JPH0668552B2 - Continuous melting device for cut nuclear fuel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a continuous melting apparatus for cut nuclear fuel, and more particularly to a continuous melting process of a nuclear fuel accompanied by a toxic and corrosive solution and a dissolved gas by a small facility. Processability, workability,
The present invention relates to a continuous melting device for nuclear fuel with improved safety and maintainability.

[Prior Art] Conventionally, a dissolving device using nitric acid for cut nuclear fuel is
A screw type closed type continuous dissolution tank as shown in FIG. 4 is used.

In FIG. 4, 1 is a material inlet, 2'is a cylindrical container, 3'is a spiral rotary screw, 4 is a waste gas outlet, 5 is a nitric acid inlet, 6 is a wash water inlet, and 7 is a metal. One-sided discharge port, 9 is a wash water outlet, and 10 is a solution discharge port.

The nuclear fuel cut pieces introduced from the material introduction port 1 are introduced into the spiral helical screw 3'having a gradient. Nitric acid is introduced into the cylindrical container 2 ′ from the nitric acid charging port 5, and the cut pieces of nuclear fuel proceed at a constant rotation speed while contacting with the nitric acid solution. The dissolved nuclear fuel becomes nitrate and is discharged and collected from the solution discharge port 10 at the lower left portion of the rotor. The undissolved metal piece proceeds while rotating further, is cleaned with nitric acid in the cleaning zone, moves to the draining zone, and the metal piece in which the nuclear fuel is dissolved is collected from the metal piece discharge port 7.

However, the conventional continuous dissolving tank has the following drawbacks.

Since the melting zone, the washing zone, and the draining zone are provided inside the rotor, and the material inlet for the nuclear fuel cut pieces and the outlet for the dissolving liquid are disposed in the axial direction, the apparatus is too large.

Since the shaft exists at the center of the rotor, the movement space of the cut pieces is limited, and the diameter must be increased in order to prevent mechanical troubles such as bridges.

Since the cut pieces of nuclear fuel proceed up the slope, the return phenomenon of the cut pieces is likely to occur, which makes it difficult to stably transfer the cut pieces.

Since there is no stirring mechanism inside the rotor and outside the rotor and there is a climbing gradient, the slurry easily accumulates in the lower part of the tank, and troubles such as clogging are likely to occur. In addition, the heat transfer and stirring effects that require melting in the rotor are very low.

Since there is a seal part in the liquid contact part of the dissolution tank main body, there is a problem in reliability of containing a highly toxic and corrosive solution.

Since the net stretched on the outer circumference of the rotor cannot be separated from the gas discharge nozzle, the mist generated during melting is not sufficiently separated, and mist with strong toxicity and corrosiveness may accompany the exhaust gas. .

It is impossible to do maintenance remotely.

As described above, the conventional continuous melting apparatus for nuclear fuel has many problems in terms of reaction efficiency, workability, safety, and maintainability.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems of the conventional type, prevents the accumulation of slurry, enhances the dissolution effect, and prevents the generation of highly toxic and corrosive mist. It is an object of the present invention to provide a continuous melting apparatus for cut nuclear fuel, which has high workability, high safety, and easy maintenance.

[Means and Actions for Solving the Problems] The present inventors have completed the present invention as a result of various studies on the above problems.

That is, according to the present invention, a hollow rotor having an air circulation hole in the lower part of a melting tank body for melting cut nuclear fuel and accommodating a hollow spiral continuous screw therein is horizontally installed. The material inlet and the nitric acid inlet are provided at the beginning and the end of the rotor, respectively, from above the melting tank body, the metal piece outlet is provided at the bottom of the rotor end, and the solution outlet is provided at the side. A cut nuclear fuel, comprising a waste gas discharge port above the tank main body, a cooling means provided at an upper part inside the main body, and a gas guide plate and a gas blowing pipe respectively provided at a lower part of the rotor. Continuous melting device.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a continuous melting apparatus for cut nuclear fuel showing an embodiment of the present invention, FIG. 2 is an enlarged view showing a rotor portion of FIG. 1, and FIG. 3 is a metal attached to the continuous melting apparatus. The washing part and discharging part of the piece are shown respectively.

In FIGS. 1 to 3, 1 is a material charging port, 2 is a rotor, 3 is a hollow spiral screw, 4 is a waste gas discharging port, 5 is a nitric acid charging port, 7 is a metal piece discharging port, and 10 is a solution. Discharge port, 11 is a gas guide plate, 12 is a gas blowing pipe, 1
3 is a heating means, 14 is a carry-out basket, 15 is a cleaning unit,
Reference numeral 16 is a discharge distributor, 17 is a receiving basket, and 18 is a cooling means. In addition, A is a melting tank main body, B is a rotor start end portion, and C is a rotor end portion.

The nuclear fuel cutting pieces are introduced into the starting end portion B on the left side of the rotor 2 from the material inlet 1 above the melting tank body A. On the other hand, nitric acid is introduced from the terminal end C on the right side of the rotor 2 from the nitric acid charging port 5 above the dissolution tank main body A. And the nuclear fuel cut piece is the rotor 2
Inside, it is contacted with nitric acid and dissolved. The rotor 2 is horizontally installed in the lower part of the melting tank main body A.

The rotor 2 is provided with holes (not shown) for stirring by pressurized gas in the lower half thereof, for example, holes having a diameter of 3 mm are formed at intervals of 7 mm, and the inner peripheral surface has a hollow spiral shape. Is provided with a continuous screw 3 and a gas guide plate 11 is provided below the rotor 2. The gas blowing pipe 1 installed at the lower portion of the rotor 2 is provided in the hole for introducing the stirring air.
It is possible to introduce the pressurized gas from No. 2 and to reliably send the gas into the rotor 2 by the gas guide plate 11 provided at the lower portion of the rotor 2, so that sufficient stirring and heat transfer are performed. In this way, the rotor 2 which is installed horizontally and provided with the agitating means by air makes sufficient contact between the cut nuclear fuel and the nitric acid solution, and the nuclear fuel cut pieces do not accumulate in the rotor 2 and 2 By the time it reaches the end on the right side, the nuclear fuel in the cut piece is completely melted.

The rotation speed of the rotor 2 can be arbitrarily changed, but it is preferable to rotate the rotor 2 at a frequency that secures a residence time necessary for melting, and in about 3 to 4 hours, the nuclear fuel cut pieces will dissolve the nuclear fuel. , Reaches the end portion on the right side of the rotor 2. Further, by using ceramic for the rotary bearing rubbing portion of the rotor 2, deterioration of the rubbing portion due to the fine powder slurry under hot nitric acid heated by the heating means 13 can be suppressed. The rotor 2 and the peripheral rubbing portion of the rotor are integrally formed with the melting tank main body lid, and are designed to be easily maintained.

The waste gas discharge port 4 is for removing the gas generated by melting and the gas used for stirring. In the present invention, since the cooling means 18 such as a cooling jacket is provided in the upper portion of the melting tank body, the gas can be discharged without entraining mist in the exhaust gas.

The gas blowing pipe 12 is installed at the bottom of the melting tank below the rotor 2, and pressurized gas is introduced through a hole provided in the lower half of the rotor 2. At this time, the gas guide plate 11 introduces the gas into the rotor 2. As well as being surely introduced, regular convection is caused, and the efficiency of stirring and heat conduction of the solution is achieved. Further, the solution is discharged from the solution discharge port 10 provided on the side of the rotor end portion C, and the metal piece is discharged from the metal piece discharge port 7 provided below the rotor end portion C.

In addition, as shown in FIG. 2, the rotor 2 accommodates the hollow screw 3 on the inner peripheral surface thereof and does not have a shaft for rotation, so that a sufficient reaction space can be secured, and a mechanical device such as a bridge is provided. No trouble will occur. In the lower half of the rotor 2, a hole for stirring with a pressurized gas (for example, a diameter of 3 mm,
7 mm pitch) and a gas guide plate 11 at the bottom of the rotor 2.
Is provided, as described above, the stirring and heat conduction of the solution are sufficiently performed, and the dissolution reaction with nitric acid is effectively performed. Note that the solution discharge port 10 is omitted in FIG.

Further, FIG. 3 shows a cleaning part and a discharging part of the metal cutting pieces after melting in the continuous melting device as described above, in which the nuclear fuel discharged from the metal piece discharging port 7 is melted metal. The cut pieces enter the carry-out basket 14, are pulled up, are cleaned with nitric acid at the cleaning port 15, and are introduced into the receiving basket 17 via the discharge distributor 16.

Although not shown in the drawing, a slurry washing pipe, a dissolution liquid return pipe for further concentrating the dissolution liquid, and the like are provided in the rotor 2.

As described above, according to the continuous melting apparatus of the present invention,
The following effects can be obtained.

By improving the rotor structure, the size of the melting tank body can be reduced.

The metal pieces can be quantitatively moved in the solution without mechanical troubles such as catching of the metal pieces and a bridge phenomenon.

With the guide plate and gas blowing pipe attached to the lower part of the rotor, liquid circulation inside and outside the rotor can be actively performed,
It promotes heat conduction and mass transfer, which gives a good dissolution effect.

Since there is no seal in the liquid contact part of the dissolution tank that holds the solution inside, there is no risk of liquid leakage, and the reliability of containing these liquids has increased.

Since the rotating part is integrated with the melting tank main body cover, it can be easily removed remotely and maintenance is easy.

Mist can be sufficiently removed from the gas generated by melting.

The reliability of the bearing portion against corrosion and abrasion is significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the continuous melting apparatus of the present invention, FIG. 2 is an enlarged view of the rotor portion of FIG. 1, and FIG. 3 is attached to the continuous melting apparatus of the present invention. The figure which shows the washing | cleaning part and discharge part of a metal cutting piece, FIG. 4 is sectional drawing which shows the conventional melting apparatus. 1: Material input port, 2: Rotor, 2 ': Cylindrical container, 3, 3': Screw, 4: Waste gas outlet, 5: Nitric acid inlet, 6: Wash water inlet, 7: Metal fragment outlet, 8: Washing waste liquid outlet, 9: Washing water outlet, 10: Dissolution liquid outlet, 11: Gas guide plate, 12: Gas blowing pipe, 13: Heating means, 14: Carry-out basket, 15: Washing part, 16: For discharging Distributor, 17: receiving basket, 18: cooling means, A: melting tank body, B: rotor start end, C: rotor end.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shinya Kumagai 26-2 Shirattoridai, Shirattoridai, Midori-ku, Yokohama-shi, Kanagawa Prefecture 545 (72) Inventor, Kazuhiro Tabuchi 140-23, Kamakura-shi, Kanagawa Prefecture

Claims (3)

[Claims] 1. A hollow rotor having an air passage hole in the lower portion of a melting tank body for melting the cut nuclear fuel and containing a hollow spiral continuous screw therein is installed horizontally. The material inlet and the nitric acid inlet are provided at the beginning and the end of the rotor, respectively, from above the melting tank body, the metal piece outlet is provided at the bottom of the rotor end, and the solution outlet is provided at the side. A cut nuclear fuel, comprising a waste gas discharge port above the tank main body, a cooling means provided at an upper part inside the main body, and a gas guide plate and a gas blowing pipe respectively provided at a lower part of the rotor. Continuous melting device. 2. The continuous melting apparatus for cut nuclear fuel according to claim 1, wherein the rotor and the peripheral rubbing portion of the rotor are integrally dropped with the melting tank main body lid structure. 3. A cleaning / discharging portion for a metal cutting piece is attached to a metal piece discharging port at the rotor end portion.
A continuous melting apparatus for the cut nuclear fuel according to the item.