JPH05188180A - Clad picking apparatus - Google Patents

Abstract

PURPOSE:To obtain a clad removing apparatus, which can prevent the leakage of clad water from a pickup container and to decrease the exposure dose of radiation for a worker to a large extent when the clad, which is removed from fuel, is picked up. CONSTITUTION:A clad removing apparatus concerned has a pickup container 8 for picking up clad water, an airtight container 1 having an observing window 5, which monitors the water level of the pickup container 8 as a water-level detecting means, and a vacuum pump 11 for reducing the pressure in the airtight container 1. A leak valve 7 opens the pressure-reduced airtight container 1 to release the pressure to the atmosphere. A hose 9 introduces the clad water as a clad-water introducing pipe. A pinch valve 10 is an opening and closing device for opening and closing the flow path of the hose 9. The apparatus is constituted by providing these parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clad collecting device for collecting a radioactive clad from an instrument such as a nuclear fuel assembly of a nuclear reactor to which the radioactive clad is attached.

[0002]

2. Description of the Related Art In a nuclear reactor such as a boiling water reactor, during operation, metallic impurities such as iron oxide contained in a coolant, so-called cladding, adheres to the surface of the fuel body. This cladding is
Cooling may be incomplete depending on the amount of adhesion or properties, and the health of the fuel may be adversely affected. In addition, since this clad is activated, the primary cooling system is contaminated, which causes radioactive exposure of workers or work environment pollution during periodic inspections.

For this reason, it is important to control water quality for the purpose of reducing radioactivity. It is necessary to sample the clad adhering to the surface of the fuel assembly to investigate the amount or properties of the clad.

FIG. 2 is an overall view showing a sampling condition of a conventional cladding. The clad is sampled at the pool site 29 of the fuel storage pool 15 in which the fuel assembly 17 is stored in water. The poolside 29 is a lifting / lowering device for the fuel assemblies 17 used in the irradiation fuel assembly inspection, which is one of the periodical inspections, such as the attachment / detachment of the fuel channel (not shown) that is the outer frame of the fuel assemblies 17. A fuel channel attaching / detaching machine 16 is installed.

A fuel assembly is attached to the fuel channel attaching / detaching machine 16.
Load 17 and sample according to the following procedure. An operator 18 rides on the operation table 26 of the fuel channel attaching / detaching machine 16 and operates the clad removing jig 19 suspended by the hook 25 of the crane to remove the clad adhering to the surface of the fuel assembly 17. This clad removing jig 19 has a long operation pole 27.
A plastic spatula (not shown) or brush 28 on the tip of the
Is installed and configured. The removed clad is collected by pumping it with a pump 21 via a hose 23 into a collection container 23 prepared as pool water 29 as clad water from a collection port 20 installed around a spatula or a brush 28. .. Alternatively, the clad water is sucked by using the vacuum pump 21, once collected in the buffer tank 22, and then transferred to the collection container 23. The collection container 23 is transferred, and the clad water is filtered by a filter (not shown). The clad is collected in the filter in this filter and then sent to the analysis step.

[0006]

Up to now, the cladding has been sampled by the above method. In the process of collecting the clad removed from the fuel together with water in the collection container, if the clad water is sampled directly into the collection container, operation error such as delay in switching off the pump or closing the valve may occur. May occur. At this time, the clad water overflows from the collection container and scatters,
It may contaminate the surroundings and the body of the worker. As described above, there is a problem in that decontamination requires a great deal of labor and time before work safety or work recovery. In addition, when the pump breaks down, the pump is contaminated with clad water, so it is necessary to take protective measures against this contamination and carry out repair work, resulting in poor worker exposure and poor workability. There were challenges. In addition, when replacing with a new pump, the used pump must be discarded, so that there is a problem that the amount of waste treated increases.

To solve these problems, there is a sampling method using a vacuum pump. According to this method
Since the vacuum pump does not come into contact with the clad water, the above problems up to the repair are solved. Further, in order to eliminate operator's mistakes in operation, a float switch is provided in the buffer tank to detect the water level, and the signal is used to close the valve, thereby reducing human error.

However, there is a case in which the clad is interposed between the float and the shaft of the float switch that moves up and down along the axis according to the water level, and the float does not operate smoothly. Due to this malfunction of the float, a malfunction may occur, the buffer tank may be filled with water, and the clad water may flow into the vacuum pump. Also in this case, there is a problem that the contaminated water flows out from the vacuum pump to contaminate the surroundings and the worker is exposed to the radiation during repair. Also, after the work is completed, the used equipment is contaminated, so there is a problem in waste treatment, and even when stored in a controlled area, there is a problem in decontamination due to the high dose rate especially in the buffer tank. there were.

The present invention has been made in view of the above points, and an object of the present invention is to provide a clad collecting device which is easy to handle and has high safety in collecting the clad removed from the fuel. ..

[0010]

In order to achieve the above object, the present invention has a collection container for collecting the clad water, and an opening / closing lid for putting the collection container in and out, and controlling the water level of the collection container. An airtight container having a water level detecting means for monitoring, a vacuum pump connected to the outside of the airtight container to depressurize the airtight container, a leak valve connected to the airtight container to open the depressurized airtight container to the atmosphere, and the airtight It is characterized by comprising a clad water introducing pipe that penetrates the container and introduces the clad water into the sampling container, and an opening / closing device that is disposed in the clad water introducing pipe and that opens and closes the flow path of the clad water introducing pipe. A clad collecting device is provided.

[0011]

With this structure, the collection container for collecting the clad water is housed in the airtight container provided with the water level detection means to form a double container structure. The clad water is introduced into the sampling container via the clad water introducing pipe that penetrates the airtight container. This clad water is transferred by depressurizing the airtight container with a vacuum pump. Further, the flow rate of the clad water is adjusted by opening and closing an opening / closing device provided in the middle part of the clad water introducing pipe. When the collection container in which the clad water is collected is taken out from the airtight container, it is necessary to open the leak valve connected to the airtight container and open the depressurized airtight container to the atmosphere.

As described above, the airtight container containing the sampling container is decompressed. The airtight container is depressurized and the clad water is introduced into the sampling container. The water level in this collection container can be confirmed by the water level detection means set in the airtight container. After the clad water is filled in the collection container, close the switchgear,
Stop the vacuum pump. The amount of the clad water collected is adjusted by operating the vacuum pump and opening / closing the opening / closing device.
After the collection is completed, the leak valve is opened to open the airtight container to the atmosphere, the collection container is taken out from the airtight container, and a series of collection work is completed.

Even if the switchgear is forgotten to be closed during sampling and the clad water overflows from the sampling container, the sampling container is housed in an airtight container to form a double-vessel structure. The clad water is not accumulated in the airtight container without scattering to the outside of the container and is not discharged to the outside. Further, the wetted portion of the clad water that causes contamination is limited to the clad water introduction pipe and the collection container during normal operation. In this way, the vacuum pump, which is the drive unit, does not come into contact with the clad water, so it is not contaminated, and maintenance and inspection of main equipment such as the vacuum pump can be easily performed, and the exposure of workers can be reduced. it can.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a side view showing a clad collecting apparatus according to the present invention partially cut away. In addition, FIG. 1 is a schematic view showing a conventional clad sampling state in FIG. 2, in which a clad sampling device including a vacuum pump 21, a buffer tank 22 and a sampling container 23 is replaced with a clad sampling device according to the present invention. The hose 24 is replaced with the hose 9.

The outer frame of the present clad extracting device is formed by a cylindrical airtight container 1. On the upper surface of the airtight container 1, there is installed an opening / closing lid which is rotatably fixed by a hinge 33 and airtightly held by an O-ring 2. A set screw 4 for tightening and fixing the opening / closing lid 3 and the body of the airtight container 1.
And an eye hook 34 for transferring the entire apparatus are airtight containers 1.
Installed on top of the. A peep window 5 as a water level detecting means is provided at a position facing the side surface of the airtight container 1.
The other viewing window is not shown. Further, a pressure gauge 6 for detecting the pressure inside the airtight container 1 and a leak valve 7 for opening the depressurized airtight container 1 to the atmosphere are provided with the airtight container 1
Connected to the side of.

Inside the airtight container 1, a translucent resin sampling container 8 is housed. In this collection container 8, a translucent resin hose 9 which is a clad water introduction pipe penetrates the side wall of the airtight container 1 from the collection port 20 of the clad removing jig 19 shown in FIG. Be introduced through. A pinch valve 10, which is an opening / closing device that opens and closes the flow path by pressing the hose 9, is arranged in the middle of the hose 9. This pinch valve 10 is for opening and closing the flow path by pressing the elastic hose 9, and has a feature that the clad water does not stay because it has no pocket part in the middle of the flow path. ing. The flow rate of the clad water can be adjusted by disposing an opening / closing device such as a valve or a cock instead of the pinch valve 10 in the middle of the hose 9.

A vacuum pump 11 for reducing the pressure of the airtight container 1 is installed outside the airtight container 1. This vacuum pump 11
Is a valve 13 for opening and closing the flow path through the pipe 12.
Is connected to the inside of the airtight container 1 via. Next, the operation of this embodiment having such a configuration will be described.

After loosening the set screw 4 and opening the opening / closing lid 3, the collection container 8 is housed in the airtight container 1. In order to confirm the amount of clad water collected in advance in this collection container 8,
Show the scale. The collected sampling container 8 is positioned so that the scale can be confirmed through the observation window 5, and then the tip of the hose 9 is put into the sampling container 8 having the inner lid 14. After closing the opening / closing lid 3, the opening / closing lid 3 is fixed to the main body of the airtight container 1 with the set screw 4. The valve 13 on the suction side of the vacuum pump 11 is opened, and the leak valve 7 and the pinch valve 10
Make sure that is closed. The switch of the vacuum pump 11 is turned on to reduce the pressure in the airtight container 1. When the indication of the dynamometer 6 indicates a predetermined pressure, the pinch valve 10 is opened.
Cladding water is introduced into the collection container 8 via the hose 9. The water level in the collection container 8 is monitored by the sight glass 5. Since the inside of the airtight container 1 is dark, this water level may be difficult to see. In this case, the collection container 8 is illuminated with a lighting tool (not shown) from a facing viewing window (not shown). When the water level reaches a predetermined level, the vacuum pump 11 is stopped, the leak valve 7 is opened, and the airtight container 1 is opened to the atmosphere. Collection of the clad water is completed by loosening the set screw 4 and opening the opening / closing lid 3 and taking out the collection container 8.

Even if the pinch valve 10 is forgotten to be closed during collection and the clad water overflows from the collection container 8, the clad water is immediately sealed because the double container structure is constructed.
It does not scatter to the outside and can be retained in the airtight container 1.

When it is desired to change the time required to collect a fixed amount of clad water, there is a method of changing to a vacuum pump 7 of a type having different performance or adjusting the opening / closing amount of the pinch valve 10 and the valve 13.

The time for collecting a fixed amount is determined by the degree of straightness in the airtight container 1. This degree of vacuum can be lowered to some extent according to the operating time of the vacuum pump 11.
When the inside of the airtight container 1 is evacuated for a predetermined time and then kept airtight, the airtight container 1 can maintain a certain degree of vacuum. When the clad water is collected from a state where a certain degree of vacuum is maintained, the clad water is collected at a speed corresponding to this degree of vacuum. The sampling time can be changed by measuring the operating time of the vacuum pump 11 with a stopwatch (not shown) in advance so as to obtain the optimum sampling time or by adjusting the indicated value of the pressure gauge 6 as a guide. In this case, in order to temporarily seal the inside of the airtight container 1 after the inside of the airtight container 1 is evacuated by the vacuum pump 11 for a certain time, the valve 13
Then, the vacuum pump 11 is stopped. After that, the pinch valve 10 is opened to collect the clad water in the collection container 8.

At the time of collection, care must be taken that the device is contaminated, since the clad water that causes contamination is handled. In the device according to the present invention, the portion where the clad water comes in contact is limited to only the hose 9 and the collection container 8. The vacuum pump 11, which is the other drive unit, is not contaminated during normal operation.

It is necessary to drain the clad water remaining in the hose 9 at the time of cleaning up after using this device. Since the vacuum pump 11 used in this embodiment is a pump for both depressurization and pressurization, it is possible to drain water in two directions. One of them is a method of sucking the clad water remaining in the hose 9. The other is a method of extracting residual water by pressurizing the inside of the airtight container 1. In the method described later, the pipe 12 is spliced from the suction port 31 of the vacuum pump 11 to the discharge port 32 on the pressurizing side. The apparatus of the present embodiment is an apparatus for collecting by collecting the clad together with water, so that the object to be sucked is not limited to the clad. If there is a small metal piece or dust deposited in water that is small enough to be sucked by a vacuum pump and smaller than the inner diameter of the hose, it can be collected in a state in which the original shape is relatively not damaged.

As described above, according to this embodiment, since the present apparatus is composed of a combination of simple parts and can be collected by a simple valve operation, the workability is very good. The amount of clad water collected can be monitored at any time through the observation window to monitor the water level in the collection container, so work can be performed with peace of mind. In addition, since the amount to be collected can be adjusted arbitrarily, the required amount can be efficiently collected. Also, even if clad water overflows from the collection container due to forgetting to close the pinch valve during clad water collection, the clad water has a double structure, so the clad water does not immediately scatter and is kept in an airtight container. Stays in
Contamination spread is prevented and it can be handled safely.

Further, the clad collecting device according to the present embodiment is constructed so that the portion where the clad water comes into contact with the clad water during collecting is the minimum necessary. Therefore, after use, if the hose contaminated with the clad water and the collection container are disposed of, it is not necessary to decontaminate the remaining main part of the device, so the treatment of the device is easy. .. Also, since the main equipment such as the vacuum pump, which is the driving part, is not contaminated, the maintenance and inspection of this device is easy, and the radiation exposure of the operator can be greatly reduced.

[0027]

As described above, according to the clad residual device according to the present invention, in collecting the clad removed from the fuel, by duplicating the collection container, the contamination by the clad water can be expanded. It is possible to prevent and significantly reduce the radiation exposure amount of the worker.

[Brief description of drawings]

FIG. 1 is a side view showing a clad extracting device according to an embodiment of the present invention with a part thereof cut away.

FIG. 2 is an overall view showing a conventional clad sampling condition.

[Explanation of symbols]

 1 ... Airtight container 3 ... Open / close lid 5 ... Peep window 7 ... Leak valve 8 ... Collection container 9 ... Hose 10 ... Pinch valve 11 ... Vacuum pump

Claims (1)

[Claims] 1. An airtight container having a collection container for collecting the clad water, an opening / closing lid for putting the collection container in and out, and a water level detecting means for monitoring the water level of the collection container, and an outside of the airtight container. A vacuum pump connected to depressurize the airtight container, a leak valve connected to the airtight container to open the depressurized airtight container to the atmosphere, and a clad water introduction penetrating the airtight container to introduce clad water into the sampling container A clad extracting device comprising: a pipe; and an opening / closing device which is arranged in the clad water introducing pipe and opens and closes a channel of the clad water introducing pipe.