JP3342183B2 - Reactor radial neutron reflector structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear reactor, and more particularly to a structure of a neutron reflector provided around a reactor core.

[0002]

2. Description of the Related Art In a pressurized water reactor which is currently widely used as a commercial power reactor, a buckle plate and a former plate are arranged radially outside a core formed by a large number of fuel assemblies. In particular, there are few examples of providing a neutron reflector. However, in different types of reactors, a neutron reflector is provided around the core in order to improve the neutron economy of the core and prevent neutron impact. And even in pressurized water reactors,
Recently, the installation of a neutron reflector has been proposed. 5 and 6 show an example of the structure of the neutron reflector.

In FIG. 5, the neutron reflector is formed by stacking a lowermost annular neutron reflecting member 1, an uppermost annular neutron reflecting member 3, and six intermediate annular neutron reflecting members 5. . As can be seen from the figure, each of the neutron reflecting members 1, 3, and 5 has a polygonal opening of the same shape on the inside, however, in order to prevent relative displacement in the circumferential direction, or as a positioning member at the time of assembly. A positioning key 7 extending in the axial direction is fitted on the outer peripheral portion. FIG. 6 shows the cross-sectional shape of the mounting portion of the positioning key 7. The positioning key 7 fitted in the key groove is fixed at the upper part and the lower part by an upper assembly bolt 8 and a lower assembly bolt 9, respectively. . The lowermost annular neutron reflecting member 1 is attached to a lower core plate via a lower positioning pin 6.

[0004] The assembled radial neutron reflector thus reflects neutrons radiated from the nuclear fuel of the core located within the internal opening.

[0005]

In the above-described conventional neutron reflector, when fixing the positioning key, a lower assembly bolt is used in addition to the upper assembly bolt, and the upper and lower parts are fixed. . Since the lower assembly bolt must be inserted into a narrow space and rotated, it takes a considerable amount of time to mount and tighten the assembly bolt. Since both sides must be tightened, the overall assembly time is long. The present invention has been made in view of such a problem of the conventional structure, and provides a radial neutron reflector structure of a nuclear reactor that can be easily assembled and can be assembled in a short time as a whole. It is intended to do so.

[0006]

According to the present invention, there is provided, in accordance with the present invention, an inner polygonal opening surrounding a fuel assembly forming a reactor core, and an inner surface of a core vessel surrounding and supporting the core. In a radial neutron reflector of a nuclear reactor configured by stacking a plurality of annular members having circular outer surfaces facing each other, an inverted T-shaped keyway is formed on the outer peripheral portion of the lowermost annular member, and A linear keyway connected to the leg of the inverted T-shaped keyway is formed on the outer peripheral portion of the annular member to form a long-legged inverted T-shaped keyway as a whole. A plurality of the annular members are integrated by fitting a T-shaped key member and fastening and fixing the long leg end of the T-shaped key member with a mounting bolt penetrating the lowermost annular member.

[0007]

When assembling the radial neutron reflector of the above construction, first, the horizontal portion of the long leg T-shaped key member is fitted into the inverted T-shaped key groove of the lowermost annular member. The posture is inverted, and the long legs extend upward. Next, the intermediate annular members are sequentially stacked.
Positioning is performed by fitting to the front legs. Finally, the uppermost annular member is stacked. This is screwed into the long leg end of the T-shaped key member through the mounting bolt and tightened. In this way, the horizontal portion of the T-shaped key member abuts against the shoulder of the inverted T-shaped keyway, and each annular member is firmly integrated into a radial neutron reflector.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the internal structure of a pressurized water reactor 10 incorporating a radial neutron reflector 30 according to the present invention. In brief, the lower part of the reactor vessel 11 is closed by a hemispherical shell-like end plate 11a, and the upper opening is closed by a removable upper lid 12. A plurality of control rod drive mechanisms 13 are erected on the upper lid 12. A reactor core vessel 14 is suspended and supported in the reactor vessel 11, and a lower core support plate 15 is integrally supported at the lowermost portion thereof, and a lower core plate 16 is further supported thereon.

A plurality of fuel assemblies 17, partially shown, are loaded on a lower core plate 16 to form a core. The control rod 18 inserted into and removed from the selected fuel assembly 17 is moved up and down by the control rod drive mechanism 13.
Upper furnace internal structure 21 including a large number of guide cylinders 19 for guiding 8
Is provided. The radial neutron reflector 30 is mounted on the lower core plate 16 and occupies a space between the core vessels 14 in the core.

In the pressurized water reactor 10 having the above-described structure, the coolant flows in through the inlet nozzle 11 b, flows down the down canoe part 22, and reverses in the lower plenum 23. The inverted coolant flow flows through holes (not shown) in the lower core support plate 15 and the lower core plate 16, enters the core, flows between and in the fuel assemblies 17, and absorbs nuclear reaction heat in the fuel rods. The coolant that has become hot in this way joins and mixes in the upper plenum 24, flows out of the outlet nozzle 11c, and generates steam for driving the power generation turbine.

FIG. 2 shows the overall structure of the radial neutron reflector 30 according to the present invention. The neutron reflector 30 is
Basically, the lowermost annular member 31, the uppermost annular member 33, and a suitable number (six in this embodiment) of intermediate annular members 35 are stacked. The inner opening 33a of the uppermost annular member 33 is basically rectangular and has a stepped corner, which is adapted to the arrangement of the fuel assemblies 17 forming the core. It is shaped and faces the side surface of the surrounding fuel assembly 17 at a narrow interval. Other annular members 31, 3
The shape of the inner opening 5 is the same. As is clear from FIG. 2, each annular member 31, 33, 35 is positioned by an inverted T-shaped key.

FIGS. 3 and 4 show the fitted state of the T-shaped key 37. FIG. An inverted T-shaped keyway 31a is formed in the lowermost annular member 31, and a linear keyway 35a connected to the keyway 31a is also formed in the middle annular member 35, and these are aligned. Further, the uppermost annular member 33 includes
A short-length linear key groove 33b is formed, and a bolt hole aligned with this is formed. Then, the long leg T-shaped key 37 is fitted into the long leg inverted T-shaped key groove formed by the key grooves 31a, 35a, 33b in cooperation with each other, and the upper assembly bolt 39 and the tightening nut are inserted through the bolt holes. 41.

To assemble the radial neutron reflector 30 shown in FIGS. 2, 3 and 4, first, the lowermost annular member 31 is placed as shown, and the horizontal portion of the T-shaped key 37 is inverted T-shaped. It fits in the key groove 31a. That is, the T-shaped key 37 is
The posture is inverted, and the long leg 37a extends upward. The annular members 35 are stacked one after another such that the key groove 35a fits into the long leg 37a of the T-shaped key 37. Finally, the annular member 33 is stacked so that the key groove 33b is fitted to the upper end of the long leg 37a of the T-shaped key 37. After a while
If the upper assembly bolt 39 is screwed into the upper end of the long leg 37a and the tightening nut 41 is screwed into the assembly bolt 39 and tightened, the horizontal portion of the T-shaped key 37 abuts the local portion of the inverted T-shaped keyway 31a, The annular members 31, 33, 35 are integrated.

The thus assembled and integrated radial neutron reflector 30 is inserted into the core vessel 14 and placed on the lower core plate 16, but is positioned by the positioning pins 26. .

[0015]

As described above, according to the present invention,
An inverted T-shaped keyway is formed in the lowermost annular member of the radial neutron reflector, and a linear keyway connected thereto is formed in the middle and uppermost annular members to form a long leg inverted T-shaped keyway as a whole. It is formed and fitted with an inverted T-shaped key member, and the upper end of the long leg is tightened to assemble and integrate. Therefore, the assembly work only needs to be performed at the upper side, and the neutron can be easily and quickly assembled. The reflector can be completed.

[Brief description of the drawings]

1 is a sectional elevation view of a pressurized water reactor incorporating a radial neutron reflector according to the present invention.

FIG. 2 is an overall perspective view of a radial neutron reflector according to the embodiment of the present invention.

FIG. 3 is an elevational sectional view showing a main part of the embodiment.

FIG. 4 is a partial side view taken along the line IV-IV in FIG. 3;

FIG. 5 is an overall perspective view of a conventional device.

FIG. 6 is a vertical sectional view showing a main part of a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Pressurized water reactor, 11 ... Reactor vessel, 14 ... Core vessel, 16 ... Lower core plate, 17 ... Fuel assembly, 30 ... Neutron reflector, 31 ... Annular member, 31a ... Inverted T-shaped keyway, 3
3 ... annular member, 33a ... inner opening, 33b ... keyway, 3
5 ... annular member, 35a ... key groove, 37 ... T-shaped key, 37
a ... Long legs.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hirokazu Shomura 1-1-1, Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo Prefecture Inside the Mitsubishi Heavy Industries, Ltd.Kobe Shipyard (72) Inventor Kazuhide Shokuhin Hyogo-ku, Kobe-shi, Hyogo 1-1 1-1 Tazakicho Inside Kobe Shipyard, Mitsubishi Heavy Industries, Ltd. (56) References JP-A-1-296193 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21C 11 / 06 G21C 7/28 G21C 5/00

Claims (1)

(57) [Claims] An annular member having an inner opening surrounding a group of fuel assemblies forming a core of a nuclear reactor and a circular outer peripheral surface facing an inner surface of a core vessel surrounding and supporting the core is stacked. In the radial neutron reflector of the nuclear reactor, the inverted T-shaped key groove is formed on the outer peripheral portion of the lowermost one of the plurality of annular members, and the inverted T-shaped key groove is formed on the outer peripheral portion of the other annular members. Forming a linear keyway that is continuous with the shaped keyway, and fitting a long-legged T-shaped key member into the inverted T-shaped keyway and the linear keyway; Characterized by being fastened and fixed by mounting bolts penetrating the uppermost one of the plurality of annular members.