JPH02167609A - Ultrasonic machining device - Google Patents

Abstract

PURPOSE:To enable radiative work powder and fuel work powder to be recovered with high rate of recovery by carrying out the dry cutting or the like of pile fuel pellet or radiative material in a cell with remote control without using any abrasives. CONSTITUTION:A supersonic machining device is provided with a ultrasonic vibration drill working device body 11, vibrator cooling device 12 and workpiece sample dust collector device 13 which are provided in a cell 16 surrounded by a screen wall 14 and screen window 15 and connected to each other through cooling pipes 17 and dust collecting pipes 18. The respective devices are operatively supplied with electric power from the outside of the cell 16. A ultrasonic vibrator working part 21 is provided on the distal end of a longitudinal vibration horn tool 24 with a connected for connecting a cooling material pipe 17 between a sintered hard tipped drill 25 removably attached by a remote control manipulator and the vibrator cooling device 12.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention utilizes ultrasonic technology that enables efficient drilling or cutting of nuclear reactor fuel pellets and radioactive materials in a dry state by remote control within a cell. This relates to processing equipment.

The present invention includes, for example, (1) hollow processing of nuclear reactor fuel pellets, (2) thermocouples and S
Deep processing of pellets to attach various sensors such as iC temperature monitors and wire monitors for measuring neutron irradiation amount, ■ Spent reactor fuel that has a particularly high burnup and is baked on the inside of the cladding tube and has a high hardness. Collecting from long cladding tubes, completely removing them, and cutting for recovery; ■ Cutting of ceramics such as B4C, a highly radioactive and highly hard absorption material for control rods used in nuclear reactors, etc. This device can be used in nuclear reactor fuel manufacturing facilities, post-irradiation testing facilities for fuel and materials, and reassembly facilities for irradiated test specimens.

[Prior art] For drilling, cutting, removing, etc. of solid reactor fuel before use or spent, a simple wet-type lathe drilling machine or a wet-type ultrasonic vibration drilling process using an abrasive material is used. The device is in use.

[Problem to be solved by the invention] However, in conventional wet processing equipment, processing is required to separate cooling oil and paper powder as an abrasive from processing fuel, and fission products and coolant moisture are required. There were problems such as corrosion of the cladding due to reaction products with the fuel, an increase in the amount of radioactive waste including processed fuel powder, and a low fuel recovery rate.

Since such problems are caused by the wet processing method, it is conceivable to use conventional equipment as is for dry processing, but this has not been put into practical use due to the following problems.

■With conventional equipment, the amount of heat generated in the fuel machining section at the tip of the tool is not controlled, so the machining section tends to reach high temperatures, resulting in softening and deformation of the drill cutting edge and the inability to cut.

In the case of conventional ultrasonic vibration drilling equipment, in addition to the above-mentioned problems, there is also the problem that if an abrasive is not used, the wear and loss of the drill cutting edge becomes more significant.

- In these processing devices, if the drill cutting edge becomes worn or deformed, the cutting edge is likely to hit unevenly in the processing area, causing drill breakage.

In this way, if the conventional device is used as is for dry machining, the drill cutting edge will have to be replaced frequently, so it will not be practical.

In addition, conventional wet-type and dry-type devices do not allow for remote control using a manipulator, so they cannot be installed inside a cell (a compartment surrounded by a shielding wall that houses the test equipment for handling highly radioactive materials).

For the purpose of removing solid fuel from the cladding tube of spent nuclear reactor fuel, there is a technique for removing the fuel by applying a unidirectional pushing force only to the fuel. In the case of low-burnup fuel, it is possible to remove the fuel using a simple extrusion-type fuel removal device like this, but in the case of high-burnup fuel, the fuel and cladding stick together, and the sticking force is strong. Therefore, it is difficult to extract the fuel without damaging the cladding by simple extrusion processing at room temperature.

An object of the present invention is to solve the above technical problems. That is, deep drilling of pellets of any diameter and length of reactor fuel, including high hardness states of 800 or higher on the Pinkers hardness, cutting for extraction, removal, and recovery of fuel from fuel-containing cladding tubes, etc. An object of the present invention is to provide a remote-controlled ultrasonic machining device that can perform this process dryly and with a fuel recovery rate of 99% or more without using an abrasive while maintaining the integrity of the workpiece. .

[! 1ull] The present invention, which can solve the above-mentioned technical problems, is an ultrasonic horn tool with a carbide chimp drill attached to the tip of a fat ultrasonic longitudinal vibration horn tool, which can be freely attached and detached using a remote control manipulator. A dry-type ultrasonic vibration drilling machine main body having a vibrator processing section, a collet chuck-type sample holding section that can also be remotely controlled, and a processing sample powder receiving tank; A vibrator cooling device that cools the oscillator, a processed sample dust collector equipped with a Cl pre-filter and a high-performance air filter, and a drill wear condition monitoring mechanism, a drill defect detection mechanism, This is an ultrasonic machining device equipped with a mechanism that maintains and adjusts the optimal pressing load of the drill cutting edge during machining and prevents overload.

Here, for example, the drill wear state monitoring mechanism has a cutting speed meter, and the drill chipping detection mechanism has a mechanism that detects an abnormal decrease in ultrasonic output and activates a machining stop switch. In addition, the mechanism for maintaining and adjusting the optimal pressing load of the drill cutting edge during machining and for preventing overload is provided by upper and lower slide plates installed on the bed of the ultrasonic transducer processing section, and a mechanism installed between the two slide plates. It consists of an overload prevention spring, a span adjustment screw for the overload prevention spring, and a limit switch that is activated to stop the machining operation when a reaction force of a machining part exceeding a specified value is applied to the overload prevention spring.

[Function] In the present invention, the main body of the ultrasonic vibration drilling machine, the vibrator cooling device, and the processed sample dust collection device are installed in the cell and can be remotely controlled by a manipulator, so they can be safely used even with highly radioactive and hard materials. Since the present invention is a dry processing device, there is no contamination of impurities and all the various problems associated with wet methods can be solved.

The wear condition of the drill is monitored using a cutting speed meter. If the tip of the drill is heavily worn and the sample approaches abnormal heat generation, the cutting speed will drop dramatically, so by monitoring the cutting speed, it is possible to predict the onset of abnormal heat generation and detect when it is time to replace the drill. Furthermore, when a drill chipping occurs, the ultrasonic output drops rapidly, so by attaching an output abnormality drop detection switch to the ultrasonic output indicator, the machining operation is stopped when a chipping occurs.

Furthermore, if an excessive load is applied to the drill cutting edge, damage to the cutting edge, accelerated wear, abnormal heating of the sample, damage to the sample, etc. will occur.

In the present invention, the mechanism that maintains and adjusts the optimal pressing load of the drill cutting edge and prevents overload solves these problems and enables efficient cutting.

[Embodiment] FIG. 1 is a schematic diagram showing an embodiment of an ultrasonic processing apparatus according to the present invention. As shown in the figure, the present invention includes an ultrasonic vibration drilling device main body 11, a vibrator cooling device 12, and a processing sample M1 dust device 13, which are surrounded by a shielding wall 14 and a shielding window 15. This configuration is installed inside a cell 16. The ultrasonic vibration drilling device main body 11, the vibrator cooling device 12, and the processed sample collection device 13 are mechanically coupled through a coolant pipe 17 and a dust collection pipe 18, respectively. Further, each device operates by being supplied with power from outside the cell.

Furthermore, although not shown in the drawings, a control device that controls the operation of each of these devices and performs measurements is installed outside the cell.

The details of the ultrasonic vibration drilling device main body 11 are shown in Fig. 2A,
This ultrasonic vibration drilling device main body 11 shown in B is as follows:
This dry processing device is equipped with an ultrasonic transducer processing section 21 provided on one side of a bed section 20 forming a base, and a sample holding section and a sample driving section provided on the opposite side, and can be remotely controlled. .

The ultrasonic transducer processing section 21 has a longitudinally vibrating horn tool 24, a drill 25 with a carbide tip that can be attached and detached by a remote control manipulator at the tip of the horn tool, and a coolant pipe connected to the transducer cooling device. It is provided with a connection part 26 for the purpose.

The sample holding section includes a collet chuck 29 for fixing the sample 28 for processing, and a lever 30 for tightening the collet chuck. It consists of a collet chuck replacement handle 31, etc., and the sample drive section includes a sample rotation motor 33, a step motor 34 for feeding the processed sample, various limit switches, a striker 35, etc.

In addition, approximately in the center of the bed section 20, there is provided a processed sample receiver M36 for collecting sample grains, fragments, etc. that fall during processing, and a dust collection box 37 made of acrylic resin for preventing processed samples from scattering. A dust collection vibrator 18 is attached to the upper part of the box 37, which is connected to the processing sample dust collection device.

In the above-mentioned ultrasonic vibration drilling apparatus main body 11, in order to facilitate the processing of long samples, when processing from one side of a fuel sample of 80 to 100 m5 reaches near the center of the sample, - The structure allows reprocessing by automatically stopping processing and inverting the sample at the collet chuck section.

As shown in FIG. 3, the vibrator cooling VT unit 12 includes a cooling oil tank 41 for storing cooling oil, an oil level gauge 42, a cooling pump 43 for circulating the cooling oil, a thermometer 44 for measuring the temperature of the cooling oil, etc. As shown in FIG. 1, it is connected to the ultrasonic vibrator processing section 21 of the ultrasonic vibration drilling apparatus main body 11 via a coolant pipe 17.

As shown in FIG. 4, the processed sample dust collector 13 includes a pre-filter 51 that traps slightly larger particles (approximately 0.3 μm in diameter or larger) and a high-performance air filter that collects smaller particles. The filter 52 is arranged in two stages in series, and also includes a blower 53 and a differential pressure gauge 54 that monitors the dust collection status of the filter and indicates when to replace the filter in case of clogging. As the pre-filter 51, for example, a paper filter with a mesh size of about 0.3 μm is used.

A control device that measures and controls each of the above devices from outside the cell is composed of a transducer cooling device drive system, a sample rotation feed control system, an ultrasonic oscillation control system, and the like.

In the apparatus according to the present invention, since it is used under a high radiation dose rate, the collet chuck operation, which is frequently used or replaced among the ultrasonic vibration drilling apparatus main body 11, the vibrator cooling device 12, and the processed sample dust collector 13, is used. The part, horn tool, etc. are all either simple lever type or rotary type using a torque wrench, and the dust collection filters are also divided and assembled so that they can be disassembled and replaced using a manipulator. ing.

Next, an example of an ultrasonic vibrating part is shown in FIGS. 5A-C. This ultrasonic vibrating part has a structure in which a drill 25 is attached to the tip of a 4I vibrating horn tool 24. By replacing it with a new one, it is possible to process samples of any diameter and any hardness. With such a tool, it is possible to process up to nuclear reactor fuel with a hardness of about HV-1000. However, the harder the material is, the faster the tip of the drill wears out and the longer it takes to process it. When precision machining is required, it is divided into two stages: rough machining and finishing machining, and when sampling samples, a hollow circular drill is used. If the drill and the horn tool are separated, costs can be reduced, but in order to further improve remote operability, the drill and the horn tool may be integrated.

Now, in the present invention, the following mechanism is further added to perform dry processing. These are a drill wear state monitoring 81 side, a drill missing tJI detection mechanism, a mechanism for maintaining and adjusting the optimum pressing load of the drill cutting edge during machining, and a mechanism for preventing overload.

Dry cutting of highly hard nuclear reactor fuel may generate an increased amount of heat during processing, and the increased temperature will soften the drill bit, making it impossible to cut. Moreover, as the temperature rises, it has a negative effect on the sample.

As a result of trying various studies to prevent these problems, it became clear that the increase in heat generation at the tip of the drill and drill wear are closely related, and it is important to use this to properly understand the condition of the drill. It was found that dry processing was possible.

First, it was found that when the tip of the drill wears out by 40 to 50% or more, the cutting speed decreases rapidly, and if the tip wears out by 60% or more, the heat generation at the sample and the tip of the drill increases significantly. This relationship is the sixth
As shown in the figure, the cutting speed (s
m/min). Drill tip wear rate is 60
The region exceeding % is the sample heat generation region. Therefore, in order to solve this problem, the present invention uses a cutting speed meter and a cutting speed recorder to detect the degree of wear on the drill, and takes advantage of the fact that when the tip of the drill is heavily worn and the sample approaches a heat-generating state, the cutting speed drops dramatically. The system uses a mechanism that predicts the start of abnormal heat generation and detects when it is time to replace the drill.

Next, as shown in FIG. 7, it was found that when a drill breakage occurs during dry machining, the ultrasonic output decreases to about 1/2. Taking advantage of this fact, we installed an abnormal output drop detection switch on the ultrasonic output indicator and provided a mechanism to stop the machining operation when a drill breakage occurs, thereby preventing damage to the fuel cladding tube and fuel of the sample.

If an excessive load is applied to the drill cutting edge through which ultrasonic vibrations are transmitted, damage to the cutting edge, progression of wear, abnormal heating of the sample, damage to the sample, etc. will occur. In order to prevent these problems, it is necessary to keep the pressing load of the drill cutting edge at an optimum value at all times during sample processing. Figure 8 shows the drill tip pressing load (kg) determined using Hv-800 alumina sintered body as a simulated fuel.
It shows the relationship between and cutting speed. As is clear from the figure, the best cutting efficiency is shown when the drill tip pressing load is in the range of 0.8 to 1.2 kg, cutting speed is low when the load is 0.7 kg or less, and conversely, when the load is 1.4 kg or more, the cutting efficiency is low. The wear rate increases and the cutting speed also rapidly decreases.In the present invention, in consideration of this relationship, the a side is incorporated so that the pressing load of the drill cutting edge against the processed sample is optimized. An example is shown in FIG.

This mechanism is provided between an upper slide board 63 on which the sample holding device 61 is mounted and a lower slide board 62 on which these are mounted and driven at a constant speed. That is, both slides′
g! Between 62 and 63, there are provided an overload prevention spring 64, its span adjustment screw 65, and a limit switch 66 that is activated to stop the machining operation when the overload prevention spring 64 is subjected to a reaction force on the machining part that exceeds a specified value. It is something that The overload prevention spring 64 is also illustrated in FIG. 2B.

During cutting, the step motor 34 (see Figure 2 A)
The lower slide plate 62 is driven at a constant speed in the direction of the white arrow a. A driving force is applied to the upper slide plate 63 via the overload prevention spring 64, and a reaction force of the processed portion is applied in the opposite direction (white arrow b). The span of the overload prevention spring 64 is set to the optimum cutting pressing load using the adjustment screw 65, and cutting is performed. In this way, the excessive 9L load prevention spring 64 also plays a role as an optimal pressing load element to the drill tip.If the pressing load of the drill tip exceeds the specified value, the overload prevention spring
contracts in response to the reaction force, and the limit switch 66 is activated. As a result, the step motor 34 for feeding the processing sample
Then, the sample rotation motor 33 is stopped, and the processing operation is stopped.

Now, generally speaking, in order to increase the machining speed using ultrasonic waves, it is sufficient to increase the amplitude of the ultrasonic vibrations of the tip machining tool.
For this purpose, it is best to increase the electrical input to the vibrator or to lower the resonant frequency of the vibrator as much as possible.However, if the vibrator frequency is low, there is a risk that the sound will become audible.
Practically speaking, a frequency in the range of 16 to 30 kHz is selected. Considering that this unit will be installed in an airtight cell, a resonance frequency of around 16 kHz was selected, and under this condition electric power can be maximized. Adopts an ultrasonic vibration control system. In reality, the control device is equipped with an ultrasonic vibration adjustment switch, which allows the maximum output to be adjusted and maintained.

In the cutting process of nuclear reactor fuel, it is strongly required to recover fuel materials such as fuel fragments and fuel products with a high recovery rate without mixing substances other than fuel and with a high recovery rate. In fuel removal processing of plutonium mixed oxide fuel, recovery on the order of 0.1 g is desired. In addition, it is important to reduce the level of contamination caused by scattering fuel particles during reactor fuel processing and to reduce radioactive waste during decontamination. The sample is moved and processed in a processed sample receiving tank provided in the center, and the fuel phase and debris that fall during processing are first collected, and the pulverized fuel phase is collected in a processed sample collection as shown in Figure 4. Dust equipment is designed to increase recovery rates. Fine fuel powder in the air sucked from the dust collection box 37 of the main body is passed through the pre-filter 51.
be trapped in The fine powder trapped in the prefilter 51 can be collected by disassembling and taking out the prefilter 51 itself from the collector 11 device. The high-performance air filter 52't' traps the fuel phase that has passed through the pre-filter 51, and prevents contamination due to scattering of fuel particles within the cell, thereby reducing radioactive waste during decontamination.

Next, Table 1 shows examples of recovery when sintered alumina pellets, which are simulated fuel, are processed using the apparatus shown in this example. As shown in the table, the recovery rate was very good, with an average of 99%.
% or more.

Table 1 The simulated fuel pellets used in the tests were homogeneous cemented carbide alumina sintered bodies shrink-fitted into a stainless steel a cladding tube, and were dense with no fine cranks. However, a typical workpiece in reality is a cladding tube containing oxide fuel pellets, and such spent nuclear reactor fuel pellets have many minute holes and cranks.

Therefore, it can be judged that it is extremely easy to fragment and become fine powder, and can be processed more easily than the case of the densely packed simulated fuel pellet 7). Therefore, with the device of the present invention, it is possible to perform deep hole machining and cutting of ultrahard nuclear reactor fuel with a Pinkers hardness of 800 or more using a remote control manipulator in a dry manner without using an abrasive material, and furthermore, it is possible to perform fuel processing using a remote control manipulator. Powder can be recovered with high efficiency of 99.9% or more.

Although a preferred embodiment of the present invention has been described above in detail, the present invention is not limited to only such a configuration.

In the above embodiment, the main body of the ultrasonic vibration drilling apparatus has a horizontal structure, but it may also have a vertical structure in which the ultrasonic vibrator processing section is installed vertically and the processed sample section is driven vertically. Furthermore, although the above embodiment uses a method in which the sample holding section is driven, a structure may be adopted in which the sample holding section is fixed and the ultrasonic transducer processing section is moved.

The device according to the present invention can be used for the following purposes.

■ Efficient recovery of only the fuel from spent reactor fuel-containing cladding while the cladding remains healthy, and collection of cladding samples to examine the irradiation characteristics of the material; ■ To measure fuel temperature. Reactor fuel processing to create holes for embedding thermocouples and wire monitors for neutron irradiation measurement, hole drilling for making hollow fuel pellets, and deep hole drilling for fuel for other purposes. B from the highly radioactive control rods used in the nuclear reactor.
It can be used for collecting C pellet pieces, etc.

[Effects of the Invention] In the present invention, as described above, the main body of the ultrasonic vibration drilling processing device, the vibrator cooling device, and the processing sample dust collection device are installed in the cell, and they are made operable by a remote control manipulator, We have installed a mechanism that monitors and detects various conditions of the drill and maintains and adjusts the optimum pressing load of the drill cutting edge, making it possible to perform dry-type deep hole drilling and cutting of ultra-hard nuclear reactor fuel with a Pinkers hardness of 800 or higher. This method can be carried out without using abrasive materials, and radioactive processed powder and fuel processed powder can be recovered with a high recovery rate of over 99%.

By utilizing such a device of the present invention, it is possible to extend the life of a reactor fuel assembly, which is a key technology in nuclear reactor technology, and to promote the development of highly reliable and high-performance reactor fuel.

Furthermore, it is possible to process fuel with an extremely high recovery rate, and since it is a dry process, reactor fuel can be recovered without contamination with impurities, making it possible to effectively reuse the reactor fuel. In addition, it can prevent radioactive contamination due to scattering of reactor fuel powder in the working environment, reduce the amount of radioactive waste including reactor fuel materials, and reduce the level of radioactive materials released into the environment around the test facility after irradiation. It has many excellent effects, such as being able to maintain the

[Brief explanation of the drawing]

Fig. 1 is a schematic horizontal view showing one embodiment of the ultrasonic machining device according to the present invention, Fig. 2 A and B are a front view and a plan view of the main body of the ultrasonic vibration drilling device, and Fig. 3 is a vibrator. A front view of the cooling device, Figure 4 is a front view of the processed sample dust collector, and Figures 5 A and B.
, C are a front view of an ultrasonic transducer part, an enlarged view of a drill cutting edge, and a side view thereof, respectively. Furthermore, Fig. 6 is an explanatory diagram showing the relationship between drill tip wear degree and cutting speed, Fig. 7 is an explanatory diagram showing the output change when drill chipping occurs, and Fig. 8 is an explanatory diagram showing the relationship between cutting speed and drill tip pressing load. FIG. 9 is an explanatory diagram showing a mechanism for maintaining and adjusting the optimum pressing load of the drill cutting edge during machining and for preventing overload.

Claims (1)

[Claims] 1. (a) An ultrasonic vibrator processing section in which a drill with a carbide tip that can be freely attached and detached by a remote control manipulator is attached to the tip of an ultrasonic longitudinal vibration horn tool, and a collet that can also be remotely controlled. (b) a vibrator cooling device that cools the ultrasonic vibrator processing section by circulating a coolant; (c) A processing sample dust collector equipped with a pre-filter and a high-performance air filter is installed in the cell, as well as a drill wear condition monitoring mechanism, a drill chipping detection mechanism, and an optimal pressing load of the drill cutting edge during machining. An ultrasonic processing device characterized by having a mechanism for holding/adjusting and preventing overload. 2. The ultrasonic machining apparatus according to claim 1, wherein the mechanism for monitoring the wear state of the drill includes a cutting speed meter. 3. The ultrasonic machining apparatus according to claim 1, wherein the drill defect detection mechanism includes an abnormal decrease detection switch of ultrasonic output. 4. The mechanism that maintains and adjusts the optimal pressing load of the drill cutting edge during machining and prevents overload is provided by upper and lower slide plates installed on the bed of the ultrasonic transducer processing section, and between both slide plates. 2. The overload prevention spring comprising: an overload prevention spring; a span adjustment screw for the overload prevention spring; and a limit switch that is activated to stop the machining operation when a reaction force of a machining part exceeding a specified value is applied to the overload prevention spring. ultrasonic processing equipment.