JP4324896B2 - Gas recovery device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas recovery apparatus, and more particularly to an apparatus suitable for recovering a gas (gas) generated during cutting or processing of a reactor internal structure in a preventive maintenance technique for nuclear plant structural materials.
[0002]
[Prior art]
Replacement of the internal structure of the nuclear reactor in the BWR power plant with new materials, etc., or disposal after the end of its useful life is under consideration. Since the existing in-furnace structure itself is radioactive or attached with radioactive cladding, cutting associated with replacement or dismantling is mainly performed in water from the viewpoint of reducing exposure. Although the cutting method will be described here, the same applies to processing such as welding.
[0003]
As the cutting method, thermal cutting by plasma or electric discharge, or mechanical cutting by a water jet containing a cutter or an auxiliary material is used. When the thermal cutting is performed, the cut portion becomes a high temperature, and water electrolysis occurs in the electric discharge machining, so that hydrogen, oxygen, carbon monoxide, carbon dioxide and the like are generated.
[0004]
These gases (gases) generated at the time of cutting incorporate structural elements of the structural material, and the gas has high radioactivity, so that the gas is recovered with high efficiency and the radiation level on the work floor is kept low. is required.
[0005]
As a method for recovering the gas generated at the time of cutting, there are known a method of sucking as gas-liquid mixed water to perform gas-water separation and a method of providing a hood. The steam-water separation method is a method of collecting gas so that the flow rate of water is slower than the rising speed of bubbles in the container.
[0006]
In this method, the container diameter and container length are determined, and when gas-liquid mixed water is introduced, bubbles accumulate in the upper part of the container at a low flow rate, and the gas is usually discharged from the conduit provided in the upper part. Is. JP-A-6-119191 is an example of the air-water separation.
[0007]
[Problems to be solved by the invention]
In the nuclear reactor, it is necessary to cut the water at a depth of 20m to 30m, and in order to suck water from the pump, a large suction pressure is required. The inside is also low pressure.
[0008]
Conventionally, the conduit for discharging the gas in the air / water separation container has been opened to the atmosphere or into the water. However, as the suction depth of the pump increases, the air / water separation container increases as the suction pressure of the pump increases. Since the pressure inside becomes lower and also lower than the atmospheric pressure, it becomes difficult for the separated gas to move through the conduit.
[0009]
The gas staying in the container is sucked into the pump and discharged together with the waste water, or the staying further proceeds while remaining in the container. Therefore, there is a possibility that complete suction cannot be performed.
[0010]
From the above, gas (gas) can be easily discharged when sucked from the surface of the water, but if the difference between the suction head and the water head is large, the pressure in the container is greatly reduced, making it difficult to discharge the gas. There is a problem of becoming.
[0011]
The problem of the present invention is that the gas generated during the cutting or processing of the reactor internal structure contains radioactive components, and the generated gas is highly efficient and safe in order to reduce exposure during work as much as possible. It is to reliably collected.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention devised means for further reducing the pressure in the exhaust system from the pressure in the steam separator.
[0013]
That is, a suction pump that sucks gas-liquid mixed water containing a gas generated during cutting or processing of the reactor internal structure from a suction port near the cutting or processing unit, and provided between the suction pump and the suction port A gas-liquid separator that separates the sucked gas-liquid mixed water into gas and liquid, an exhaust pump that sucks and exhausts the gas in the gas-liquid separator, and the suction pressure of the exhaust pump is The gas recovery apparatus is configured by including an adjusting means for adjusting to a value lower than the suction pressure of the suction pump .
[0014]
In addition, for leaks at the suction port near the gas generation site and gas that could not be separated from water, it can be safely and reliably collected using an antistatic conductive cover that can cover the entire cutting area. I did it.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a main work process (step: S) when the present invention is applied to repair work in a nuclear reactor.
[0016]
As shown in FIG. 1, after stopping the reactor (S1), the lid of the pressure vessel is removed and opened (S2), and uranium fuel is first taken out and stored (S3). Next, the equipment in the furnace that interferes with the work is taken out (S4), and a repair device is installed (S5).
[0017]
Next, repair work is performed (S6). At this time, the present invention is applied to the case of recovering gas generated during cutting or processing. After the repair work, the repair device is removed (S7), the stored fuel is returned to the reactor (S8), the equipment inside the reactor is reinstalled (S9), the pressure vessel lid is closed (S10), and the reactor Is activated (S11).
[0018]
Here, the term “processing” refers to the case where it is generated by stirring when water is sprayed on the material, such as when part or all of the existing structural material is welded, the case where the surface of other materials is processed, due to heating by a heater, etc. Etc.
[0019]
This is because the radioactive cladding is also attached to the surface as well as cutting the radioactive parts of the structural material in the reactor, and these radioactive claddings are included in the gas generated when processing only the surface. This is because there is a possibility.
[0020]
Moreover, although the embodiment of the gas recovery process of the present invention in the above work process is shown below, when taking out in-furnace equipment other than the above repair work, for example, in handling work such as replacement or disposal of the in-furnace structure The present invention can be applied when there is a risk of generating a gas containing a radioactive substance.
[0021]
Hereinafter, an embodiment of the gas recovery process according to the present invention in the above-described work process and the like will be described. FIG. 2 shows a first embodiment of a gas recovery apparatus to which the present invention is applied. As shown in FIG. 2, when cutting the in-furnace structure installed in the pressure vessel 10, for example, the cutting device 21 accessing the cutting material 1 is operated by the power source 22 to perform the cutting operation.
[0022]
The gas (gas) generated in this operation becomes gas-liquid mixed water and is sucked from the suction port near the cutting portion, passes through the steam / water separator 4, the pump 3, and the purification filter 6, and is atomized from the sprinkling port 15. Drained into the furnace well 11.
[0023]
Further, the gas separated by the steam separator 4 passes through the exhaust pump 5, passes through the air filter 8, and is discharged by the blower 9. A hood 16 is provided on the rear stage side of the exhaust pump 5 in order to reliably recover the gas.
[0024]
When the gas flow is reduced and the gas is exhausted in the steam / water separator 4, if the suction part, that is, the cutting site is at the lower part of the pressure vessel 10 or if the flow rate of the pump 3 is large, the steam / water separator 4 Becomes low pressure.
[0025]
FIG. 6 shows the relationship between the pump flow rate and the pressure in the steam separator. It can be seen that the lower the water depth in the suction section and the higher the flow rate, the lower the pressure. Therefore, in FIG. 2, the exhaust pump 5 is installed in the exhaust system of the steam separator 4, and the exhaust system can be exhausted by making the pressure of the exhaust system lower than the pressure in the steam separator.
[0026]
A jet pump was used as an example of the exhaust pump. At this time, since the pressure in the steam separator is determined by the pump flow rate and the water depth, the pressure in the exhaust system is grasped using the correlation shown in FIG. 6, and further, as shown in FIG. The pump can adjust the pressure of the exhaust system by the driving water flow rate.
[0027]
Therefore, exhaust can be performed by adjusting the valve 17 in advance or during suction to set an appropriate flow rate. The exhaust pump 5 can be driven without changing the water level and turbidity in the reactor well by using the clean water that has passed through the purification filter 6.
[0028]
According to the first embodiment, the gas exhausted by the exhaust pump 5 is sucked by the blower 9 and passes through the air filter 8 so that the radioactive component is filtered and released. Therefore, since the gas can be exhausted and collected with high efficiency, it is possible to suppress the radioactivity concentration on the floor, to achieve the minimum necessary exposure of the worker, and to prevent troubles in the work.
[0029]
FIG. 3 shows a second embodiment of the gas recovery apparatus to which the present invention is applied. FIG. 3 shows a configuration in which the pressure P1 in the steam separator and the pressure P2 in the exhaust system can be monitored by pressure gauges 71 and 72, respectively, in the configuration of FIG.
[0030]
In the apparatus of FIG. 2, the jet pump flow rate is adjusted based on the relationship between the pump flow rate and the steam-water separator internal pressure, and the relationship between the jet pump and the suction pressure. However, since the pressure during operation is monitored in this example, the flow rate can be set and adjusted even when used at an arbitrary flow rate and depth.
[0031]
According to the second embodiment, the flow rate of the jet pump is adjusted from the pressure P1 in the steam separator, and P1> P2 is set so that the pressure P2 of the exhaust system becomes low. Exhaust at flow rate and water depth is possible.
[0032]
FIG. 4 shows a third embodiment of the gas recovery apparatus to which the present invention is applied. When the amount of gas contained in the sucked gas-liquid mixed water is small, it is not always necessary to perform the exhaust operation. The example shown in FIG. 4 is an example in which the gas separated by the steam separator 4 is small, and the gas accumulated in the steam separator is discharged after a certain time has elapsed. The opening and closing of the solenoid valve 18 for adjusting the amount of water is periodically operated by the timer 13.
[0033]
According to the third embodiment, since the gas can be collected periodically by the timer, it is possible to prevent the exhaust pump from operating before the gas is accumulated, and the simple configuration. The timer allows efficient gas recovery.
[0034]
The gas that has been separated into the steam and water stays in the upper part of the steam and water separator 4, and the retention amount increases with the passage of time, and the water level in the steam and water separator decreases. In order to guide the suction water to the steam separator, it is desirable that the water surface in the steam separator is above the suction port of the steam separator. Considering the size of the air / water separator, the water surface can be held above the suction port.
[0035]
FIG. 5 shows a fourth embodiment of a gas recovery apparatus to which the present invention is applied. This example is an embodiment that can be applied when the amount of gas generated is irregular or when the effect of the steam separator 4 is not constant.
[0036]
In FIG. 5, a liquid level gauge 14 for detecting the water level in the steam separator is provided, the liquid level in the steam separator is monitored, and a preset liquid level is obtained when a large amount of gas is sucked. In this embodiment, the solenoid valve 18 is opened and the gas is discharged when it falls below. It is desirable to set the liquid level as described in the third embodiment of FIG.
[0037]
According to the fourth embodiment, the gas amount in the steam separator is detected, and the gas is recovered according to the gas amount above a certain level. Recovery can be performed.
[0038]
FIG. 8 is a diagram showing a fifth embodiment of a gas recovery method and apparatus to which the present invention is applied. In the first embodiment, the gas separated by the steam separator 4 is guided to the air filter 8, but if the separation efficiency is not 100%, it passes through the purification filter 6, and there is residual gas at the water spout 15. To do.
[0039]
Residual gas may be released into the air, leading to an increase in radioactivity concentration. In the example of FIG. 8, a conductive cover 12 is provided so as to cover the reactor well 11 in order to collect the residual gas and the gas that could not be sucked by the suction port of the work site.
[0040]
The gas in the conductive cover 12 is sucked by the blower 9, and when passing through the air filter 8, the radioactive substance is filtered and released as clean air. In addition, the conductive cover 12 needs to have conductivity in order to prevent adsorption of gas components due to static electricity, and a resin sheet is suitable for the material because of the ease of installation work. is there.
[0041]
According to the fifth embodiment, the remaining gas such as the gas remaining in the water spout and the gas that could not be sucked from the suction port can be recovered almost completely. Therefore, these residual gases are prevented from being released into the air, and an increase in radioactivity concentration in the air can be suppressed.
[0042]
According to the above embodiment, by using the device for forcibly exhausting the gas in the steam-water separation container and the conductive cover that can cover the entire cutting area, the gas containing the radioactive component can be efficiently produced. In addition, it can be recovered safely and reliably.
[0043]
【The invention's effect】
According to the present invention, it is possible to efficiently recover a gas containing a radioactive component generated during cutting or processing of a reactor internal structure, and the gas component released into water is electrostatically adsorbed to a hood or the like. The radiation level on the work floor can be kept low, and exposure during work can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing a work process during repair work to which the present invention is applied.
FIG. 2 is a diagram showing a first embodiment of a gas recovery apparatus of the present invention.
FIG. 3 is a diagram showing a second embodiment of the present invention.
FIG. 4 is a diagram showing a third embodiment of the present invention.
FIG. 5 is a diagram showing a fourth embodiment of the present invention.
FIG. 6 is a diagram showing the relationship between the pump flow rate and the pressure in the steam / water separator.
FIG. 7 is a diagram showing a relationship between a jet pump flow rate and a suction pressure.
FIG. 8 is a view showing a fifth embodiment of the gas recovery apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cutting material 3 Suction pump 4 Air-water separator 5 Exhaust pump 6 Purification filter 8 Air filter 9 Blower 10 Pressure vessel 11 Reactor well 12 Conductive cover 13 Timer 14 Liquid level indicator 15 Water spout 16 Hood 17 Valve 18 Solenoid valve 21 Cutting device 22 Power supply 71, 72 Pressure gauge

Claims (9)

A suction pump for sucking gas-liquid mixed water containing gas generated during cutting or processing of the reactor internal structure from a suction port near the cutting or processing unit , and provided between the suction pump and the suction port; A gas-liquid separator that separates the sucked gas-liquid mixed water into a gas and a liquid; an exhaust pump that sucks and exhausts the gas in the gas-liquid separator ; and a suction pressure of the exhaust pump A gas recovery apparatus comprising adjusting means for adjusting to a value lower than the suction pressure . The exhaust pump is a jet pump driven by water that has passed through a purification filter via the gas-liquid separator and the suction pump, and the adjusting means is a valve that adjusts the flow rate of the driving fluid of the jet pump. The gas recovery apparatus according to claim 1 . The gas recovery apparatus according to claim 1 , further comprising a timer for performing driving of the exhaust pump at a preset time interval. The gas recovery apparatus according to claim 1 , further comprising a liquid level meter for driving the exhaust pump at a preset liquid level in the steam separator. To recover the suction leak gas or gas which has passed through the gas-liquid separator, from cutting or machining point of the reactor structure, consisting comprises a conductive cover for covering the reactor well claims 1 to 4 A gas recovery device according to any one of the above. The gas recovery apparatus according to any one of claims 1 to 5 , further comprising an air filter for purifying the gas separated by the gas-liquid separator. The gas generated during the cutting or processing of the reactor internal structure includes bubbles generated by agitation when water is sprayed on the material surface, steam generated by heating, or bubbles generated by a jet flow when a substance collides. The gas recovery device according to any one of claims 1 to 6 , wherein the gas recovery device is included. After opening the reactor pressure vessel and taking out uranium fuel and equipment interfering with the work, the reactor internal structure was cut or processed, and after the work was completed, the uranium fuel and equipment were reinstalled. In the method of handling a reactor internal structure, the gas generated during the cutting or processing of the reactor internal structure is recovered by the gas recovery device according to any one of claims 1 to 7. How to handle reactor internals. The method for handling a reactor internal structure according to claim 8 , wherein the cutting or processing operation of the reactor internal structure is performed for repair, replacement or disposal of the reactor internal structure.

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