JP4218187B2 - Metal sludge measuring instrument for glass melting furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass melting furnace used when vitrifying high-level radioactive waste liquid, and more particularly to a measuring device for metal sludge generated in the glass melting process.
[0002]
[Prior art]
The high-level radioactive liquid waste generated after the reprocessing of spent nuclear fuel has extremely high radiation and decay heat, and is difficult to dispose of in the liquid state. After being sent into the glass melting furnace 1 and being melted together with a glass raw material such as borosilicate glass at a high temperature and packed in a corrosion-resistant stainless steel container called a canister c, the glass solidified body is stabilized. It is planned to dispose deeply underground after natural cooling for a period.
[0003]
As shown in the figure, this glass melting furnace 1 has a downhole 3 through which the inner bottom part of the furnace body 2 is narrowed in a funnel shape (square pyramid shape) and the molten glass in the furnace 2 flows down at the lowermost end part thereof. A bottom electrode 4 is provided, and a pair of main electrodes 5 and 5 and auxiliary electrodes 6 and 6 are provided therein.
[0004]
And after throwing in a high level radioactive waste liquid and a glass raw material from the inlet 7 provided in the ceiling wall of this furnace main body 2, first, by supplying an electric current between the main electrodes 5 and 5, the high level near the surface layer part is carried out. The radioactive liquid waste and the glass raw material are sufficiently melted together, and then electricity is passed between the auxiliary electrodes 6 and 6 located in the lower part to melt the high-level radioactive liquid waste and the glass raw material in the lower layer part, and finally, After flowing the electricity between the bottom electrode 4 and the main electrodes 5 and 5 to melt the whole, the falling nozzle 8 extending from the falling hole 3 is heated by the surrounding electric heating coil 9 and the solidified glass clogged in the inside is heated. By melting and extracting, the molten glass in the furnace 2 is caused to flow down into the canister c located at the lower part thereof and hermetically accommodated as a glass solidified body therein.
[0005]
The gas generated in the melting furnace 1 is exhausted as an off-gas from the exhaust port 7a, and radioactive substances are completely collected and removed by a HEPA filter or the like (not shown) so as to be released into the atmosphere. It has become.
[0006]
[Problems to be solved by the invention]
By the way, in such a glass melting process, a platinum-based metal such as ruthenium or palladium contained in the high-level radioactive liquid waste may precipitate as a metal oxide to generate a metal sludge having a large specific gravity. It accumulates on the bottom electrode 4 and grows along the inclined surface 2a, eventually reaches the auxiliary electrode 6 or the main electrode 5 and short-circuits between the electrodes, and a large current flows locally to cause the electrodes 4, 5, 6 may be inconvenient.
[0007]
Therefore, it is necessary to accurately and quickly grasp the presence and amount of metal sludge accumulated in the furnace body 2, but no method for accurately grasping it has been proposed at present.
[0008]
In order to facilitate the outflow of this metal sludge, it is conceivable to process the upper surface of the bottom electrode 4 into a funnel shape. This is not a good idea because it causes problems such as blocking.
[0009]
Therefore, the present invention has been devised in order to effectively solve such problems, and the purpose thereof is a novel glass melting furnace capable of accurately grasping the presence / absence and amount of deposition of metal sludge. A metal sludge detector is provided.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is inserted into the furnace body in a metal sludge measuring instrument which is inserted into the furnace body of a glass melting furnace and measures the deposition state of the metal sludge deposited on the inner bottom thereof. A pair of electrodes are inserted into a tubular measuring instrument body having a closed tip, the electrodes are insulated and supported in the measuring instrument body with an insulating material, and the insertion instrument tip side surface of the measuring instrument body is opened. The tip of the electrode is exposed and positioned in the opening.
[0011]
That is, when such a metal sludge measuring instrument is inserted into the furnace body and energized between the electrodes, the conductivity of the metal sludge is higher than that of the molten glass. Of course, it is possible to detect whether or not metal sludge is deposited, and it is also possible to accurately grasp the deposition status at the same time by measuring the insertion position.
[0012]
The detector body closes the insertion tip and opens the side surface of the insertion tip, and the conductivity is measured by flowing metal sludge into the inside from the side opening. Even if the insertion tip of the measuring instrument main body collides with the furnace wall or the furnace bottom, the electrode can be detected without any damage, and highly reliable detection can be performed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, a preferred embodiment for carrying out the present invention will be described with reference to the accompanying drawings.
[0014]
FIG. 1 shows an embodiment of a metal sludge measuring instrument 10 for a glass melting furnace according to the present invention.
[0015]
As shown in the figure, this metal sludge measuring instrument 10 has a pair of rod-like electrodes 12 and 12 inserted in parallel into a tubular measuring instrument body 11 whose tip is closed, and the electrodes 12 and 12 are heat resistant such as ceramic. The insulating body 13 is insulated and supported in the measuring instrument main body 11. Further, an opening 14 is formed on the side surface of the insertion tip of the measuring instrument main body 11, and the electrode 12 is positioned in the opening 14 with the tip of the electrode 12 exposed. . Further, a power supply circuit is connected to the other end of the electrodes 12, 12, and a power supply unit 15 for supplying current to the circuit and a resistance measuring device 16 for measuring the electric resistance flowing through the circuit are connected. Yes.
[0016]
In order to measure the presence / absence of metal sludge and the amount of deposition by the metal sludge measuring instrument 10 of the present invention having such a configuration, first, an insertion formed on the ceiling wall 2b of the furnace body 2 as shown in FIG. While inserting from the hole 2c, supplying the electric current between the electrodes 12 and 12, the front-end | tip is located in arbitrary positions in the furnace main body 2, for example, the bottom electrode 4. FIG. Here, if metal sludge is present on the bottom electrode 4, the metal sludge flows into the electrodes 12, 12 from the opening 14 at the tip of the measuring instrument body 11, and the current resistance between the electrodes 12, 12. Since the value rapidly decreases, the current resistance value is detected by the resistance measuring device 16 so that the presence of the metal sludge at that portion can be reliably grasped.
[0017]
Thereafter, when the tip of the measuring instrument main body 11 is moved along the slope 2a of the furnace wall from such a state as shown in FIG. 2, the resistance value hardly changes in the portion where the metal sludge is accumulated, Since the resistance value suddenly changes (increases) when the metal sludge disappears, by observing the movement of the measuring instrument body 11 and the change in resistance value, of course, the presence or absence of metal sludge in the furnace body 2 Accumulated amount, accumulated part, etc. can be grasped. Further, since the measuring instrument main body 11 is in a state in which the tip is closed and the electrodes 12 and 12 are protected, there is no possibility that the electrodes 12 and 12 are directly contacted or collide with the furnace wall to be damaged.
[0018]
The metal sludge is not always generated only on the furnace bottom, that is, on the bottom electrode 4. That is, as described above, in the initial stage of melting, current is passed only between the main electrodes 5 and 5 to melt only the upper layer portion, and the glass raw material at the bottom portion is in an unmelted state, so that it is generated in layers in the middle portion. In some cases. Therefore, in such a molten state, the metal sludge measuring device 10 of the present invention is moved along the layer boundary line, so that the deposition state of the metal sludge on the layer boundary line can be accurately grasped.
[0019]
In addition, since the inside and the periphery of the glass melting furnace 1 are under a very high level of radiation, these operations are performed remotely by a manipulator, an ITV camera, or the like provided in the vicinity thereof. Not too long.
[0020]
【The invention's effect】
In short, according to the present invention, the presence / absence of metal sludge and the amount of deposition can be accurately grasped, so that it is possible to avoid a short-circuit accident of the in-furnace electrode. In addition, the possibility of occurrence of a short-circuit accident due to the deposition state of metal sludge can be obtained in advance in a trial operation or a mock-up test of a glass melting furnace, so that the effect of improving the furnace bottom structure can be accurately evaluated. An excellent effect such as being able to do so can be exhibited.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a metal sludge measuring instrument for a glass melting furnace according to the present invention.
FIG. 2 is a conceptual diagram showing a method for measuring the state of metal sludge accumulation using the metal sludge measuring instrument according to the present invention.
FIG. 3 is an explanatory view showing a configuration of a conventional glass melting furnace.
4 is a cross-sectional view taken along line XX in FIG.
FIG. 5 is a partially enlarged view showing a portion y in FIG. 3;
[Explanation of symbols]
2 Furnace body
10 Metal sludge measuring instrument
11 Measuring instrument body
12 electrodes
13 Insulation material
14 opening
15 Power supply
16 Resistance measuring instrument

Claims (1)

A metal sludge measuring instrument that is inserted into a furnace body of a glass melting furnace and measures the deposition state of the metal sludge accumulated therein, a pair of pipes in the tubular measuring instrument body having a closed tip inserted into the furnace body. The electrode is inserted into the measuring instrument body with an insulating material, and the insertion tip side surface of the measuring instrument body is opened and the tip of the electrode is exposed in the opening. A metal sludge measuring instrument for a glass melting furnace, characterized in that

Images