JP3909412B2 - Reactor pressure vessel bottom drain piping inspection method and inspection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pipe inspection method in a nuclear power plant, and more particularly to a method and apparatus for inspecting an RPV bottom drain pipe in a pedestal below an RPV.
[0002]
[Prior art]
Inside the pedestal located below the reactor pressure vessel (RPV: Reactor Pressure Vessel), there is a control rod drive device (CRD: Control Rod Drive System) around the RPV bottom drain pipe, and a neutron measurement monitoring device (ICM: In Core). A monitoring system is being established.
[0003]
As an example of such a pipe inspection method in the pedestal, there is a radiographic testing (RT) device using a small traveling vehicle using a dedicated rail. (See Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Application No. 10-338806
[Problems to be solved by the invention]
When the above conventional technology is applied to inspection of RPV bottom drain piping in a pedestal of a nuclear power plant, the following problems occur.
[0006]
Within the pedestal, several hundred CRD housings fixed to the RPV stand, and the distance between them is as narrow as about 145 mm. A CRD operation cable is connected under each CRD housing, and a CRD automatic exchanger is provided at the bottom of the pedestal.
[0007]
The gap between the cables connecting them is only about 300 mm, and the bent portion (elbow portion) of the RPV bottom drain pipe to be inspected is in the center portion about 2 m away from the pedestal wall. Furthermore, due to the influence of the deposits in the reactor water, the ambient atmospheric dose is high, so it is difficult to perform work in the pedestal (particularly in the center) for a long time.
[0008]
Thus, the RPV bottom drain piping in the pedestal is in an extremely difficult environment for humans to approach and check directly. When applying the prior art described in Patent Document 1 above, it is necessary to install a traveling rail in the RPV lower pedestal. If this rail installation space and a traveling space for a small traveling vehicle cannot be secured, an inspection is required. It becomes impossible.
[0009]
For example, when the CRD casing support is installed around the RPV bottom drain pipe, or depending on the thickness of the heat insulating material for keeping the RPV drain pipe warm, the rail installation becomes impossible. In other words, it has been difficult to check the RPV bottom drain with high reliability using the conventional technology.
[0010]
An object of the present invention is to provide a pipe inspection method and a pipe inspection apparatus capable of reliably and accurately inspecting a pipe in a narrow part while reducing the exposure of an RPV bottom drain pipe in a pedestal of a nuclear power plant. It is to provide.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the reactor pressure vessel bottom drain piping inspection method according to the present invention provides a radiation irradiation port at the tip when inspecting the bottom drain piping in the pedestal located below the reactor pressure vessel. And adjusting the length of the first length-adjustable rod having the radiation irradiation port on one side of the inspection target portion, and an imaging member that projects a radiographic image of the inspection target portion on the tip portion Adjusting the length of the mounted second length-adjustable rod, installing the imaging member on the radiation receiving side of the inspection target part, and the inspection target part by the radiation irradiated from the radiation irradiation port The image is inspected by copying the image onto the imaging member.
[0012]
According to the present invention, since the length of the rod can be adjusted, the rod can be brought into a narrow pedestal. The rod can be extended around the pedestal and a radiation source or an imaging member can be installed in the inspection target portion. Therefore, unlike the conventional case, there is no need to install a small traveling vehicle traveling rail in the pedestal, and it is possible to photograph the RPV bottom drain pipe as long as a space in which these rods can be inserted is secured.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The outline of the embodiment of the present invention is that when inspecting and shooting an RPV bottom drain pipe in a narrow pedestal of a nuclear power plant, a short hollow rod that can be divided or stretched is extended on-site, and a tip part is installed in an inspection target part. A radiation source is attached to the tip of the cable and transferred to the tip of the rod through the hollow portion of the rod.
[0014]
A rod having an imaging member such as a film attached to the tip is similarly installed on the side of the inspection target that receives radiation. After radiation imaging, pull out the radiation source, shrink the rod, and withdraw. As a result, safe and reliable inspection can be performed in a narrow environment where CRD and ICM housings are forested around.
[0015]
First, an environment in which a drain pipe in a pedestal to be inspected in the present invention is provided will be described. FIG. 2 is a schematic longitudinal cross-sectional view in a primary containment vessel (PCV) and FIG. 3 is a schematic cross-sectional view in a pedestal. As shown in FIG. 2, the pedestal 2 is located below the cylindrical RPV 1 in the PCV.
[0016]
Detailed view of a part of FIG. 3 and AA arrow view are shown in FIGS. The pedestal 2 is a cylindrical space having a diameter of about 5.6 m and a height of about 4.5 m, for example. In the pedestal 2, several hundreds of CRD housings 3 fixed to the RPV 1 stand, and for example, the interval is as narrow as about 145 mm. A cable 5 for CRD operation is connected under each CRD housing 3.
[0017]
An RPV bottom drain pipe 4 for discharging the reactor water in the RPV 1 is connected to the bottom (furnace bottom) of the central portion of the RPV 1. The RPV bottom drain pipe 4 extends vertically downward from the furnace bottom, changes its direction in the horizontal direction via the elbow socket 6 at a slightly lowered position (see FIG. 4), and extends in the direction of the wall side of the pedestal 2.
[0018]
For example, the diameter of the RPV bottom drain pipe 4 is about 60 mm, and the diameter of the elbow socket 6 is about 76 mm. A portion (horizontal portion) extending in the horizontal direction of the RPV bottom drain pipe 4 is covered with a heat insulating material 7.
[0019]
For example, the height of the space through which the RPV bottom drain pipe 4 passes is about 300 mm from the floor of the pedestal 2, and the elbow portion 6 of the RPV bottom drain pipe 4 to be inspected is about 2 m away from the side wall of the pedestal 2. Located in the center.
[0020]
In the present invention, RPV bottom drain piping under the above environment is inspected by RT imaging. RT is a nondestructive inspection in which a transmission image of radiation is directly photographed on a film.
[0021]
Specifically, when the object is irradiated with radiation emitted from the radiation source, a part of the radiation is reflected, but a part of the radiation is transmitted through the object and reflected on the film on the opposite side. Since radiation has the property that the reflectance and transmittance differ depending on the material of the object, a transmission image of the object is displayed on the film. Based on this transmission image, it is possible to determine the presence or absence of defects and the thickness of the object.
[0022]
Based on the above, embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing an embodiment in which the pipe inspection method of the present invention is applied to an RPV bottom drain pipe in a pedestal at a nuclear power plant.
[0023]
First, the reactor is stopped in step S1 of FIG. In step S2, RPV1 is released, fuel in RPV1 is taken out, and moved to a fuel pool adjacent to RPV1.
[0024]
In step S3, the apparatus transfer rods 8 and 10 are extended in the pedestal 2 so that the radiation irradiation port 13 (see FIG. 6) and the imaging member 9 reach the RPV bottom drain pipe 4 to be inspected. The length of the rod is a length that can easily reach the RPV bottom drain pipe 4 from the scaffold in the pedestal 2, and the length can be adjusted.
[0025]
Next, in step S4, the rod mounting tool 12 is fixed to the CRD housing 3 and the ICM housing 14, and the radiation transfer rod 8 having the irradiation port 13 attached to the tip thereof as an axis and the imaging member 9 attached to the tip. By moving the imaging member transfer rod 10 being moved, the respective radiation rods 13 and the imaging member 9 are placed so that the inspection target portion of the RPV bottom drain pipe 4 is sandwiched therebetween.
[0026]
In the pedestal 2, there is a space in the circumferential direction in which an operator can move. By using this space, the radiation transfer rod 8 and the imaging member transfer rod 10 can be brought into a predetermined place. is there.
[0027]
In step S5, air is injected into the air injection bag 15 attached to each rod to inflate the air bag. The inflated air bag 15 comes into contact with the CRD housing 3 and the ICM housing 14 standing in the vicinity, whereby the rod is fixed to the CRD housing 3 and the ICM housing 14, and there is no need to provide a new fixing member.
[0028]
Further, in step 6, a radiation source is attached to the distal end portion of the source transfer cable 11. This is inserted into the radiation transfer rod 8, and the radiation source is transferred to the irradiation port. This is to handle the radiation source after fixing the rod in order to reduce the exposure from the radiation source by the worker. It is good. Thus, the pipe inspection in step S7 is possible.
[0029]
An example of a rod-type RPV bottom drain inspection apparatus is shown in FIGS. FIG. 7 is a BB arrow view of FIG. In this RPV bottom drain pipe inspection apparatus, a radiation source is transferred by a radiation source transfer cable 11 in a hollow radiation transfer rod 8, and the radiation is irradiated from the tip (irradiation port 13) of the radiation transfer rod 8. This is an RT imaging apparatus in which an inspection object part is imaged on a plate-like imaging member 9 installed on the opposite side of the inspection object.
[0030]
Since the radiation source and the imaging member reach the target position through the shaft rod, the CRD housing 3, the ICM housing 14, and others are closely packed, and the RPV bottom drain pipe 4 that is difficult for workers to approach. Remote RT imaging is possible.
[0031]
An example of the schematic configuration and basic operation of the inspection apparatus using the RT method will be described with reference to FIGS. This inspection device includes an imaging member 9, an imaging member transfer rod 10, a radiation transfer rod 8, a radiation source transfer cable 11, a CRD housing fixture 12, a radiation irradiation port 13, a control device, and the like as an RT imaging device. The control device is installed on a scaffold along the inner wall of the pedestal, but is not shown in the figure.
[0032]
Next, a method for inspecting the elbow portion 6 of the RPV bottom drain pipe 4 by irradiating radiation from the radiation source transferred to the radiation transfer rod tip 13 (radiation irradiation port) will be described. The radiation irradiated from the radiation source passes through the elbow portion 6 of the RPV bottom drain pipe to be inspected and is projected on the imaging member 9 provided on the opposite side.
[0033]
At this time, as shown in the layout diagram of FIG. If the distance between the radiation source and the inspection object is short, the radiation emitted from the point-like radiation source hits the inspection object before it spreads sufficiently, and the inspection range becomes small. In order to prevent this, the RPV bottom drain pipe 4 can be inspected by securing a certain distance from the RPV bottom drain pipe 4 and irradiating the radiation.
[0034]
In addition, when a necessary part is photographed by one irradiation (see FIG. 9), it is good. However, when an insufficient part occurs, the photographing part is shifted in two times (see FIG. 10) or divided into several times. Take a picture.
[0035]
After completion of the above photographing, the radiation source is collected in step S8, the air in the air injection bag 15 is removed, and the CRD housing fixture 12 is removed. This process corresponds to steps S9 and S10.
[0036]
Next, in step S11, the imaging member transfer rod 10 and the radiation transfer rod 8 are reduced and collected. After the inspection device is collected, the imaging member 9 is developed (image processing), and the state inside the pipe is confirmed.
[0037]
Next, fuel is restored from the fuel pool into the RPV 1 in step S12, and the reactor is restarted in step S13. A series of inspection work is completed by the above steps S1 to S13.
[0038]
Further, in a state where the fuel is taken out from the RPV 1, a series of operations such as attachment of the radiation transfer rod 8 and the imaging member transfer rod 10 are performed in the peripheral portion (near the side wall) in the pedestal 2, thereby It is possible to reduce exposure.
[0039]
By using the method as described above, it is possible to inspect the drain pipe 4 in the pedestal 2 that has been difficult to inspect until now, and can greatly contribute to preventive maintenance of the pipe.
[0040]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the RPV bottom drain piping in the narrow part in the pedestal of a nuclear power plant can be inspected reliably and correctly, aiming at reduction of an operator's exposure.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an embodiment in which a pipe inspection method of the present invention is applied to an RPV bottom drain pipe in a pedestal in a nuclear power plant.
FIG. 2 is a schematic longitudinal sectional view in the PCV.
FIG. 3 is a schematic longitudinal sectional view in the pedestal.
4 is a detailed view of a part a in FIG. 3;
5 is an AA arrow view of FIG. 3;
FIG. 6 is a schematic configuration diagram of an inspection apparatus using an RT method.
7 is a BB arrow view of FIG. 6;
FIG. 8 is a device layout diagram of a radiation irradiation unit in RPV bottom drain tube RT imaging.
FIG. 9 is a diagram illustrating a shooting procedure (single shooting) of an RT shooting target portion;
FIG. 10 is a diagram illustrating a shooting procedure (two shots) of an RT shooting target portion.
[Explanation of symbols]
1 RPV
2 Pedestal 3 CRD housing 4 RPV bottom drain pipe 5 CRD operation cable 6 Elbow socket 7 Insulating material 8 Radiation transfer rod 9 Imaging member 10 Imaging member transfer rod 11 Radiation source transfer cable 12 CRD housing fixture 13 Radiation source irradiation port 14 ICM Housing 15 Air injection bag

Claims (5)

  When inspecting the bottom drain pipe in the pedestal located on the lower side of the reactor pressure vessel, the length of the first length-adjustable rod having the radiation irradiation port at the tip is adjusted, and the radiation irradiation is performed. Adjusting the length of the second length-adjustable rod having the mouth installed on one side of the inspection target portion and mounting the imaging member for imaging the radiographic image of the inspection target portion at the tip portion; The reactor pressure vessel bottom drain piping is characterized in that the inspection target portion is placed on the radiation receiving side, and an image of the inspection target portion due to the radiation irradiated from the radiation irradiation port is copied and inspected on the imaging member. Inspection method.   2. The inspection method according to claim 1, wherein the first and second length-adjustable rods are configured to be split or extendable, and installation work of the rods is performed in a peripheral portion in the pedestal. Reactor pressure vessel bottom drain piping inspection method.   The inspection method according to any one of claims 1 to 2, wherein the first and second rods are provided with an air injection bag, and each of the air injection bags is inflated by injecting air into the air injection bag. A method for inspecting a reactor pressure vessel bottom drain pipe, wherein the air injection bag is brought into contact with a CRD housing and an ICM housing around the rod to fix the rod.   The inspection method according to any one of claims 1 to 3, wherein the first length-adjustable rod is a hollow rod, and the rod is transported through a hollow portion of the rod to receive radiation at the radiation irradiation port. A reactor pressure vessel bottom drain piping inspection method characterized by installing a power source. The first and second rods, which are used in the inspection method according to any one of claims 1 to 4 and are adjustable in length, wherein the tip part is installed in the inspection target part, and the first rod tip part A radiation source installed at the radiation irradiation port of the first, an imaging member attached to the tip of the second rod and capturing an image of the inspection target portion by the radiation emitted from the radiation source, and the first and second A reactor pressure vessel bottom drain pipe inspection device comprising a fixing member for fixing a rod to a CRD housing and an ICM housing around the rod.

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