WO2016060418A1

WO2016060418A1 - Method for separating high heat dissipative nuclide in chloride lithium salt using zone refining method

Info

Publication number: WO2016060418A1
Application number: PCT/KR2015/010715
Authority: WO
Inventors: 이종현; 심문수; 김대영; 황일순
Original assignee: 충남대학교산학협력단
Priority date: 2014-10-16
Filing date: 2015-10-12
Publication date: 2016-04-21
Also published as: KR20160044748A

Abstract

The present invention relates to a method for separating high heat dissipative nuclides in chloride lithium salt using a zone refining method. Specifically, the method for separating high heat dissipative nuclides according to the present invention subjects salt waste containing high heat dissipative nuclides comprising Cs and Sr to zone refinement, thereby segregating and eliminating radioactive nuclides contained in the salt waste.

Description

Separation method of high heat radiation nuclide in lithium chloride salt

The present invention relates to a method for isolating high heat radiation nuclides in lithium chloride salts using a zone purification method. Specifically, the heat radiation nuclides in lithium chloride molten salts are separated and removed, and the lithium chloride salts from which the nuclides are removed are subjected to a pyroprocessing process. The present invention relates to a method for separating high-heat radiation nuclides that can be recycled.

Pyroprocessing, a recycling technology of spent fuel generated after nuclear power generation, is a dry treatment process that can reduce the half-life to 1/1000 and reduce the volume to 1/20. Currently, the Korea Atomic Energy Research Institute (KAERI) It is a technology under study.

Pyroprocessing consists of deladding, voloxidation, electroreduction, electrorefining and electrowinning.

Pyroprocessing generates a large amount of waste molten salt because it undergoes processes of electroreduction, electrorefining and electrorefining. Such waste molten salt is solidified and disposed of in a stable state. Therefore, there is a need to minimize radioactive waste in terms of economic and environmental aspects of the process.

In order to reduce the amount of LiCl and eutectic salt (LiCl-KCl) wastes generated during pyroprocessing, it is necessary to separate and dispose only the nuclides in the salt waste and recycle the remaining salts. Although molten salt research has been conducted worldwide, it is concentrated on eutectic salt wastes, and the use of oxide fuels involves an electrolytic reduction process, and studies on the used LiCl wastes are insufficient. In addition, unlike eutectic salts, conventional techniques such as ion exchange method using zeolite, oxygen dispersion method, and precipitant addition method are applicable to LiCl waste because of the high working condition of 610 ° C or higher. There is no limit. Therefore, the development of alternative technology for the treatment of radioactive LiCl waste is very urgent situation.

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide a method that can effectively recycle salt waste by removing Cs and Sr present in the radioactive waste waste generated in the pyroprocessing process of spent nuclear fuel. It is to provide a method of minimizing energy consumption and effectively separating high heat radiation nuclides.

Hereinafter, a manufacturing method of the present invention will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided by way of example so that the spirit of the invention to those skilled in the art can fully convey. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, if there is no other definition in the technical terms and scientific terms used, it has a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs, the gist of the present invention in the following description and the accompanying drawings Descriptions of well-known functions and configurations that may be unnecessarily blurred are omitted.

The high heat radiation nuclide separation method according to the present invention is characterized by zone refining salt wastes of lithium chloride containing high heat radiation nuclides including Cs and Sr to segregate and remove radionuclides contained in salt wastes. have.

The impurity separation process using zone refining is based on the difference in solubility between solids of impurities. This is also the same principle of casting segregation. In other words, pure crystals and impurities remain in the remaining liquid phase. In the liquid coagulation process, there are changes in the temperature at which the crystals are formed according to the impurity concentration and the temperature in the liquid phase, and there may be a compound between the known material (object to be purified) and impurities. Knowledge is needed.

1 is a state diagram between LiCl-Cs-Sr which is a salt waste (base material). As can be seen in the state diagram of FIG. 1, as the impurity concentrations such as Cs and Sr increase, it can be seen that the melting temperature of the salt waste is continuously lowered, and the impurities are moved to the liquid phase through solid-phase transformation. . In addition, the separation efficiency is very excellent because there is no compound, it can be seen that the removal of highly heat-resistant nuclides by the zone purification at 40 mol% in the case of Cs, 38 mol% or less in the case of Sr.

That is, in the method according to an embodiment of the present invention, the salt waste may be a lithium chloride salt containing a high heat radiation nuclide, and the high heat radiation nuclide may include Cs and Sr.

According to one embodiment of the present invention, by using a zone refining method, segregation of high heat radiation nuclides from salt wastes, and separation and removal of regions with high heat radiation nuclides segregated, thereby recycling molten salts, which are radioactive wastes generated in a pyroprocessing process. This makes it possible to suppress the generation of radioactive nuclear waste that is disposed of. In addition, by using the zone refining method, the area in which the salt waste is melted can be minimized, thereby minimizing the energy required to remove the highly heat-resistant nuclide.

Specifically, the high heat radiation nuclide separation method according to an embodiment of the present invention comprises the steps of charging the salt waste into the tubular container; And refining the salt waste using a heater that wraps around the circumferential surface of the tubular vessel and moves in the longitudinal direction of the tubular vessel.

In this case, the tubular container may be a hermetically sealed container, and the inside thereof may be an inert gas atmosphere. Inert gases include argon, nitrogen, helium and mixed gas thereof. The length and diameter of the tubular vessel may be appropriately modified depending on the treatment capacity of the salt waste to be treated. As a specific and non-limiting example, the diameter of the tubular container may be 1 to 10 cm, the length of the tubular container may be 60 to 500 cm. The cross section of the tubular container may be circular in terms of uniform heating.

The heater may be in the form of a ring surrounding the tubular vessel, and may be moved by means of a moving means in the longitudinal direction of the tubular vessel, specifically from one end of the tubular vessel to the other. By the heater, at least the salt wastes in the region where the heater is located may be melted, and in particular, may be heated to a temperature of 650 to 720 ℃ by the heater.

At this time, the width (length) of the salt waste melted by the heater forms a stable solid / liquid interface, and can accommodate impurities (radionuclides) that are pushed into the liquid phase as the heater moves, and is different from one end of the tubular container. As long as the concentration of impurities concentrated in the liquid phase can be maintained at 40 mol% or less for Cs and / or 38 mol% or less for Sr, melting as small as possible in terms of minimizing energy consumption is preferable. As a specific example, the width (length) of the salt waste melted by the heater may be 5 to 15 cm.

In the method of separating high heat radiation nuclides according to an embodiment of the present invention, as shown in FIG. 2, in order to improve treatment efficiency of salt waste, zone refining may be performed while simultaneously moving two or more heaters spaced apart from each other. Can be. The salt waste is partially melted by the heater, but as the heater moves, the salt solidifies at the work / liquid interface, and the salt melts at the other solid-liquid interface, and the melting region also moves. At this time, by the two or more heaters spaced apart from each other in the longitudinal direction of the tubular container, as the melting and solidification of the salt waste is repeated, the purity of the solidified salt can be increased, and also the melting and solidification is repeated by two or more rarers Even if the impurity concentration is slightly higher than the equilibrium concentration at the solid / liquid interface due to the rapid movement of the heater, the purity of the salt finally obtained can be increased. The number of heaters to be provided may be appropriately changed in consideration of the amount of salt waste to be treated or the length of the tubular container, and as a specific example, two to four heaters may be provided at the same time.

The moving speed of the heater is preferably a speed that can increase the treatment efficiency without excessively increasing the impurity concentration at the solid / liquid interface beyond the equilibrium concentration. As a specific example, the moving speed of the heater may be 1 mm / minute to 7 mm / minute.

Independently of the number of heaters provided in the vessel, the heater may be repeatedly moved 1 to 20 times from one end of the tubular vessel to the other end. Through such repeated movements, the purity of the salt finally obtained can be increased, and the process speed (moving speed of the heater) can be improved.

After zone purification has been performed, the salt zone containing impurities segregated, including high heat radiation nuclides, can be separated off and then the remaining purified salt can be recycled to the spent fuel pyroprocessing process. At this time, the separation removal is of course to remove the separation region having a concentration higher than the concentration of the high heat radiation nuclides contained in the salt waste.

In the method according to an embodiment of the present invention, the tubular container into which the salt waste is loaded may be a quartz tube, and the salt waste may be contained in a boat made of SUS material located in the quartz tube.

The high heat radiation nuclide separation method according to the present invention is capable of separating and removing the high heat radiation nuclides present in the molten salt, and recycling the recovered molten salt, thereby suppressing radioactive nuclear waste generation.

1 is a state diagram between LiCl-Cs-Sr,

2 is a diagram illustrating one conceptual diagram of a zone refining performed by three heaters,

3 is a view showing the measurement of the concentration of impurities by position of the purified salt according to an embodiment of the present invention.

(Example)

41000 ppm (ppm by mass) of Lis (98.2%, Samjeon Chemical Co., Ltd.), CsCl (99.0%, Samjeon Chemical Co., Ltd.) and SrCl ₂ (98.5% Samjeon Chemical Co., Ltd.) A mixed salt was prepared by mixing LiCl, CsCl, and SrCl ₂ to contain 15000 ppm (ppm by mass) of Sr.

Subsequently, after the mixed salt prepared in a 600 mm long SUS304 boat was filled, the boat was charged into a quartz tube having a length of 2000 mm and a diameter of 40 mm. After the inside of the quartz tube was made into an argon gas atmosphere and both ends of the tube were sealed with silicon, three ring-shaped heaters surrounding the quartz tube were moved from one end of the tube to the other end. At this time, all the heaters maintained a temperature of 700 ℃, the melt width by each heater was 10cm, the movement speed of the heater was 5mm / min. The spacing between heaters was kept 5 cm so that the melting areas by adjacent heaters did not overlap.

After moving 3 heaters 3 times, 6 times, 9 times, 12 times, 15 times, or 18 times, the salt in the boat is divided into 5 parts by 1cm according to the position, and the Cs and Sr concentrations are used by ICP-OES And analyzed. 3 is a view showing the measurement of the concentration of Cs and Sr according to the number of times of repeated movement of the heater, the position of the salt in the boat. In FIG. 3, the unit of location is cm, and a portion including one end of the boat at which the movement of the heater starts is 1, and a portion including one end at which the movement of the heater is finished is 5.

As can be seen from Figure 3, the Cs concentration was confirmed that the impurities reduced to about 1/40 from the initial concentration of 41000ppm to 1320ppm. Sr was reduced to about 1/10 from the initial concentration of 15000ppm to 1220ppm. In this case, the yield was about 20% (vol%), and the removal efficiency of the impurities can be further increased by controlling the moving speed of the heater, the length of the melting section, the internal stirring of the liquid phase, and the length of the solid section.

In the present invention as described above has been described by specific embodiments and limited embodiments and drawings, but this is only provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments, the present invention Those skilled in the art can make various modifications and variations from this description.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and all the things that are equivalent to or equivalent to the claims as well as the following claims will belong to the scope of the present invention. .

Claims

A method of separating high heat radiation nuclides by zone refining salt wastes of lithium chloride containing high heat radiation nuclides including Cs and Sr to segregate and remove radionuclides contained in salt wastes.
The method of claim 1,

Charging the salt waste into a tubular container; And

Zone purification of the waste waste using a heater that wraps around the circumferential surface of the tubular vessel and moves in the longitudinal direction of the tubular vessel;

High heat radiation nuclide separation method comprising a.
The method of claim 2,

The zone refining is a high heat radiation nuclide separation method is performed while moving at least two heaters spaced apart from each other at the same time.
The method of claim 2,

The heater is a high heat dissipation nuclide separation method to move repeatedly from 2 to 20 times from one end of the tubular vessel to the other end.
The method of claim 2,

The tubular container is a quartz tube, the salt waste is a high heat radiation nuclide separation method (SUS) boat is located in the quartz tube (SUS).