embodiment.

The details of the fuel rod 8 will be described with reference to FIGS. 7 to 10.

As described above, the fuel rod 8 is configured in the shape of a rod extending in the vertical direction. As shown in FIG. 7, the fuel rod 8 has a nuclear fuel 8A, a tubular member 8B, an upper end plug 8C, a lower end plug 8D, and an elastic member 8E.

The nuclear fuel 8A contains uranium, which is a nuclear fuel material. The nuclear fuel 8A has pellets having a cylindrical shape, and a plurality of nuclear fuels 8A are provided in one fuel rod 8.

The tubular member 8B is formed in a tubular shape so as to store a plurality of nuclear fuels 8A forming a plurality of pellets along the vertical direction.

The upper end plug 8C is formed in a substantially cylindrical shape and is fixed to the upper end of the tubular member 8B to close the opening at the upper end of the tubular shape of the tubular member 8B. Therefore, the upper end plug 8C constitutes the upper end of the fuel rod 8.

The lower end plug 8D is formed in a substantially cylindrical shape and is fixed to the lower end of the tubular member 8B to close the opening at the lower end of the tubular shape of the tubular member 8B. Therefore, the lower end plug 8D constitutes the lower end of the fuel rod 8.

The elastic member 8E is provided inside the tubular member 8B between the nuclear fuel 8A at the uppermost position and the upper end plug 8C, and the nuclear fuel 8A is directed toward the lower end plug 8D on the lower end side of the tubular member 8B by an elastic force. Encourage. Therefore, the plurality of nuclear fuels 8A housed inside the tubular member 8B are pressed toward the lower end plug 8D by the elastic member 8E, and their movement in the vertical direction is restricted and supported.

The fuel rod 8 has a lower core support plate 3C attached to the lower end of the core tank 3A, and the grid 9 and the control member guide tube 11 and the neutron reflector 12 are arranged inside the core tank 3A. It is inserted into cell 9A from above. The fuel rod 8 is supported in such a manner that the lower end plug 8D constituting the lower end is directly placed on the flat portion of the upper surface 3Cb of the lower core support plate 3C. The lower core support plate 3C is formed with a through hole 3Ca penetrating in the vertical direction, but the fuel rod 8 does not pass through the through hole 3Ca and is directly connected to the flat portion of the upper surface 3Cb of the lower core support plate 3C. Be placed. The fuel rod 8 does not pass through the through hole 3Ca because at least the outer diameter of the lower end plug 8D is formed to be larger than the inner diameter of the through hole 3Ca. Alternatively, the fuel rod 8 is inserted into the cell 9A of the grid 9 and is restrained from moving in the horizontal direction, so that the fuel rod 8 avoids the position of the through hole 3Ca and does not pass through the through hole 3Ca. The upper core support plate 3B is arranged above the fuel rods 8. The upper core support plate 3B is formed with a through hole 3Ba penetrating in the vertical direction, but the fuel rod 8 does not pass through the through hole 3Ba, and the upper core support plate 3B and the lower core support plate 3C are formed. Placed in between. A space is formed between the upper end plug 8C constituting the upper end of the fuel rod 8 and the upper core support plate 3B. The fuel rod 8 does not pass through the through hole 3Ba because at least the outer diameter of the upper end plug 8C is formed to be larger than the inner diameter of the through hole 3Ba. Alternatively, the fuel rod 8 is inserted into the cell 9A of the grid 9 and is restrained from moving in the horizontal direction, so that the fuel rod 8 avoids the position of the through hole 3Ba and does not pass through the through hole 3Ba. As shown by the arrows in FIG. 7, the through hole 3Ba of the upper core support plate 3B and the through hole 3Ca of the lower core support plate 3C allow the primary coolant to pass through the inside of the core 7 in which the fuel rods 8 are arranged. In this way, the core 7 is configured. Further, as shown in FIG. 2, a control member drive mechanism 4 is installed. The control member drive mechanism 4 is supported by the support member 20 at a position above the core tank 3A.

Here, since the lower end plug 8D constituting the lower end of the fuel rod 8 is formed in a cylindrical shape, the bottom surface 8Da is flat and the side surface 8Db is formed in an annular shape. As shown in FIGS. 7 to 10, a notch 8Dc is formed as a communication portion. The notch 8Dc is formed from the bottom surface 8Da of the lower end plug 8D to the side surface 8Db. The notch 8Dc does not lead to the inside of the tubular member 8B. The notch 8Dc is formed in a tapered shape so as to extend outward from the bottom surface 8Da of the lower end plug 8D toward the side surface 8Db. The notch 8Dc allows the side surface 8Db to pass from the bottom surface 8Da of the lower end plug 8D to the through hole 3Ca of the lower core support plate 3C in a configuration in which the fuel rods 8 are placed directly on the lower core support plate 3C. Therefore, as shown by the arrows in FIG. 7, the primary coolant passes through the lower core support plate 3C from the lower side of the lower core support plate 3C through the through hole 3Ca, and is adjacent to the fuel rods via the notch 8Dc. It is guided to the gap 9Aa of 8. Then, the primary coolant guided to the gap 9Aa of the fuel rods passes through the upper core support plate 3B through the through hole 3Ba of the upper core support plate 3B and is sent above the core 7.

In the embodiment, the notches 8Dc are arranged at a plurality of locations in the circumferential direction of the lower end plug 8D. The notches 8Dc of the lower end plug 8D shown in FIGS. 7 and 8 are formed at four locations in the circumferential direction of the lower end plug 8D, and the flat portion of the bottom surface 8Da of the lower end plug 8D is formed in a cross shape in a bottom view. There is. Therefore, in the lower end plug 8D shown in FIGS. 7 and 8, when the through holes 3Ca of the lower core support plate 3C are arranged in a grid pattern in a plan view and the fuel rods 8 are arranged in a grid pattern in a plan view. The bottom surface 8Da is placed in contact with the flat portion of the top surface 3Cb of the lower core support plate 3C, and the notch 8Dc can be configured to communicate with the four through holes 3Ca in the vertical direction. Further, the notches 8Dc of the lower end plug 8D shown in FIG. 9 are formed at two locations in the circumferential direction of the lower end plug 8D, and the flat portion of the bottom surface 8Da of the lower end plug 8D is formed in a single character shape in the bottom view. .. Therefore, the lower end plug 8D shown in FIG. 9 has a bottom surface 8Da when the through holes 3Ca of the lower core support plate 3C are arranged in a grid pattern in a plan view and the fuel rods 8 are arranged in a grid pattern in a plan view. It is placed in contact with the flat portion of the upper surface 3Cb of the lower core support plate 3C, and the notch 8Dc can be configured to communicate with the four through holes 3Ca in the vertical direction. Further, the notches 8Dc of the lower end plug 8D shown in FIG. 10 are formed at three locations in the circumferential direction of the lower end plug 8D, and the flat portion of the bottom surface 8Da of the lower end plug 8D has a three-way arrangement plate shape in the bottom view. It is formed. Therefore, the lower end plug 8D shown in FIG. 10 has a bottom surface when the through holes 3Ca of the lower core support plate 3C are arranged in a triangular lattice pattern in a plan view and the fuel rods 8 are arranged in a triangular lattice pattern in a plan view. 8Da is placed in contact with the flat portion of the upper surface 3Cb of the lower core support plate 3C, and the notch 8Dc can be configured to communicate with the three through holes 3Ca in the vertical direction. In addition to the notch 8Dc, the communication portion may be a through hole formed from the bottom surface 8Da of the lower end plug 8D to the side surface 8Db, although not explicitly shown in the drawing.

FIG. 11 is a schematic cross-sectional view of another example of the core according to the embodiment.

In the core 7 shown in FIG. 5, the control member 10 is formed in the shape of an isotropic arrangement plate in a plan view, whereas in the core 7 shown in FIG. 11, the control member 10'is formed in a circular shape in a plan view. .. The control member 10'is formed in a cylindrical shape extending in the vertical direction, and although not specified in the figure, the control material divided into the cylindrical shape is collectively covered with a covering material. The control member 10'is arranged between the predetermined fuel rods 8. As shown in FIG. 11, a plurality of control members 10'are evenly arranged at equal intervals in the core 7 composed of the fuel rods 8, so that the reactivity of each fuel rod 8 can be controlled to be constant. Further, although not explicitly shown in the figure, the control member 10'is configured so that it can be inserted or removed from the cylindrical control member guide tube extending in the vertical direction. This control member guide pipe is provided in a portion where the fuel rods 8 arranged in a triangular lattice shape or a grid pattern are not arranged in a plan view, and is joined to the grid 9 by welding or the like. Although the control member 10'shown in FIG. 11 has a structure thicker than that of one fuel rod 8, it may have a thickness equivalent to that of one fuel rod 8.

As described above, in the core structure of the embodiment, all the fuel rods 8 of the core 7 are independently arranged in a triangular lattice pattern.

Therefore, according to the core structure of the embodiment, the fuel rods 8 are arranged in a triangular lattice pattern, so that the fuel rods 8 are densely configured as compared with the case where the fuel assembly is used. Therefore, as compared with the core using the fuel assembly, the extra gap between the columnar core and the core tank 3A can be reduced, the fuel load can be increased, and the amount of neutron leakage from the core can be reduced. As a result, according to the core structure of the embodiment, the filling rate of nuclear fuel can be improved, the fuel load can be maximized, and the core 7 can be downsized and the life of the core 7 can be extended. ..

Here, by densely arranging the fuel rods 8, it is possible to reduce the size of the core and extend the life of the core. However, if the fuel rods 8 are brought too close to each other, the void reactivity becomes positive, so that the void reactivity becomes positive. The fuel rods 8 are arranged at a distance that allows the reactivity to be negative. The void reactivity refers to the reactivity that occurs inside the core through the generation of voids (air bubbles) or changes in the amount of voids due to boiling of the primary coolant or other causes.

Further, in the core structure of the embodiment, a control member guide pipe 11 arranged between predetermined fuel rods 8 and a control member 10 inserted into the control member guide pipe 11 are provided, and the control member 10 is a fuel. The control member guide pipe 11 is formed as a plate body 10A along the triangular grid-like arrangement of the rods 8, and the control member guide pipe 11 is provided along the triangular grid-like arrangement of the fuel rods 8 so that the control member 10 as the plate body 10A can be inserted. ing.

Therefore, according to the core structure of the embodiment, the control member 10 and the control member guide pipe 11 can coexist with the fuel rods 8 arranged in a triangular lattice pattern. Specifically, the exclusion region of the fuel rods 8 can be minimized with respect to the fuel rods 8 arranged in a triangular lattice pattern, which can contribute to an increase in the fuel load amount. As a result, according to the core structure of the embodiment, the affinity with the triangular lattice arrangement of the fuel rods 8 can be improved, and the strength of the fuel structure can be increased. For example, as shown in FIG. 11, in the cylindrical control member 10', the exclusion region of the fuel rods 8 cannot be minimized with respect to the fuel rods 8 arranged in a triangular lattice pattern, and the fuel rods 8 are arranged in a triangular lattice pattern. Affinity is low. Further, by forming the control member 10 as the plate body 10A, a large surface area of the control member 10 can be secured, the neutron absorption capacity is increased, and the value of the control member 10 is increased. For example, as a configuration for securing a large surface area, a cylindrical control member 10'can be considered as shown in FIG. 11, but the self-shielding effect makes it difficult for neutrons to be absorbed inside the cylinder. On the other hand, in the case of the control member 10 having the plate body 10A, the surface area can be increased and the neutron absorption capacity can be secured while reducing the thickness from the surface to the inside. As a result, according to the core structure of the embodiment, it is possible to secure the reactor shutdown capacity and achieve both structural feasibility in which the number of control member drive mechanisms 4 can be reduced without increasing the number of control members 10. In the core structure of the embodiment, the reactor shutdown capacity achieves a predetermined subcriticality by inserting all control members 10 at low temperature zero output. In order to secure the reactor shutdown capacity, it is necessary to increase the number of control members 10, which leads to an increase in the size of the core 7. However, according to the core structure of the embodiment, the reactor shutdown capacity is secured and the control member 10 is used. The number of control member drive mechanisms 4 can be reduced without increasing the number, which can contribute to the miniaturization of the core 7.

Further, in the core structure of the embodiment, the control member 10 is formed in the shape of an isotropically arranged plate in which the plate bodies 10A are combined when viewed from the insertion direction.

According to the core structure of the embodiment, the affinity with the triangular lattice arrangement of the fuel rods 8 can be further improved by the control member 10 having the shape of the isotropic arrangement plate, and the strength of the fuel structure can be further increased.

Further, in the core structure of the embodiment, the control member 10 has a control material 10Aa divided into a plurality of parts, and a covering material 10Ab that collectively covers each control material 10Aa.

According to the core structure of the embodiment, by covering the control material 10Aa with the coating material 10Ab, the change in the dimensions of the control member 10 due to the irradiation of the control material 10Aa with neutrons can be suppressed, and the leakage of gas generated from the control material 10Aa can be suppressed. Can be suppressed.

Further, in the core structure of the embodiment, a flammable poison is added to the control member guide pipe 11.

According to the core structure of the embodiment, the reactivity is excessive at the initial stage of combustion of the nuclear fuel, and neutrons are absorbed by the combustible poison, so that the excess reactivity at the initial stage of operation can be reduced. Generally, the number of control members 10 is increased in order to reduce the excess reactivity at the initial stage of operation, but according to the core structure of the embodiment, the number of required control members 10 can be reduced. Further, since the flammable poison is converted into a nuclide that does not absorb neutrons after absorbing neutrons, the reactivity does not decrease after the initial operation.

Further, in the core structure of the embodiment, a neutron reflector 12 arranged on the outer periphery of the core 7 and surrounding each fuel rod 8 is provided, and the neutron reflector 12 is any one of beryllium oxide, aluminum oxide, and magnesium oxide. It is made of a reflective material 12A containing one.

Beryllium, aluminum, and magnesium have a smaller neutron absorption cross section than stainless steel, and have a larger neutron scattering cross section with respect to the neutron absorption cross section, so that they have high neutron reflection capability. Further, as a result, according to the core structure of the embodiment, the thickness of the neutron reflector 12 can be formed to be thinner than that of stainless steel. In addition to its neutron reflection function, beryllium consumes one neutron and emits two neutrons by a neutron reaction, and splits into two alpha particles. This beryllium neutron reaction emits more neutrons than it consumes, increasing the number of neutrons in the system. As a result, according to the core structure of the embodiment, nuclear characteristics (criticality) are obtained because the fissionable material having a high neutron reflection efficiency and less than the critical mass is brought into a critical state or the fission reaction at the critical mass is increased. Is improved, and the life of the core can be extended.

Further, in the core structure of the embodiment, the neutron reflector 12 further includes a stainless steel reinforcing material 12B on the outer periphery of the reflector 12A.

In the case of the neutron reflector 12 having only the reflector 12A, the structural strength and the shielding performance are insufficient, and the strength and the shielding characteristics tend to be deteriorated. Therefore, according to the core structure of the embodiment, the shortage due to the reflector 12A can be compensated for by reinforcing and shielding with the stainless steel reinforcing material 12B.

Further, in the core structure of the embodiment, a grid 9 having a cell 9A through which each fuel rod 8 is inserted is provided, and the grid 9 is configured in a honeycomb structure in which the cell 9A is formed in a hexagonal shape.

By inserting each fuel rod 8 into the cell 9A, a plurality of fuel rods 8 can be independently arranged in a triangular lattice pattern. Cell 9A does not fix each fuel rod 8 by insertion and does not support them individually. Further, the cell 9A is provided with a gap 9Aa between the fuel rods 8 through which the primary coolant passes. Generally, when the fuel rods 8 are supported, an elastic member for supporting the fuel rods 8 is provided on the grid 9, but it is difficult to make the fuel rods 8 denser because the elastic members are provided. Therefore, according to the core structure of the embodiment, only the fuel rods 8 are inserted into the cell 9A, and a dense structure is realized together with a triangular lattice-like arrangement as a structure having no special support structure. Further, according to the core structure of the embodiment, the fuel rods 8 are only inserted into the cell 9A, and the structure does not have a special support structure. While realizing a dense structure, primary cooling is performed between the fuel rods 8. A gap 9Aa through which the material passes can be created.

Further, in the core structure of the embodiment, a plurality of fuel rods 8 are arranged between the upper core support plate 3B and the lower core support plate 3C, and the lower end is directly placed and supported on the lower core support plate 3C. There is.

In a core structure using a fuel assembly, an upper nozzle is arranged at the upper end of the fuel assembly, a lower nozzle is arranged at the lower end, and a spring that supports the fuel assembly between the upper core support plate and the lower core support plate. Parts such as a mechanism are provided. On the other hand, in the core structure of the embodiment, the fuel rods 8 are arranged between the upper core support plate 3B and the lower core support plate 3C, and the lower end of the fuel rods 8 is placed directly on the lower core support plate 3C. I support it. As a result, according to the core structure of the embodiment, the height of the core 7 can be reduced and the size can be reduced by not using parts such as the upper nozzle, the lower nozzle, and the spring mechanism.

The lower end plug 8D of the embodiment is fixed to the lower end of the fuel rod 8 and has a communication portion (notch 8Dc) leading from the bottom surface 8Da to the side surface 8Db.

In the embodiment, the fuel rod 8 is directly placed and supported on the upper surface 3Cb of the lower core support plate 3C in which the through hole 3Ca is formed. For this structure, the lower end plug 8D of the fuel rod 8 is made to pass the side surface 8Db from the bottom surface 8Da to the through hole 3Ca of the lower core support plate 3C by the notch 8Dc. Therefore, the primary coolant passes from the lower side of the lower core support plate 3C through the lower core support plate 3C through the through hole 3Ca, and is sent around the adjacent fuel rods 8 via the notch 8Dc. As a result, according to the lower end plug 8D of the embodiment, the primary coolant can be passed from the bottom surface 8Da to the side surface 8Db at the lower end of the fuel rod 8, and the flow path of the primary coolant to the fuel rod 8 is secured. be able to.

Further, in the lower end plug 8D of the embodiment, the communication portion (notch 8Dc) is formed so as to extend outward from the bottom surface 8Da to the side surface 8Db.

According to the lower end plug 8D of the embodiment, the primary coolant can be guided along the periphery of the fuel rod 8.

Further, in the lower end plug 8D of the embodiment, a plurality of communication portions (notches 8Dc) are arranged in the circumferential direction.

According to the lower end plug 8D of the embodiment, the primary coolant can be sent around the fuel rod 8 at a plurality of places.

Further, in the lower end plug 8D of the embodiment, the bottom surface 8Da is formed flat.

According to the lower end plug 8D of the embodiment, the fuel rod 8 can be stably placed.

Further, in the lower end plug 8D of the embodiment, the notches 8Dc are formed at four points in the circumferential direction, and the bottom surface 8Da is formed in a cross shape in the bottom view.

According to the lower end plug 8D of the embodiment, the primary coolant can be sent around the fuel rods 8 at a plurality of places, and the fuel rods 8 can be stably placed.

Further, the fuel rod 8 of the embodiment is supported by being directly placed on the upper surface 3Cb of the lower core support plate 3C in which the above-mentioned lower end plug 8D is fixed to the lower end and the through hole 3Ca is formed.

According to the fuel rod 8 of the embodiment, the height of the core 7 is reduced and the size is reduced by not using parts such as the upper nozzle, the lower nozzle, and the spring mechanism as compared with the case where the fuel assembly is used. Can be done.

Further, the reactor 1 of the embodiment includes a reactor vessel 2, a core 7 having the above-mentioned core structure and arranged inside the reactor vessel 2, and a reactor vessel arranged inside the reactor vessel 2. While the secondary coolant is supplied from the outside of 2, the steam generator 5 in which the steam of the secondary coolant is discharged to the outside of the reactor vessel 2 and the secondary coolant arranged inside the reactor vessel 2 A primary coolant pump 6 that circulates the primary coolant that exchanges heat with the core 7 and the steam generator 5, and a control member drive mechanism 4 that is arranged inside the reactor vessel 2 and inserts and removes the control member 10 from the core 7. , Equipped with.

According to the reactor 1 of the embodiment, the steam generator 5, the primary coolant pump 6, the control member drive mechanism 4, and the reactor vessel 2 are provided with a compact core 7 while reducing the size of the core 7. It can be configured as an integrated type placed inside.

1 Reactor 2 Reactor vessel 2A Container body 2B Container lid 3 Core support structure 3A Core tank 3Aa Through hole 3B Upper core support plate 3Ba Through hole 3C Lower core support plate 3Ca Through hole 3Cb Top surface 4 Control member drive mechanism 5 Steam generation Instrument 6 Primary coolant pump 7 Core 8 Fuel rod 8A Nuclear fuel 8B Cylindrical member 8C Upper end plug 8D Lower end plug 8Da Bottom 8Db Side surface 8Dc Notch (communication part)
8E Elastic member 9 Grid 9A Cell 9Aa Gap 10 Control member 10A Plate body 10Aa Control material 10Ab Covering material 10Ac Lattice 11 Control member Guide tube 12 Neutron reflector 12A Reflector 12B Reinforcing material 20 Support member

Claims (9)

A core structure in which all fuel rods in the core are independently arranged in a triangular grid pattern. A control member guide pipe arranged between the predetermined fuel rods and a control member inserted into the control member guide pipe are provided.
The control member is formed as a plate body along the triangular grid-like arrangement of the fuel rods, and the control member guide pipe has the triangular grid-like arrangement of the fuel rods so that the control member, which is a plate body, can be inserted. The core structure according to claim 1, which is provided along the same line. The core structure according to claim 2, wherein the control member is formed in the shape of an isotropically arranged plate in which the plates are combined when viewed from the insertion direction. The core structure according to claim 2 or 3, wherein the control member includes a control material divided into a plurality of parts and a covering material that collectively covers each of the control materials. The core structure according to any one of claims 2 to 4, wherein the control member guide tube is added with a flammable poison. A neutron reflector located on the outer periphery of the core and surrounding each of the fuel rods is provided.
The core structure according to any one of claims 1 to 5, wherein the neutron reflector is made of a reflective material containing any one of beryllium oxide, aluminum oxide, and magnesium oxide. The core structure according to claim 6, wherein the neutron reflector further includes a reinforcing material of stainless steel on the outer periphery of the reflector. A grid with cells through which each of the fuel rods is inserted
The core structure according to any one of claims 1 to 7, wherein the grid has a honeycomb structure in which the cells are formed in a hexagonal shape. Reactor vessel and
A core having the core structure according to any one of claims 1 to 8 and arranged inside the reactor vessel, and a core.
A steam generator arranged inside the reactor vessel and supplying the secondary coolant from the outside of the reactor vessel while discharging the steam of the secondary coolant to the outside of the reactor vessel.
A primary coolant pump that circulates a primary coolant that is arranged inside the reactor vessel and exchanges heat with the secondary coolant between the core and the steam generator.
A control member drive mechanism that is placed inside the reactor vessel and inserts and removes the control member from the core.
Equipped with a nuclear reactor.

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