KR101567720B1 - Solidification System and Its Method for Pelletized Radioactive Waste Using Low Melting Metal - Google Patents

Abstract

The present invention relates to a solidification system for pelletized radioactive waste using low-melting metal, and a method thereof. The solidification system comprises an electric furnace (10) which heats low-melting metal to melt; a casting mold (20) into which a low-melting metal in a liquid state, molten by the electric furnace (10), and a sintered pellet (1) are injected; a pressurizing device (30) which pressurizes the sintered pellet (1) and the low-melting metal injected into the casting mold (20); and a drum (40) which accommodates a solidified material molded by the casting mold. According to the above-mentioned configuration, the present invention can safely and stably treat a sintered pellet including a radiative material.

Description

Technical Field [0001] The present invention relates to a solidification system of a radioactive waste pellet sintered body using a low melting point metal,

The present invention relates to a system for solidifying a pellet of a radioactive waste pellet using a low melting point metal and a method thereof, and more particularly to a system for solidifying a pellet of a radioactive waste pellet using a low melting point metal, and more particularly to a method for pulverizing radioactive waste such as concentrated liquor, waste water, and sludge generated in a nuclear power plant or a nuclear power plant, A pellet sintered body obtained by sintering the pellets formed together is solidified by using a metal having a low melting point such as lead, tin and bismuth, thereby making it possible to more stably store the radioactive waste. To a solidification system of a pellet-sintered body and a method thereof.

During the operation or maintenance of a nuclear power plant, large amounts of radioactive liquid wastes such as concentrated wastes are generated. These radioactive liquid wastes are first evaporated and treated through a waste liquid evaporator, (CWDS), and the like. Finally, an ion exchange resin or the like is used in the process of treating the radioactive liquid waste by using the liquid waste disposal apparatus, and sludge is generated , Which are also treated as radioactive waste.

On the other hand, according to the "Regulations on the Delivery of Medium and Low-Level Radioactive Waste" and "Regulations on the Method of Acquisition of Radioactive Waste", it is necessary to solidify the homogeneous wastes (concentrated wastes, waste water, sludge, incineration ash), and the solidified solidifies the structural stability, It is required to pass test standards such as rational number measurement. In other countries, similar regulations are prepared and the low-level radioactive waste is treated and managed.

Methods for treating medium- and low-level radioactive waste through solidification, which have been developed and used so far, include cement solidification, asphalt solidification, polymer solidification and paraffin solidification.

Cement has excellent properties as a solidifying agent of radioactive waste, it is easy to obtain, cheap, sufficient strength and long-term safety can be expected. Although the method of treating radioactive waste using the cement solidification method has various advantages, The present invention provides a new cement solidification method that improves the utilization rate of the cement. The cement consolidation method has been developed for PWR (pressurized light water reactor type) nuclear power plant containing borate. The use of the new cement hardening method improves the utilization rate, but there still remains the problem that the amount of waste increases.

The asphalt solidification method is a waste treatment method that mixes low level radioactive waste generated from nuclear power plants and spent fuel reprocessing facilities together with heated and melted asphalt and stably in a solid body. Most of the remaining water in the waste is removed It has a superior sweetening effect and an excellent anti-ablative effect as compared with the cement hardening method, but has a disadvantage that the solidified body itself is combustible and vulnerable to fire.

In addition, the plastic solidification method is a method of using a thermosetting plastic or a thermoplastic plastic to achieve a high curing efficiency, but the drawback is that the solid body itself is flammable like an asphalt solid.

In addition, in the case of the paraffin solidification method, there is a problem that it is difficult to meet the test standards such as the immersion and leaching test and flammability test specified in the acceptance standard and the delivery regulation due to the physical / chemical characteristics of the paraffin as the solidifying agent.

In order to solve the problems of the above-described conventional low-level radioactive waste disposal method through solidification, a solidification method through a pellet sintered body has been proposed. In this method, the radioactive waste of a medium to low level is first dried and pulverized and then mixed with a small amount of binder In this method, pellets are made into pelletized sintered bodies. In this method, the amount of waste can be greatly reduced to about 1/7 of the conventional cement solidification method. In addition, a solidifying agent or a solidifying agent can be selected. It is possible to solidify the composition even if it is only put into the container, and the sensitivity is not influenced by the kind of the solidifying agent.

However, in spite of the above advantages, the pellet sintered body does not satisfy the discharge allowance criterion because the radioactive material is contained in the pellet sintered body. Therefore, in order to dispose the pellet sintered body, the pellet sintered body must be stabilized by solidifying it again. There is no need to develop a system and a method for effectively solidifying the pellet sintered body.

KR 10-1188680 B1 KR 10-2008-0078531 A JP 1996-110397 A JP 1999-148997 A

The present invention has been accomplished in view of the above-mentioned needs, and it is an object of the present invention to provide a pelletized sintered body having pelletized flammable or nonflammable radioactive waste generated in a nuclear power plant by solidifying the pelletized sintered body using a low melting point metal, The present invention provides a solidification system and method for a radioactive waste pellet using a metal.

An object of the present invention is to provide a solidification system for a pellet of a radioactive waste pellet, comprising: an electric furnace for heating and melting a low melting point metal; A casting mold into which a low melting point metal and a pellet sintered body are injected into a liquid phase molten by an electric furnace; A pellet sintered body injected into the casting mold and a pressurizing device for pressurizing the low melting point metal; And a drum for receiving the solid body molded by the casting mold.

Another object of the present invention is to provide a solidification system for a radioactive waste pellet sintered body, wherein the solidification system comprises an electric furnace for heating and melting the low melting point metal; A drum into which a low melting point metal and a pellet sintered body are melted by an electric furnace; And a vibrating device provided on the outer circumferential surface of the drum for causing the pellet-sintered body injected into the drum and the low-melting-point metal to be excited.

The present invention is characterized in that the pressure device comprises a cylinder, a piston which is moved up and down in the cylinder, a piston rod connected to the piston, and a pressure plate installed at the lower end of the piston rod.

The present invention is also characterized in that the pressure plate of the pressure device is provided with a structure in which the transfer jig can be detachably attached so that the solid body formed by the casting mold can be easily removed.

In addition, the present invention is characterized in that a spacer is provided inside the drum to prevent the solidified body from flowing.

Another object of the present invention is to provide a method for solidifying a pellet of a radioactive waste pellet, comprising the steps of: preparing a pellet sintered body and a casting mold; A low-melting-point metal melting step of melting a metal having a low melting point into a liquid phase; A molten metal injection step of injecting a molten low-melting metal into a cylindrical casting mold, and then pouring the pelletized sintered body into a cylindrical shaped body; A solidification step of cooling the formed body formed by the molten metal injection step to obtain a solid body in a solid state; And a solid casting step in which the solid body produced by the solidifying step is taken out of the casting mold and placed in the interior of the drum and the upper open end of the drum is sealed.

Another object of the present invention is to provide a method for solidifying a pellet of a radioactive waste pellet, comprising the steps of: preparing a pellet sintered body and a casting mold; A low-melting-point metal melting step of melting a metal having a low melting point into a liquid phase; A molten metal injection step of injecting molten low melting point metal into a cylindrical drum and then injecting the pellet sintered body and injecting the molten low melting point metal again to form a cylindrical shaped body; And a solidification step of cooling the formed body by the molten metal injection step to obtain a solid body in a solid state.

Further, the present invention is characterized in that the step of injecting the molten metal further comprises a step of pressing the pellet sintered body and the low melting point metal injected into the casting mold by a pressurizing device.

In addition, the present invention is characterized in that the step of injecting molten metal is performed in a state in which a clamp is installed to prevent the pellet sintered body from floating inside the drum.

The present invention solidifies the pellet sintered body containing radioactive waste by using a low melting point metal such as chemically stable lead, thereby making it possible to more securely and safely dispose of the radioactive waste.

Further, in the present invention, when a pellet-sintered body is fixed by a low-melting-point metal and solidified, a clamp is provided in the drum to solidify the pellet so that the pellet compact is uniformly distributed in the solidified body.

The present invention effectively removes air bubbles or the like when a melted metal is injected into a drum or a casting mold, thereby preventing an air layer from being formed in the solidified body.

FIGS. 1A and 1B are views schematically showing a system for solidifying a solid state radioactive waste using a low melting point metal according to the present invention,
2 is a front view showing an example of an electric furnace and a tilting unit according to the present invention;
3 is a sectional view showing an example of a casting mold and a pressurizing device according to the present invention,
4 is a sectional view showing an example of a drum and a fixing unit according to the present invention,
Fig. 5 (a) is a process chart showing a method of solidifying a solid body of radioactive waste using a low-melting-point metal according to the first embodiment,
Fig. 5 (b) is a process chart showing a method of solidifying a solid state radioactive waste using the low melting point metal according to the second embodiment in order. Fig.

Hereinafter, the structure and operation of the present invention will be described in more detail with reference to the accompanying drawings, which show preferred embodiments.

The present invention relates to a system and a method for solidifying a radioactive waste solid body using a low-melting-point metal capable of effectively solidifying and treating a solid body formed by pelletizing flammable or non-radioactive radioactive waste generated in a nuclear power plant by using a low melting point metal The solidification system of the present invention is provided with an electric furnace 10, a casting mold 20, a pressurizing device 30, a cooling device 21 and a drum 40 as shown in FIG. 1 Since the solidification method according to the present invention solidifies the solid body using these systems, the method for solidifying the solidification system using the solidification system is described below, As an example.

In the present invention, depending on how solidification of the radioactive waste solid body using the low melting point metal is achieved, that is, as shown in FIGS. 1A and 1B, the casting mold 20 is used to form a cylindrical solid body Depending on whether the molded solid 20 is solidified by a method in which the molded solid is injected again into the drum 40 or solidified in such a manner that a solid body is formed by using the drum 40 without using the casting mold 20, Hereinafter, the two-wobbling method will be described as one embodiment.

≪ Example 1 >

In the first embodiment, as shown in Figs. 1A and 5A, the molten low-melting point metal 2 is first injected into the pellet sintered body 1 using the casting mold 20 to form a cylindrical solid body, And then solidifying the cylindrical solid is injected into the drum again.

(1) preparation step (S100)

In this step, the waste that does not satisfy the disposal suitability, etc. is dried and pulverized, and then a small amount of binder is mixed and molded into pellets and then sintered. The pellet sintered body 1, Preparing a casting mold 20 or the like for injecting a metal, wherein the pellet sintered body 1 is prepared while being injected into the hopper.

(2) melting the low melting point metal (S110)

This step is a step of melting a metal having a low melting point into a liquid phase using an electric furnace 10 or the like.

The low melting point metal (2) used in the present invention is selected from any one of lead, tin and bismuth or a combination thereof, which is easy to handle among low melting point metals (2) The pellet sintered body 1 may exist in a stable state when solidifying the pelletized sintered body 1 by using them, so that the solidified body can be treated and stored more safely.

In the present invention, the electric furnace 10 is used for melting the low melting point metal 2, and the electric furnace 10 used in the present invention is formed by melting the low melting point metal 2 The tilting unit 11 is tilted by 90 degrees or more so that the casting mold 20 can be easily injected into the casting mold 20. To this end, the electric furnace 10 is provided with a support frame 11A, An electric furnace 10 is rotatably installed on the support frame 11A and a drive unit 11B connected to the rotary shaft 11C of the electric furnace 10 is provided at one side of the upper portion of the support frame 11A, It is preferable that the electric furnace 10 is tilted by the operation so that the electric furnace 10 can be tilted at an appropriate speed by providing a speed reducer (not shown) between the drive unit 11B and the rotary shaft 11C Do.

In addition, when the low melting point metal 2 is melted by using the electric furnace 10, many noxious gases are generated in this process. Therefore, the electric furnace 10 is provided with a gas collecting device 12 are installed.

(3) Molten metal injection step (S120)

This step is performed by injecting the pellet compact 1 prepared by the preparing step S100 and the low melting point metal melting step S120 and the molten low melting point metal 2 into the cylindrical casting mold 20, , Wherein a predetermined amount of the low melting point metal (2) is first introduced, and then the pellet compact (1) is inserted.

The casting mold 20 used in the present invention has a cylindrical shape with an open upper part as shown in FIG. 3, and the inner diameter of the casting mold 20 at this time is determined by the shape of the solidified material molded by the casting mold 20 The inner diameter of the drum 40 is equal to or slightly smaller than the inner diameter of the drum 40 so as to be easily accommodated in the drum 40.

When the molten low melting point metal is injected into the casting mold 20 into which the pellet sintered body 1 is injected to form the molded body, the pellet sintered body floats due to buoyancy of the melted low melting point metal 2, Since the air layer can be formed in the molded solid because of the presence of bubbles in the molten metal, a certain amount of the molten low melting point metal 2 is supplied to the casting mold 20, And then pressurized by the pressurizing device 30 to remove the air layer generated in the course of the pellet sintered body 1 being charged.

3, the pressure device 30 used in the present invention includes a cylinder 31 positioned above the casting mold 20, a piston 32 moved up and down in the cylinder 31, A piston rod 33 connected to the piston 32 in a downward direction and a pressure plate 34 installed at a lower end of the piston rod 33. The pressure plate 34 is a cylinder in which air, And it is preferable that the size of the eye is smaller than the size (diameter) of the pellet sintered body 1.

Therefore, when the solidified body is molded, first, in the state in which the heating unit provided on the outer circumferential surface of the casting mold 20 is operated, a pellet sintered body having a volume equivalent to 15-20% of the internal volume of the casting mold 20, Melting metal 2 is injected into the casting mold 20 by tilting the electric furnace 1 and then the pressurizing device 30 is placed on the casting mold 20 to operate the casting mold 20, The pressure plate 34 is gradually lowered through the opened upper space of the mold 20 and the molten low melting point metal 3 and the pellet sintered body 1 are simultaneously pressed to remove the bubbles.

In this case the pressure plate 34 is attached to the pressing device (30) is 5 ~ 10 cm / sec while having a slow descent speed, and pressing at a pressure of less than 5 kg _f / cm ^2, this is solidified in a compact structure is formed by.

After the low melting point metal is injected by the above process, the molten metal is cooled to obtain a solidified solid. Then, the solidified material is taken out of the casting mold 20 and put in a cylindrical drum 40. In general, The solidified material can be easily removed from the casting mold 20 because the volume of the metal is reduced. However, in the present invention, as shown in FIG. 3, The transfer jig 35 has a structure in which the transfer jig 35 is connected to the pressure plate 34 by means of bolts or the like so that the transfer jig 35 can have a size of 30 to 40% So that the entire solid body can be easily removed when the solid body is removed from the casting mold 20 by using the transfer jig 35 It is preferred.

(4) solidification step (S130)

This step is a step of cooling the molded body formed by the molten metal injection step (S120) to make a solid body in a solid state, thereby further stabilizing the radioactive waste, wherein the cooling can be performed by either of the air cooling system and the water cooling system However, in order to speed up the solidification process, it is preferable to cool the water-cooled type. To this end, a water jacket is installed on the outer circumferential surface of the casting mold 20 separately from the above-mentioned heating device.

(5) Solid holding stage (S140)

In this step, the solid body solidified by the solidification step (S400) is taken out of the casting mold 20, put into the inside of the disposal drum 40, and closed on the open upper side of the drum 40, The solid body containing the pellet sintered body 1 is placed in the drum 40 and the drum 40 having the solid body placed thereon is transported to a storage place or a permanent repository in a nuclear power plant, Permanently disposed.

When the solid body is placed in the drum 40, the size of the solidified body may be smaller than the inner diameter of the drum 40 due to contraction or the like during the formation of the solidified body. As a result, In this case, the solid object can easily flow in the drum 40, so that when the solid object is transported or handled, the solid material flows into the solid material to damage the drum 40 Problems can arise.

In order to solve this problem, in the present invention, a spacer (not shown) is provided in the gap between the drum 40 and the solid body, wherein the spacer is made of stainless steel and has a concavo-convex structure.

≪ Example 2 >

The pellet sintered body 1 is injected into the drum 40 as shown in FIG. 1B and FIG. 5B immediately without using the casting mold 20 as in Embodiment 1, And solidifying the solidified by injecting a point metal and cooling it.

(1) preparation step (S200)

This step is a step of drying and pulverizing wastes which do not satisfy disposal suitability, and then mixing a small amount of binder to form pellets and then sintering the pellet sintered body 1, A cylindrical drum 40 for injecting a metal, and the like. At this time, the pellet sintered body 1 is prepared while being injected into the hopper.

(2) melting the low melting point metal (S210)

This step is a step of melting a metal having a low melting point into a liquid phase using an electric furnace or the like, which is the same as the first embodiment, and thus a detailed description thereof will be omitted.

(3) Molten metal injection step (S220)

This step is performed by injecting the pellet compact 1 prepared by the preparing step S200 and the low melting point metal melting step S210 and the molten low melting point metal 2 into the cylindrical drum 40, In this step, a predetermined amount of the molten low melting point metal 2 is first introduced, then the pellet sintered body 1 is charged, and the molten low melting point metal 2 is injected again.

The molten metal is uniformly distributed between the pellet sintered bodies 1 when the molten low melting point metal is injected into the drum into which the pellet sintered body is injected and at the same time the physical reaction and bubbles generated by boiling of the molten metal are removed In order to achieve this, in the present invention, a vibration device 50 capable of being detachably attached to the outer circumferential surface of the drum 40 is provided, and when the molten metal is injected into the drum, the drum is excited, And the molten metal is uniformly distributed between the pellet sintered bodies 1.

The vibration device 50 used in the present invention is a vibration device 50 provided with a magnetic distortion converter made of Fe-Co, Diferal, and Ni material, wherein the magnitude of the vibration is controlled by adjusting the resonance frequency.

When the liquid molten metal is injected into the interior of the die 40 in which the pellet sintered body 1 is accommodated, as described in the first embodiment, the pellet sintered body 1 is buoyant by the buoyancy of the melted low melting point metal 2, The pellet sintered body 1 is uniformly distributed and the solidified body of a dense structure can not be formed. Accordingly, in the present invention, the pellet sintered body 1 is provided with the clamp 60 inside the drum 40, The clamp 60 used in the present invention is configured such that the upper fixed plate 61 and the lower fixed plate 62 in the form of a disk and the upper and lower fixing plates 61 and 62 are connected And the upper and lower fixing plates 61 and 62 are connected to each other by a nut being engaged with the threads.

Therefore, in molding the molded body, first, a lower fixing plate 62 with a plurality of connecting rods 63 sandwiched therebetween is installed in the drum 40, and then an amount of 15-20% of the inner volume of the drum 40 After the pellet sintered body 1 is poured, the upper fixing plate 62 is positioned at the upper end of the connecting rod 63 and engaged.

After the pellet sintered body is positioned between the upper and lower fixing plates 61 and 62 of the clamp 60 by the above process, the vibration device 50 Melting metal 2 is injected into the drum 40 while the drum 40 is operated to tilt the electric furnace 10 so that the molten low melting point metal 2 is melted into the pellet sintered body 1, and the bubbles in the molten metal are removed by the vibration at this time.

(4) solidification step (S230)

This step is a step for cooling the formed body formed into a cylindrical shape inside the drum 40 by the molten metal injection step (S220) to make a solid body in a solid state, Water-cooled type.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the pellet sintered body is solidified by using a metal having a low melting point such as lead, tin or bismuth, so that the radioactive waste can be more stably disposed.

1: pellet sintered body 2: low melting point metal
10: electric furnace 11: tilting unit
11A: Support frame 11B: Drive unit
11C: rotating shaft 12: gas collecting device
20: casting mold 21: cooling device
30: pressurizing device 31: cylinder
32: piston 33: rod
34: pressure plate 40: drum
50: Vibrating device 60: Clamp
61: upper fixing plate 62: lower fixing plate
63: connecting rod

Claims (11)

A solidification system for solidifying and treating a pellet sintered body containing radioactive waste,
The solidification system comprises an electric furnace (10) for heating and melting any one low melting point metal selected from lead, tin and bismuth;
A casting mold 20 into which a pellet compact 1 and a low melting point metal in a liquid phase melted by the electric furnace 10 are injected;
A pellet sintered body (1) injected into the casting mold (20) and a pressurizing device (30) for pressurizing the low melting point metal;
And a drum (40) for receiving a solid body formed by the casting mold (20)
A spacer having a concavo-convex structure is provided in the drum 40 so that the solid body does not flow,
The pressure device 30 includes a cylinder 31, a piston 32 which is moved up and down in the cylinder 31, a piston rod 33 connected to the piston 32, And a pressure plate 34 provided at the lower end of the pressure plate 34,
A plurality of conveying jigs 35 are installed on the bottom surface of the pressure plate 34 of the pressurizing device 30 so that the entirety of the solid formed by the casting mold can be easily removed,
Wherein the size of the transfer jig (35) is formed to have a length corresponding to 30 to 40% of the height of the solidification body.
delete delete delete A solidification system for solidifying and treating a pellet sintered body containing radioactive waste,
The solidification system comprises an electric furnace (10) for heating and melting any one low melting point metal selected from lead, tin and bismuth;
A drum 40 into which the low melting point metal of the liquid phase melted by the electric furnace 10 and the pellet sintered compact 1 are injected;
And a vibration device (50) provided on the outer circumferential surface of the drum (40) for causing the pellet sintered body (1) injected into the drum (40)
A clamp 60 composed of a connecting rod 63 connecting the upper and lower fixing plates 61 and 62 and the upper and lower fixing plates 61 and 62 so as to prevent the pellet sintered body from floating in the drum 40, Respectively,
Wherein the vibration device (50) is a vibration device equipped with a magnetic distortion converter, and is configured to adjust a resonance frequency, wherein the solidification system comprises a low melting point metal. delete delete delete delete delete delete

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