JP2003294889A - Recovering method for platinum group element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover platinum group elements along with vitrification processing. <P>SOLUTION: After glass cullet 4 of iron phosphate is fused in a heating vessel 5 usable repeatedly, waste liquid 2 containing platinum group elements M is put into the vessel 5, and fused glass G mixed with the waste liquid 2 is transferred into another storage vessel 6. By repeating these operations, work for sealing radionuclides in vitrified glass S inside the vessel 6 is performed, and platinum group elements M which adhere to the internal bottom of the vessel 5 is caused to grow laminarly, and these platinum group elements M are separated from the vessel 5 and recovered. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a platinum group element recovery method.

[0002]

2. Description of the Related Art Waste liquid generated by reprocessing spent fuel is vitrified in a waste liquid treatment facility and then stored in a waste storage facility.

FIG. 2 shows an example of a glass melting furnace constituting a waste liquid treatment facility. This glass melting furnace has a melting space 11 having a shape in which a horizontal opening cross section is gradually reduced downward from an intermediate portion in the vertical direction. And a melting furnace body 12 formed of a refractory material.

At the upper part of the melting furnace body 12, a raw material supply pipe 1
3, the waste liquid supply pipe 14 and the exhaust pipe 15 are the melting space 11
Connected to communicate with.

Inside the melting furnace body 12, there is a melting space 11
A pair of main electrodes 16 facing each other in the vertical middle portion and a pair of bottom electrodes 17 facing in the vicinity of the bottom of the melting space 11 are provided so as to be immersed in the molten glass G stored in the melting space 11.

At the bottom of the melting furnace body 12, a melting space 11
A downflow nozzle 18 communicating with the downflow nozzle 18, an induction heating coil 19 surrounding the downflow nozzle 18, and an air injection pipe 20 capable of blowing cooling air to the downflow nozzle 18.

Further, below the melting furnace body 12, there is provided a carrier truck 22 on which a container 21 for storage is placed and which can be laterally moved directly below the downflow nozzle 18.

In the glass melting furnace shown in FIG. 2, the raw material glass (borosilicate glass) fed from the raw material supply pipe 13 into the melting space 11 is heated by a heater (not shown) attached to the melting furnace main body 12. Melted, main electrode 16 and bottom electrode 1
Power is supplied to 7 to keep the molten glass G in the melting space 11 warm so as not to be solidified by Joule heat.

At this time, the glass is solidified in the downflow nozzle 18 and the outflow of the molten glass G from the melting space 11 to the outside is prevented.

In this state, when the raw material glass is fed from the raw material supply pipe 13 into the melting space 11, the raw material glass is melted into the molten glass G, and the waste liquid supply pipe 14 causes the melting space 11 to flow.
When the waste liquid generated by the wet reprocessing of the spent fuel is fed into the inside, the waste liquid is mixed with the molten glass G.

In the vitrification treatment of the waste liquid, the container 21 is placed on the carrier 22 and the carrier 22 is moved so that the container 21 is located immediately below the downflow nozzle 18.

Next, the downflow nozzle 18 is heated by supplying electric power to the induction heating coil 19 to melt the glass solidified in the downflow nozzle 18, and the molten glass G mixed with the waste liquid is passed through the downflow nozzle. 18 to container 21
Let it flow out.

When the filling amount of the molten glass G into the container 21 approaches the set value, the heating of the downflow nozzle 18 by the induction heating coil 19 is interrupted, and if necessary, the air injection pipe 20 transfers to the downflow nozzle 18. Blow air.

As a result, the glass is solidified in the downflow nozzle 18, and the downflow of the molten glass G is stopped.

When the container 21 is naturally cooled by air, the molten glass G is solidified, and various radioactive nuclides contained in the waste liquid are contained in the solidified glass S.

[0016]

The waste liquid generated by the reprocessing of the spent fuel contains uranium fission products as
When a small amount of platinum group element (ruthenium, rhodium, palladium, etc.) is contained and the platinum group element which is a conductive substance is deposited on the inner bottom portion of the melting furnace body 12, a short circuit is caused between the bottom electrodes 17 due to current flow. It is feared that the molten glass G cannot be maintained at a temperature suitable for flowing down.

However, it is impossible to selectively recover only the platinum group element from the molten glass G kept warm by Joule heat.

It is also conceivable to recover the platinum group element contained in the waste liquid by electrolytic deposition before performing the vitrification treatment. For that purpose, an electrolytic deposition facility is separately prepared. There must be.

The present invention has been made in view of the above situation, and an object thereof is to enable efficient recovery of platinum group elements in parallel with vitrification treatment.

[0020]

In order to achieve the above object, in the platinum group element recovery method according to claim 1 of the present invention, the raw material glass is melted in a heating container that can be repeatedly used. On top of that, a radioactive waste liquid containing a very small amount of platinum group element is put into the heating container, and the molten glass mixed with the radioactive waste liquid is transferred from the heating container to the storage container by repeating the operation. A platinum group element layer is formed on the inner bottom of the heating vessel, and the platinum group element is separated from the heating vessel.

In the platinum group element recovery method according to the second aspect of the present invention, the heating container is made of nonmetal and the raw material glass is iron phosphate glass.

In any of the methods for recovering a platinum group element according to claim 1 or 2 of the present invention, a single heating container is repeatedly used for the step of heating the raw material glass and the step of mixing the radioactive waste liquid with the molten glass. After being used, the platinum group element adhering to the inner bottom portion of the heating container is grown in layers, and then the platinum group element is separated from the heating container and recovered.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an example of an embodiment of a platinum group element recovery method of the present invention. In carrying out the recovery method, a high frequency induction heating furnace 1 and a waste liquid 2 generated by wet reprocessing of spent fuel are used. Container 3 for handling, and container 5 for heating for melting iron phosphate glass cullet 4
And a container 6 for storage for forming a vitrified body.

The high frequency induction heating furnace 1 is formed by embedding an induction heating coil 8 in a furnace body 7 made of refractory and into which a container 5 can be inserted.

The container 5 is made of silicon carbide, which is a non-metal material having conductivity and excellent heat resistance.

The container 6 is made of a metal material having high rigidity such as steel or stainless steel.

First, in the furnace body 7 of the high frequency induction heating furnace 1,
The container 5 containing the iron phosphate glass cullet 4 is inserted, and the container 5 is heated by passing a high-frequency current through the induction heating coil 8 to set the iron phosphate glass cullet 4 to 1000 to
It is melted at an ambient temperature of about 1200 ° C.

The high temperature iron phosphate glass in the molten state significantly corrodes the metal, but since the container 5 is made of silicon carbide, it is possible to avoid the corrosion of the container 5.

When the iron phosphate glass cullet 4 is sufficiently melted, when the waste liquid 2 previously stored in the container 3 is mixed with the molten glass G in the container 5, various radioactive substances contained in the waste liquid 2 are mixed. Among the nuclides, the platinum group element M precipitates and adheres to the inner bottom of the container 5.

Further, the container 5 is taken out of the high-frequency induction heating furnace 1, and the molten glass G mixed with the waste liquid 2 is transferred to the container 6 and naturally cooled by air, so that the molten glass G is solidified in the container 6, As a result, the radionuclide other than the platinum group element contained in the waste liquid 2 is contained in the solidified glass S.

The temperature of the molten glass G transferred to the container 6 is
Since the temperature of the container 5 has started to drop since it was taken out of the high-frequency induction heating furnace 1, the container 6 made of a metal material is not corroded.

When the vitrification treatment as described above is repeated using the single container 5, the platinum group element M attached to the inner bottom of the container 5 becomes layered.

The platinum group element M is separated and recovered from the inner bottom of the container 5 by mechanical means or the use of a laser beam.

As described above, in the platinum group element recovery method shown in FIG. 1, the single container 5 is repeatedly used for the step of heating the iron phosphate glass cullet 4 and the step of mixing the waste liquid 2 with the molten glass G, Since the radionuclide other than the platinum group element is contained in the solidified glass S in the container 6, the platinum group element M adhering to the inner bottom of the container 5 is grown in layers and separated from the container 5. The platinum group element M can be efficiently recovered in parallel with the vitrification treatment.

The method for recovering the platinum group element of the present invention is not limited to the above-described embodiment, but the glass raw material is put into a container formed of a heat resistant material such as alumina and the container is heated by a heater or It goes without saying that the glass raw material can be melted by heating with a plasma heating device, and other changes can be made without departing from the scope of the present invention.

[0037]

As described above, according to the platinum group element recovery method of the present invention, a single heating container is repeatedly used in the step of heating the raw glass and the step of mixing the radioactive waste liquid with the molten glass. , The radionuclide is contained in the solidified glass in the storage container, and the platinum group element adhering to the inner bottom of the heating container is grown in layers and separated from the heating container. In parallel, the platinum group element can be efficiently recovered, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a procedure of an example of a platinum group element recovery method of the present invention.

FIG. 2 is a conceptual diagram showing an example of a glass melting furnace.

[Explanation of symbols]

2 Waste liquid (radioactive waste liquid) 4 Iron phosphate glass cullet (raw glass) 5 containers (heating containers) 6 containers (storage containers) G molten glass M platinum group element

Claims (2)

[Claims] 1. A method in which a raw glass is melted in a heating container that can be repeatedly used, and then a radioactive liquid waste containing a minute amount of a platinum group element is put into the heating container to mix the radioactive liquid waste. By repeating the operation of moving the molten glass from the heating container into the storage container, a layer of the platinum group element is formed on the inner bottom of the heating container, and the platinum group element is separated from the heating container. A characteristic platinum group element recovery method. 2. The method for recovering a platinum group element according to claim 1, wherein the heating container is made of non-metal and the raw material glass is iron phosphate glass.