JPH0711593B2 - Radioactive solid waste cutting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radioactive solid waste cutting device, and more particularly to a spent fuel channel box which is a highly radioactive solid waste generated from a boiling water nuclear power plant ( The present invention relates to a radioactive solid waste cutting device suitable for application to cutting volume reduction processing such as FCB).

[Conventional technology]

In the conventional apparatus, as described in JP-A-59-187298, a potential difference is provided between the object to be cut and the cutting torch, an arc or plasma is generated during this, and the object to be cut is melted and cut by its thermal energy. It was something to do. However, in this method, it is a basic cutting condition that the object to be cut is a conductor,
It is impossible to cut non-conductors such as ceramics. However, the longer the period of use of the FCB to be cut by this device, that is, the higher the burnup, the higher the degree of burnup, the more the ceramic-like non-conductor adheres to the surface of the FCB. There is a problem that an arc or plasma is difficult to generate between the cutting torch and stable cutting cannot be performed. As a countermeasure for this, it is conceivable to remove the deposits on the surface of the FCB in advance and then perform a cutting procedure, but this complicates the work procedure and results in poor work efficiency. Also, in the conventional device, the cutting torch is fixed,
The structure is such that the object to be cut is moved and cut, but this is because such a structure requires the fixing of the cutting torch because of the adoption of the polar water jet cutting method and the like. It was also in summer.

In this structure, since the object to be cut is moved and cut in water, the water depth must be at least twice the depth of the object to be cut and the sum of both the water depth for shielding.

As a result, the overall length of the device becomes very large,
The depth of pool water installed by this device must be deep.

In addition, the conventional cutting technique is a method in which a potential difference is created between the cutting torch and the object to be cut, and plasma or arc is generated during this cutting, so that the cutting torch is used to maintain plasma or arc stability for cutting. It is necessary to keep a constant distance (standoff) from the object to be cut. If the plasma or arc is extinguished,
Highly accurate initial position setting (standoff setting) is required to start cutting, and workability is considerably troublesome.

Furthermore, in the hot-water type water cutting, by-products such as molten cutting waste and suspended solids in water that are generated during cutting are increased, so that the life of the filter is short and the amount of the filter as secondary waste is also small. Many.

[Problems to be solved by the invention]

As explained above, the conventional device cannot be applied to the underwater cutting of a workpiece with a ceramic-like non-conductor attached to the surface, such as a comparatively high baking degree FCB, and the cutting torch is fixed and By adopting a structure that moves and cuts the object to be cut that is radioactive solid waste, the entire device becomes large,
There were problems such as the pool water depth for installing the equipment was deep.

An object of the present invention is to provide a radioactive solid waste cutting device capable of stably cutting radioactive solid waste to which non-conductors are attached in water, suppressing pollution of pool water, and preventing workers from being exposed to radiation. To do.

[Means for solving problems]

The feature of the present invention that can achieve the above-mentioned object is a partition that is installed in pool water and that stores a radioactive solid waste that is an object to be cut to which a non-conductor is attached by separating it from the surrounding environment, and the radioactive in the partition. A non-transfer type underwater plasma cutting torch for cutting solid waste, a drive mechanism for moving the cutting torch, a support for supporting the radioactive solid waste in the partition wall, and controlling the drive mechanism A control panel, a means provided at the upper end of the partition wall to collect gas in the partition wall, dilute the gas with the atmosphere and exhaust the gas, and a means provided at the lower end part of the partition wall to cut off the radioactive solid exhaust gas. And a means for purifying the water in the partition wall.

[Action]

The cutting torch provides a potential difference between the nozzle caps of the electrode rod, flows a rare gas such as argon gas into the space formed by the electrode rod and the nozzle cap, and ejects it from the tip of the nozzle cap in a plasma state. The plasma heat cuts the object to be cut. Therefore, plasma is always obtained in a stable state regardless of the change in standoff during cutting. That is, since the non-transfer type underwater plasma type cutting torch is used, the radioactive solid waste to which the non-conductor is attached can be stably cut in water.

Further, according to the present invention, since it has means for collecting the gas in the partition wall, diluting it with the atmosphere and exhausting it, the gas is diffused into the pool water and discharged above the pool water surface. This can prevent workers from being exposed to radiation.
Moreover, since there is a means provided at the lower end of the partition wall for collecting the molten cutting waste generated by cutting the radioactive solid exhaust and a means for purifying the water in the partition wall, the recovery of the molten cutting waste and the water in the partition wall Can perform purification, melt cutting waste,
In addition, it is possible to suppress pool water pollution due to diffusion of floating water in the partition wall into the surrounding pool water.

Furthermore, specifically, since the cutting torch is connected with a flexible hose and a cable, by providing the cutting torch with a guide rail or the like on the side surface of the partition wall of the device,
It is possible to move up and down along this guide rail and move it along the cutting line of radioactive solid waste (FCB), which is the object to be cut.

〔Example〕

In this embodiment, the non-transfer type underwater plasma arc is adopted as the cutting method. Generally, in plasma arc cutting (transfer type), a potential difference is provided between the cutting torch and the object to be cut,
A noble gas typified by argon gas is passed through this to generate a plasma flow, and the thermal energy of this plasma melts and cuts the object to be cut. For example, ordinary gas cutting cannot cut the object. It is known as suitable for stainless steel and the like. Further, this method is suitable for cutting thick plates due to its large thermal energy, and recently it has become a mainstream of underwater cutting as a basic technology of reactor dismantling technology. ing. However, this cutting technique, as shown in Fig. 1, has a potential difference between the cutting torch and the object to be cut, so it is suitable for cutting metal with non-conductive deposits on the surface like high burnup FCB. Was unsuitable. Further, even during cutting, maintaining a constant distance between the object to be cut and the cutting torch (hereinafter referred to as a standoff) has been a condition for ensuring cutting ability. On the other hand, in the non-transfer type underwater plasma arc cutting, as shown in FIG. 2, no potential difference is provided between the cutting torch and the object to be cut, and the potential difference is between the electrode rod and the nozzle cap in the cutting torch. It is provided between the two, and a rare gas is passed between them to generate a plasma flow, which is jetted from the nozzle by the gas flow to melt and cut the object to be cut. This cutting method is generally not used much because it has inferior cutting ability compared to the transfer method described above.
Especially, it is not considered to be used for underwater cutting. In this example, an experiment was carried out in consideration of using a non-transfer type plasma arc cutting torch in water, emphasizing cutting performance capable of cutting a non-conductor. As a result, it was found that even if the non-transfer type cutting torch is used in water, it is possible to cut a high burnup FCB having a non-conductor deposit with stable performance. The potential difference for generating the plasma flow is provided between the electrode rod and the nozzle cap in the cutting torch, so that the stable plasma flow can be generated. Also, since the cutting torch can be connected to its power source and gas supply device etc. with a flexible tube or cable, it is not necessary to have a fixed structure like a conventional transfer type torch,
It is also possible to have a structure in which the object to be cut is fixed and the cutting torch is moved along the cutting line.

An embodiment of the present invention will be described below with reference to FIGS.

The structure of the cutting device is shown in FIGS. 3 to 5, the plasma system configuration is shown in FIG. 6, and the system of the device is shown in FIG. Further, FIG. 8 shows a procedure of FCB cutting work by this device.

The cutting device is installed in the pool 31 along the pool wall 33 with the gantry 1 fixed to the floor 34. The device is a pedestal 1, a frame 2 extending from the pedestal 1 to a lower part, a partition wall 5 for accommodating an FCB41 as an object to be cut, a guide 3 and a support 4 for accommodating and fixing the FCB41, and cutting torches 16a, 16b for cutting lines of the FCB41. Guide rail 11, sprocket 12, torch support 15 and drive motor 9, speed reducer for moving along
10, a sprocket 7a, 7b, a chain 6, a dross recovery box 13 generated during cutting, a gas recovery box 21, and the like.

The door 17 of the partition wall 5 provided on the device base 1 and the frame 2 fixed to the floor 34 and the pool wall 33 is opened. In this state, the FCB 41 as the object to be cut is moved underwater in the pool 31 and fixed to the device. At this time, cut the cutting line of FCB41 torch 16a, 1
The FCB 41 is fixedly installed on the upper part of the guide 3 and on the lower part of the support 4 in order to set a fixed position with respect to 6b.
In this state, the door 17 is closed and the blower 42 and the pump 43 are activated. The cutting torches 16a and 16b are set at the lower end or the upper end with respect to the FCB 41, and this setting is performed by the operation of the drive motor 9. That is, the operation of the drive motor 9 is transmitted to the torch support base 15 on which the cutting torches 16a and 16b are installed via the reduction gear 10, the shaft 20, the sprockets 7a and 7b, and the chain 6.
The torch support base 15 moves along the guide rail 11, and the guide rail 11 is prepositioned with respect to the cutting line of the FCB 41. Therefore, the cutting torches 16a and 16b set on the upper or lower end of the FCB41 are plasma ignited, and the torch is moved up and down in that state, so that the FCB41 has an L-shaped piece that is an efficient shape for storage and volume reduction. Can be cut into In addition,
The plasma torch 16 always supplies the shield gas from the gas supply device 54 via the flexible hose 22 in a normal state. Also, it is important to make the plasma torch 16 main body waterproof. Without this consideration, the plasma torch 16
Plasma generation cannot be obtained due to poor insulation inside. Plasma generation from the plasma torch 16 is performed by operating the operation panel 53 while the shield gas is flowing,
The procedure is performed by first replacing the shield gas with a rare gas such as argon gas, and then providing a potential difference between the electrode rod 61 and the nozzle cap 62 using the arc power supply device 52.

The cooling water circulation device 51 (Fig. 6) is provided to prevent the plasma torch 16 from overheating. However, as in the case of FCB cutting, if the plasma torch 16 has an underwater cooling effect as long as it is about 200A. It can be omitted because it can be expected.

Gas and plasma torch 16a, 1 generated during cutting of FCB41
The recovery of the gas supplied to 6b is collected in the gas recovery box 21 (Fig. 7), further diluted by the blower 42 and exhausted. Also,
Drop dross generated during cutting is collected by the dross collection box 13, and floating clod is sucked by the pump 43, purified by the filter unit 44, and drained into the pool. The differential pressure gauge 45 is provided to confirm the life of the filter unit 44.

After the cutting of the FCB41 is completed, the cleaning operation in the partition wall 5 is performed in a short time, the operation of the pump 43 is stopped, the door 17 is opened, and the FCB41 L
The cut pieces are taken out from the partition wall and stored in the storage area in the pool 31.

The above description has been made by taking the spent fuel channel box as an example of highly radioactive anti-body waste, but the cutting work of the used control rods etc. can be performed in the same manner as this procedure.

According to this embodiment, by adopting the non-transfer type underwater plasma cutting method, not only the working efficiency can be significantly improved, but also the amount of by-products generated due to cutting can be reduced,
The amount of filters as secondary waste can be reduced. Further, the cutting device can be downsized, simplified and rationalized.

According to the present embodiment, it is possible to stably cut the FCB having the non-conductor deposit (oxide), and the cutting torch has a movable structure. As a result, the cutting device can be reduced to about half of the conventional one, and the water depth of the pool in which the cutting device is installed can be greatly reduced. Also, since the cutting torch is a non-transfer type, it is easy to position the torch when returning the torch to the uncut part and recutting when there is an uncut part (in the case of a transfer type torch, the uncut part is If the torch is not accurately positioned (set the stun off) at the end, no arc is generated, or an uncut portion remains.

In this embodiment, since the gas generated during cutting by the gas recovery box 21 and the gas released from the plasma torch into the partition wall are collected and exhausted, the gas diffuses into the pool water and is released above the pool water surface. This can prevent workers from being exposed to radiation. Further, it is possible to collect the molten cutting waste and purify the water in the partition wall, and it is possible to suppress the pool water pollution due to the diffusion of the molten cutting waste and the suspended matter in the water in the partition wall into the surrounding pool water.

Further, in the present embodiment, not only the cutting gas is supplied to the plasma torch at the time of cutting, but also the waterproof gas is supplied to the plasma torch at the time of non-cutting, so that it is possible to prevent water from entering the plasma torch. Can be protected.

〔The invention's effect〕

According to the present invention, since the non-transfer type underwater plasma type cutting torch is used, the radioactive solid waste to which the non-conductor is attached can be stably cut in water.
Further, the present invention is capable of collecting gas in the partition wall, diluting it with the atmosphere and exhausting it, collecting molten cutting waste, and purifying water in the partition wall, so that it is possible to prevent the worker from being exposed to radiation. In addition, it is possible to suppress pool water contamination due to diffusion of molten cutting waste and suspended solids in water in the partition wall into surrounding pool water.

[Brief description of drawings]

1 is a principle diagram of a transfer type plasma cutting device, FIG. 2 is a principle diagram of a non-transfer type plasma cutting device, FIG. 3 is a front view showing an embodiment of the device of the present invention, and FIG. 4 is FIG. Fig. 5 is a side view of Fig. 5, Fig. 5 is a sectional view taken along line VV of Fig. 3, Fig. 6 is a configuration diagram for explaining a plasma arc system, Fig. 7 is a system diagram as one embodiment of the device of the present invention, and Fig. 8 (A)-(f) is a figure which shows the procedure of the cutting operation of FCB. 1 ... Frame, 2 ... Frame, 3 ... Guide, 4 ... Support, 5 ... Partition, 6 ... Chain, 7a, 7b ... Sprocket, 8 ... Top lid, 9 ... Drive motor, 10 ... … Reduction gear, 11 …… Guide rail, 12 …… Sprocket, 13 ……
Dross collection box, 14 …… Movement stand, 15 …… Torch support stand, 16
a, 16b ... Cutting torch, 17 ... Door, 18 ... Foundation base, 19 ...
… Handrails, 20 …… Shafts, 21 …… Gas collection boxes, 22 …… Flexible hoses and cables, 31 …… Pools, 32… Water, 33 …… Pool walls, 34 …… Floor, 41 …… FCB, 42… … Blower, 43 …… Pump, 44 …… Filter unit, 45 ……
Differential pressure gauge, 51 …… cooling water circulation device, 52 …… arc power supply device, 53 …… operation panel, 54 …… gas supply device, 55 …… relay station.

Claims (1)

[Claims] 1. A partition that is installed in pool water and that stores radioactive solid waste, which is an object to be cut and has non-conductors attached thereto, separated from the surrounding environment, and cuts the radioactive solid waste in the partition. A non-transfer type underwater plasma type cutting torch, and a drive mechanism for moving the cutting torch,
The cutting torch, a gas supply device for supplying a cutting gas at the time of cutting and a waterproof gas at the time of non-cutting, a support for supporting the radioactive solid waste in the partition wall, and a control panel for controlling the drive mechanism. Means for repairing the gas in the partition wall, diluting it with the atmosphere and exhausting it, and molten cutting waste generated by cutting the radioactive solid exhaust material provided at the lower end part of the partition wall, A radioactive solid waste cutting device comprising means for collecting water and means for purifying water in the partition wall.