JPH0519096A - Decontamination method of radioactive solution - Google Patents

Abstract

PURPOSE:To remove a precious metal element, an alkaline earth element and an alkaline element by performing electrolysis reduction by the use of a liquid metal electrode after a precipitant is previously added and a transition metal element is deposited to remove. CONSTITUTION:Elements such as iron, copper and chromium are contained in a storage tank 1, a radioactive waste liquid containing other elements such as precious metal, alkali and alkaline earth are held and come in a deposit production tank 4. A recipitant such as hydroxide, alkaline metal and alkaline earth is supplied to the production tank 4 from a basic recipitant supply tank 2. As the result, the elements such as iron, copper and chromium are deposited from the waste liquid, the deposit is transmitted to a deposit temporary storage tank 6 and the waste liquid is sent out to an electrolytic cell 7. Liquid metal immersed in the waste liquid is made a cathod, voltage is applied and the elements such as precious metal, alkali and alkaline earth are reduced to take in the liquid metal. Next, it is separated and recovered by a liquid metal recovery tank 9. Furthermore the waste liquid purged of these elements is transmitted to a waste liquid recovery tank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing radioactive elements from a waste liquid containing radioactive elements, and more particularly to a transition metal element, a noble metal element, an alkaline earth element and an alkali element such as reprocessing high level waste liquid at the same time. A method suitable for treating the containing solution.

[0002]

2. Description of the Related Art As a method for removing an alkali metal from a radioactive waste liquid, a method for electrochemically removing sodium using a mercury cathode immersed in a solution is disclosed in JP-A-64-50998.

That is, a radioactive waste liquid containing a sodium compound is electrolyzed with mercury as a cathode, a metal containing sodium is separated in the form of an amalgam, a metal containing sodium is separated and purified from the amalgam, and mercury is recycled to an electrolytic cell. According to the principle of recovering sodium in the form of amalgam by the method described above.

[0004]

When electrolysis using a mercury cathode is performed in a solution containing a transition metal such as a high-level waste liquid of a reprocessing plant, a high oxidation number transition metal ion such as trivalent iron ion is generated. It is reduced on mercury and converted to soluble low-oxidation ions such as divalent iron ions, which are oxidized in solution back to high-oxidation ions. Therefore, there is a problem that the potential of the mercury cathode cannot be maintained at a potential required for reducing the precious metal element, the alkaline earth element, and the alkaline element.

An object of the present invention is to remove noble metal elements, alkaline earth elements and alkali elements from general industrial waste liquid containing transition metal elements (particularly typified by radioactive waste liquid of a reprocessing plant).

[0006]

The above-mentioned problem that the mercury cathode potential cannot be maintained is solved by adding a precipitant to the solution in advance to remove the transition metal element by precipitation, and then electrolytically reducing it with a liquid metal electrode.

[0007]

[Function] Hydroxide, alkali metal,
Alkaline earth metals, oxides of alkali metals and oxides of alkaline earth metals have a function of converting transition metal ions in a solution into hydroxides and precipitating them. Further, hydrogen sulfide and metal sulfide have an action of precipitating a transition metal element as a sulfide. Liquid metals such as mercury are easy to form alloys, and have the action of reducing the metal elements such as noble metal elements, alkali elements, and alkaline earth elements in the aqueous solution and the glass melt, precipitating them in the metal state, and incorporating them.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 is a waste liquid storage tank containing one or more elements of iron, copper, chromium, manganese, vanadium, arsenic, cadmium and antimony, and ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold , Holds radioactive waste liquid containing one or more of alkaline earth elements and alkaline elements. This waste liquid is sent to the precipitation production tank 4. Reference numeral 2 is a basic precipitant supply tank, which contains hydroxide, alkali metal, alkaline earth metal,
At least one of alkali metal oxides and alkaline earth metal oxides is supplied to the precipitation tank. At least one element of iron, copper, chromium, manganese, vanadium, arsenic, cadmium and antimony is precipitated from the waste liquid in the precipitation generation tank. Then, the waste liquid and the precipitate are sent to the separation tank 5 for separation. The separated precipitate is sent to the temporary precipitation storage tank 6, and the waste liquid is sent to the electrolytic tank 7. A liquid metal storage tank 8 holds a liquid metal, preferably mercury. The liquid metal is sent to the electrolytic cell 7. In the electrolytic cell 7, a liquid metal immersed in the waste liquid is used as a cathode to apply a potential, and one or more elements of ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements, and alkali elements are used. Is taken up in the liquid metal and removed from the waste liquid. The liquid metal that takes in these elements is sent to the liquid metal recovery tank 9. Also,
The waste liquid from which these elements have been removed is sent to the waste liquid recovery tank 10. According to this embodiment, without interference by iron, copper, chromium, manganese, vanadium, arsenic, cadmium and antimony,
Ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements and alkaline elements can be taken into the liquid metal and removed from the waste liquid.

Next, another embodiment of the present invention will be described with reference to FIG. 1 is a waste liquid storage tank, which contains iron, copper, chromium,
Contains one or more elements of manganese, vanadium, arsenic, cadmium, antimony, and one or more of ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements, alkali elements Retains radioactive waste liquid containing the element. This waste liquid is sent to the precipitation production tank 4. Reference numeral 3 denotes a sulfide precipitant supply tank, which supplies at least one of hydrogen sulfide and metal sulfide to the precipitation generation tank. At least one element of iron, copper, chromium, manganese, vanadium, arsenic, cadmium and antimony is precipitated from the waste liquid in the precipitation generation tank. Then, the waste liquid and the precipitate are sent to the separation tank 5 for separation. The separated precipitate is stored in the temporary sedimentation tank 6, and the waste liquid is stored in the electrolytic tank 7.
Send to. A liquid metal storage tank 8 holds a liquid metal, preferably mercury. The liquid metal is sent to the electrolytic cell 7. In the electrolytic cell 7, a potential is applied with the liquid metal immersed in the waste liquid as a cathode,
At least one element selected from ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements, and alkaline elements is reduced and taken into the liquid metal to be removed from the waste liquid. The liquid metal that takes in these elements is sent to the liquid metal recovery tank 9. The waste liquid from which these elements have been removed is sent to the waste liquid recovery tank 10. According to the present embodiment, ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements, alkali elements without interference by iron, copper, chromium, manganese, vanadium, arsenic, cadmium and antimony. Can be taken up in liquid metal and removed from the waste liquid.

Next, another embodiment of the present invention will be described with reference to FIG. 1 is a waste liquid storage tank, which contains iron, copper, chromium,
Contains one or more elements of manganese, vanadium, arsenic, cadmium, antimony, and one or more of ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements, alkali elements Retains radioactive waste liquid containing the element. This waste liquid is sent to the precipitation production tank 4. Reference numeral 3 denotes a sulfide precipitant supply tank, which supplies at least one of hydrogen sulfide and metal sulfide to the precipitation generation tank. At least one element of iron, copper, chromium, manganese, vanadium, arsenic, cadmium and antimony is precipitated from the waste liquid in the precipitation generation tank. Then, the waste liquid and the precipitate are sent to the separation tank 5 for separation. The separated precipitate is sent to the temporary settling storage tank 6. The waste liquid is sent to the glass melting tank 11. In the glass melting tank, a glass containing boric acid, silicic acid, or phosphoric acid as a main component is mixed with a waste liquid, heated to be converted into a glass melt, and sent to the electrolytic tank 7.
A reduction electrode metal storage tank 12 holds a liquid metal, preferably gold. The reducing electrode metal is sent to the electrolytic cell 7. Electrolyzer 7
Then, the reducing electrode metal is melted into a liquid metal, and the liquid metal immersed in the glass melt is used as a cathode to apply a potential,
At least one element selected from ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements and alkali elements is reduced and taken into the liquid metal and removed from the glass melt. The liquid metal that takes in the element is sent to the liquid metal recovery tank 9. Also,
The glass melt from which these elements have been removed is sent to the waste liquid recovery tank 10. According to the present embodiment, ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements, alkali elements without interference by iron, copper, chromium, manganese, vanadium, arsenic, cadmium and antimony. Can be taken up in liquid metal and removed from the waste liquid.

[0011]

According to the present invention, a transition metal element is removed from a solution by a precipitant, so that an alkali metal, an alkaline earth metal or a noble metal is reduced on a liquid metal electrode and taken up on the electrode to be removed from the solution. it can.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a radioactive waste liquid decontamination apparatus.

FIG. 2 is a block diagram of another embodiment of the radioactive waste liquid decontamination device.

FIG. 3 is a block diagram of a radioactive waste liquid decontamination apparatus using a glass melt.

[Explanation of symbols]

1 ... Waste liquid storage tank, 2 ... Basic precipitant supply tank, 4 ... Precipitation generating tank, 5 ... Precipitation separation tank, 6 ... Temporary precipitation tank, 7 ... Electrolysis tank,
8 ... Liquid metal storage tank, 9 ... Liquid metal recovery tank, 10 ... Waste liquid recovery tank.

Continued front page    (72) Inventor Baba             1168 Moriyama-cho, Hitachi-shi, Ibaraki Japan             Tate Seisakusho Energy Research Institute (72) Inventor Takashi Ikeda             1168 Moriyama-cho, Hitachi-shi, Ibaraki Japan             Tate Seisakusho Energy Research Institute (72) Inventor Koichi Chino             1168 Moriyama-cho, Hitachi-shi, Ibaraki Japan             Tate Seisakusho Energy Research Institute

Claims (6)

[Claims] 1. A method of decontaminating a radioactive solution by electrolysis, the amount of all or some elements of iron, copper, chromium, manganese, vanadium, arsenic, cadmium and antimony dissolved in the radioactive solution. Of the ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum,
A method for decontaminating a radioactive solution, which comprises reducing the amount of some or all of platinum, gold, alkaline earth elements and alkali elements. 2. The method for decontaminating a radioactive solution according to claim 1, wherein a part or all of the elements are precipitated using a precipitating agent. 3. The solution according to claim 2, wherein any or all of hydroxide, alkali metal, alkaline earth metal, alkali metal oxide and alkaline earth metal oxide are used as a precipitant. Iron by making it basic,
A method for decontaminating radioactive solutions by precipitating some or all of copper, chromium, manganese, vanadium, arsenic, cadmium and antimony. 4. The method according to claim 2, wherein any or all of hydrogen sulfide and metal sulfide is used as a precipitant.
A method for decontaminating radioactive solutions by converting some or all of the elements of iron, copper, chromium, manganese, vanadium, arsenic, cadmium, and antimony to sulfides and precipitating them. 5. The method according to claim 1, 2, 3 or 4, wherein a liquid metal, preferably mercury, is used as an electrode and a negative potential is applied to the electrode, ruthenium, rhodium palladium, silver,
A method for decontaminating a radioactive solution by dissolving some or all of iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements, and alkaline elements in a liquid metal. 6. The liquid metal as claimed in claim 1, 2, 3 or 4, wherein the solution is converted into a glass melt containing boric acid, silicic acid or phosphoric acid as a main component and immersed in the glass melt. Is a liquid metal containing ruthenium, rhodium palladium, silver, iridium, tungsten, molybdenum, platinum, gold, alkaline earth elements, alkali elements, or some elements of the liquid metal. A method for decontaminating radioactive solutions by reducing the amount of these elements by dissolving in them.