JP4936770B2 - Molten metal level management method and molten metal level management system - Google Patents

Description

  The present invention relates to a molten metal level management method and a molten metal level management system.

  Of the low-level radioactive waste generated at nuclear power plants, for example, miscellaneous solid waste is packed in drums and then filled with mortar, and the drums are disposed of in a predetermined burial site. Since the burial area is limited, it is preferable to reduce the volume of miscellaneous solid waste and reduce the number of drum cans to be buried.

  Therefore, as a technique for reducing the volume of miscellaneous solid waste, a melting volume reduction facility using a high frequency induction heating method has been proposed. In this facility, miscellaneous solid waste, which is an object to be melted, is melted and reduced and solidified in a canister set in a melting furnace, and then packed together with the canister in a drum can. Then, the drum can is filled with a solidified material such as mortar to form a waste body.

With regard to a melting furnace control method in such a melting facility, for example, a tuyere where a high temperature combustion zone is formed in the lower part of the furnace and a waste layer is formed on the high temperature combustion zone, and oxygen-containing gas is blown into the high temperature combustion zone A waste melting furnace for thermally decomposing the waste to melt ash and incombustible content in the waste and discharging the melt from the outlet. A waste melting furnace comprising: means for measuring temperature; and means for adjusting the temperature of the oxygen-containing gas blown to the tuyere based on the measured temperature of the melt (Patent Document 1) Have been proposed).
JP 2003-74823 A

  By the way, in a melting furnace, a voltage is applied to a high-frequency induction coil in the melting furnace to generate a magnetic field and Joule heat resulting from the magnetic field, thereby increasing the temperature in the canister and melting an object to be melted. . This melting may be for a melting object that has been previously charged into the canister or for a melting object that has been additionally charged after the volume of the melting object has been reduced.

  However, when the miscellaneous solid waste, which is an object to be melted, put into the canister in this way contains a predetermined amount or more of metal powder or metal pieces, problems are likely to occur in the melting process. The problem is caused by the fact that a large amount of iron oxide is generated in the canister due to the introduction of the metal powder and the like, and this large amount of iron oxide generates carbon monoxide. The carbon monoxide generated here rises in the molten metal in the canister toward the liquid surface, that is, in the atmosphere, and there is a concern that the molten metal itself may be rapidly increased. Therefore, this rise in the molten metal level led to the spilling of molten metal from the canister, which forced the automatic shutdown of the melting furnace and subsequent complicated recovery measures. As a result, the volume reduction processing efficiency of miscellaneous solid waste is reduced, leading to deterioration in processing costs and labor.

  Accordingly, the present invention has been made in view of the above problems, and provides a molten metal level management method and a molten metal level management system that enables efficient melting management of miscellaneous solid waste in consideration of metal powder and the like. Main purpose.

The molten metal level management method of the present invention that solves the above-mentioned problem is a molten metal level management method in a low-level radioactive waste volume reduction facility , and a predetermined amount or more of metal powder or metal pieces are contained in the low-level radioactive waste. Sorting and excluding the metal powder or metal pieces from the melting target in the melting furnace before melting, a metal powder etc. exclusion procedure, and a melt level detection procedure for detecting the melt level in the melting furnace provided in the volume reduction equipment, A level determination procedure for determining whether the detected molten metal level has risen above a predetermined range, and a melting furnace temperature lowering process when it is determined by the determination that the molten metal level has risen above a predetermined range. And a temperature lowering procedure to be performed.

  In the molten metal level management method, the temperature reduction procedure may be a process of reducing the melting furnace temperature to around 1480 ° C.

The molten metal level management system of the present invention is a molten metal level management system in a low-level radioactive waste volume reduction facility , and selects a predetermined amount or more of metal powder or metal pieces from the low-level radioactive waste, Exclusion means for excluding the metal powder or metal pieces from the melting target in the melting furnace before melting, molten metal level detecting means for detecting the molten metal level in the melting furnace provided in the volume reduction equipment, and the detected Level determining means for determining whether or not the molten metal level has risen above a predetermined range, and temperature lowering means for performing a melting furnace temperature lowering process when it is determined by the determination that the molten metal level has risen above a predetermined range. And.

  In the molten metal level management system, the temperature lowering means may lower the melting furnace temperature to around 1480 ° C.

  According to the present invention, efficient melting management of miscellaneous solid waste in consideration of metal powder and the like becomes possible.

  Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing the overall configuration of a radioactive waste treatment facility to which the present invention is applied. Previously, the present applicant has developed a volume reduction facility 300 for miscellaneous solid waste shown in FIG. In the present embodiment, it is assumed that the miscellaneous solid waste volume reduction system 300 implements the miscellaneous solid waste melt level management system of the present invention and at the same time performs the miscellaneous solid waste melt level management method.

  The miscellaneous solid waste volume reduction facility 300 includes a pretreatment facility 1 for sorting miscellaneous solid waste, a melting facility 2 for melting fusible waste among the sorted miscellaneous solid waste, It consists of a mortar solidification facility 3 in which a drum can containing molten waste after completion is filled with mortar to form a solidified product 37 and a storage facility 4 for temporarily storing the solidified product 37.

  The pretreatment facility 1 separates miscellaneous solid wastes 5 having different properties (materials, dimensions, shapes, etc.) generated at nuclear power generation facilities into wastes 6 not to be treated, direct fillers 7 and melted objects 8 A sorting table 9 is provided.

  Moreover, the cutting machine 10 which cut | disconnects the to-be-melted object 8 in the magnitude | size which is easy to fuse | melt, the storage means 13 which accommodates the to-be-melted object 8 in each of the charging container 11 and the canister 12, and melting | fusing equipment 2 and an unloading means 16 for unloading the drum 15 filled directly with the filler 7 to the mortar solidification facility 3.

  The sorting table 9 includes a rotating unit 17 such as a turntable that receives and rotates the miscellaneous solid waste 5 sent from the nuclear power generation facility, and a fixed unit 18 that supports the rotating unit 17. The sorting work of the miscellaneous solid waste 5 in the sorting table 9 may be performed by manual work of a plurality of personnel arranged so as to surround the rotating unit 17. The miscellaneous solid waste 5 is classified into, for example, three categories of non-processing target waste 6, direct filling 7, and melting target 8.

  The sorting table 9 sorts out a predetermined amount or more of metal powder or metal pieces from the low-level radioactive waste in the present invention, and removes the metal powder or metal pieces from the melting target in the melting furnace 21. It becomes an exclusion means. Therefore, for example, an appropriate sensor or mechanism for identifying a characteristic or form peculiar to a predetermined amount or more of metal powder or metal piece is provided, and the predetermined amount or more of metal powder or metal piece is included in the miscellaneous solid waste. It is preferable to sort and exclude miscellaneous solid waste.

  The non-processable waste 6 is, for example, harmful substances such as lead and flammable substances. The toxic substances are carried out to a storage, and the flammable substances are incinerated separately in an incineration facility.

  On the other hand, the direct filler 7 is a non-ferrous metal such as brass and flame retardant waste such as vinyl chlorides and rubbers, which adversely affect the melting equipment 2 by melting. The direct filling 8 is filled in the drum can 15 as it is, for example, manually, and is carried out to the mortar solidification facility 3 by the carrying-out means 16 such as a movable carriage or a crane.

  Further, the object to be melted 8 is an incombustible material such as metals such as carbon steel and stainless steel, concrete, heat insulating material, and glass inorganic materials whose volume can be reduced by melting. Of the melted object 8, large miscellaneous solid waste or irregularly shaped miscellaneous solid waste is cut by the cutting machine 10 into a size that can enter the input container 11 or the canister 12. These melting objects 8 are stored in the charging container 11 or the canister 12 by storage means 13 such as a manual operation or a conveyor, and are transported to the melting facility 2 by the transporting means 14 such as a crane or a conveyor.

  On the other hand, the melting equipment 2 has a substantially cylindrical shape, and has a melting furnace 21 around which a high-frequency induction coil 20 is spirally wound. Further, from the lower side of the melting furnace 21, the canister 12 previously packed with the object 8 to be melted is lifted and loaded inside the high-frequency induction coil 20. After the melting is finished, the canister 12 is lowered and the cooling device 22. A moving device 23 is provided.

  Further, the melting facility 2 lowers the charging container 11 from the upper side of the melting furnace 21 into a marginal space in the canister 12 generated by melting and reducing the volume of the initially loaded melting target object 8. 11 is provided with a charging device 24 for charging the melted object 8 into the canister 12 by opening the gate at the bottom.

  In addition, a monitoring camera 25 that constantly monitors the melting state inside the canister 12, a flue 26 that discharges the exhaust generated from the melting furnace 21, a filter 27 that filters dust in the exhaust, and an exhaust gas blower that sucks exhaust gas And an exhaust treatment device 29 that renders the exhaust sucked by the exhaust gas blower harmless. The monitoring camera 25 serves as a molten metal level detecting means for detecting the molten metal level in the melting furnace 21 in the present invention.

  Further, in order to facilitate handling of the canister 12 such as loading the canister 12 into the furnace and taking it out of the furnace, and for measuring the outer surface temperature of the canister 12, the inner wall of the melting furnace 21 and the canister 12 There is a gap between them.

  In such a melting facility 2, a magnetic field is generated by applying a voltage to the high-frequency induction coil 20 in the melting furnace 21, and Joule heat is generated to raise the temperature inside the canister 12 to about 1500 ° C. The object 8 is melted. When there is room in the canister, the melting object 8 in the charging container 11 is melted while being sequentially added into the canister 12, and the additional charging is continued until a predetermined molten metal level is reached. The molten metal level and the molten state are constantly monitored by the monitoring camera 25 provided near the upper portion of the melting furnace 21 overlooking the inside of the canister 12.

  Further, a flue 26 for exhaust discharge is opened near the upper portion of the melting furnace 21, and a flue pipe 30 is connected to the flue 26. The flue pipe 30 is connected to an exhaust treatment device 29 through a filter 27. Due to the suction operation of the exhaust gas blower, the inside of the melting furnace is always kept at a negative pressure to prevent external diffusion of the exhaust gas. Further, the exhaust gas is filtered by the filter 27 to remove dust in the exhaust gas, and then passed through the exhaust treatment device 29 to be harmless and discharged into the atmosphere.

  The molten waste 31 after the end of melting in the canister 12 is taken out of the melting furnace 21 together with the canister 12 by the canister moving device 23, and is conveyed to the cooling device 22. Further, the molten waste 31 cooled to the predetermined temperature by the outside air or the like in the cooling device 22 is accommodated in the drum can 32 together with the canister 12.

  FIG. 2 is a schematic diagram of a melting facility including a melt level management system for miscellaneous solid waste in the present embodiment. As shown in FIG. 2, the melting facility 2 in the present embodiment includes a molten metal level detection means 25 (e.g., a monitoring camera) that detects a molten metal level in the melting furnace 21 provided in the volume reduction facility 300, and the detection. Level determining means 201 for determining whether or not the molten metal level has risen above a predetermined range, and a temperature decrease for performing a melting furnace temperature lowering process when it is determined by the determination that the molten metal level has risen above a predetermined range A molten metal level management system 200 comprising means 202 is provided.

  The molten metal level management system 200 is a computer provided in the melting facility 2 and acquires molten metal level information from the molten metal level detecting means 25. On the other hand, the molten metal level information and the allowance of the molten metal level stored in its own memory are obtained. Compare with rising range. From this comparison, it is determined whether or not the melt level in the current melting furnace 21, that is, the canister 12, has risen above a predetermined range. If this determination result is equal to or greater than the predetermined range, a melting furnace temperature lowering instruction is generated and notified to the temperature lowering means 202.

  The molten metal level detection means 25 can adopt not only the example of the monitoring camera 25 described above but also various other level detection means. The temperature lowering means 202 is also a device that circulates or conveys a cooling medium around the outer periphery of the canister 12, or a device that can simply reduce the voltage applied to the high-frequency induction coil 20, the canister 12, Depending on the form and structure of the melting furnace 21, it can be adopted as appropriate.

  FIG. 3 is a flowchart showing the processing procedure of the miscellaneous solid waste molten metal level management method in the present embodiment. Next, the processing procedure of the molten metal level management method for miscellaneous solid waste will be described. First, sorting and removal of a predetermined amount or more of metal powder or metal pieces from the low-level radioactive waste is performed in the sorting table 9 as a means for excluding metal powder or the like (s1000). A predetermined amount or more of the metal powder or metal piece selected and removed here is directly filled into the drum can 15 as the filling material 7 and is carried out to the mortar solidification facility 3 by the carrying-out means 16.

  On the other hand, the molten metal level in the melting furnace 21 (canister 12) is detected by a molten metal level detecting means such as the monitoring camera 25 (s1001). The level determination unit 201 compares the detected molten metal level with a predetermined allowable increase range (predetermined range level) (s1002), and determines whether or not it is greater than or equal to a predetermined range (s1003). If it is determined that the molten metal level is below the predetermined range (s1003: NO), the process returns to step s1001, and the normal operation state is maintained.

  On the other hand, when it is determined that the molten metal level is equal to or higher than the predetermined range (s1003: YES), the level determination unit 201 instructs the temperature reduction unit 202 to perform a melting furnace temperature reduction process. Receiving this, the temperature lowering means 202 performs an appropriate temperature lowering process, for example, by blowing air around the canister 12 or circulating a cooling medium (s1004). This temperature reduction process is performed in the canister 12, that is, until the melting temperature drops below a predetermined temperature (eg, about 1480 ° C.) (s 1005: NO → s 1004). If the melting temperature has dropped below the predetermined temperature (s1005: YES), this flow ends.

  According to the present invention, efficient melting management of miscellaneous solid waste in consideration of metal powder and the like becomes possible.

  As mentioned above, although embodiment of this invention was described concretely based on the embodiment, it is not limited to this and can be variously changed in the range which does not deviate from the summary.

It is explanatory drawing which shows the whole structure of the radioactive waste processing equipment to which this invention is applied. It is a melting facility schematic diagram including the molten metal level management system for miscellaneous solid waste in this embodiment. It is a flowchart which shows the process sequence of the molten metal level management method in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pretreatment equipment 2 Melting equipment 3 Mortar solidification equipment 4 Storage equipment 5 Miscellaneous solid waste 6 Unprocessed waste 7 Direct filling 8 Melting target 9 Sorting table, metal powder etc. exclusion means 10 Cutting machine 11 Input container 12 Canister DESCRIPTION OF SYMBOLS 13 Storage means 14, 16 Unloading means 15, 32 Drum can 17 Rotating part 18 Fixed part 20 High frequency induction coil 21 Melting furnace 22 Cooling device 23 Moving device 24 Input device, input means 25 Monitoring camera, molten metal level detection means 26 Flue 27 Filter DESCRIPTION OF SYMBOLS 29 Exhaust treatment apparatus 30 Flue pipe 31 Molten waste 33 Solidification material silo 34 Solidification material charging machine 35 Kneading machine 36 Hopper 37 Filled solidified body 200 Molten metal level management system 201 Level judgment means 202 Temperature reduction means 300 Miscellaneous solid disposal Material melting equipment s1001 Molten metal level detection procedure s1002 Level judgment Order s1004 temperature reduction procedure

Claims (4)

A method for managing a melt level in a volume reduction facility for low-level radioactive waste,
Sorting out a predetermined amount or more of metal powder or metal pieces from low-level radioactive waste, and excluding this metal powder or metal pieces from the melting target in the melting furnace before melting,
A molten metal level detection procedure for detecting a molten metal level in a melting furnace provided in the volume reduction facility, a level determination procedure for determining whether the detected molten metal level has risen above a predetermined range, and the molten metal level is predetermined by the determination. A temperature lowering procedure for performing a melting furnace temperature lowering process when it is determined that the temperature is higher than the range;
A molten metal level management method comprising: In claim 1 ,
The molten metal level management method, wherein the temperature lowering procedure is a process of lowering the melting furnace temperature to around 1480 ° C. A melt level management system for low-level radioactive waste volume reduction equipment,
A metal powder or metal piece of a predetermined amount or more is selected from the low-level radioactive waste, and this metal powder or metal piece is excluded from melting target in the melting furnace before melting, etc.
A molten metal level detecting means for detecting a molten metal level in a melting furnace provided in the volume reduction equipment, a level determining means for determining whether the detected molten metal level has risen above a predetermined range, and the molten metal level is predetermined by the determination. A temperature lowering means for performing a melting furnace temperature lowering process when it is determined that the temperature is higher than the range;
A molten metal level management system characterized by comprising: In claim 3 ,
The molten metal level management system characterized in that the temperature lowering means lowers the melting furnace temperature to around 1480 ° C.

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