JPS62289800A - Decontaminator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Field of Industrial Application) The present invention is a method for cleaning the inside of a nozzle of a reactor pressure vessel installed in a nuclear power plant, for example. Regarding decontamination equipment.

(Prior Art) A nozzle 1 of a nuclear reactor pressure vessel is provided with a thermal sleeve 2, as shown in FIG. 2 to the piping 4 connected to the pipe 2 without causing any significant thermal stress.

An annular space 5 with one end closed is formed between the nozzle 1 and the V-maru sleeve 2 by welding the outer piping side end of the maru sleeve 2 to the nozzle 1. 1! Rust, scale, etc. with strong radioactivity generated from piping, equipment, etc. during furnace operation! The accumulation of ray contaminants during non-destructive testing to confirm the soundness of nozzle welds results in exposure to radiation during work, making the work more difficult.

Therefore, before conducting a non-destructive inspection of the nozzle weld,
High-speed water is injected into the annular space to remove radioactive contaminants that have accumulated inside the nozzle, thereby reducing the length of the nozzle by 4 meters during non-destructive testing.

(Problems to be Solved by the Invention) As mentioned above, the high-speed water injection device, which injects high-speed water into the air and cleans the wall surface by the WJ impact generated when the high-speed water jet collides, cannot be used underwater. In this case, unlike a water jet in the air, the jet spreads and decelerates significantly, making it impossible to collide the water jet over the entire wall surface of the annular space formed between the nozzle and the nozzle.

Therefore, the present invention solves the above-mentioned problems by forming a flow of water in the annular space at one end with a narrow gap, so that the substances accumulated in the annular space can be reliably discharged. The purpose is to provide decontamination equipment.

[Structure of the invention]

(Means for solving the problem) In the decontamination device of the present invention, a pressure water supply device for supplying pressure water is connected to a nozzle header having a water injection nozzle, and the nozzle header can be remotely controlled. The pipe clamping device is configured to connect the water injection nozzle of the nozzle header to a predetermined position relative to the arrangement to be treated.

(Function) In the decontamination apparatus of the present invention, by operating a remotely controllable pipe clamp device, the nozzle header is attached to the outer surface of the pipe, and the water jet nozzle is attached to the annular shape formed by the pipe and a member located outside the pipe. When the pressurized water supply device is operated, pressure water is injected from the water injection nozzle into the annular space, forming a circulating flow within the annular space, and this circulating flow causes the annular Materials deposited in the space are discharged.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In Fig. 1, the same members as in Fig. 1 are given the same reference numerals.

In FIG.
A nozzle header with a curved surface corresponding to the outer peripheral surface of the nozzle header,
This nozzle header 10 has piping 4 as shown in FIG.
The pipe 4 is sheathed so as to be located on a perpendicular line 11 passing through the center of the pipe 4. The nozzle header 10 is connected via a conduit 12 to a pump 13 provided outside the reactor pressure vessel.

As shown in FIG. The thermal sleeve 2 is designed to inject into the annular space 5 formed between the nozzle 1 and the thermal sleeve 2. Furthermore, clamp attachments 16.16 are provided on both sides of the nozzle header 100 via single-nozzle members 15.15.

The clamping device 16i is of a hydraulic, pneumatic or electromagnetic type, for example, and includes a drive source 17 and a control unit.
11 devices 18.

Further, the diameter of the water injection nozzle 14 is set to be smaller than the radial width of the annular space 50.

Next, the effect will be explained.

When decontaminating the inside of a reactor pressure vessel nozzle in a nuclear power plant, first, the nozzle header 10 is lowered from the top of the pressure vessel to a predetermined position of the pressure vessel nozzle 1, the control device 18 is activated, and the piping is installed with the clamp attachment 16.16. Hold 4. This completes the fixing of the nozzle header 10 to the piping 4.

Next, the pump 13 is actuated to inject pressurized water from the water injection nozzle 14 provided in the nozzle header 10 into the annular space 5 formed between the nozzle 1 and the round sleeve.

The flow velocity of the jet stream from the water jet nozzle 14 is 7 m/sec ~
At 20 m/sec, the flow in the annular space 5 does not change significantly within the range of the nozzle outlet flow velocity, as shown in Fig. 3, and the jet from the jet DI nozzle becomes a free jet and greatly changes. It does not spread and goes straight to the bottom RB of the annular space 5. The jet flow that has reached the bottom part is divided into left and right parts, proceeds in the circumferential direction, and merges around 180 degrees from the injection nozzle position to form a flow heading toward the inlet. At the part where the jet splits into left and right,
A pair of large, stable vortices are formed, and upstream, a small, unstable vortex is created along the jet.

That is, a dead water region where the flow is very small exists near 180° at the bottom of the annular space, and large dead water regions occur near 90° J3 and 270° at the entrance.

The difference in the decontamination effect due to the change in the installation position of the injection nozzle with respect to the annular space 5 when a radioactive contaminant with a higher specific gravity than water is deposited in the annular space 5 will be shown below.

When the jet was applied vertically from the top, most of the radioactive contaminants were discharged, but some of the radioactive contaminants deposited in the dead water area at the bottom remained at the bottom without being discharged. In addition, the released rJ4 that had accumulated in the dead water area at the entrance
The line pollutants will descend and be discharged as the lower eJ PEA pollutants are discharged.

If the jet is applied from a horizontal position, the radioactive contaminants will not be discharged and will remain in the dead water region generated below the entrance of the annular space.

When a jet is applied vertically from the bottom, radioactive contaminants located at the bottom of the annular space tend to be rolled up by the jet and discharged by the reverse flow near the top, but radioactive contaminants with relatively large particle sizes The substance does not reach the backflow area and remains somewhat in the horizontal area.

When the jet stream is moved by an angle θ from the top in the vertical direction, as shown in FIG.
9 shifts from the 180° position to the 270° side by an angle θ, and the dead water area 20 of the artificial part shifts from the 90° position to the 270° side.
Shift to the ° side by an angle θ.

That is, as the position of the water injection nozzle 14 is increased from the angle θ position on the vertical line to the angle θ, the dead water area 19 at the bottom
Because the radioactive contaminants move downward due to gravity, θ-15
All the radioactive contaminants deposited there will be discharged within 30°.

On the other hand, as the angle θ increases, the dead water area Lm 20 at the inlet also moves downward, so if θ exceeds 45 degrees, radioactive contaminants will be deposited there and remain without being discharged.

In the above embodiment, the water injection nozzle was moved clockwise, but it goes without saying that the same effect can be achieved if the water injection nozzle is moved counterclockwise.

FIGS. 5 and 6 show other embodiments of the present invention. In the embodiment shown in FIG. Nozzle holes 31, 31, .

In one embodiment shown in the sixth [A], the water injection nozzle 110
An elongated slit/hole 41 having the same curvature as that of the annular space is provided in the annular space. The width of this slit box 410 is set smaller than the radial width of the annular space.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to discharge the substances accumulated in the annular space h It has the effect of being able to reliably decontaminate radioactive contaminants that accumulate on a pressure vessel, and also being able to be used as a nozzle inner surface cooling device when welding and repairing a pressure vessel nozzle part.

[Brief explanation of drawings]

Figure 1 is a diagram showing the state of use in front of the decontamination station according to the present invention, Figure 2 is a diagram taken along the line ■-■ in Figure 1, and Figure 3 is a diagram showing the state of water flow formed in the annular space. Figure 4 is a diagram showing the variation of the dead water area depending on the position of the water injection nozzle with respect to the piping,
FIG. 5 J3 and FIG. 6 are diagrams showing other embodiments of the present invention,
FIG. 7 is a sectional view showing the nozzle portion of the pressure vessel. 1... Nozzle, 2... Gumar sleeve, 5...
Annular space, 10... Nozzle header, 14... Water injection nozzle, 16... Clamp device, 18... II
12υ device. Applicant's representative Embryo - Male - ■ Figure 1 Figure 5 Figure 6

Claims (1)

[Claims] 1. A nozzle header having a water injection nozzle, a remotely controllable piping clamp device connected to the nozzle header to position the water injection nozzle of the nozzle header at a predetermined position with respect to the piping, and A decontamination device having a pressure water supply device for feeding pressure water to a water injection nozzle. 2. The decontamination device according to claim 1, wherein the diameter of the water injection nozzle is set smaller than the radial width of the annular space formed by the pressure vessel nozzle and the thermal sleeve. 3. The decontamination device according to claim 1 or 2, wherein a plurality of water jet nozzles are arranged on the same circle.