GB2343899A

GB2343899A - Electrolytic treatment of nuclear waste

Info

Publication number: GB2343899A
Application number: GB9927452A
Authority: GB
Inventors: Michitaka Saso; Masaaki Kaneko; Shinya Miyamoto; Yoshikazu Matsubayashi; Yasushi Yamaguchi; Atsushi Nakajima; Nobuyuki Ikenaga
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1998-11-19
Filing date: 1999-11-19
Publication date: 2000-05-24
Anticipated expiration: 2019-11-19
Also published as: GB9927217D0; JP2000144274A; GB2343899B; FR2786205A1; GB9927452D0; FR2786205B1

Abstract

In a method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, a nitric acid solution is used as an electrolytic solution and the electrolytic solution is heated at a temperature of preferably more than 60{C so as to improve an electrolytic rate. The electrolytic solution is agitated by an ultrasonic generator to recover an oxide generated by an electrolytic treatment without hindering electrolysis and to make uniform an electrolytic state. In modifications a zirconium oxide film formed on the surface of the zirconium is continuously exfoliated while electrolysing and irradiating with ultrasonic waves. Alternatively the zirconium waste may be impacted, or agitated.

Description

ELECTROLYTIC TREATMENT METHOD OF ZIRCONIUM AND APPARATUS THEREFOR BACKGROUND OF THE INVENTION The present invention relates to treatment method and treatment apparatus of zirconium, and in particular, to a treatment method of a zirconium waste composed of a zirconium metal or an alloy thereof, or a spent fuel cladding tube, an enriched plutonium can or the like and also relates to a treatment apparatus thereof.

A spent fuel used in a nuclear power plant is transported to a reprocessing plant, and in the reprocessing plant, a fuel cladding tube composed of zirconium alloy is cut off, and then, is dissolved by a nitric acid solution. Uranium and plutonium dissolved in a nitric acid solution are separated and refined to be recycled.

On the other hand, the cut-off fuel cladding tube is stored in a water tank in a state of being untreated.

The cut-off fuel cladding tube is temporarily stored in the tank and, for this reason, a waste storage space is required for storing the waste. Further, an equipment is required for maintaining a water quality in the tank.

Therefore, a development of volume reduction and solidification for the cut fuel cladding tube has been demanded.

Moreover, the reprocessing plant is provided with equipments such as an enriched plutonium can, an dissolution vessel and an iodine removing tank, which handle a nitric acid at a high temperature, and these equipments are composed of a zirconium metal or an alloy thereof. These equipments will be disposed after being used for a predetermined period. Thus, these equipments must be treated as a solid zirconium waste, and for this reason, a development of volume reduction and solidification has been demanded. Treatment methods such as cutting, compressing and melting is reported as the method for treating the zirconium metal.

However, according to these methods as described above, a metal having a relatively high activity is handled, and therefore, it is required to severely perform an atmosphere control and a treatment for a radioactive gas generated in treating the metal. Moreover, in order to finally dispose a metallic waste composed of zirconium, a method of burying the metal waste in a stratum has been considered.

In a groundwater under stratum environment considered at present, zirconium in the form of IV-valent is more stable. After compressing, cutting or melting the zirconium metal, the zirconium metal is filled up in a container. However, according to the treatment method mentioned above, it is considered that the water will come into the container in the future. In such case, the zirconium reacts with the water to be oxidized, and then, considered that a hydrogen gas will be generated. Thus, a metallic waste makes a chemical reaction with an oxide, and then, a volume varies, and a generated gas is accumulated.

For this reason, there is an anxiety that an integrity or safety is lost in a disposal facility.

Moreover, the following methods have been known.

That is, there are a method of restricting a natural inflammation of zirconium metal, and an electrolytic treatment method for securing an adaptability to the final disposal, that is, the integrity of a disposal facility.

However, according to such electrolytic treatment method, with an acceleration of electrolytic reaction, a zirconium oxide layer having a very low conductivity is generated on a surface of the zirconium waste, and a current in electrolysis lowers, and as a result, a treatment rate is made slow.

Furthermore, in the conventional zirconium metal treatment (compressing, cutting and melting), there is also provided a problem such that, in order to restrict a natural inflammation, a gas system must be controlled, it is difficult to avoid a chemical reaction under environmental conditions at or after the final disposal.

According to the electrolytic technology for avoiding the above matters, there is a problem that a treatment rate is lowered at a time of the in electrolytic treatment.

Furthermore, at a time of the removal of fuel cladding or cutting of a metal (zirconium) such as spent fuel in a dissolving process thereof, there is a fear that a mechanical failure may be easily caused.

SUMMARY OF THE INVENTION It is an object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide an electrolytic treatment method of zirconium, which can change zirconium of a zirconium waste or spent fuel into an oxide suitable for a disposal environment and can perform an oxidation treatment without lowering a treatment rate and also to provide a treatment apparatus thereof.

Another object of the present invention is to provide an electrolytic treatment method of zirconium of a zirconium waste or spent fuel and a treatment apparatus therefor, which can facilitate an exfoliation of oxide generated on a surface of the zirconium.

These and other objects can be achieved according to the present invention by providing, in one aspect, a method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that a nitric acid solution is used as an electrolytic solution and the electrolytic solution is heated so as to improve an electrolytic rate.

In this aspect, the electrolytic solution is preferably heated at a temperature of more than 60 C. The zirconium waste is used as an anode for the electorolytic treatment.

In another aspect, there is provided a method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that a film layer of zirconium oxide formed on a surface of the zirconium is continuously exfoliated to keep an electrolytic treatment rate while irradiating an ultrasonic wave.

In a further aspect, there is provided a method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that only the zirconium waste or a spent fuel is arranged in an electrolytic solution to improve a current efficiency and, in order to keep an electrolytic treatment rate, an impact is continuously applied to accelerate an exfoliation of a zirconium oxide thin film layer formed on the surface of the zirconium.

In a still further aspect, there is provided a method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that an electrolytic solution is agitated to recover an oxide generated by an electrolytic treatment without hindering electrolysis and to make uniform an electrolytic state.

In this aspect, the electrolytic solution is agitated by an ultrasonic wave or mechanical means.

In a still further aspect, there is provided a method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that, in order to improve a current efficiency, only the zirconium waste or a spent fuel is arranged in an electrolytic solution in an electrolyzer, and the electrolytic solution is heated to accelerate an exfoliation of a film layer of a zirconium oxide formed on the surface of the zirconium waste or the spent fuel, an ultrasonic wave is irradiated to the heated electrolytic solution and an entire structure of the electrolyzer, and pressure and impact are applied to the whole of the zirconium.

In a still further aspect of the present invention, there is provided an apparatus for treating a zirconium waste or a spent fuel, comprising: an electrolyzer in which an electrolytic solution is stored; an electrolytic cell located in the electrolyzer, and having a passage hole through which the electrolytic solution passes and adapted to arrange the zirconium waste or a spent fuel; an anode contacting the zirconium waste or the spent fuel; a cathode contacting the electrolytic solution in the electrolyzer ; a direct current power source for applying a DC voltage to the anode and the cathode; a heating medium line attached to the electrolyzer and adapted to heat the electrolytic solution; and agitating means for agitating the electrolytic solution such as nitric acid solution.

In this aspect, the agitating means is a mechanical agitator or ultrasonic generator.

The apparatus may further comprises an off-gas treatment equipment for recovering a hydrogen gas, a carbon dioxide gas or a nitrogen oxide generated in the electrolyzer during the oxidation treatment.

In a still further aspect, there is provided a method of treating a zirconium waste composed of zirconium or a zirconium alloy through an oxidation treatment with electrolysis, characterized in that a zirconium waste is disposed in a waste storage cell having a number of holes at a bottom surface thereof, an oxide generated by an electrolytic treatment is continuously dropped from the waste storage cell so as to circulate the electrolytic solution in the waste storage cell.

In a still further aspect of the present invention, there is provided a method of treating a spent fuel in a cladding tube formed of a zirconium alloy through an oxidation treatment with electrolysis, characterized in that a spent fuel is used as an anode and a nitric acid solution is used as electrolytic solution to dissolve the cladding tube and a fuel element in contact to the nitric acid solution.

According to the present invention of the characters mentioned above, in the electrolytic oxidation treatment method of a zirconium waste composed of zirconium or a zirconium alloy, at the time of the electrolysis, the electrolytic solution is heated while irradiating the ultrasonic wave, and a pressure or impact is continuously applied from the upper portion to the whole zirconium and zirconium alloy. It is therefore possible to prevent a electrolytic reaction rate from lowering.

Moreover, in particular, in the case where a solid waste is relatively small, and its surface is covered with an oxide, the electrolytic solution is agitated so as to supply the solution into the waste storage cell. It is therefore possible to make uniform the state of the solution in the vicinity of a reactive portion of the electrolytic solution and to remove a zirconium oxide thin piece having a very low conductivity from an inner surface of the electrolytic cell.

Furthermore, according to the preferred embodiment, at the time of cutting the spent fuel (fuel assembly) and dissolving the same at the time of reprocessing the spent fuel, the removal of cladding and fuel dissolution can be achieved at the same time with less mechanical defect or damage.

The nature and further characteristic features of the present invention will be made clear from the following descriptions made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIG. 1 is a longitudinal section schematically showing one embodiment of an electrolytic treatment test apparatus of a zirconium waste according to the present invention; FIG. 2 is a longitudinal section schematically showing an electrolytic treatment test apparatus used in one embodiment of an electrolytic treatment method of a zirconium waste according to the present invention; FIG. 3 is a characteristic diagram showing an oxidation reaction start time dependency on a temperature of electrolytic solution in an example 1 of the electrolytic treatment method of a zirconium waste according to the present invention; FIG. 4 is a diagram showing a comparison between an electrolysis start time by heating in an example 2 and that at an ordinary temperature; FIG. 5 is a characteristic diagram showing a change of a current value when an ultrasonic wave (400 W) is irradiated in an example 3; FIG. 6 is a characteristic diagram showing a change of a current value when no ultrasonic wave is irradiated in the example 3; and FIG. 7 is a characteristic diagram showing a change of a current value when an ultrasonic wave (350 W) is irradiated in an example 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electrolytic treatment apparatus of a zirconium waste according to the present invention will be described hereunder with reference to FIG. 1.

In FIG. 1, a reference numeral 1 denotes an electrolyzer, and an upper cover 2 is attached to an upper opening of the electrolyzer 1 to be removable. In the electrolyzer 1, an electrolytic cell 3 is located through a support member 4, and a bottom portion of the electrolytic cell 3 is provided with a perforated plate 5 which has many fine holes functioning as flow passage holes of an electrolytic solution.

In the electrolytic cell 3, a zirconium waste 6, which is a target for an electrolytic treatment, is collected on the perforated plate 5, and a plate-like anode 7 is placed on the zirconium waste 6. The zirconium waste 6 includes, for example, cut small pieces of the spent fuel cladding tube and the enriched plutonium can, more specifically, a zirconium metal or an alloy thereof.

An electrolytic solution 8 such as nitric acid solution is stored in the electrolyzer 1, and a cathode 9 is immersed in the electrolytic solution 8 between an inner surface of the electrolyzer 1 and an outer surface of the electrolytic cell 3. The anode 7 and the cathode 9 are respectively connected to a direct current power source 12 via lead wires 10 and 11 penetrating through the upper cover 2. These lead wires 10 and 11 penetrate through an insulating member 13 mounted to the upper cover 2 so as to ensure an electrical isolation between the electrolyzer 1 and these wires.

The electrolyzer 1 is located on a base 14 provided with a magnetic stirrer 15. An agitator 16 is arranged on the bottom surface of the electrolyzer 1 facing the magnetic stirrer 15. When the magnetic stirrer 15 starts to be operated, the agitator 16 is rotated to agitate the electrolytic solution 8.

The electrolyzer 1 is attached with a jacket 17 for heating the electrolytic solution 8 at the outer surface from substantially the middle portion to a downward portion. The jacket 17 is connected with a heating medium line 18 which extends from the right-hand upward portion of the jacket 17 to the left-hand downward portion thereof as viewed in FIG. 1. The heating medium line 18 is provided with a temperature controller 19 and a circulating pump 20.

The temperature controller 19 keeps a heating medium to a predetermined temperature and drives the circulating pump 20 to supply the heating medium to the jacket 17, and thus, the heating medium is circulated through the heating medium line 18. The electrolytic solution 8 stored in the electrolyzer 1 is heated by the heating medium, and thereby, it is possible to improve an electrolytic rate as compared with the case of using a nitric acid solution as the electrolytic solution 8.

In this embodiment, the electrolytic cell 3 received in the electrolyzer 1 is filled up with the electrolytic solution 8 flowing through the perforated plate 5. When a voltage is then applied to the cathode 9, an electrochemical reaction takes place in the zirconium waste 6, and thus, a base metal (Zr) of the zirconium waste 6 is melted in the electrolytic solution 8. The metal is melted, and thereby, it is possible to remove a radioactive material adhering to the metal surface.

Moreover, in place of the agitator 16, an ultrasonic vibrator may be used. In the case of using the ultrasonic vibrator, the ultrasonic vibrator is connected to an ultrasonic generator so that an ultrasonic wave is irradiated into the electrolytic solution 8. It is thereby possible to keep a treatment rate at the electrolysis and to continuously exfoliate a zirconium oxide thin film layer which is formed on the surface of the zirconium waste 6 and has a very low conductivity, while irradiating an ultrasonic wave from an ultrasonic generator.

Next, the following is a description on each of examples 1 to 6 of an electrolytic treatment method of a zirconium waste according to the present invention.

(Example 1) An example 1 of the present invention will be described below with reference to FIG. 2 and FIG. 3.

This example 1 is correspondent to the invention defined in claim 1, and relates to an oxidation treatment method of a zirconium waste composed of zirconium or a zirconium alloy with electrolysis. In the case of using a nitric acid solution as an electrolytic solution, in order to improve an electrolytic reaction rate, the electrolytic solution is heated.

In FIG. 2 schematically showing an electrolytic treatment test equipment, a reference numeral 21 denotes an electrolyzer, 22 denotes a simulated waste, 23 denotes a zirconium oxide, 24 denotes an anode, 25 denotes a cathode, and 26 denotes an electrolytic solution.

A simulated waste 22, which is called as"hull" such as zirconium and a zirconium alloy generated when disassembling a facility such as a nuclear power plant handling a radioactive material, is arranged and immersed in the electrolytic treatment bath 21 as shown in FIG. 2 so that only the lower portion of the waste 22 contacts the solution. The surface of the simulated waste 22 is subjected to the oxidation treatment, and then, is covered with a zirconium dioxide.

With the use of the electrolytic treatment test equipment, a zirconium alloy was electrolyzed. A 10-normal nitric acid (HNO3) solution was used as the electrolytic solution 26. The cathode 25, which is subjected to a platinum treatment, was immersed in the electrolytic solution 26, and then, the anode 24, which is subjected to a platinum treatment, was contacted to the zirconium and a zirconium alloy outside the solution.

Thereafter, a direct current of 15V was applied to the anode 24 from a current source for an hour, and thus, an electrolytic treatment was carried out.

The electrolysis did not take place at a normal temperature. However, the electrolysis took place at a temperature of 40 C or more, preferably more than 60 C, (see FIG. 3). At this temperature, the electrolytic treatment start time showed a tendency to become effectively short with a rise of temperature.

Furthermore, when a spent fuel, in place of the zirconium waste, is treated, that is, the spent fuel is cut and dissolved at the fuel reprocessing time, the same apparatus shown in FIG. 1 is used. In this case, a fuel assembly (spent fuel) is arranged in the electrolytic cell 3 in place of the zirconium waste 6, the spent fuel is made as an anode and only the lower portion thereof is contacted to the electrolytic solution. Further, in such case, since the fuel assembly is usually in a suspended state, the electrolytic cell 3 may be eliminated.

(Example 2) In this example 2, like the example 1, with the use of the electrolytic treatment test equipment shown in FIG. 2, an electrolysis was carried out. A nitric acid concentration of the electrolytic solution 26 was used as a parameter, and then, an electrolysis was carried out in each of the ordinary temperature case and the case where the electrolytic solution 26 was heated to 80 C. In this case, a DC constant voltage of 14V was applied for an hour, and the electrolytic treatment was carried out. An electrolysis start time of each case was shown in FIG. 4.

In the ordinary temperature, in any cases, the electrolysis was started after a predetermined time elapsed. On the contrary, in the case where the electrolytic solution was heated to 80 C, the electrolysis was started just after the current conduction, and then, an oxide was steadily generated.

(Example 3) In this example 3, in an oxidation treatment of zirconium waste with electrolysis, in order to keep a treatment rate in the electrolysis, a zirconium oxide thin film layer, which is generated on the surface of the zirconium waste and has a very low electric conductivity, was continuously exfoliated while irradiating an ultrasonic wave.

In the case where the zirconium waste is relatively small (having a size easily disposed in the electrolytic cell), and its surface is covered with an oxide, in order to improve a current efficiency, only the waste is arranged in a solution. In the oxidation treatment method having an oxidation treatment structure, in order to keep an electrolytic treatment rate, an impact is continuously given to the whole of zirconium and zirconium alloy to accelerate an exfoliation of a zirconium oxide thin film layer generated on the surface of the zirconium.

With the use of the electrolytic treatment apparatus shown in FIG. 1, electrolysis was carried out. A 10-normal nitric acid (HNOa) solution heated to 800 C was used as the electrolytic solution 8, and a DC voltage of 14V was applied from the direct current power source 12 for an hour, and thus, electrolytic treatment was carried out.

FIG. 5 shows an elapsed-time change of current in the case of irradiating an ultrasonic wave of 400W, and FIG. 6 shows an elapsed-time change of current in the case of irradiating no ultrasonic wave.

Although a current value was high just after electrolysis starts, in any cases, the current value lowered with the elapsed time. Further, although in the case of carrying out an ultrasonic irradiation, the minimum current value is 10A, in the case of carrying out no ultrasonic irradiation, the current conduction almost stopped after the elapsed time of 45 minutes, and then, the electrolytic treatment stopped.

In the case of carrying out no ultrasonic irradiation, just after no current flows (after 45 minutes elapsed), an impact of 0.98 kg m2/sec2 was given to the electrolytic cell from the upper portion of the cell for 30 seconds over ten times. As a result, after 50 minutes elapsed, the current flowed, and then, the electrolysis was again started.

(Example 4) In this example 4, in the case where the zirconium waste is relatively small, and its surface is covered with an oxide, in order to improve a current efficiency, only the waste was arranged in the solution. In the oxidation treatment apparatus having an oxidation treatment structure, in order to keep an electrolytic treatment rate, a pressure was applied from the upper portion to the whole of zirconium and zirconium alloy to accelerate an exfoliation of a zirconium oxide thin film layer generated on the surface of zirconium.

Further, in the case where the zirconium waste is relatively small, and its surface is covered with an oxide, in an oxide recovery vessel having a fine hole structure of recovering an oxide generated by an electrolytic treatment without hindering the electrolysis, the electrolytic solution was agitated in order to make uniform an electrolytic solution state in the electrolytic cell.

Further, in the case where the zirconium waste is relatively small, and its surface is covered with an oxide, in order to continuously drop an oxide generated by electrolytic treatment from a waste storage cell, the waste storage cell has a fine hole structure at the bottom surface thereof, and the electrolytic solution is circulated in the waste storage cell.

Moreover, in the case where the zirconium waste is relatively small, and its surface is covered with an oxide, in order to improve a current efficiency, only the waste is arranged in the solution. In the oxidation treatment apparatus having an oxidation treatment structure, a heating section is provided in order to accelerate an exfoliation of the zirconium oxide thin film layer on the surface, and there is provided a structure such that an ultrasonic wave is irradiated to the whole of electrolyzer, and further, a pressure and impact are applied to the whole of zirconium waste.

Like the example 3, with the use of the electrolytic treatment apparatus shown in FIG. 1, electrolysis was carried out. A DC voltage of 14V was applied to the electrolytic solution for an hour, and then, an electrolytic treatment was carried out while irradiating an ultrasonic wave of 350W.

In addition, an agitator is located in the electrolyzer 1, and the electrolytic solution 8 is agitated by means of the magnetic stirrer 15 from the outside of the electrolyzer 1 so as to make uniform the solution in the electrolyzer 1 and the electrolytic cell 3. At this time, a weight of 5 kg is applied to the simulated waste in the electrolytic cell 3.

FIG. 7 shows an elapsed change of the current.

After 15 minutes from the starting of the electrolysis, a current value remarkably lowered. After 16 minutes from the electrolysis start, an impact of 0.98 kg m2/sec2 was given to the electrolytic cell from the upper portion of the electrolysis cell for 15 seconds over five times.

Thereafter, the current value became constant at 20A, and the electrolysis was steadily took place without lowering a treatment rate.

(Example 5) In the case where the zirconium waste has a structure like a tank, in order to remove only radioactive material adhering to an inner surface of the tank, an electrolytic solution was put into the tank, and a cathode was arranged in the tank, and the waste was used as an anode so that electrolysis is carried out only to the inner surface of the tank, thus the radioactive material being removed.

Moreover, in the case where the zirconium waste has a structure like a tank, in order to improve a current efficiency, a heating section is provided to accelerate an exfoliation of zirconium oxide thin film layer on the inner surface of the tank, and there is provided a structure of irradiating ultrasonic wave to the whole of electrolyzer, and thus, it becomes possible to remove a radioactive material on only the inner surface of the tank in the electrolytic treatment apparatus.

A zircaloy pipe is cut, and then, a lower portion of the cut pipe was closed by a silicon plug cured by tetrafluoride ethylene resin seal, and 10-normal nitric acid solution was added to in the simulated waste as an electrolytic solution. A platinum wire was arranged in the waste, and then, a direct current power source was connected so that the simulated waste became an anode and the platinum wire became an cathode. Further, a DC voltage of 14V was applied from the source for 10 minutes, and thus, electrolysis was carried out.

During the electrolysis, it was confirmed that a black thin piece was continuously exfoliated from the entire surface contacting the electrolytic solution. After the electrolysis, the black thin piece material stored therein was recovered, and then, a composition analysis was made by an X-ray diffraction, and as a result, it was found to be a zirconium dioxide.

(Example 6) In this example 6, in an off-gas system in the case where the zirconium waste has a structure like a tank, there is provided an off-gas treatment equipment having a function of recovering a hydrogen gas, a carbon dioxide gas, a nitrogen oxide generated in the oxidation treatment.

An off-gas line including a gas washing bottle (bubbler) was attached to an upper portion of the simulated waste described in the example 5. A 10-normal sodium hydroxide solution of 250 ml was put in the gas washing bottle. A 10-normal nitric acid solution was used as an electrolytic solution, and a platinum wire was arranged therein, and further, was connected to a direct current power source so that the simulated waste became an anode and the platinum wire becomes a cathode, and a DC voltage of 14V was applied from the source for an hour.

In addition, a nitrogen carrier gas was introduced into the electrolyzer with a flow rate of 11/min. At the time of the electrolysis, it was found that a NOx gas was generated. In this case, a gas concentration of NOx on an outlet of the off-gas line was less than a detective limit.

According to the present invention of the characters mentioned hereinbefore, suitable functions and effects can be achieved as mentioned in the SUMMARY OF THE INVENTION.

Further, it is to be noted that the present invention is not limited to the described embodiments (examples) and many other changes and modifications may be made without departing from the scopes of the appended claims.

Claims

WHAT IS CLAIMED IS 1. A method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that a nitric acid solution is used as an electrolytic solution and the electrolytic solution is heated so as to improve an electrolytic rate.
2. A treating method according to claim 1, wherein said electrolytic solution is heated at a temperature of more than 60 C.
3. A treating method according to claim 1, wherein the zirconium waste constitutes an anode for the electrolytic treatment.
4. A method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that a film layer of zirconium oxide formed on an surface of the zirconium is continuously exfoliated to keep an electrolytic treatment rate while irradiating an ultrasonic wave.
5. A method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that only the zirconium waste or a spent fuel is arranged in an electrolytic solution to improve a current efficiency and, in order to keep an electrolytic treatment rate, an impact is continuously applied from an upper portion to the whole of the zirconium waste or spent fuel to accelerate an exfoliation of a zirconium oxide thin film layer formed on the surface of the zirconium waste or the spent fuel.
6. A method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that an electrolytic solution is agitated to recover an oxide generated by an electrolytic treatment without hindering electrolysis and to make uniform an electrolytic state.
7. A treating method according to claim 6, wherein said electrolytic solution is agitated by an ultrasonic wave or mechanical means.
8. A method of treating zirconium of a zirconium waste composed of zirconium or zirconium alloy or a spent fuel through an oxidation treatment with electrolysis, characterized in that, in order to improve a current efficiency, only the zirconium waste or a spent fuel is arranged in an electrolytic solution of an electrolyzer, and the electrolytic solution is heated to accelerate an exfoliation of a film layer of a zirconium oxide formed on the surface of the zirconium waste or the spent fuel, an ultrasonic wave is irradiated to the heated electrolytic solution and an entire structure of the electrolyzer, and pressure and impact are applied to the whole of the zirconium waste or the spent fuel.
9. An apparatus for treating a zirconium waste or a spent fuel, comprising: an electrolyzer in which an electrolytic solution is stored; an electrolytic cell located in the electrolyzer, and having a passage hole through which the electrolytic solution passes and adapted to arrange the zirconium waste or a spent fuel; an anode contacting the zirconium waste or the spent fuel; a cathode contacting the electrolytic solution in the electrolyzer; a direct current power source for applying a DC voltage to the anode and the cathode; a heating medium line attached to the electrolyzer and adapted to heat the electrolytic solution; and agitating means for agitating the electrolytic solution.
10. A treating apparatus according to claim 9, wherein said agitating means is a mechanical agitator.
11. A treating apparatus according to claim 9, wherein said agitating means is an ultrasonic generator.
12. A treating apparatus according to claim 9, further comprising an off-gas treatment equipment for recovering a hydrogen gas, a carbon dioxide gas or a nitrogen oxide generated in the electrolyzer during the oxidation treatment.
13. A treating apparatus according to claim 9, wherein the electrolytic solution is a nitric acid solution.
14. A method of treating a zirconium waste composed of zirconium or a zirconium alloy through an oxidation treatment with electrolysis, characterized in that a zirconium waste is disposed in a waste storage cell having a number of holes at a bottom surface thereof, an oxide generated by an electrolytic treatment is continuously dropped from the waste storage cell so as to circulate the electrolytic solution in the waste storage cell.
15. A method of treating a spent fuel in a cladding tube formed of a zirconium alloy through an oxidation treatment with electrolysis, characterized in that a spent fuel is used as an anode and a nitric acid solution is used as electrolytic solution to dissolve the cladding tube and a fuel element in contact to the nitric acid solution.