JP2002365390A - Boiling water reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiling water reactor, enabling the easy removable of a CRD in an optional position to above the reactor by improving the structural limitation of a fuel support part in a K-lattice core structure reactor. SOLUTION: In this boiling water reactor comprising a core, formed by housing two or more fuel assemblies 2 and cross control rods 3 in the core shroud 4 of a reactor pressure vessel 1, a core support member is constituted as an assembly of core support blocks 22 formed of two or more split bodies having a size, capable of passing in the lattice frame internal space of an upper lattice plate 12 and closely laid in the horizontal direction, and the circumference of the assembly of core support blocks is held by a core support ring 23 fixed to the core shroud. Each core support block 22, independently comprises a control rod insert hole and a cooling water passage opening, and it is supported from underside on each upper end of a control rod guide pipe 13, rising from the bottom part side of the reactor pressure vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiling water reactor in which control rods are arranged in a staggered manner at the core of a reactor pressure vessel. The present invention relates to a boiling water reactor having a reactor internal structure configured so that a control rod drive mechanism (hereinafter, referred to as “CRD”) is pulled out above a reactor and can be maintained.

[0002]

2. Description of the Related Art Conventionally, in a boiling water reactor, generally, a cross-shaped control rod constituting a core in a reactor pressure vessel is arranged in a lattice pattern with respect to a horizontal cross section of the core.

First, the configuration of a reactor pressure vessel of an improved boiling water reactor having such a control rod arrangement will be described with reference to FIG.

[0004] A reactor pressure vessel 1 contains cooling water also serving as a moderator and a reactor core. This core includes a plurality of fuel assemblies 2 and control rods 3 and the like, and is housed in a core shroud 4. The coolant flows upward from the bottom of the reactor pressure vessel 2 through the reactor core, and when passing through the reactor core, the temperature of the coolant is increased by the nuclear reaction heat of the reactor core to be in a gas-liquid two-phase flow state. The coolant in the two-phase flow state flows into the steam separator 5 installed above the core, where it is separated into water and steam. Among them, the steam is introduced into a steam dryer 6 installed on the steam separator 5 and is dried to become dry steam. This dry steam is transferred to a steam turbine (not shown) via a main steam pipe 7 connected to the reactor pressure vessel 1 and is used for power generation.

[0005] Thereafter, the steam is returned to the reactor pressure vessel 1 via a feed water sparger 8 via a condenser, a feed water heater and the like (not shown), and together with the water separated by the steam separator 5, Descend downcomer 9. The cooling water is further pressurized by an internal pump 10 installed annularly in the lower part of the reactor pressure vessel 2 and then sent to the lower part of the core after being pressurized. On the other hand, in the core shroud 4 for housing the fuel assembly 2, a core support plate 11 is installed at a position below the fuel as a core support member.
The upper lattice plate 12 is installed on the upper part of. The core support plate 11 and the upper lattice plate 12 are firmly fixed to the core shroud, and usually remain fixed even when the fuel assemblies 2 and the control rods 3 are removed during the periodic inspection of the reactor.

FIG. 13 shows a support structure of the fuel assembly 2 in the core shroud 4 in the reactor pressure vessel 1 shown in FIG. As shown in FIG. 13, the core support plate 11 has an upper plate 11b having a large number of circular holes 11a for holding the core support hardware 15, and the upper plate 11b
Is fixed to the core shroud 4 by a retaining ring (not shown) provided around the core. The fuel support 15 has a hole 15a for mounting and holding the fuel assembly 2 and supplying cooling water, and a hole 15a through which the control rod 3 is inserted.
b is open. The control rod 3 is guided around by a control rod guide tube 13, which penetrates a hole 11 a of an upper plate 11 b of a core support plate 11 and is located on a CRD housing 14 at a furnace bottom. It is installed in. Four fuel assemblies 2 are placed above the control rod guide tube 13.
A fuel support 15 for supporting the body is inserted and installed.
Thereby, the lateral support of the fuel assembly 2 is performed by the upper grid plate 12 and the core support plate 11, and the fuel support 15, the control rod guide tube 13, and the CRD housing 14 support the weight of the fuel assembly 2. are doing.

As described above, the control rod guide tube 1
The control rod 3 is accommodated in the CRD housing 14, and the CRD (not shown) is accommodated in the CRD housing 14. The control rod 3 is inserted into and pulled out of the core by the CRD, The burnup is controlled.

Here, as means for increasing the burnup of the fuel and increasing the output per unit volume of the nuclear reactor, while increasing the size of the fuel assembly 2 and increasing the size of the fuel grid,
The control rods arranged in a square lattice (go board shape) in the above-mentioned conventional boiling water reactor (such an arrangement is hereinafter referred to as “C
In addition to the "grid," a staggered arrangement in which control rods are newly arranged at diagonal positions (such an arrangement is hereinafter referred to as "K lattice") may be considered as a means of increasing the value of control rods in fuel design. ing.

FIG. 14 shows a large-capacity boiling water reactor structure employing such a K-lattice core, and FIG.
Four cross sections for each elevation in the figure (sections along line AA, section B-B, section C-C, and section D-D)
Are shown for each quadrant.

The first quadrant in FIG. 15 shows the arrangement of the CRD housing 14 corresponding to the cross section taken along line AA in FIG. 14, and the fourth quadrant shows the control rod guide tube 13 corresponding to the cross section taken along line BB in FIG. 1 shows a cross section and arrangement of the hologram. The third quadrant shows the lower cross-sectional structure of the core support plate 11 corresponding to the CC line cross section, and the second quadrant shows the upper plate 11b of the core support plate 11 corresponding to the DD line cross section. Shows the structure.

In the K lattice core, since the control rods 3 approach in a staggered arrangement, when the control rod guide tubes 13 are formed in a cylindrical shape surrounding the cross-shaped control rods 3, the control rod guide tubes 13 interfere with each other. They cannot be arranged at intervals.
For this reason, in the K lattice core, the control rod guide tube 13 has a cross-shaped cross-sectional shape as shown in the cross-sectional area along the line BB in FIG. As a result, the control rod guide tube 13 is moved to C in FIG.
-C line sectional area and the in-core guide tube 16 shown in FIG.
Also, interference with the in-core stabilizer 17 for holding the in-core guide tube 16 and the cross beam 18 for reinforcing the core support plate 11 is avoided.

On the other hand, in the K lattice core considered up to now, the control rods and the fuel assemblies can be pulled out from the upper plate 11b of the core support plate 11 as shown in the sectional area along the line DD in FIG. For this purpose, a circular hole 19 and a cross-shaped hole 20 are formed. The circular hole 19 is located in the space within the frame of the lattice 21 of the upper lattice plate 12 as shown for reference in a part of the cross-sectional area along the line D-D, and the cross-shaped hole 20 is located immediately below the intersection of the lattice 21. are doing. Under such a configuration, FIG.
A fuel support fitting similar to the fuel support fitting 15 shown in FIG. 12 is inserted into a circular hole 19 of a core support plate similar to the core support plate 11 also shown in FIG. And, like the C lattice core, the fuel support fitting 15 is connected to the cross-shaped control rod guide tube 13 at the lower portion thereof to support the weight of the fuel assembly 2,
A cruciform control rod guide tube 13 penetrates the cruciform hole 20 of the core support plate 11, and does not support the fuel at this position.

[0013]

When the fuel support system using the core support plate 11 is applied to the K lattice core, as shown in the second quadrant (cross section along line DD) of FIG. The opening area of the upper plate of the plate 11 is large and the ligament of the upper plate is small, and it is very difficult to secure the strength of the upper plate.

The control rod guide tube 13 located in the cross-shaped hole 20 of the upper plate 11b of the core support plate 11 is deformed inward by an external pressure acting during operation, and the core support tube 13 is deformed inward. The bypass leak at the joint with the plate 11 increases.

Further, the control rod guide tube 13 at this position must pass through the cross-shaped hole 20 of the core support plate 11 at the time of attachment and detachment.
There is a problem that it is necessary to ensure high dimensional accuracy over the entire length of the device.

In the maintenance work at the time of the periodic inspection, the CRD is removed from the CRD housing 14 and then removed under the reactor pressure vessel 1, subjected to maintenance in the repair room, and mounted again in the CRD housing. Is taking. On the other hand, conventionally, in a reactor configuration having a C lattice core, a technique has been proposed in which a CRD can be pulled out above a reactor pressure vessel, thereby facilitating work by pulling out above. For example, JP 2
000-214288).

However, when such a technique is applied to a K-lattice core, the CRD located immediately below the lattice cannot pass through the cross-shaped opening of the core support plate, and furthermore, the CRD is located at the center.
Even if it is expanded to the size that can pass through, the total length of the CRD is about 1 m longer than the dimension from the lattice lower surface of the upper lattice plate to the upper plate of the core support plate. Could not be applied.

The present invention solves the above-mentioned problems, and
It is an object of the present invention to provide a boiling water reactor in which a structural limitation of a fuel support portion is improved in a lattice core reactor and a CRD at an arbitrary position can be easily removed above the reactor.

[0019]

According to the first aspect of the present invention, a plurality of fuel assemblies and a cross-shaped control rod are accommodated in a core shroud of a reactor pressure vessel to constitute a core, and the control rod is squared. While being arranged in a lattice shape and also arranged at diagonal positions of a square lattice to form a staggered arrangement, the upper end of the fuel assembly is supported by a square lattice-shaped upper lattice plate provided at an upper position of the core shroud. A lower end supported by a core support member provided at a lower position of the core shroud, wherein the core support member functions as a differential pressure wall for supplying cooling water to the fuel assembly from below. In the nuclear reactor, the core support member includes:
A core support block composed of a plurality of divided bodies having a size that can pass through the space inside the lattice frame of the upper lattice plate is configured as an aggregate spread horizontally, and the periphery of the aggregate of the core support blocks is the core. The core support block is held by a core support ring fixed to a shroud, and each of the core support blocks individually has a control rod insertion hole and an opening for cooling water passage, and a control rod guide rising from the bottom side of the reactor pressure vessel. A boiling water reactor is provided, which is supported at the upper end of each tube from below.

According to the second aspect of the present invention, in the boiling water reactor according to the first aspect, the core support block has a quadrangular shape in plan view, and has an opening for passing cooling water in the center of the side. A boiling water reactor having a semicircular notch and arranged so that a diagonal direction matches a blade direction of a cross-shaped control rod.

According to a third aspect of the present invention, in the boiling water reactor according to the first or second aspect, a hole through which a control rod can be inserted and a passage for supplying cooling water are provided on the upper surface of the core support block. A boiling water reactor equipped with a fuel support fitting having the same is provided.

According to a fourth aspect of the present invention, in the boiling water reactor according to the third aspect, the fuel support fitting has a downwardly-facing cylinder that can be inserted into an opening of the core support block. Provided is a boiling water reactor having an orifice for adjusting a flow rate of cooling water.

According to a fifth aspect of the present invention, in the boiling water reactor according to the third or fourth aspect, a concave portion is provided on an upper surface of a core support block located immediately below a fuel support, and a lower surface of the fuel support is provided. And a projection corresponding to the recess, and the core support block and the fuel support fitting are positioned by fitting the recess and the projection, thereby providing a boiling water reactor.

[0024] In the invention according to claim 6, claims 3 to 5 are provided.
In the boiling water reactor according to any one of the above, a cross-shaped frame into which a control rod blade is inserted and a projection protruding outward from the frame are provided on the upper surface of the core support block, and There is provided a boiling water nuclear reactor characterized in that grooves are provided on the side surface to engage with the projections, and the grooves and the projections are used as positioning portions for sliding when the fuel support is lowered from above.

According to the seventh aspect of the present invention, the first to sixth aspects are provided.
In the boiling water reactor according to any one of the above, the surface where each core support block is in contact with each other, the surface where the cylinder of the fuel support bracket and the opening of the core support block are in contact, or on both contact surfaces, A boiling water reactor is provided with a seal structure using a labyrinth, a seal structure using a step, or a seal structure using a seal ring.

In the invention according to claim 8, claims 1 to 7 are provided.
In the boiling water reactor according to any one of the above, the fuel assembly is located at the center position of the side of all the core support blocks or some core support blocks located immediately below the fuel support fittings. Provided is a boiling water reactor having a semi-cylindrical projection that forms a circular opening that can be installed.

According to the ninth aspect of the present invention, the first to eighth aspects are provided.
In the boiling water reactor according to any one of the above, a horizontal support grid for engaging with the control rod guide tube is provided below the core support block, and the support grid is fixedly supported on the core shroud. To provide a boiling water reactor.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a boiling water reactor according to the present invention will be described below with reference to FIGS. The same components as in the conventional example are shown in FIG.
The description will be made using the same reference numerals as those shown in FIGS.

(Overall Configuration) FIG. 1 is a longitudinal sectional view showing the overall configuration of a reactor pressure vessel according to the present embodiment, and FIG.
Cross section of each elevation in FIG. 1 (cross section taken along line EE, cross section taken along line FF, cross section taken along line GG, and cross section taken along line HH)
It is a figure which shows a shape as each quadrant.

As shown in FIG. 1, in the reactor pressure vessel 1 of the present embodiment, the reactor pressure vessel 1 contains cooling water also serving as a moderator and a core. This core includes a plurality of fuel assemblies 2 and control rods 3 and the like, and is housed in a core shroud 4. The coolant flows upward from the bottom of the reactor pressure vessel 2 through the reactor core, and when passing through the reactor core, the temperature of the coolant is increased by the nuclear reaction heat of the reactor core to be in a gas-liquid two-phase flow state. The coolant in the two-phase flow state flows into the steam separator 5 installed above the core, where it is separated into water and steam. Among them, the steam is introduced into a steam dryer 6 installed on the steam separator 5 and is dried to become dry steam. This dry steam is transferred to a steam turbine (not shown) via a main steam pipe 7 connected to the reactor pressure vessel 1 and is used for power generation.

Thereafter, the steam is returned to the reactor pressure vessel 1 via a feed water sparger 8 via a condenser, a feed water heater and the like (not shown), and together with the water separated by the steam separator 5, Descend downcomer 9. The cooling water is further pressurized by an internal pump 10 installed annularly in the lower part of the reactor pressure vessel 2 and then sent to the lower part of the core after being pressurized.

In such a configuration, in the present embodiment, an assembly of a core support block 22, which will be described later, is installed as a core support member at a lower position of the fuel in a core shroud 4 that accommodates the fuel assembly 2; An upper lattice plate 12 is provided above the shroud 4.

The first quadrant in FIG. 2 shows the shape and arrangement of the control rod guide tube along the line EE, and the second quadrant shows the shape and arrangement of the control rod guide tube at the top of the control rod guide tube. The structure of is shown. The third quadrant shows the support structure of the lower end of the fuel assembly in a cross section taken along the line GG, and the fourth quadrant shows the grid arrangement of the upper grid plate in a cross section taken along the HH line.

As shown in the sectional area along the line EE in FIG.
The control rod guide tube 13 has a cross shape, and the lower end is C-shaped.
It is supported in the RD housing 14 in the axial direction. A rectangular core support block 22 is attached to the top of the control rod guide tube 13 as shown in the sectional area taken along line FF in FIG. The core support block 22 includes the upper grid plate 12.
The core support block 22 is formed as an aggregate in which the core support blocks 22 are spread in the horizontal direction. Core support block 22
Is held by a core support ring 23 fixed to the core shroud 4. Further, each core support block 22 has a control rod insertion hole and an opening for cooling water passage, and is supported from below on the upper end of the control rod guide tube 13 rising from the bottom side of the reactor pressure vessel 1. You. The core support block 22 is, as described above,
It has a rectangular shape in plan view, has a semicircular notch as an opening for cooling water passage in the center of the side, and is arranged so that the diagonal direction matches the blade direction of the cross control rod. You.

More specifically, a square core support block 2
The diagonal line 2 is aligned with the direction of the blade of the control rod 3 as shown in the cross-sectional area taken along line FF, whereby the core support block 22 is connected to the grid 21 of the upper grid plate (partially shown). ). The core support block 22 is spread over the entire surface at a position where the upper plate of the conventional core support plate is installed, as shown in the cross-sectional area along the line FF of FIG. 2, and is held by the core support ring 23 at the outermost periphery. I have. The core support ring 23 includes the core shroud 4.
Are fixed and fixed by stud bolts or the like. Further, a notch 22a of a semicircular arc is provided at the center of one side of the core support block 22, thereby forming an opening for passing cooling water along the vertical direction. The adjacent core support block 22 forms a cylindrical hole serving as a cooling water flow path.

As shown in the cross-sectional area along the line FF in FIG. 2, the core support block 22 located in the space within the frame of the lattice 21 of the upper lattice plate 12 includes: As shown in the cross-sectional area taken along the line GG of FIG. 2, a fuel support bracket 15a is provided, and the fuel support bracket 15a is provided.
The fuel assembly 2 is installed on the upper side. The cross-sectional structure at the position of the upper grid plate is shown in the cross-sectional area taken along the line HH in FIG. 2, and the control rod 3 is also disposed immediately below the intersection of the space in the grid frame and the grid (not shown). .

With such a configuration, the reactor pressure vessel 1
In the lower plenum portion 4a, the lower trunk 4b of the core shroud 4, the core support block 22, and the core support ring 23
Thus, a differential pressure wall is formed. The cooling water supplied by being pressurized by the internal pump 10 is
The fuel is supplied to the fuel assembly 2 through the opening of the core support block 22. In the present embodiment, the upper lattice plate 12
Both types of control rod guide tubes 13 just below the opening in the frame of the lattice 21 and the intersection of the lattice 21 have a core support block 22 of the same shape at the top, and this serves to reinforce the portion forming the differential pressure wall. Play. This solves the problems of the strength of the core support plate 11 and the control rod guide tube 13, the deformation of the control rod guide tube 13, and the restriction on the dimensional accuracy, which are found in the conventional structure.

FIG. 3 is an enlarged plan view showing a state in which the fuel support 15a is mounted on the core support block 22, and FIG.
3 shows a support structure of the lower end portion of the fuel assembly 2 taken along the line II in FIG.

As shown in these figures, as shown in FIG.
At the lower end of 5a, four cylinders 15b are provided, and these cylinders 15b are inserted and installed in openings formed on each side of the core support block 22. An orifice 15c for adjusting the flow rate is provided inside each cylinder 15b so that the cooling water introduced into the fuel support 15a flows evenly in the furnace. Regarding the core support block 22 on which the fuel support bracket 15a is not installed, the control rod 3
A cross-shaped frame 22b corresponding to the height of the fuel support bracket 15a is provided upright.

Further, as shown in the right half of FIGS. 3 and 4, on the upper surface of the core support block 22 located immediately below the fuel support fitting 15a, for example, a circular concave portion 22c having a central portion depressed is provided. , The convex portion 15e which engages with the concave portion 22c.
Are provided on the lower surface of the fuel support fitting 15a, and by fitting these concave and convex portions 12c and 15e, the fuel support fitting 15a is positioned at the center of the core support block 22 and a lateral load such as an earthquake load is applied to the fuel support fitting 15a. To prevent the displacement when acting on the surface.

A projection 22d is provided on the upper surface of the core support block 22 which is located diagonally to the fuel support member 15a and where the fuel support member 15a is not installed, and which protrudes horizontally from the outer surface of the cross-shaped frame 22b. On the other hand, a groove 15d that engages with the projection 22d is provided on the side surface of the fuel support 15a at a position facing the projection 22d. When the fuel support 15a is installed on the core support block 22 by remote control, the protrusions 22
By engaging the groove 15d with the groove 15d, the fuel supporting member 15a can be installed at a specified angle by using the groove 15d as a guide for positioning downward from above.

FIGS. 5 to 7 exemplify a seal structure between the core support blocks 22 and in a plane where the core support block 22 and the fuel support 15a are joined.

FIG. 5 shows a seal structure in which a labyrinth 24 is provided on one outer surface of the adjacent core support blocks 22, for example, for sealing between adjacent surfaces of the core support blocks 22.

FIG. 6 shows a sealing structure in which mutually adjacent steps 25 are provided on adjacent side surfaces of the core support block 22.

By applying these structures, it is possible to suppress the amount of bypass leak of the coolant from the upper and lower contact surfaces of the core support block 22.

The structure for suppressing the leak shown in FIGS. 5 and 6 can be applied to the joint surface between the opening of the core support block 22 and the cylinder of the fuel support fitting 15a.

FIG. 7 shows a seal structure of a hole where the core support block 22 and the fuel support 15a are fitted. In the example of FIG. 7, the seal ring 26 is
The ring 26 is fitted into the ring-shaped groove on the outer peripheral portion of FIG. 1A, and the ring 26 is brought into contact with the outer surface of the core support block 22 disposed on both sides thereof to seal the gap between the two.

FIG. 8 shows another example of the structure of the core support block 22. The core support block 22 is intended to be located immediately below the fuel support fitting 15a. That is, as shown in FIG. 8, a semi-cylindrical projection 27 is provided at the center of one side of the core support block 22, and a circular opening is formed inside the projection 27. According to such a configuration, since the fuel support fitting 15a is engaged only with the core support block 22 immediately below it, the core support block 2
This facilitates the management of the gap at the joint between the fuel tank 2 and the fuel support 15a, and is effective in suppressing the amount of leakage from the core support block 22. In such a core support block 22, since the fuel assembly 2 can be held by the semi-cylindrical projection 27, the fuel support fitting 15a is provided.
And the fuel assembly 2 can be directly installed on such a core support block 22.

FIG. 9 is a plan view showing an example of the structure of the fuel lower support structure of the support block 22, and FIG.
It is J sectional drawing. In this example, the core support block 22
, A support grid 28 in the form of a square grid fixed to the core shroud 4 and the like is provided. This support grid 2
A protrusion 13a projecting horizontally from a part of the outer periphery of the control rod guide tube 13 is fitted to the grid portion 8 in a joined state with a corner portion in the grid.

According to such a configuration, the positioning and horizontal movement of the control rod guide tube 13 are restrained by the support grid 28, so that the workability at the time of installing and removing the control rod guide tube 13 is improved and the earthquake resistance is improved. Is improved.

The support grid 28 may be fixed to the core support ring 23 described above, or may be fixed to the core shroud 4.

Further, in this embodiment, by forming a guide hole along the vertical direction at the intersection of the support grid 28, for example, the in-core guide tube 16 can be formed as in the conventional configuration shown in FIGS. 14 and 15. The function as the held in-core stabilizer 17 can also be used together.

In this embodiment, austenitic stainless steel is used as a constituent material of the core support block 22. For the core support ring 23, a nickel-base alloy steel having a smaller coefficient of thermal expansion than that of the austenitic stainless steel is applied. With such a material configuration, when the inside of the reactor pressure vessel 1 is in a high temperature state during normal operation, the core support ring 23 can tighten the core support block 22 from the outer periphery due to a difference in thermal expansion. During the operation of the core support block 22, it is possible to maintain a stable fixed state without rattling.

FIGS. 11A to 11E show the fuel assembly 2, the control rod 3, and the fuel support 15 in the above-described configuration.
FIG. 3A is an explanatory view showing the action of pulling out the control rod guide tube 13 and the CRD 29 above the reactor pressure vessel 1 at the time of a periodic inspection or the like along a procedure. In particular, the figure shows a procedure for removing the CRD 29 immediately below the intersection of the upper lattice plate 12 which is difficult to remove.

First, the upper lid of the reactor pressure vessel 1 and the in-furnace structures such as the steam dryer 6 and the steam separator 5 were removed and removed from the furnace, and as shown in FIG. The fuel assembly 2 located above the CRD 29 to be withdrawn is removed upward by a crane or the like (not shown),
The control rod 3 is removed as shown in FIG. In this case, as shown in FIG. 11B, the control rods 3 disposed immediately below the intersections of the lattices 21 of the upper lattice plate 12 to be pulled out are horizontally moved in advance on the fuel support 15a as shown in FIG.
Pull up after dodging the intersection of grid 21.

Next, as shown in FIG. 11 (C), the fuel support 15a placed on the control rod guide tube 13 is removed. Thereafter, by rotating the CRD 29 below the reactor pressure vessel 1, the control rod guide tube 13 and the CRD 2 are rotated.
Then, the control rod guide tube 13 is pulled out integrally with the core support block 22 as shown in FIG. 11 (D). As a result, in the core portion, the space above the CRD 29 is opened. Then, as shown in FIG. 11E, finally, the CRD 29 is pulled out and the upper lattice plate 1 is pulled out.
2 moves horizontally to the space position within the frame of the lattice 21 at a position below 2,
Pull out above the reactor pressure vessel 1. As a result, the control rod 3, the fuel support 15a, the core block 22, the control rod guide tube 13, and the CDR 29, which are arranged at the intersections of the lattices 21 of the upper lattice plate 12, are all pulled out above the reactor pressure vessel 1. Removal can be completed.

The CRD can be restored in the reverse procedure of the removal.

According to the above embodiment, the cross-shaped control rods 3 are arranged in a staggered manner in the horizontal section of the core, and the control rods 3
In a boiling water reactor having a configuration in which the CRD 29 and the control rod guide tube 13 for supporting the reactor so as to be able to move up and down at the reactor bottom side can be pulled out above the reactor pressure vessel 1, the control rod guide tube 1
3, core support blocks 22 for supporting the fuel assemblies are removably mounted on the tops of the fuel cell assemblies 3 respectively adjacent to each other,
By surrounding the outermost periphery of the assembly of these core support blocks 22 with a core support ring 23 fixed to the core shroud 4, a differential pressure wall for supplying cooling water to the fuel assembly 2 is formed. By removing the fuel support fitting 15a and the core support block 22 below it, the CRD 2
9 can be withdrawn above the reactor pressure vessel 1.

The core support block 22 is provided on the upper surface thereof and holds the fuel assembly 2 via a fuel support fitting 15a having a passage for supplying cooling water. This can prevent the occurrence of a bypass leak of the cooling water due to the above.

The core support block 22 has a quadrangular shape in a plan view, its diagonal line coincides with the direction of the blade of the control rod 3, and a semicircular opening is provided at the center of one side. Is the grid 2 of the upper grid plate 12
Those located in the space within the lattice frame immediately below the intersection of 1 can have the same shape, and have dimensions that allow them to pass through the frame of the upper lattice plate 12. Further, the core support block 22 can also play a role of reinforcing the control rod guide tube 13.

Further, four cylinders 15b which can be inserted into the opening of the core support block 22 are provided at the lower end of the fuel support fitting 15a, and the orifices 15c for adjusting the flow rate of the cooling water are provided inside each of the cylinders 15b. As a result, a cooling water passage is secured for each fuel assembly 2, and the orifice size is changed according to the fuel arrangement, thereby achieving a uniform cooling water flow rate.

A concave portion 22c is provided on the upper surface of the core support block 22 located immediately below the fuel support member 15a, and a convex portion 15e corresponding to the concave portion 22c is provided on the lower surface of the fuel support member 15a. Convex part 15
e, the core support block 22 and the fuel support fitting 15
The fuel support 15a is positioned with respect to the core support block 22 by fitting the fuel support 15a, and the lateral displacement of the fuel support 15a during an earthquake can be prevented.

Further, a cross-shaped frame 22 is formed on the upper surface of the core support block 22 disposed at a diagonal position of the fuel support 15a.
b, a projection 22d is provided on the frame 22b, a groove 15d is provided on the side surface of the fuel support fitting 15a to engage with the projection 22d, and when the fuel support fitting 15a is installed from above, the projection 22d is formed in the groove 15d. Due to the slidable configuration, rotation during operation can be prevented as a reference for the orientation when the fuel support 15a is installed from above.

One or two of the two positions in the plane where the core support block 22 contacts each other and in the plane where the cylinder 15b of the fuel support fitting 15a and the opening of the core support block 22 contact each other. , A seal with a labyrinth 24, a step 25 or a piston ring 26
, The amount of coolant leakage from the contact surface between the core support block 22 and the fuel support fitting 15a can be suppressed.

The core support block 22 located immediately below the fuel support 15a is provided with a semi-cylindrical projection 27 at the center of one side of the square so as to have a circular opening. 15a can be fitted only to the fuel support block 22 located immediately below, so that the gap between the fitting portion between the core support ring 23 and the fuel support fitting 15a can be reduced, and the amount of coolant leakage can be suppressed. .

Further, when the fuel assembly 2 is installed directly in the opening of the core support block 22, the number of parts of the core support structure can be reduced.

Further, a support grid 28 supported by the core shroud 4 and engaged with the control rod guide tube 13 is provided below the core support block 22 so that the control rod guide tube 13 can be positioned by the core support block 22. The horizontal movement can be restricted.

Further, by using austenitic stainless steel as the material of the core support block 22 and using nickel-base alloy steel as the material of the core support ring, the core can be used during the high temperature operation of the reactor based on the difference in the coefficient of thermal expansion. The core support block 22 is pressed by the support ring 23, and the gap can be absorbed.

Further, by combining the CRD 29 with a type that can be pulled up above the reactor, the space under the pressure vessel can be reduced and the height of the reactor building can be reduced as compared with the conventional type in which the CRD 29 is removed below the reactor. Reduction and improvement of earthquake resistance are achieved.

[0070]

As described in detail above, according to the boiling water reactor of the present invention, the restrictions on the strength, size, etc. of each structure in the reactor internal structure to which the K lattice core is applied are removed. The CRD at any position can be removed above the reactor together with the fuel assemblies, control rods, fuel support fittings, control rod guide tubes, and core support blocks located thereabove. Therefore, the concept of the upper drawing CRD can be applied to the K lattice type core, and a space for inserting and pulling out the CRD main body below the reactor pressure vessel becomes unnecessary, and the height of the reactor building is reduced. This has the effect of reducing the amount of material, the amount of material involved, and improving the earthquake resistance.

[Brief description of the drawings]

FIG. 1 is an overall sectional view showing a configuration of a reactor internal structure of a boiling water reactor according to the present invention.

FIG. 2 is a sectional view taken along line EE, line FF, line GG, and line H of FIG.
FIG. 2 is an enlarged cross-sectional view showing the reactor internal structure along the line H divided into quadrants.

FIG. 3 is an enlarged plan view showing a core support block and a fuel support fitting shown in FIG. 2;

FIG. 4 is a sectional view taken along line II of FIG. 3;

FIG. 5 is an enlarged sectional view showing an example of a contact surface sealing structure of a core support block according to an embodiment of the present invention.

FIG. 6 is an enlarged sectional view showing another example of the configuration of the seal structure shown in FIG. 5;

FIG. 7 is an enlarged cross-sectional view showing another configuration example different from the seal structure shown in FIGS. 5 and 6;

FIG. 8 is a plan view showing another configuration example of the core support block according to the present invention.

FIG. 9 is a plan view showing a configuration of a lower structure of a core support block according to the present invention.

FIG. 10 is a sectional view taken along line JJ of FIG. 9;

FIGS. 11A to 11E show CRs in the embodiment.
Explanatory drawing which shows the removal procedure of D.

FIG. 12 is an overall sectional view showing a reactor pressure vessel to which a conventional C-shaped core is applied.

FIG. 13 is an enlarged perspective view showing the conventional core support structure shown in FIG.

FIG. 14 is an overall sectional view showing a conventional large-capacity reactor pressure vessel to which a large core is applied.

FIG. 15 is an enlarged sectional view showing the reactor internal structure along lines AA, BB, CC and DD in FIG.

[Explanation of symbols]

 Reference Signs List 2 reactor pressure vessel 4 core shroud 13 control rod guide tube 15a fuel support fitting 15b cylinder 15c orifice 15d groove 22 core support block 22a notch 22b cross-shaped frame 22c concave step 22d protrusion 23 core support ring 24 labyrinth 25 Step 26 Piston ring 27 Projection 28 Support grid 29 Control rod drive mechanism (CRD)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G21C 3/32 P (72) Inventor Hiroyuki Nojima 2-4 Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Toshiba Inside Keihin Works (72) Inventor Fumihiko Ishibashi 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Inside Toshiba Yokohama Works

Claims (9)

[Claims] 1. A reactor core comprising a plurality of fuel assemblies and cruciform control rods housed in a core shroud of a reactor pressure vessel, wherein the control rods are arranged in a square lattice and diagonal positions of the square lattice. And the upper end of the fuel assembly is supported by a square lattice-shaped upper lattice plate provided at an upper position of the core shroud, while the lower end is provided at a lower position of the core shroud. The core support member is configured to be supported by a core support member, and the core support member is a boiling water reactor that functions as a differential pressure wall for supplying cooling water to the fuel assembly from below. A core support block consisting of a plurality of divided bodies of a size that can pass through the space inside the lattice frame of the lattice plate is configured as an aggregate spread horizontally, and the core support block The assembly is held around a core support ring fixed to the core shroud, and each of the core support blocks has a control rod insertion hole and an opening for cooling water passage, and the bottom of the reactor pressure vessel. A boiling water reactor characterized by being supported from below on the upper end of a control rod guide tube rising from the side. 2. The boiling water reactor according to claim 1, wherein the core support block has a quadrangular shape in a plan view, and has a semicircular notch as a cooling water passage opening at a center of a side of the core support block. And a diagonal direction is arranged so as to coincide with the blade direction of the cross-shaped control rod. 3. The boiling water reactor according to claim 1, further comprising a fuel support having a hole through which a control rod can be inserted and a passage for supplying cooling water, on an upper surface of the core support block. A boiling water reactor. 4. The boiling water reactor according to claim 3, wherein the fuel support bracket has a downward cylinder that can be inserted into an opening of the core support block, and the inside of the cylinder has a cooling water flow rate adjusting element. A boiling water reactor having an orifice. 5. The boiling water reactor according to claim 3, wherein a recess is provided on an upper surface of a core support block located immediately below the fuel support, and a lower surface of the fuel support corresponds to the recess. A boiling water reactor, wherein a convex portion is provided, and the core support block and the fuel support fitting are positioned by fitting the concave portion and the convex portion. 6. The boiling water reactor according to claim 3, wherein a control rod blade is inserted into the upper surface of the core support block, and the cross-shaped frame protrudes outward from the frame. Protrusions are provided, and grooves for engaging with the protrusions are provided on side surfaces of the fuel support fitting, and these grooves and protrusions are used as sliding positioning portions when the fuel support fitting is lowered from above. Boiling water reactor. 7. The boiling water reactor according to claim 1, wherein a surface of each core support block in contact with each other, and a cylinder of the fuel support fitting and an opening of the core support block contact each other. A boiling water reactor having a seal structure using a labyrinth, a seal structure using a step, or a seal structure using a seal ring provided on a surface or both contact surfaces. 8. The boiling water reactor according to claim 1, wherein all of the core support blocks or a part of the core support blocks located immediately below the fuel support fittings are provided with the core support blocks. A boiling water reactor having a semi-cylindrical projection forming a circular opening in which a fuel assembly can be installed at a center position of a side. 9. The boiling water reactor according to claim 1, further comprising a horizontal support grid provided with a control rod guide tube at a position below the core support block. A boiling water reactor fixedly supported by a shroud.