JP2007271492A - Method and system for managing molten metal level - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the efficient melting management of miscellaneous solid waste which takes metal power and the like into consideration. <P>SOLUTION: A method for managing the molten metal level in facilities for a volume reduction of low-level radioactive waste is characterized in that the weight ratio of borax to silica sand is set at 1:1 when the borax and the silica sand are poured into the molten metal in a melting furnace included in the volume-reduction facilities so as to restrain the molten metal level from rising. <P>COPYRIGHT: (C)2008,JPO&INPIT

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.

  Regarding the control method of the melting furnace in such a melting facility, for example, waste is accommodated in a graphite-containing crucible, and the waste is induction-heated by an induction coil disposed on the outer periphery of the graphite-containing crucible, so that a slag layer and a metal A waste melting method of separating and melting into layers, wherein the induction coil has a higher temperature than a metal layer located in a lower part of the graphite-containing crucible in a slag layer located in the upper part of the graphite-containing crucible. A waste melting method (see Patent Document 1) that performs induction heating by controlling the output and melts the slag layer so as to reduce the surface tension has been proposed.

In addition, a multi-stage monitoring port is provided on the bottom wall of the waste melting furnace, and the inside of the furnace is monitored from any of the monitoring ports by any one of an imager, luminance meter, color measuring device, and infrared sensor. Based on one of the average brightness, brightness, chromaticity, infrared amount, and emissivity of each, it is determined whether the level of the monitoring port of each stage is the level of the waste accumulation layer or the level of the space Thus, a method for measuring a layer height level in a waste melting furnace (see Patent Document 2) characterized by obtaining a layer height level has also been proposed.
JP 2002-30354 A JP 2003-121243 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 includes a melting target object that has been input into the canister in advance and a melting target object that is additionally input after the volume of the melting target is 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 problems is a molten metal level management method in a low-level radioactive waste volume reduction facility, wherein the amount of borax for suppressing an increase in molten metal level is greater than the amount of silica sand input. The molten metal is introduced into the molten metal in the melting furnace provided in the volume reduction equipment (first invention).

  A second invention is a method for managing a melt level in a volume reduction facility for low-level radioactive waste according to the first invention, wherein the rise in the melt level is charged into a melt in a melting furnace provided in the volume reduction facility. The weight ratio of borax and quartz sand for suppression is 1: 1.

  A third invention is characterized in that, in the first or second invention, an input weight of the borax for each melting furnace is 1 kg, and an input weight of the silica sand for each melting furnace is 1 kg.

  According to a fourth invention, in any one of the first to third inventions, a molten metal level detection procedure for detecting a molten metal level in a melting furnace provided in the volume reduction facility, and the detected molten metal level rises to a predetermined range or more. A level determination procedure for determining whether the molten metal level has risen to a predetermined range or more by the determination, and an additive charging procedure for charging the borax and quartz sand into the molten metal in the melting furnace. , Including.

  According to a fifth invention, in any one of the first to fourth inventions, a predetermined amount or more of metal powder or metal pieces is selected from low-level radioactive waste, and the metal powder or metal pieces are melted in the melting furnace. It includes a procedure for excluding metal powder, etc., which is excluded from the target.

  A sixth aspect of the invention is a molten metal level management system in a low-level radioactive waste volume reduction facility, wherein the molten metal level detection means detects the level of the molten metal in the melting furnace provided in the volume reduction facility, and the detected molten metal. Level determining means for determining whether the level has risen above a predetermined range, and when the determination determines that the molten metal level has risen above a predetermined range, the borax and quartz sand are transferred to the molten metal in the melting furnace. And an additive charging means to be charged.

  A seventh invention is the metal according to the sixth invention, wherein a metal powder or a metal piece of a predetermined amount or more is selected from the low-level radioactive waste, and the metal powder or the metal piece is excluded from the melting object in the melting furnace. It includes an exclusion means such as powder.

  In addition, the problems disclosed by the present application and the solutions thereof will be clarified by the embodiments of the present invention and the drawings.

  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 obtain a solidified solid body, and a storage facility 4 for temporarily storing the solidified solidified body.

  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 the charging container 11 and the canister 12, respectively, and the charging container 11 and the canister 12 are melting 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 selects a predetermined amount or more of metal powder or metal pieces from the low-level radioactive waste in the present invention, and excludes the metal powder or metal pieces from the melting object in the melting furnace 21. It becomes a 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 the exhaust And an exhaust treatment device 29 for detoxifying the exhaust sucked by the exhaust gas blower. 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 determination means 201 for determining whether or not the molten metal level has risen above a predetermined range, and when it is determined by the determination that the molten metal level has risen above the predetermined range, borax and quartz sand are removed from the molten metal in the melting furnace. A molten metal level management system 200 comprising an additive charging means 202 for charging into the battery 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 the determination result is equal to or greater than the predetermined range, an instruction for adding molten borax and silica sand is generated and notified to the additive charging means 202.

  Here, the borax is in the molten metal, and it is possible to ensure fluidity at the molten metal level by suppressing the viscosity of the molten metal itself. On the other hand, the silica sand can suppress the generation of carbon monoxide due to the iron oxide generated in the molten metal. Accordingly, the present invention suppresses the viscosity of the molten metal with borax to improve the fluidity, and also causes the generation of carbon monoxide that rises in the molten metal toward the liquid surface, that is, the atmosphere and causes the molten metal itself to increase in level. This is an approach to the problem of increasing the melt level from both sides of the viscosity and carbon monoxide.

  Moreover, it is preferable that the weight ratio of the borax and the silica sand for suppressing the rise of the melt level to be introduced into the melt in the melting furnace 21 is 1: 1. Alternatively, the input weight of the borax for each melting furnace 21 (the canister 12) may be 1 kg, and the input weight of the silica sand for each melting furnace 21 (the canister 12) may be 1 kg. In any case, the weight ratio of borax and silica sand to be introduced was 0.6: 1 in the past, so the amount of borax input was increased compared to that of silica sand and the viscosity of the molten metal was considered. I can say that.

  As the borax and silica sand, for example, borax: Na2 ↓ B4 ↓ O7 ↓ 10H2 ↓ and quartz sand: ferrosilicon can be assumed, but borax and silica sand with other components are also applicable. It is.

  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. Also, the additive charging means 202 can be appropriately employed according to the form and structure of the canister 12 and the melting furnace 21 as long as it is an apparatus capable of charging borax and silica sand into the molten metal in the canister 12. .

  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 a predetermined range (s1003: YES), the level determining unit 201 instructs the additive charging unit 202 to perform a charging process on the molten borax and quartz sand. Do. In response to this, the additive charging means 202 opens a predetermined amount of the additive storage container 204 (e.g., hoof) by opening the open / close door 203 provided at a position facing the molten metal surface of the canister 12 for a predetermined time. The borax and silica sand are introduced at a weight ratio of 1: 1 sand to silica sand, or 1 kg of borax: 1 kg of silicate sand (s1004), and this flow ends. This borax and quartz sand molten metal charging process increases the fluidity by suppressing the viscosity of the molten metal with borax, and also raises the level of the molten metal itself by rising toward the liquid surface, that is, the atmosphere. The generation of carbon is suppressed by silicon.

  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 object 9 Sorting table, metal powder exclusion means 10 Cutting machine 11 Input container 12 Canister 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 25 Monitoring camera, molten metal level detecting means 26 Flue 27 Filter 29 Exhaust treatment device 30 Flue pipe 31 Molten waste 33 Solidified material silo 34 Solidified material charging machine 35 Kneader 36 Hopper 37 Filled solidified body 200 Molten metal level control system 201 Level judgment means 202 Additive charging means 203 Opening / closing door 204 Additive storage Container 300 Miscellaneous solid waste melting equipment

Claims (7)

  A method for managing the level of molten metal in a volume reduction facility for low-level radioactive waste, wherein the amount of borax for suppressing the rise in the level of molten metal is greater than the amount of silica sand, and is introduced into the molten metal in the melting furnace provided in the volume reduction facility. A molten metal level management method characterized by:   2. The method for managing a molten metal level in a low-volume radioactive waste volume reduction facility according to claim 1, wherein the borax and silica sand are used to suppress an increase in the molten metal level and are introduced into the molten metal in the melting furnace provided in the volume reduction facility. The molten metal level management method, wherein the weight ratio is 1: 1.   The molten metal level management method according to claim 1 or 2, wherein an input weight of the borax for each melting furnace is 1 kg, and an input weight of the silica sand for each melting furnace is 1 kg.   In any one of Claims 1-3, the molten metal level detection procedure which detects the molten metal level in the melting furnace with which the said volume reduction equipment is provided, and the level determination procedure which determines whether the detected molten metal level is rising beyond the predetermined range And an additive charging procedure for charging the borax and silica sand into the molten metal in the melting furnace when it is determined by the determination that the molten metal level has risen above a predetermined range. Melt level management method.   In any one of Claims 1-4, the metal powder etc. which sort out the metal powder or metal piece more than predetermined amount from the low level radioactive waste, and exclude this metal powder or metal piece from the melting object in the said melting furnace A molten metal level management method comprising an exclusion procedure.   A melt level management system in a low-level radioactive waste volume reduction facility, wherein the melt level detection means detects a melt level in a melting furnace provided in the volume reduction facility, and the detected melt level exceeds a predetermined range. Level determining means for determining whether or not it has risen, and additive charging means for charging the borax and silica sand into the molten metal in the melting furnace when it is determined by the determination that the molten metal level has risen above a predetermined range And a molten metal level management system. The metal powder or the like is excluded from the melting object in the melting furnace according to claim 6, including a predetermined amount or more of the metal powder or the metal piece from the low-level radioactive waste. A molten metal level management system.

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