JPH08200961A - Production for storage container - Google Patents

Abstract

PURPOSE: To minimize environmental pollution and to facilitate the maintenance of manufacturing processes by guiding and dissolving a metallic solidified material supplied to a low temperature crucible, then, interrupting a high frequency current to a coil and rotating the crucible about a vertical axis. CONSTITUTION: A low temperature crucible 1 is provided with a conductive cooling wall formed with an assembly of segments 11 electrically insulated from one another by slits. In the periphery of the low temperature crucible 1, a current supply coil 2 in which a cooling member can flow is spirally provided and connected to a high frequency power source 3 through a switching device 4. The low temperature crucible 1 is housed in an atmosphere adjusting chamber 6 and a metallic solidified material is fed thereto from a material feeder 5 and dissolved under induction heating to be a molten member 13. Then, after a high frequency current is stopped, the crucible 1 is rotated around a vertical axis, the molten member 13 is formed in the shape of a storage container 14 with a bottom having a space in its inner part and an outer part to which the inner wall of the crucible 1 is transferred by using center of gravity and centrifugal force acting on the molten member 13. After the rotation of the crucible is stopped, the molten member is solidified by removing heat from the segments of the crucible 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a solidified metal body contaminated by a substance harmful to the environment or a solidified metal body chemically polluted and chemically active as a material to produce a container made of a material containing a pollutant. On how to do.

[0002]

2. Description of the Related Art Conventionally, a rotary hearth type plasma melting furnace (PACT) developed by Retech of the United States has been used as an apparatus for manufacturing a container using a solidified metal material contaminated by environmentally harmful substances.
(See J. of the RANDEC, No. 9, 1993, P. 65-70).

This PACT has the following features 1) to 3).

1) Centrifugal force enables uniform agitation,
The melted and solidified product becomes homogeneous and stable.

2) There is a high degree of freedom regarding the shape of the material.

3) Since hot water is discharged by adjusting the number of revolutions, no special device such as a special valve or tilting of the furnace is required.

However, this device has the following disadvantages.

At least two devices, a melting device and a centrifugal casting device, are required.

In particular, when the object to be treated is a contaminated material, the following drawbacks become more serious.

Since refractory is used for the lining of the melting furnace, it is necessary to replace it periodically. In particular, when the material to be melted is a contaminated material, the refractory generated in the maintenance process becomes contaminated secondary waste, and it is necessary to treat it in another process.

In particular, when the target of melting is an activated metal solidified product, the frequency of generation of secondary waste is high.

It is necessary to supply a gas such as Ar (carrier gas) to the torch in order to generate a plasma arc. For this reason, it is necessary to increase the size of the exhaust gas treatment facility, and the energy lost as sensible heat of gas is large.

Since the plasma torch is a consumable item, it needs to be replaced regularly. Especially when contaminated material is targeted, the replacement operation must be performed remotely, which complicates the apparatus.

There is an idea that the following publicly known techniques may be used in order to solve the above-mentioned drawbacks.

This technique is a series of methods for melting a melting material in a cooling crucible made of a material having a melting point lower than that of the melting material without contaminating the melting material with the crucible material. This basic technology has already been applied for a patent in Germany in 1931 (see German Patent No. 518499). Since then, many patents related to low temperature crucibles have been filed. For example, French patent N
O.87-00814 (Japanese Patent Laid-Open No. 63-192543) proposes a crucible shape for continuous processing.

These techniques are: 1) Easy to maintain because the device is simple.

2) Since the cooled low temperature wall is used as the wall of the melting furnace, the melting material is not contaminated by the material of the furnace wall, or the periodic replacement due to the exhaustion of the material of the furnace wall is not necessary.

And the like. However, in general, there are restrictions on the molding conditions of products, and many of the shapes of products obtained by applying these devices are solid. In particular, a method for manufacturing a hollow and bottomed container has not been proposed in the past.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to produce a container by a melt rotomolding method, which is one of the centrifugal casting methods, mainly using a contaminated metal solidified material as a material.
It is an object of the present invention to provide a method for facilitating the maintenance of the manufacturing process while minimizing the pollution of the environment due to the production of materials and secondary contaminated waste in the manufacturing process.

[0020]

The gist of the present invention resides in the following method of manufacturing a container.

A low-temperature crucible provided with a conductive cooling wall made of an assembly of segments electrically insulated from each other by a slit, a current-carrying coil formed by multiplying the crucible in multiple turns, and a high-frequency power supply for supplying a high-frequency current to the coil. , Switch device for high-frequency current, material supply device for supplying solidified metal to low-temperature crucible, atmosphere control chamber, inert gas supply device,
A method of manufacturing a container using an apparatus equipped with a segment cooling device, a low-temperature crucible rotating device, and an exhaust gas treatment device, after induction melting of the material of the solidified metal supplied to the low-temperature crucible, and then high frequency to the energizing coil. A method for manufacturing a container made of a solidified metal by cutting off the supply of electric current and rotating the crucible around a vertical axis.

The above-mentioned "solidified metal" is not limited to a metal, but refers to a material having a slight electric conductivity.

[0023]

Operation An example of the structure of the apparatus used in the method of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 (a) is a schematic vertical sectional view showing the structure of the above apparatus, and FIG. 1 (b) is a plan view of only the low temperature crucible. FIG.
As shown in (a), this device consists of a low temperature crucible 1 and this crucible 1
Energizing coil 2 which is made up of multiple turns, a high-frequency power source 3 for supplying a high-frequency current to this coil, a high-frequency current switching device 4, a material supply device 5 for supplying a metal solidification material 12 to the crucible 1, an atmosphere adjusting chamber 6 At least a device 7 for supplying an inert gas into the chamber 6, a cooling device 8 for the segment 11 of the crucible 1, a rotating device 9 for the crucible 1 and an exhaust gas treatment device 15 are provided. As shown in FIG. 1 (b), the low temperature crucible 1 has a slit 10 arranged at least along the opening and in a direction in which gravity acts to exhibit an electrical insulating function.
It has a conductive cooling wall composed of an assembly of a plurality of segments 11 which are divided by and are electrically insulated from each other.
In addition, as shown in FIG. 1 (a), the vertical cross-sectional shape is a wine cup shape in which the horizontal cross-section gradually decreases along the direction of gravity.

The slit 10 is provided substantially along the direction in which gravity acts, and is generally provided not at the entire height of the low temperature crucible 1 but at a part thereof, but its position is limited in the apparatus used in the method of the present invention. Not something to do. That is, FIG.
In the above, the portion where the slit 10 does not exist is provided at the lower end of the crucible 1, but this position may be provided only at the upper end of the crucible 1, or at the upper and lower ends, or may not exist. . Even in such a crucible, the required basic electromagnetic effect is the same as that of the crucible 1 in FIG.

At the lower end of the low temperature crucible 1, cooling pipes for supplying cooling water to the inside of each segment 11 are gathered and connected to the cooling device 8, so that the low temperature crucible 1 can withstand high temperatures. it can. The material of the crucible 1 is generally a metal material excellent in heat conduction and electric conduction (for example, copper, silver, stainless steel, etc.), but the material is not necessarily limited to metal and may be graphite, for example.

At the lower end of the low temperature crucible 1 is arranged a rotating device 9 for rotating the crucible 1 around a vertical axis and having a rotation speed control mechanism.

Around the low-temperature crucible 1, a current-carrying coil 2 through which a cooling body can flow is arranged in a spirally wound manner. The energizing coil 2 is connected to a high frequency power source 3 via a high frequency current switching device 4. Here, the switchgear 4 need not be a simple switchgear, but may be, for example, an output control device of a high frequency power source having a similar function.

Above the low temperature crucible 1, a material supply device 5 including a storage of the metal solidified material 12 is arranged. At least the low-temperature crucible 1 is housed in an atmosphere adjusting chamber 6, and the inside of the chamber 6 can be placed under an atmosphere of an inert gas such as Ar or He, or under conditions such as pressurization and depressurization.
Therefore, an inert gas supply device 7 is arranged in the chamber 6, and an exhaust gas treatment device 15 for environmental protection is further arranged.

In the method of the present invention, the first step is shown in FIG.
As shown in (a), the solidified metal material is supplied to the low temperature crucible 1 and the temperature is raised to a melting temperature or higher by induction heating to be melted to form a melt 13, which realizes easy molding conditions.

FIG. 2 is a diagram showing the concept of the second step of the process of the present invention (centrifugal casting).

As a second step, after stopping the high-frequency current supplied to the induction coil 2, the crucible 1 is rotated around the vertical axis, and the gravity and centrifugal force acting on the melt 13 are utilized to obtain the state shown in FIG. As shown in the figure, the container is formed into a bottomed container 14 having a space inside and a transfer of the inner wall of the crucible 1 to the outside, and then the rotation is stopped. Storage container molded in this way
14 is solidified by heat removal from the water-cooled low-temperature wall (segment) of the crucible 1 and becomes a solidified metal container.

When molding such a bottomed container, a desirable range of the rotation speed (angular speed) of the crucible 1 is 2 to 100 ra.
Although it is about d / s, it is generally desirable to reduce the rotation speed as the solidification progresses. That is, 0.1
About 1 to 10 rad / s for about 1 min, then 0.1 to every minute
Decrease at 0.5 rad / s and stop rotation when there is no melt.

A desirable pressure range in the atmosphere adjusting chamber 6 during the above series of treatments is about 10 to 10,000 hPa.

Taking the case where the metal solidified body is a metal material as an example, the function of each constituent device with respect to the metal material in the process of manufacturing the metal container by the method of the present invention will be described.

In manufacturing the container, first, cooling water is supplied to the apparatus, and then the atmospheric gas is degassed and replaced, and in some cases, the atmospheric gas is constantly supplied to obtain a predetermined processing atmosphere. Generally, the target range of the atmosphere adjustment is in the vicinity of the device that handles the material, and for example, a high frequency power source is often excluded from the target, but the present invention does not limit the target device of the atmosphere adjustment. After adjusting the atmosphere, a predetermined amount of the metal material is charged into the low temperature crucible through the metal material supply device by utilizing the action of gravity.

Then, the switching device for the high frequency current is closed to increase the output of the high frequency power supply. The induced current flowing through the outer wall surface of the low temperature crucible generated by the energizing coil is guided to the inner wall of the low temperature crucible because the slit having the insulating function is present in the low temperature crucible, and the electromagnetic field is generated in the crucible. That is, in general, a crucible made of a metal material that does not transmit an electromagnetic field has an effect of transmitting an electromagnetic field inside the crucible because it has a structure having a slit.

As the output of the high frequency power source is further increased, the value of the induced current flowing mainly in the vicinity of the surface of the metal material is increased, and the metal material is melted under the action of induction heating. At this time,
An electromagnetic force is generated in the melt within a range of the skin depth and perpendicular to the surface thereof. In general, the shape of the free surface of the melt is determined by the condition that satisfies the force equilibrium relationship between electromagnetic force and gravity, surface tension, momentum of the melt, etc.
By selecting appropriate operating conditions, it is also possible to separate the time-averaged shape of the melt from the low temperature crucible and raise it to an oval shape. When the melt is separated from the low temperature crucible, the effect of significantly reducing the loss of thermal energy due to the low temperature crucible appears. Further, the action of electromagnetic stirring appears inside the melt due to the generation of the non-uniform electromagnetic force, and the melting of the charged metallic material is promoted.

Upon dissolution, at least the following a. To d.
It is more desirable to supply the low temperature crucible with a lubricant satisfying the above condition.

A. The melting temperature is 100 to 200 higher than that of the material.
℃ low.

B. Does not decompose or vaporize during the melting process.

C. Does not react with molten metal.

D. Electric conductivity and thermal conductivity are smaller than those of metallic materials.

Naturally, the type of lubricant to be selected depends on the material of the target material. When the optimum lubricant is selected, there will be a lubricant (not shown) between the melt and the low temperature crucible in the low temperature crucible, and the lubricant on the side in contact with the melt will melt. Therefore, the lubricant on the side in contact with the low temperature crucible can be solidified. The presence of the lubricant generally exerts an effect of promoting reduction of energy loss and an effect of increasing the heating efficiency of the material.

As such a lubricant, calcium fluoride (CaF ₂ ), magnesium fluoride (MgF ₂ ), or a mixture of both can be used. It is more desirable that the lubricant to be added is as small as possible and that the effect of reducing the amount of heat removed is exhibited. The desirable range of addition of the lubricant is about 0.1 to 10 mass% with respect to the solid metal.

Since the lubricant is contaminated by the material, it is conceivable that if a large amount of the lubricant is required, another process may be necessary for treating the lubricant.

When the lubricant is added, another supply device may be provided in the chamber, but the supply may be performed together with the material.

After confirming that a predetermined weight of material was completely melted in the low temperature crucible, the switch for high frequency current was opened to shut off the current, and the rotating device was driven to move the low temperature crucible around the vertical axis. Rotate. Due to the action of centrifugal force, surface tension, and gravity, the melt is pressed against the inner wall of the low temperature crucible and is cooled, and at the same time, the central part (near the rotation axis) of the melt is depressed and approaches the shape of the low temperature crucible.

In the solidification process of the melt, it is more preferable that the rotational speed (angular speed) of the low temperature crucible is lowered as described above. The solidification process proceeds from the outside of the melt close to the low temperature crucible, and when the solidification progresses to a certain extent, the rotation speed of the low temperature crucible is reduced, and the unsolidified portion has a relatively large effect of gravity, resulting in the low temperature crucible. The bottom of the container is formed. In this way, a bottomed container is obtained.

In general, the container is solidified and shrunk, and the opening cross-sectional area of the low temperature crucible increases upward. Therefore, the low temperature crucible is accommodated by directing a slight impact to the low temperature crucible. The container can be easily taken out. If a lubricant is used, it will be easier to take out.

The secondary contaminated waste of the lubricant generated in the series of processing steps can be disposed of in a storage container obtained as required, whereby the disposal can be rationalized.

The method of the present invention is a closed treatment, does not require a crucible refractory, and does not melt the crucible wall. Therefore, environmental pollution caused by materials in the manufacturing process and generation of secondary polluted waste due to crucible materials, etc. And the maintenance of the device during the manufacturing process can be facilitated.

[0053]

EXAMPLE As an application example of the present invention, the apparatus having the constitution shown in FIGS. 1 and 2 is used as a solidified material, zircaloy, which is a material of a nuclear fuel cladding tube generated in a reprocessing step of spent nuclear fuel of a pressurized water reactor. Was used to manufacture a container made of Zircaloy. In consideration of the safety of the manufacturing test, a simulated nuclear fuel cladding tube before use in a nuclear reactor was used instead of treating the spent nuclear fuel cladding tube itself.

At the same time, ²³⁸ Pu, ²³⁹ Pu, ²⁴⁰ Pu, ²⁴¹ Pu, which are thought to be attached to the nuclear fuel cladding,
²⁴² Pu, ²⁴¹ Am, ²⁴³ Am, ²⁴² Cm and ²⁴⁴ Cm etc.
The lanthanide-based element oxides shown in Table 1 were added in an amount of 1 mass% with respect to the zircaloy material.

[0055]

[Table 1]

The composition of zircaloy is as mass% Sn: 1.5, F
e: 0.1, Cr: 0.1, and most of the rest is Zr. Its melting temperature is 1800 to 1850 ° C. and its density is 6.55 g / cm ³ .

As a lubricant, in mass% CaF ₂ : 75, MgF ₂ :
About 25 mass% of Zircaloy material was added to the mixture of 25.

The other conditions were as follows.

Material of low temperature crucible: Cu Shape of low temperature crucible: hemisphere with inner radius of 15 cm below intermediate height, cylindrical shape with radius of 15 cm and height of 35 cm above intermediate height Wall thickness of low temperature crucible: 30 mm Slit: direction is gravity Direction of action, width 0.01 cm, length 5
32 pieces are arranged at intervals of about 29 mm along the circumference of 4 cm. Crucible rotation speed: maximum angular rotation speed 50 rad / s High frequency power supply: maximum output 500 kW, frequency 30 kHz Current coil material: Cu (water cooling inside) Current coil: Number of turns 8. Rolling height 40 cm Initial loading Zircaloy material weight: Approx. 50 kg (lump) Lubricating initial loading weight: 2.5 kg Under the above conditions, 200 liters / min and 50 liters of cooling water are supplied to the low temperature crucible and the energizing coil, respectively. While supplying at a flow rate of / min, the high frequency power supply, its switchgear, the exhaust gas treatment device and the cooling water pump of the cooling device were sealed in an atmosphere control chamber. Then, the chamber was evacuated with a vacuum pump for about 20 min, and the atmospheric pressure was reduced to 0.1 Pa or less for 5 min.
For more than 0.1% of impurities in the chamber.
R gas was introduced at a supply rate of 100 liter / min, and the pressure was maintained at 50 hPa or less than atmospheric pressure.

Subsequently, the output of the high frequency power source was gradually increased, and finally, a high frequency current having an effective value of 2 kA and a frequency of 30 kHz was supplied to the energizing coil. A part of the initially charged zircaloy material was dissolved by applying electricity for about 1 minute, and most of it was dissolved after 12 minutes. After that, additional charging of the lubricant was started from the lubricant supply device provided in the chamber separately from the bulk zircaloy material from the material supply device. Over a period of 15 minutes, 50 kg of zircaloy material and 2.5 kg of lubricant were charged into the crucible little by little to prevent the melt from scattering outside the crucible. At the time of charging, the Zircaloy material was immediately dissolved, and the melt was separated from the cooling wall to rise like an egg, and it was confirmed that it was subjected to electromagnetic stirring. In addition, it was confirmed that the lubricant was distributed around the melt. At this time, the temperature of the melt was about 1800 to 1850 ° C.

After that, the energization from the high frequency power source was stopped, the low temperature crucible was rotated at an angular velocity of 20 rad / s for the first 3 min, and then decelerated at 0.5 rad / s per minute, and after 10 min, the melt was melted. The angular velocity was set to 0 rad / s after confirming that it did not exist. The centrifugal force disappeared during the deceleration process, and the unsolidified melt existing on the side wall of the container fell along the side wall of the crucible due to the action of gravity and accumulated at the bottom of the container-like melt. After that, it was cooled for about 20 minutes to be completely solidified and taken out as a hollow container with a bottom made of zircaloy.

The obtained container has an outer diameter of 30 cm, a cylindrical portion height of 30 cm, a dome outer diameter of 15 cm, an average wall thickness of 4.5 cm, and a total weight of 10 cm.
At 0 kg, the bottom was projecting.

Inside the container, a non-metal solidified body containing CaF ₂ and MgF ₂ as main components was observed. No non-metal solidified body was found on the outside of the container, but a similar non-metal solidified body was found inside the low temperature crucible in the form of being inserted into the slit. When this was analyzed, most of them had the same composition as the lubricant, and some lanthanide-based oxides were also contained.

The material of the low temperature crucible, Cu, was not detected in the non-metal solidified body obtained from the inside of the low temperature crucible,
Even if it was operated at a temperature of about 50 ° C, it was possible to withstand high temperature operation for a long time without requiring maintenance such as regular replacement of the low temperature crucible.

Since the periodical replacement of the low temperature crucible component is small as described above, it means that the pollution of the environment by the secondary contaminated waste can be minimized. Therefore, the method of the present invention is used as a process for treating the contaminated metal solidified body. Very good.

[0066]

According to the method of the present invention, it is possible to manufacture a container for containing a pollutant by using a contaminated material and shielding it from the environment. The structure of the device is simple, the maintenance is easy, and the amount of secondary contaminated waste can be minimized.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of an apparatus for realizing a method of the present invention and a concept of a processing step (dissolution) in a first step. (a)
Is a vertical sectional view, and (b) is a plan view of the crucible.

FIG. 2 is a second treatment step (centrifugal casting) of the method of the present invention.
It is a figure which shows the concept of.

[Explanation of symbols]

1: Low temperature crucible, 2: Energizing coil, 3: High frequency power supply, 4: High frequency current switching device, 5: Material supply device, 6: Atmosphere adjusting chamber, 7: Inert gas supply device, 8: Cooling device, 9: Rotating device, 10: slit, 11: segment, 12: solidified material,
13: Melt, 14: Storage container, 15: Exhaust gas treatment device

Claims (1)

[Claims] 1. A low temperature crucible having a conductive cooling wall made of an assembly of segments electrically insulated from each other by a slit, a current-carrying coil formed by multiplying the crucible in multiple turns, and a high-frequency current is supplied to the coil. High-frequency power source, high-frequency current switchgear, material supply device for supplying solidified metal to low-temperature crucible, atmosphere control chamber, inert gas supply device,
A method of manufacturing a container using an apparatus equipped with a segment cooling device, a low-temperature crucible rotating device, and an exhaust gas treatment device, after induction melting of the material of the solidified metal supplied to the low-temperature crucible, and then high frequency to the energizing coil. A method for manufacturing a container made of a solidified metal by cutting off the supply of electric current and rotating the crucible around a vertical axis.