JPH0460499A - Structure of penetration part of nuclear reactor shielding - Google Patents

Abstract

PURPOSE:To enable decreasing shielding extent of radiation down to almost the same level of a shielding wall by providing a shielding member consisting of a gamma-ray shielding material and a neutron shielding material, at one of outer and inner side penetration hole provided at a penetrating part. CONSTITUTION:A shielding member 11 is placed outside a penetration hole 10 and the member 11 is constituted of rectangular flat plane shaped gamma-ray shielding material 12 and a neutron shielding material 13 which are integrally fitted together. Also, this shielding member 11 is formed to be a size larger than an area which can be seen directly from outside a nuclear reactor shielding wall 4 to a nuclear reactor pressure vessel 2 side, and is supported by a supporter body 14 extending from the shielding wall 4, and floor 15. At a vicinity of the penetration hole 10, an access hole is provided and the access hole is constituted to be able to be freely opened and closed by a shield plug having no hollow part in it and therewith radiation from a reactor core part 3 does not pass through directly to outside the shielding wall 4.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to a nuclear reactor pressure vessel installed to surround a nuclear reactor pressure vessel in order to shield radiation from the core of the reactor pressure vessel. The present invention relates to a structure of a penetration part of a nuclear reactor shielding wall in which a pipe or the like is passed through the peripheral wall of a cylindrical reactor shielding wall.

(Prior Art) In a nuclear power plant, generally, as shown in FIG. 10, a reactor pressure vessel 2 is housed within a reactor containment vessel 1, and a reactor core 3 is housed within this reactor pressure vessel 2. Ru. Further, a cylindrical reactor shielding wall 4 is installed around the reactor pressure vessel 2 to shield radiation. This reactor shielding wall 4 is installed on a reactor pressure vessel support pedestal 5.

One end of the piping 7 etc. is connected to the piping nozzle 6 provided in the reactor pressure vessel 1, and the other end of the piping 7 etc. passes through the penetration part 8 of the reactor shielding wall 4 and is guided to the outside. It has become.

Conventionally, as shown in FIGS. 11 to 13, the structure of the penetration part of the reactor shielding wall 4 through which the piping 7, etc. is penetrated is provided with a hole 9a having a size that takes into consideration the amount of heat transfer of the piping 7, etc. By installing a retractable shield plug 9 in the penetration part 8 of the reactor shielding wall 4 and further installing a neutron shield as necessary, the reactor pressure in the piping 7 connected to the reactor pressure vessel 2 can be reduced. A so-called shield plug structure is generally employed to ensure good accessibility during inspection of the piping nozzle section 6, which is the connection section with the container 2.

In a boiling water reactor as a conventional general light water reactor, the piping nozzle 6 provided in the reactor shielding wall 4 is
As shown in FIG. 1, it is arranged above the reactor core part 3 so that the penetration part 8 is not located within the height range of the reactor core part 3.

(Problem to be solved by the invention) However, recently improved boiling water nuclear power plants (
In BWR), due to layout constraints and to improve seismic resistance, it is desirable to lower the installation height of the reactor pressure vessel 2 than in conventional BWRs, as shown in Figure 10. There is a need to install the penetration portion 8 of the reactor shielding wall 4, such as the piping 7, within the height range of the reactor core 3.

If the same shield plug structure as the conventional example is adopted for these penetration parts 8, a large hole 9a is provided inside the shield plug 9 in consideration of the amount of heat transfer from the piping 7, etc. Radiation Ra from the reactor core 3, which is a radiation source, directly passes through these holes 9a to the outside of the reactor shielding wall 4 without any shielding.

For this reason, the radiation dose, which was conventionally reduced to about 1/100 or less, is hardly reduced in the vicinity of the penetration part 6, and the accessibility to the vicinity of the penetration part 8 during periodic inspections of nuclear power plants is affected. There is a risk that problems may occur, and
Regarding restrictions on entering the reactor building during normal operation,
It could have a big impact.

Therefore, if there is a possibility that a penetration part of the reactor shielding wall will be installed within the height of the reactor core, a structure that has sufficient radiation shielding function from the core should be used instead of the shield plug structure that has been widely used in the past. The current situation was that it was necessary to prepare for

The present invention has been made in consideration of the above-mentioned circumstances, so that even when a reactor shielding wall penetration part is installed within the reactor core height range, radiation from this penetration part can be blocked to almost the same degree as the shielding wall. It is an object of the present invention to provide a structure for a penetration part of a nuclear reactor shielding wall that can reduce the amount of water to a minimum.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the reactor shielding wall penetration structure according to the present invention provides piping, etc. to the peripheral wall of the reactor shielding wall that surrounds the reactor pressure vessel. In the penetrating structure of the reactor shielding wall having a penetrating portion, a through hole through which a pipe or the like passes is provided in the penetrating portion, and a gamma ray shielding material is provided on at least one of the outside and inside of the through hole. A shielding body made of a neutron beam shielding material is installed to cover the through-hole so that the inside of the reactor shielding wall cannot be seen directly from the outside through the through-hole.

(Function) According to the present invention, even when the reactor shielding wall penetration part is installed within the reactor core height range, the inside of the reactor pressure vessel that attempts to pass directly through the through hole provided in this penetration part Radiation (gamma rays and neutron beams) from the reactor core is absorbed by the shield installed here, thereby reducing the radiation dose near the penetration part to an extremely small amount, comparable to that of the reactor shield wall. be able to.

(Example) Hereinafter, an example of the structure of a penetration part of a nuclear reactor shield according to the present invention will be described with reference to the accompanying drawings.

FIGS. 1 and 2 show a first embodiment of the present invention, and in describing this embodiment, members that are the same as conventional members are given the same reference numerals and their explanations will be omitted. The reactor pressure vessel 2 includes piping nozzles, located on the side of the reactor core 3.
That is, the piping nozzle 6 is connected and located within the height range of the reactor core 3 (see FIG. 10).

Piping 7 extending from piping nozzle 6 of this reactor pressure vessel 2
is a through hole 10 provided in a through part 8 of the reactor shielding wall 4
It is guided to the outside through the bending part, bent at an almost right angle and placed along the reactor shielding wall 4, and then connected to a penetration part (not shown) of the reactor containment vessel. .

A shield 1 is provided on the outside of the through hole 10 at a predetermined distance.
1 is installed. This shielding body 11 is constructed by integrally joining a flat rectangular gamma ray shielding material 12 and a neutron shielding material 13, and allows direct viewing of the reactor pressure vessel 2 side from the outside of the reactor shielding wall 4. Formed to a size larger than the range,
It is supported by a support 14 extending from the reactor shielding wall 4 and a floor 15.

Further, an entrance/exit 16 is provided near the through hole 10 of the reactor shielding wall 4 to ensure accessibility. This entrance/exit 16 is configured to be openable and closable by a shield plug 17 having no internal hole, and is designed to prevent radiation from the reactor core 3 from passing directly to the outside of the reactor shielding wall 4.

As a result, among the radiation (γ rays and neutron rays) Ra from the reactor core part 3 of the reactor pressure vessel 2, all the radiation Ra that passes through the through hole 10 of the penetration part 8 of the reactor shielding wall 4 is transferred to the shield. 11, the radiation dose can be kept sufficiently low even in the vicinity of the penetration part 8, as in the case without the penetration hole 10.

Therefore, according to this embodiment, the radiation dose near the through hole 8 can be as low as that in the case without the through hole 10. There is no need to restrict access to the area, and the work can be completed smoothly. In addition, the shield 11 installed in the penetration part 8 of the reactor shielding wall 4 can be made to have the same size and thickness as the penetration parts of other reactor containment vessels, so the structure can be simplified. can.

Furthermore, regarding the inspection of the piping nozzle section 6, the inlet/outlet 16 and the shield plug 17 can be installed for entry and exit of workers, so that inspection performance equivalent to the conventional one can be ensured.

A second embodiment is shown in FIGS. 3 and 4.

This embodiment includes a γ-ray shielding material 12a and a neutron shielding material 13a.
A shield 11A consisting of a box-shaped shield 11A surrounding the entire circumference of the pipe 7 is installed outside the reactor shield wall 4.

In the case of this embodiment, the radiation Ra passing through the through hole 10 of the penetrating portion 8 is shielded by the shield 11A on the side and upper and lower surfaces of the shield 11A, so that the shielding effect can be further enhanced. The installation space for the shield 11A in front of the through hole 10, which was required in the first embodiment, can also be made smaller.

In addition, the code|symbol 18 is the fixing metal fittings of the shielding body 11B.

A third embodiment is shown in FIGS. 5 and 6.

This embodiment is similar to the shielding body 11A in the second embodiment.
A shielding body 11B consisting of a γ-ray shielding material 12b and a neutron shielding material 13b is constructed in a shape such that one side along the extending direction of the pipe 7 is open, and wheels 19 such as casters are installed on the lower surface of the shielding body 11B. This is intended to facilitate the movement of the shield 11B.

That is, in normal times, the shield 11B is fixed to the support body 14 via the shield fixing fitting 18, and when it is necessary to move the shield 11B due to inspection of the piping 7, etc.
The shielding body IIB can be moved along the guide 20.

In this embodiment, the direction in which the shield 11B moves needs to be made larger than in the second embodiment, considering the amount of movement, but inspection of the piping 7 is facilitated. .

FIG. 7 shows a fourth embodiment.

In this embodiment, when the penetration part 8 is installed on a line connecting the center of the reactor core part 3 and the piping nozzle 6, the penetration hole 10 of the penetration part 8
This embodiment is most suitable when sufficient installation space for the shield 11C cannot be secured in front of the shield 11C.

In the case of this embodiment, the pipe 7 is provided with a bend between the reactor pressure vessel 2 and the reactor shielding wall 4, and the through hole 10
A through hole 10 is provided at a portion of the front surface where a space for installing the shield 11C can be secured, and a through hole 10 is provided in this portion, from which the pipe 7 penetrates the reactor shielding wall 4.

With this configuration, it is possible to obtain the same effect as the first embodiment.

FIG. 8 shows a fifth embodiment.

In this embodiment, a γ
A shielding body 11D consisting of a radiation shielding material 12d and a neutron shielding material 13d is installed on the inner surface of the reactor shielding wall 4 via a support 14, and the inside passage of this shielding body 11D is operated as described in the fourth embodiment. Similarly, a bent pipe 7 is inserted through the pipe 7 and guided to the outside through a through hole 10 of a penetrating portion 8.

In this embodiment, since the shield LID is not installed outside the reactor shielding wall 4, it is possible to effectively use the space for arranging the structure in front of the reactor shielding wall 5.

FIG. 9 shows a sixth embodiment.

In this embodiment, a γ-ray shielding material 12e and a neutron shielding material 13e are symmetrical and separate from each other, each having a rectangular passage inside.
A shielding body 11E is constructed, and a gamma ray shielding material 12e is fixed to the outside of the reactor shielding wall 4 through the through hole 10 of the penetration part 8, and a neutron shielding material 13e is fixed to the inside through the supports 14, respectively, and the piping 7 is bent into a U-shape to form a passage for the neutron shielding material 13e,
The through hole 10 and the passage of the γ-ray shielding material 12e are sequentially inserted and routed, thereby achieving the same effect as the fourth embodiment.

〔Effect of the invention〕

Since the present invention has the above-described configuration, even when the reactor shielding wall penetration part is installed within the reactor core height range, the reactor shielding wall can pass directly through the through hole provided in the penetration part of the reactor shielding wall. Radiation (gamma rays and neutron rays) from the reactor core inside the reactor pressure vessel is absorbed by the shield, thereby reducing the radiation dose near the through hole to an extremely small amount, comparable to that of the reactor shield wall. It has the effect that it can be done.

[Brief explanation of the drawing]

FIG. 1 shows the main parts of the first embodiment of the present invention. FIG. The figure is a partial vertical sectional view showing the second embodiment of the present invention, FIG. 4 is a view taken along the line B-B in Figure 3, and FIG. 5 is a partial view showing the third embodiment of the present invention. FIG. 6 is a vertical cross-sectional view taken along line C-C in FIG. 10 is a schematic sectional view of a nuclear power plant to which the present invention is applied, FIG. 11 is a partial longitudinal sectional view showing a conventional example, and FIG. 12 is taken along line D-D in FIG. 11. 13 is a sectional view taken along line E--E in FIG. 12. 2... Nuclear pressure vessel, 3... Reactor core, 4... Reactor shielding wall, 6... Piping nozzle, 7... Piping, 8...
... Penetration part, 10... Penetration hole, 11. IIA, IIB
, 11C, IID, IIE...shielding body, 12a, 12
b. 12c, 12d, 12e-7 line shielding material, 13a. 13b, 13c, 13d, 13e...neutron shielding material,
16...Entrance/exit, 17...Shield plug, Ra・
··radiation. Figure 1 Figure Figure Figure Figure 10 Figure

Claims (1)

[Claims] In a reactor shielding wall penetration structure having a penetration part through which a pipe or the like passes through the peripheral wall of the reactor shielding wall that surrounds the reactor pressure vessel, a through hole through which the pipe or the like passes through the penetration part is provided. A shield is provided on at least one of the outside and inside of the through hole, and is made of a gamma ray shielding material and a neutron beam shielding material, and covers the through hole so that the inside of the reactor shielding wall cannot be seen directly from the outside through the through hole. A structure of a penetration part of a nuclear reactor shielding wall, characterized by having a body installed therein.