JP2013101066A - Treatment device and treatment method for used fuel containing zirconium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment device and a treatment method of used fuel containing zirconium for separating used fuel containing zirconium into nuclear fuel substances, zirconium and other fission products.SOLUTION: A treatment device for used fuel containing zirconium for separating used fuel containing zirconium into nuclear fuel substances, zirconium and fission products includes: heating means for obtaining a temperature environment of the sublimation temperature of a zirconium compound or more in the treatment device; a zirconium recovery part set in a temperature environment of the sublimation temperature of the zirconium compound or less for condensing and recovering the volatilized zirconium compound; a solid storage part for storing solids remaining in a temperature environment of the sublimation temperature of a zirconium compound or more; and a vent hole for recovering gas.

Description

  TECHNICAL FIELD The present invention relates to a spent fuel processing apparatus and method including zirconium, and more particularly to a spent fuel processing apparatus containing zirconium that separates spent fuel mixed with a zirconium cladding into uranium, zirconium and fission products. And methods.

  The chemical form of nuclear fuel used in Japanese boiling water reactors is oxide. Uranium, which is a nuclear fuel material, is formed into pellets, stored in a fuel cladding tube, loaded into a reactor core as a fuel assembly, and used for nuclear power generation.

  In nuclear power generation, the energy generated when uranium undergoes fission is changed to electricity to generate electricity, but fission products (FP) are generated in the process of fission. Many of the fission products are radioactive materials. Since the energy of radiation emitted from radioactive fission products is absorbed and converted into thermal energy, the nuclear fuel material used for nuclear power generation (hereinafter referred to as spent fuel) has a self-heating effect. For this reason, the fuel assembly loaded in the core is cooled by water.

  On the other hand, the spent fuel that has been used in the power plant is finally reprocessed after being cooled in the spent fuel pool. Reprocessing separates spent fuel into nuclear fuel materials (uranium and plutonium) and fission products. Since the separated fission product is a high-level radioactive waste, it is considered to dispose of it after vitrification.

  As a spent fuel reprocessing method, there are a fluoride volatilization method and a wet reprocessing method (PUREX method) adopted in Rokkasho reprocessing plant.

Among these, for example, the fluoride volatilization method described in Patent Document 1 is a method in which spent fuel is reacted with fluorine gas, and uranium, which is a nuclear fuel material, is recovered as gaseous uranium hexafluoride (UF ₆ ). At this time, most of the fission products react with fluorine gas to become non-volatile fluorides (hereinafter referred to as non-volatile fluoro fission products) and are separated from gaseous uranium hexafluoride UF ₆ . A part of the fission products is entrained in the gaseous uranium hexafluoride UF ₆ becomes volatile fluorides, by separation operations such as condensation and adsorption in the subsequent step, gaseous uranium hexafluoride UF ₆ and can be separated.

  As a fluorination method for spent fuel in the above-described fluoride volatilization method, two methods, a flame furnace method and a fluidized bed method, have been studied. Among them, in the flame furnace system, spent fuel powder and fluorine gas are supplied from the upper part of the flame furnace to form a high-temperature flame (1200 to 1600 ° C.) by reaction heat, and the spent fuel is caught in a high-temperature atmosphere. Turn into.

  In the fluidized bed system, in a reaction tank filled with spent fuel and fluidized material (for example, alumina), fluorine gas is supplied to the place where the spent fuel and fluidized material are agitated to fluorinate the spent fuel. . In this fluidized bed system, the reaction tank, spent fuel, and fluidized material are heated, and the temperature is 300 to 350 ° C.

  Further, as a spent fuel fluorination method, in addition to the above two, a batch method may be considered as a simple method. In this system, fluorine gas is supplied to a container in which spent fuel is stored, and the spent fuel is fluorinated. At this time, the spent fuel and the container are heated to promote the fluorination reaction, and the temperature is considered to be about 800 ° C. at the maximum.

JP 2002-257980 A

  In the fluoride volatilization method described in Patent Document 1 described above, several methods are known, but in any case, it is used in a processing apparatus (including a furnace, tank, or container type). Spent fuel needs to be arranged or supplied.

  In these systems, the fuel clad tube is removed from the fuel assembly to form a spent fuel, which is the object of processing. This means that it takes a lot of processing steps and time to obtain spent fuel from the fuel assembly in the nuclear reactor (in the flame reactor system, the spent fuel is made into powder form). Yes.

  For this reason, instead of extracting only spent fuel from the fuel assembly and performing separation and recovery by the fluoride volatilization method, separation by the fluoride volatilization method is performed while the spent fuel and the fuel cladding tube are mixed. It is desirable to be able to recover. For example, if the spent fuel and the fuel cladding tube are mixed, and the cut fuel assembly can be subjected to separation and recovery by the fluoride volatilization method as it is, the pretreatment process can be simplified and the time required for this can be reduced. It can be greatly reduced.

  The above explanation assumes processing after the fuel assembly completes the expected heat generation in the reactor, but it will also melt even if the spent fuel and the fuel cladding tube melt due to a severe accident in the reactor. It is strongly desired that separation and recovery by the fluoride volatilization method can be performed in the form of a product.

  For example, when the fuel assembly is not cooled by water in a severe accident, the spent fuel and the fuel cladding tube become high temperature due to the self-heating effect of the spent fuel, and then the heat generated by the reaction between the fuel cladding tube and water vapor further increases. It is considered that the spent fuel and the fuel cladding tube are melted by the high temperature. This melt is called corium. Since it is difficult to extract only spent fuel with corium, it is desirable that separation and recovery by the fluoride volatilization method can be performed directly in the form of a melt.

  The fluoride volatilization method and the wet reprocessing method (PUREX method) described above are methods for reprocessing spent fuel taken out from the fuel assembly. On the other hand, the object of reprocessing in the present invention is a mixture of spent fuel and fuel cladding. The mixture contains corium produced by a severe accident at a nuclear power plant.

  In the present invention, it is considered to treat a corium generated in a severe accident at a nuclear power plant or a mixture of a cut spent fuel and a fuel cladding tube by a fluoride volatilization method. Since a mixture such as corium contains a large amount of zirconium which is a material of the fuel cladding tube, it is important to handle zirconium. The handling of zirconium when applying the fluoride volatilization method is summarized below.

In the reprocessing of spent fuel by the fluoride volatilization method, zirconium, which is one of fission products, reacts with fluorine gas to become zirconium fluoride (ZrF ₄ ). The sublimation point of zirconium fluoride ZrF ₄ is 600 ° C.

For this reason, when the fluorination method in the fluoride volatilization method is the flame furnace method and the batch method, the zirconium fluoride ZrF ₄ volatilizes temporarily, but the pipe temperature of the processing apparatus is about 200 ° C., so it is condensed. It is recovered as a solid together with the non-volatile fluorinated fission product. Further, when the fluorination method in the fluoride volatilization method is a fluidized bed method, zirconium fluoride ZrF ₄ does not volatilize, and in this case as well, it is recovered as a solid together with the nonvolatile fluorinated fission product.

  Therefore, when a mixture such as corium is processed by the fluoride volatilization method for processing spent fuel, the mixture such as corium is roughly classified into a nuclear fuel material and a fission product containing zirconium. Of the recovered fission products containing zirconium, the zirconium from the cladding tube is non-radioactive and does not need to be vitrified, but the fluoride volatilization method for spent fuel treatment uses zirconium and other fission products. Because there is no separation step, zirconium and other fission products are vitrified simultaneously.

  However, since there is an upper limit to the amount of impurities (fission product + zirconium) that can be dissolved in a unit weight of vitrified material, if non-radioactive zirconium is vitrified, the processing cost increases due to an increase in the amount of vitrified material. Therefore, when a mixture such as corium is processed by the fluoride volatilization method, it is effective to separate zirconium and other fission products in order to reduce the cost.

  For such needs, for example, there is a chlorination method in which a metal fuel consisting of uranium and metal zirconium reacts with chlorine gas to separate uranium and zirconium, but the chlorine gas and zirconium oxide do not react. This chlorination method cannot be directly applied to the oxide fuel of the present invention.

  In view of the above, the present invention provides a processing apparatus and method for spent fuel containing zirconium that can separate spent fuel containing zirconium into nuclear fuel material, zirconium, and other fission products. With the goal.

  From the above, in the present invention, in the spent fuel processing apparatus containing zirconium for separating the spent fuel containing zirconium into nuclear fuel material, zirconium, and fission products, the temperature is higher than the sublimation temperature of the zirconium compound. Heating means for obtaining a temperature environment in the processing apparatus, a zirconium recovery part for condensing and recovering the volatilized zirconium compound, which is a temperature environment equal to or lower than the sublimation temperature of the zirconium compound, and a temperature equal to or higher than the sublimation temperature of the zirconium compound A solid reservoir for storing solids remaining in the environment and a vent for collecting gas were provided.

  The heating means includes a first heating means for forming a frame by reacting spent fuel containing zirconium with fluorine gas.

  The heating means is a first heating means for reacting spent fuel containing zirconium with fluorine gas to form a frame, and for heating the solid in the solid reservoir to a temperature equal to or higher than the sublimation temperature of the zirconium compound. A second heating means.

  The heating means includes a pedestal on which spent fuel containing zirconium is placed, and a third heating means for obtaining a temperature environment equal to or higher than the sublimation temperature of the zirconium compound when reacting with fluorine gas on the pedestal.

  Moreover, the heating means includes a pedestal on which spent fuel containing zirconium is placed, and after reacting with fluorine gas on the pedestal, for obtaining a temperature environment equal to or higher than the sublimation temperature of the zirconium compound when reacted with chlorine gas. 4th heating means is provided.

  The zirconium compound is zirconium fluoride.

  The zirconium compound is zirconium chloride.

  From the above, in the present invention, in the method of treating spent fuel containing zirconium for separating spent fuel containing zirconium into nuclear fuel material, zirconium and fission products, spent fuel containing zirconium is used. The solid that was treated in a temperature environment equal to or higher than the sublimation temperature of the zirconium compound, condensed and recovered from the volatilized zirconium compound in a temperature environment equal to or lower than the sublimation temperature of the zirconium compound, and remained in a temperature environment higher than the sublimation temperature of the zirconium compound And collect it in gas.

  In addition, spent fuel containing zirconium is separated into gas and solid by the first treatment in a temperature environment higher than the sublimation temperature of the zirconium compound, and the solid after the first treatment has a temperature higher than the sublimation temperature of the zirconium compound. The second treatment is performed under the temperature environment, and the zirconium compound volatilized under the temperature environment below the sublimation temperature of the zirconium compound is condensed and recovered, and the solid remaining in the temperature environment above the sublimation temperature of the zirconium compound, Collect in gas.

  In addition, spent fuel containing zirconium is reacted with fluorine gas to separate into gas and solid, and the separated solid is reacted with chlorine gas in a temperature environment equal to or higher than the sublimation temperature of zirconium chloride, and the sublimation temperature of zirconium chloride. Zirconium chloride volatilized under the following temperature environment is condensed and recovered, and is recovered by separating it into solids and gas remaining in a temperature environment equal to or higher than the sublimation temperature of zirconium chloride.

  From the above, in the present invention, the spent fuel containing zirconium is used as the fuel cladding zirconium in the method of treating spent fuel containing zirconium for separating the spent fuel containing zirconium into nuclear fuel material, zirconium and fission products. Zirconium fluoride gas is produced by reacting the spent fuel with fluorine gas at a temperature of 600 ° C. or higher, and the zirconium fluoride gas is condensed and recovered in a zirconium recovery part installed inside the reactor.

  Further, zirconium fluoride is produced by reacting the zirconium fluoride collected with the zirconium recovery part and chloride gas, and the zirconium chloride is volatilized at 350 ° C. or higher to separate the zirconium from the zirconium recovery part.

In addition, zirconium in the fuel cladding tube and spent fuel are reacted with fluorine gas at a temperature of 300 to 600 ° C., and uranium in the spent fuel is recovered as UF ₆ ; To produce a zirconium chloride gas by reacting with a chloride gas, and the zirconium chloride gas is condensed and recovered in a zirconium recovery part installed in the reactor.

  Further, boron chloride and silicon chloride gas are used as the chloride gas.

  According to the present invention, spent fuel containing zirconium can be separated into nuclear fuel material, zirconium, and other fission products.

The schematic diagram of the cross section of the processing apparatus 30 which concerns on Example 1 of this invention. The figure which summarized each part of the processing apparatus 30 of Example 1, its function, and the state of various substances. The schematic diagram of the cross section of the processing apparatus 31 which concerns on Example 2 of this invention. The figure which summarized each part and its function of the processing apparatus 31 of Example 2, and the state of various substances. The schematic diagram of the cross section of the processing apparatus 32 which concerns on Example 3 of this invention. The figure which summarized each part of the processing apparatus 32 of Example 3, its function, and the state of various substances. The schematic diagram of the cross section of the processing apparatus 32 which concerns on Example 4 of this invention. The figure which summarized each part of the processing apparatus 32 of Example 4, its function, and the state of various substances. The figure which shows the fluoride produced | generated by reaction of the mixture 3 and the fluorine gas 4. FIG.

  In the present invention, the sublimation temperature of a zirconium compound is used as a method for separating a mixture of zirconium and spent fuel into uranium, zirconium and fission products. By creating a temperature environment above the sublimation temperature and a temperature environment below the sublimation temperature in the processing apparatus, uranium, zirconium and fission products are separated.

  Specifically, it was noted that the sublimation point (600 ° C.) of zirconium fluoride as a zirconium compound is lower than the boiling point of the non-volatile fission product. This method will be described with reference to the embodiments shown in FIGS.

In the second method, attention was paid to the fact that the sublimation point (331 ° C.) of zirconium chloride (ZrCl ₄ ) as the zirconium compound was lower than the sublimation point of ZrF ₄ . This method will be described with reference to the embodiment of FIG.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

  In the present invention, spent fuel mixed with zirconium in the fuel cladding is treated. Here, the spent fuel mixed with zirconium to be treated in the present invention is, for example, a cut fuel assembly or a fuel assembly melted by a severe accident.

  This Example 1 pays attention to the fact that the sublimation point (600 ° C.) of zirconium fluoride as the zirconium compound is lower than the boiling point of the nonvolatile fission product.

  FIG. 1 is a schematic cross-sectional view of a processing apparatus 30 according to the first embodiment of the present invention. The processing apparatus 30 is formed by, for example, a flame furnace 1, and has a configuration in which the zirconium recovery unit 2 is installed inside and the solid storage chamber 20 is installed in the lower part.

The flame furnace 1 has a cylindrical shape, and supplies a mixture 3 (spent fuel mixed with zirconium in the fuel cladding tube) 3 and fluorine gas 4 from the top. Moreover, the solid storage chamber 20 which collect | recovers and stores the non-volatile fluorination fission product C is provided in the lower part. The solid storage chamber 20 has a vent 21 for collecting the uranium hexafluoride UF ₆ gas A and the volatile fluorinated fission product B.

  An outer heater 22 that can heat the inner surface of the frame furnace 1 to 200 ° C. or higher is provided on the outer periphery of the frame furnace 1. The zirconium recovery part 2 has, for example, a cylindrical shape and is installed so as to cover the inner surface of the frame furnace 1. Further, the zirconium recovery unit 2 has an internal heater (not shown) capable of adjusting the temperature.

  Next, the procedure of the processing method of the spent fuel containing zirconium will be described. The flame furnace 1 is heated to 200 ° C. or more by an external heater 22. The temperature of the zirconium recovery unit 2 is set to 200 to 550 ° C. by an internal heater (not shown). Under this temperature condition, spent fuel (hereinafter simply referred to as a mixture) 3 and fluorine gas 4 containing zirconium are supplied from the upper part of the flame furnace 1. The mixture 3 and the fluorine gas 4 generate reaction heat and react rapidly. At this time, the frame 5 which is a high temperature reaction field is formed by the reaction heat. The temperature of the flame | frame 5 is 1200-1600 degreeC.

  Under this temperature condition, the fluoride shown in FIG. 9 is generated by the reaction of the mixture 3 and the fluorine gas 4 in the flame furnace 1. In FIG. 9, the type (classification) 101 of fluoride, the chemical formula 102 of fluoride, and the boiling point 103 are described from the left. Also, as the type 101 of fluoride, the main component of fluoride is the uranium fluoride A, which is a nuclear fuel material, volatile fluorofission product B, non-volatile fluorofission product C, and cladding tube. It can be classified into a compound of zirconium (zirconium fluoride) D.

  Here, the chemical formula 102 and the boiling point 103 of the fluoride in each type are as illustrated, and detailed description thereof is omitted. However, the boiling point 103 is remarkably different for each type 101 of the classified fluorides.

As a result, the nuclear fuel material A (UF ₆ ) and the volatile FP fluoride (B) having a low boiling point do not condense inside the flame furnace 1, and gas is emitted from the vent 21 provided in the lower solid storage chamber 20. As recovered. The recovered nuclear fuel material A (UF ₆ ) and the volatile fluorinated fission product (B) can be treated in a uranium purification process to obtain high-purity UF ₆ and used again as nuclear fuel material. Also, as a uranium purification step, for example, nuclear fuel material A (UF ₆ ) and volatile FP fluorinated fission product (B) are circulated through an adsorption tower packed with an adsorbent (sodium fluoride, magnesium fluoride, etc.). There is a method of adsorbing volatile fluorinated fission products on an adsorbent.

On the other hand, zirconium fluoride D (ZrF ₄ ) sublimates in the high-temperature frame 5 and temporarily becomes gaseous. The ZrF ₄ gas diffuses into the flame furnace 1 and is cooled when approaching the zirconium recovery unit 2 having a temperature lower than that of the flame 5. The ZrF ₄ gas is condensed here as a solid and adheres to the zirconium recovery part 2.

Finally, regarding fluorides classified as non-volatile fluorinated fission products C, YF ₃ , BaF ₂ , SmF ₃ , and SrF ₂ having a high boiling point (on the order of 2000 degrees) remain solid in the frame 5. It falls into the solid storage chamber 2 provided in the lower part of the flame furnace 1 as it is, and is collect | recovered.

In addition, among the non-volatile fluorinated fission products C, SnF ₄ , CsF, and RbF having a boiling point in the range of 800 to 1400 degrees are considered to partially volatilize in the frame 5. However, since the boiling point is higher than the sublimation point (600 degrees) of zirconium fluoride D (ZrF ₄ ), the amount recovered by the zirconium recovery unit 2 is small. That is, SnF ₄ , CsF, and RbF that have volatilized in the frame 5 decrease in temperature environment as they approach the zirconium recovery unit 2, and become solid and fall when their sublimation point (for example, 850 degrees for SnF ₄ ) or less. Therefore, it is considered that the zirconium recovery part 2 is rarely reached.

Therefore, it is considered that SnF ₄ , CsF, and RbF are finally condensed and recovered by dropping into the solid storage chamber 2 provided at the lower part of the frame furnace 1. Note that the non-volatile fluorinated fission product (C) recovered in the solid storage chamber 20 in the lower part of the frame furnace 1 is converted into an oxide by high-temperature hydrolysis and then vitrified.

The mixture 3 is roughly divided into uranium (A), zirconium (D), and fission products (B, C) by the above procedure. The ZrF ₄ recovered in the zirconium recovery unit 2 is recovered individually by opening the frame furnace 1 and taking out the zirconium recovery unit 2 to the outside and then mechanically peeling it off. Or by heating the zirconium recovery unit 2 to 600 ° C. or higher, it may be separated by evaporation of the ZrF ₄ adhering. Alternatively, a method using a chloride gas (for example, BCl ₃ or SiCl ₄ ) described later, that is, supplying the chloride gas to the flame furnace 1 to convert ZrF ₄ to ZrCl ₄ and volatilizing and recovering at 350 ° C. or higher. May be.

  FIG. 2 summarizes each part (frame 5, zirconium recovery part 2, solid storage chamber 20) of the processing apparatus 30 of FIG. 1, its function, and the state of various substances in each part. This figure describes each part 201 of the processing apparatus 30, the state 202 of various substances in each part, and the function 203 of each part from the left side.

  According to this, in the frame 5, the mixture 3 (spent fuel containing zirconium) exists as nuclear fuel material A, volatile fluorinated fission product B, non-volatile fluorinated fission product C, and zirconium fluoride D. . Nuclear fuel material A, volatile fluorinated fission product B, zirconium fluoride D and some non-volatile fluorinated fission products C are gaseous, and some non-volatile fluorinated fission products C are solid. . This state is realized by setting the temperature environment to be higher than the sublimation temperature of the zirconium compound (fluoride) in the frame 5.

  Next, in the zirconium recovery part 2, zirconium fluoride D is adsorbed as a solid. This state is realized by setting the temperature environment below the sublimation temperature of the zirconium compound (fluoride) in the zirconium recovery unit 2.

  Finally, in the solid storage chamber 20, the gaseous nuclear fuel material A and the volatile fluorinated fission product B are taken out from the vent 21. In addition, the non-volatile fluorinated fission product C eventually falls as a solid and is stored in the solid storage chamber 20 regardless of whether the intermediate stage is in a gas or solid state.

  Thus, in the present invention, the mixture 3 is made into uranium (A), zirconium (D), and nuclear fission by creating in the processing apparatus a temperature environment higher than the sublimation temperature of the zirconium compound and a temperature environment lower than the sublimation temperature of the zirconium compound. The product (B, C) can be roughly divided.

FIG. 3 is a schematic cross-sectional view of a processing apparatus 31 according to another embodiment. In the flame furnace type processing apparatus 31 shown in FIG. 3, the zirconium recovery unit 2 is installed in the solid storage chamber 2. In this example, in particular, the zirconium recovery unit 2 is installed in the vicinity of the vent 21 for recovering the uranium hexafluoride UF ₆ gas A and the volatile fluorinated fission product B.

  This Example 2 also pays attention to the fact that the sublimation point (600 ° C.) of zirconium fluoride as the zirconium compound is lower than the boiling point of the nonvolatile fission product.

  In the processing apparatus 31 having this structure, the flame furnace 1 is heated to 200 ° C. or more by the external heater 22 as the first stage. However, the temperature of the zirconium collection | recovery part 2 is made into normal temperature. In this state, spent fuel 3 containing zirconium and fluorine gas 4 are supplied from the upper part of the flame furnace 1. The mixture 3 and the fluorine gas 4 generate reaction heat and react rapidly. At this time, the frame 5 which is a high temperature reaction field is formed by the reaction heat. The temperature of the flame | frame 5 is 1200-1600 degreeC.

  Under this temperature condition, the fluoride shown in FIG. 9 is generated by the reaction of the mixture 3 and the fluorine gas 4 in the flame furnace 1. Specifically, in the frame 5 portion, gaseous uranium fluoride A, gaseous volatile fluorinated fission product B, gaseous zirconium fluoride D, and solid nonvolatile fluorinated fission product Classified as C.

In the case where the mixture 3 is reacted with the fluorine gas 4 using the processing apparatus 31, the UF ₆ gas A and the non-volatile fluorinated fission product B among these substances are recovered from the vent 21 as gas as in FIG. Is done. Further, the non-volatile fluorinated fission product C is finally recovered by dropping into the solid storage chamber 2 provided at the lower part of the frame furnace 1 as in FIG.

On the other hand, in this processing method, zirconium fluoride D (ZrF ₄ ) is volatilized temporarily in the frame 5, but is cooled and condensed as it diffuses to the vicinity of the furnace wall of the flame furnace 1, and nonvolatile fluoride It falls into the solid storage chamber 2 provided in the lower part of the flame furnace 1 together with the fission product C, and is recovered as a solid.

In this state, the zirconium fluoride D (ZrF ₄ ) and the non-volatile fluorinated fission product C are dropped and stored in the solid storage chamber 2 provided in the lower part of the frame furnace 1 without being distinguished from each other. Let's separate this.

Specifically, after the supply of the mixture 3 and the fluorine gas 4 is stopped, the temperature of the zirconium recovery unit 2 that has been normal at that time is heated to about 600 ° C. or less. Next, the zirconium fluoride ZrF ₄ and the non-volatile fission product C recovered as a solid are heated to 600 to 800 ° C. Then, the zirconium fluoride ZrF ₄ is volatilized, cooled and condensed in the zirconium recovery unit 2, and separated from the non-volatile fission product C.

  FIG. 4 summarizes each part (frame 5, zirconium recovery part 2, solid storage chamber 20) and its function of the processing apparatus 31 of FIG. 3, and states of various substances in each part. This figure describes each part 301 of the processing apparatus 31, the state 302 of various substances in each part, and the function 303 of each part from the left side.

  According to this, in the frame 5, the mixture 3 (spent fuel containing zirconium) exists as nuclear fuel material A, volatile fluorinated fission product B, non-volatile fluorinated fission product C, and zirconium fluoride D. . Nuclear fuel material A, volatile fluorinated fission product B, zirconium fluoride D and some non-volatile fluorinated fission products C are gaseous, and some non-volatile fluorinated fission products C are solid. . This state is realized by setting the temperature environment to be higher than the sublimation temperature of the zirconium compound (fluoride) in the frame 5.

  At this time, in the solid storage chamber 20, the gaseous nuclear fuel material A and the volatile fluorinated fission product B are taken out from the vent 21. In addition, the non-volatile fluorinated fission product C eventually falls as a solid and is stored in the solid storage chamber 20 regardless of whether the intermediate stage is in a gas or solid state. At the same time, zirconium fluoride D also changes from a gas state to a solid and falls and is stored in the solid storage chamber 20.

In the second stage, after the supply of the mixture 3 and the fluorine gas 4 is stopped, the temperature of the zirconium recovery unit 2 that has been a normal temperature before that is heated to about 600 ° C. or less. Next, ZrF ₄ and the non-volatile fission product C recovered as a solid are heated to 600 to 800 ° C.

At this time, ZrF ₄ and the non-volatile fission product C recovered as solids are again placed in a temperature environment equal to or higher than the sublimation temperature of the zirconium compound, and ZrF ₄ (D) is sublimated, and then the zirconium recovery unit 2 , Zirconium fluoride D is adsorbed. This adsorption state is realized by setting the temperature environment below the sublimation temperature of the zirconium compound in the zirconium recovery part 2.

  4 is compared with FIG. 2, in FIG. 4, the temperature environment equal to or higher than the sublimation temperature of the zirconium compound is constructed twice. By creating a temperature environment below the sublimation temperature of the compound in the processing apparatus, the mixture 3 can be roughly divided into uranium (A), zirconium (D), and fission products (B, C).

  Hereinafter, another example of the embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view of the processing apparatus 32 of the present invention. The processing device 32 is formed of the batch type fluorination device 10 and has a configuration in which the zirconium recovery unit 2 and the pedestal 11 are installed.

  This Example 3 also pays attention to the fact that the sublimation point (600 ° C.) of zirconium fluoride as a zirconium compound is lower than the boiling point of the nonvolatile fission product.

  The batch-type fluorination apparatus 10 has a cylindrical shape, and an external heater 22 that can increase the inner surface temperature of the batch-type fluorination apparatus 10 is provided outside the batch-type fluorination apparatus 10.

  Inside the batch type fluorination apparatus 10 is provided a pedestal 11 on which a mixture 3 (spent fuel mixed with zirconium in the fuel cladding tube) 3 such as corium is placed. The pedestal 11 is provided with an internal heater (not shown) capable of adjusting the temperature, and heats the mixture 3 such as corium.

A vent for supplying the fluorine gas 4 is provided on the bottom of the batch fluorination apparatus 10, and a vent 21 for collecting the UF ₆ gas A and the volatile fluorinated fission product B is provided on the top.

  The zirconium recovery unit 2 has a cylindrical shape and is installed so as to cover the inner surface of the batch type fluorination apparatus 10. Further, the zirconium recovery unit 2 has an internal heater (not shown) capable of adjusting the temperature.

  Next, the procedure of the processing method of the spent fuel containing zirconium will be described. The mixture 3 is placed on the pedestal 11 inside the batch fluorination apparatus 10. In this state, each part of the processing device 32 is set to the following temperature environment.

  First, the surface temperature of the batch fluorination apparatus 10 is set to 200 ° C. or higher by the external heater 22 of the batch fluorination apparatus 10. Further, the mixture on the pedestal 11 is heated to 600 to 800 ° C. by an internal heater (not shown) of the pedestal 11. The temperature of the zirconium recovery unit 2 is set to 200 to 550 ° C. by an internal heater (not shown).

  In the case of FIG. 3, it is clear that the above-mentioned temperature environment conditions are the same as those of FIG. The temperature 600 to 800 ° C. of the mixture on the pedestal 11 is not less than the sublimation temperature of the zirconium compound, and the temperature 200 to 550 ° C. of the zirconium recovery part 2 is not more than the sublimation temperature of the zirconium compound. For this reason, when the fluorine gas 4 is next supplied to the batch type fluorination apparatus 10 under this temperature condition, the fluoride shown in FIG. 9 is generated by the reaction of the mixture 3 and the fluorine gas 4 as in the first embodiment. Is done.

Among the fluorides in FIG. 9, uranium hexafluoride UF ₆ (A) and the volatile fluorinated fission product B have low boiling points, so they do not condense inside the batch fluorination apparatus 10 and are vented as gas. 21 is recovered. As for the subsequent treatment, the recovered uranium hexafluoride UF ₆ (A) and the volatile fluorinated fission product B are treated in the uranium purification step to obtain high-purity uranium hexafluoride UF ₆ as in FIG. It can also be used again as nuclear fuel material.

Zirconium fluoride D (ZrF ₄ ) temporarily becomes a gas in the reaction part (on the pedestal 11) of the mixture 3 and the fluorine gas 4. When the zirconium fluoride ZrF ₄ gas diffuses and comes into contact with the zirconium recovery part 2, it is condensed as a solid. In this case, the non-volatile fluorinated fission product C has a high boiling point and remains on the pedestal 11 as a solid.

  After the above treatment, after the supply of the fluorine gas 4 is stopped, the batch fluorination apparatus 10 is opened, and the nonvolatile fluorinated fission product C is recovered. Similarly to FIG. 1, the non-volatile fluorinated fission product is converted into an oxide by high-temperature hydrolysis and then vitrified.

Spent fuel containing zirconium is roughly divided into uranium, zirconium and fission products by the above procedure. The zirconium fluoride ZrF ₄ (D) recovered in the zirconium recovery unit 2 as in FIG. 1 is mechanically peeled off after opening the batch type fluorination apparatus 10 and taking out the zirconium recovery unit 2 to the outside. It is collected individually by the above, or it is recovered by volatilization by heating. Alternatively, it is volatilized and recovered as ZrCl ₄ by a method using a chloride gas (for example, BCl ₃ or SiCl ₄ ).

  FIG. 6 summarizes each part (the pedestal 11, the zirconium recovery part 2, and the vent 21) of the processing apparatus 32 of FIG. 5, its function, and the state of various substances in each part. This figure describes each part 401 of the processing apparatus 32, the state 402 of various substances in each part, and the function 403 of each part from the left side.

  According to this, the mixture 3 (spent fuel containing zirconium) on the pedestal 11 exists as nuclear fuel material A, volatile fluorinated fission product B, non-volatile fluorinated fission product C, and zirconium fluoride D. . Nuclear fuel material A, volatile fluorinated fission product B, zirconium fluoride D and some non-volatile fluorinated fission products C are gaseous, and some non-volatile fluorinated fission products C are solid. . This state is realized by setting a temperature environment higher than the sublimation temperature of the zirconium compound in the base 11.

  Next, zirconium fluoride D is adsorbed in the zirconium recovery part 2. This state is realized by setting the temperature environment below the sublimation temperature of the zirconium compound in the zirconium recovery unit 2.

  Finally, gaseous nuclear fuel material A and volatile fluorinated fission product B are removed from the vent 21. Further, the non-volatile fluorinated fission product C remains on the pedestal 11 as a solid.

  Thus, even in the embodiment of FIG. 5 of the present invention, the mixture 3 is formed with uranium (A) by creating a temperature environment above the sublimation temperature of the zirconium compound and a temperature environment below the sublimation temperature of the zirconium compound in the processing apparatus. Zirconium (D) and fission products (B, C) can be roughly divided.

  The examples 1, 2, and 3 have been described above. In these cases, a flame furnace system or a batch system is used as a mixture fluorination apparatus. And it is the system which paid its attention to the sublimation point (600 degreeC) of a zirconium fluoride being low compared with the boiling point of a non-volatile fission product as a zirconium compound.

  Although some of these processing apparatus configurations are different, in short, a zirconium recovery section kept at 200 to 550 ° C. is provided inside. This creates a temperature environment below the sublimation point (600 ° C.) of zirconium fluoride as the zirconium compound.

On the other hand, the temperature of the reaction part of the fluorine gas and the mixture is set to 600 ° C. or higher. This reaction part is a frame and is on a pedestal. This creates a temperature environment above the sublimation point (600 ° C.) of zirconium fluoride as the zirconium compound. When fluorine gas and the mixture are reacted using this fluorination apparatus, UF ₆ , ZrF ₄ , and volatile fluorinated fission products are volatilized in the reaction part.

ZrF ₄ volatilized in the reaction part is condensed and recovered in the zirconium recovery part. Since UF ₆ and volatile fluorinated fission products are not condensed at the temperature of the zirconium recovery section, they are separated and recovered as a gas. In the case of the flame furnace method, the non-volatile fluorinated fission product is recovered as a solid by dropping to the lower part of the flame furnace.

In the case of the batch method, it is recovered as a solid by remaining as a residue in the place where the mixture is placed. UF ₆ and the volatile fluorinated fission product can be separated by, for example, a method of adsorbing the volatile fluorinated fission product to an adsorbent, which is a known method, or a rectification method.

  Hereinafter, another example of the embodiment of the present invention will be described with reference to FIG. In FIG. 7, after the partial processing in the processing device 32 of FIG. 5, the second-stage processing is performed using the processing device 32.

In this example, it was noted that the sublimation point (331 ° C.) of zirconium chloride (ZrCl ₄ ) as the zirconium compound was lower than the sublimation point of ZrF ₄ .

  In the first stage process shown in the upper part of FIG. 7, a part of the process described in FIG. 5 is performed. Although description overlaps, the mixture 3 is put on the base 11 inside the batch type fluorination apparatus 10. In this state, each part of the processing device 32 is set to the following temperature environment.

  First, the surface temperature of the batch fluorination apparatus 10 is set to 200 ° C. or higher by the external heater 22 of the batch fluorination apparatus 10. Moreover, the temperature of the mixture 3 on the base 11 is heated to 300-600 degreeC. The temperature of the zirconium recovery unit 2 is set to 200 to 300 ° C. by an internal heater (not shown).

  Next, the fluorine gas 4 is supplied to the batch type fluorination apparatus 10. The fluoride shown in FIG. 9 is generated by the reaction of the mixture 3 and the fluorine gas 4.

Among the fluorides in FIG. 9, uranium hexafluoride UF ₆ (A) and volatile fluorinated fission product B have low boiling points, so they do not condense inside the batch type fluorination apparatus 10 and are vented as gas 21 Recovered from. Uranium hexafluoride UF ₆ (A) and volatile fluorinated fission product B can be treated in a uranium purification step to obtain high-purity uranium hexafluoride UF ₆ and used again as nuclear fuel material.

In addition, since the temperature of the mixture 3 on the pedestal 11 is a state heated to 300 to 600 ° C., the zirconium fluoride D (ZrF ₄ ) is not sublimated, and is solidified with the fluorinated fission product C as a solid. Remain on top. The first stage process shown in the upper part of FIG.

In the second stage process shown in the lower part of FIG. 7, the supply of the fluorine gas 4 is stopped in this state, and then the chloride gas 12 is supplied to the batch type fluorination apparatus 10. At this time, the solid on the base 11 is heated to 350 ° C. or higher by an internal heater (not shown) of the base 11. As the chloride gas 12, for example, BCl ₃ or SiCl ₄ is used.

Zirconium fluoride D (ZrF ₄ ) reacts with the chloride gas 12 to produce zirconium chloride F (ZrCl ₄ ). Since the temperature of the reaction part of zirconium chloride F (ZrCl ₄ ) and chloride gas 12 is 350 ° C. or higher, the generated zirconium chloride F (ZrCl ₄ ) volatilizes.

Zirconium chloride F (ZrCl ₄ ) gas diffuses and comes into contact with the zirconium recovery part 2 and condenses as a solid. Although the non-volatile fission product C partially reacts with the chloride gas, most of the non-volatile fission product C remains on the pedestal 11 as the non-volatile fission product compound C.

  The waste chloride gas 14 and the waste fluoride gas 15 generated by the reaction are recovered and then condensed and recovered by cooling or adsorbed on an adsorbent such as activated alumina for processing. After the above treatment, after the supply of the chloride gas 12 is stopped, the batch fluorination apparatus 10 is opened, and the nonvolatile fission product compound G is recovered. As in the other examples, the non-volatile fission product compound G is converted into an oxide by high-temperature hydrolysis and then vitrified.

According to the above procedure, the mixture is roughly divided into uranium, zirconium and fission products. Zirconium chloride F (ZrCl ₄ ) recovered in the zirconium recovery unit 2 in the same manner as in the other examples was mechanically opened after the batch type fluorination apparatus 10 was opened and the zirconium recovery unit 2 was taken out. It is recovered individually by peeling off or recovered by volatilization by heating.

  The embodiment of the present invention described in FIG. 7 is different from the other embodiments. In addition to the fact that this is a two-step process, in another embodiment, the zirconium compound is sublimated (gasified) using the sublimation temperature (600 ° C.) of zirconium fluoride, and conversely below this temperature. It was solidified.

In this regard, in the example of FIG. 7, the sublimation temperature (331 degrees) of zirconium chloride (ZrCl ₄ ) was used as the zirconium compound. In any case, in the present invention, separation is performed by sublimation or solidification by creating a temperature environment of the sublimation temperature of the zirconium compound.

  FIG. 8 summarizes each part (the pedestal 11, the zirconium recovery part 2, and the vent 21) of the processing apparatus 32 of FIG. 7, its function, and the state of various substances in each part. This figure describes each part 501 of the processing apparatus 32, the state 502 of various substances in each part, and the function 503 of each part from the left side.

  According to this, the mixture 3 (spent fuel containing zirconium) on the pedestal 11 exists as nuclear fuel material A, volatile fluorinated fission product B, non-volatile fluorinated fission product C, and zirconium fluoride D. . Here, the nuclear fuel material A and the volatile fluorinated fission product B are gaseous, and the zirconium fluoride D and the non-volatile fluorinated fission product C are solid.

  Gaseous nuclear fuel material A and volatile fluorinated fission product B are removed from vent 21. This is the first step of forming a compound using fluorine gas.

  In the second stage treatment, a compound is formed on the pedestal 11 using chlorine gas. As a result, zirconium fluoride D changes to zirconium chloride F. At this time, the temperature environment (350 degrees or more) formed on the pedestal 11 is equal to or higher than the sublimation temperature (331 degrees) of the zirconium chloride F, and the zirconium chloride F is gasified. The temperature environment on the pedestal at this time becomes a temperature environment equal to or higher than the sublimation temperature of the zirconium compound.

  In addition, since the zirconium recovery unit 2 has a sublimation temperature (331 degrees) or less of zirconium chloride F, zirconium chloride F is adsorbed. This state is realized by setting the temperature environment below the sublimation temperature of the zirconium compound in the zirconium recovery unit 2.

  Thus, even in the embodiment of FIG. 7 of the present invention, the mixture 3 is made uranium by creating a temperature environment above the sublimation temperature of the zirconium compound (chloride) and a temperature environment below the sublimation temperature of the zirconium compound in the processing apparatus. (A), zirconium (D), and fission products (B, C) can be roughly divided.

In the embodiment described above, a batch system was used as a fluorination apparatus for the mixture, and it was noted that the sublimation point (331 ° C.) of zirconium chloride (ZrCl ₄ ) as the zirconium compound was lower than the sublimation point of ZrF ₄ .

  And the zirconium collection | recovery part kept at 200-300 degreeC in the fluorination apparatus is provided. The temperature of the reaction part of the fluorine gas and the mixture is set to 300 ° C. or higher. This method of FIG. 7 has an advantage that the temperature of the fluorination reaction can be lowered than the method of FIG.

When fluorine gas and the mixture are reacted using this fluorination apparatus, UF ₆ and volatile fluorinated fission products are volatilized in the reaction part. Since UF ₆ and volatile fluorinated fission products are not condensed at the temperature of the zirconium recovery section, they are separated and recovered as a gas.

At this time, ZrF ₄ and the non-volatile fluorinated fission product remain as solids inside the fluorination apparatus. The UF ₆ and the volatile fluorinated fission product can be separated, for example, by adsorbing the volatile fluorinated fission product on the adsorbent.

Next, a chloride gas is supplied into the fluorination apparatus. Types of chloride gas include boron chloride (BCl ₃ ) and silicon chloride (SiCl ₄ ). The temperature of the reaction part of chloride fluorine gas and ZrF ₄ · volatile fluorinated fission product is set to 350 to 600 ° C. When chloride gas is supplied, it reacts with ZrF ₄ to produce ZrCl ₄ . Since the temperature of the reaction part is higher than the sublimation point of ZrCl ₄ , ZrCl ₄ volatilizes and is condensed and recovered by the zirconium recovery part.

1: Flame furnace 2: Zirconium recovery part 3: Mixture (spent fuel mixed with zirconium in fuel cladding)
4: Fluorine gas 5: Frame 10: Batch type fluorination device 11: Pedestal 12: Chloride gas 20: Solid storage chamber 21: Vent 22: External heaters 30, 31, 32: Processing devices 101, 201, 301, 401 , 501: Types of fluoride (classification)
102, 202, 302, 402, 502: Chemical formulas of fluoride 103, 203, 303, 403, 503: Boiling point A: Uranium hexafluoride UF ₆ gas B: Volatile fluorinated fission product C: Nonvolatile fluorinated fission Product D: Zirconium fluoride (ZrF ₄ )
F: Zirconium chloride (ZrCl ₄ )

Claims (15)

In a spent fuel processing apparatus containing zirconium for separating spent fuel containing zirconium into nuclear fuel material, zirconium and fission products,
A heating means for obtaining a temperature environment equal to or higher than the sublimation temperature of the zirconium compound in the processing apparatus; and a zirconium recovery portion that is a temperature environment equal to or lower than the sublimation temperature of the zirconium compound and condenses and recovers the volatilized zirconium compound; An apparatus for treating spent fuel containing zirconium, comprising a solid reservoir for storing solids remaining in a temperature environment equal to or higher than the sublimation temperature of the zirconium compound, and a vent for collecting gas. In the processing apparatus of the spent fuel containing the zirconium according to claim 1,
The said heating means includes the 1st heating means for making the spent fuel containing zirconium react with fluorine gas, and forming a flame | frame, The processing apparatus of the spent fuel containing zirconium characterized by the above-mentioned. In the processing apparatus of the spent fuel containing the zirconium according to claim 1,
The heating means heats the solid in the solid reservoir to a temperature equal to or higher than the sublimation temperature of the zirconium compound by reacting spent fuel containing zirconium with fluorine gas to form a frame. And a second heating means for processing the spent fuel containing zirconium. In the processing apparatus of the spent fuel containing the zirconium according to claim 1,
The heating means includes a pedestal on which spent fuel containing zirconium is placed, and third heating means for obtaining a temperature environment equal to or higher than the sublimation temperature of the zirconium compound when reacting with fluorine gas on the pedestal. An apparatus for treating spent fuel containing zirconium. In the processing apparatus of the spent fuel containing the zirconium according to claim 1,
The heating means includes a pedestal on which spent fuel containing zirconium is placed, and after reacting with fluorine gas on the pedestal, for obtaining a temperature environment equal to or higher than the sublimation temperature of the zirconium compound when reacted with chlorine gas. A processing apparatus for spent fuel containing zirconium, comprising a fourth heating means. In the processing apparatus of the spent fuel containing the zirconium according to claim 1,
An apparatus for treating spent fuel containing zirconium, wherein the zirconium compound is zirconium fluoride. In the processing apparatus of the spent fuel containing the zirconium according to claim 1,
A processing apparatus for spent fuel containing zirconium, wherein the zirconium compound is zirconium chloride. In a method for treating spent fuel containing zirconium for separating spent fuel containing zirconium into nuclear fuel material, zirconium, and fission products,
The spent fuel containing zirconium is treated in a temperature environment equal to or higher than the sublimation temperature of the zirconium compound, and the zirconium compound volatilized in a temperature environment equal to or lower than the sublimation temperature of the zirconium compound is condensed and recovered. A method for treating spent fuel that is recovered in the form of gas and solids remaining in a temperature environment above the sublimation temperature. The method for treating spent fuel containing zirconium according to claim 8,
The spent fuel containing zirconium is separated into gas and solid by the first treatment under a temperature environment equal to or higher than the sublimation temperature of the zirconium compound, and the solid after the first treatment has a temperature higher than the sublimation temperature of the zirconium compound. The solid was subjected to the second treatment under the temperature environment, and the zirconium compound volatilized under the temperature environment below the sublimation temperature of the zirconium compound was collected and recovered, and remained in the temperature environment above the sublimation temperature of the zirconium compound. And the processing method of the spent fuel which is divided and collected in the gas. The method for treating spent fuel containing zirconium according to claim 9,
The spent fuel containing zirconium is reacted with fluorine gas to be separated into a gas and a solid, and the separated solid is reacted with chlorine gas in a temperature environment equal to or higher than the sublimation temperature of zirconium chloride to sublimate the zirconium chloride. A method for treating spent fuel that condenses and recovers zirconium chloride that has volatilized under a temperature environment below the temperature, and that collects the solid that remains in a temperature environment equal to or higher than the sublimation temperature of the zirconium chloride and separates it into a gas. The method for treating spent fuel containing zirconium according to claim 8,
A method for treating spent fuel containing zirconium, wherein the zirconium compound is zirconium fluoride. In a method for treating spent fuel containing zirconium for separating spent fuel containing zirconium into nuclear fuel material, zirconium, and fission products,
Zirconium fluoride in the fuel cladding tube and spent fuel are reacted with fluorine gas at a temperature of 600 ° C or higher to generate zirconium fluoride gas, and the zirconium fluoride gas is condensed in the zirconium recovery unit installed inside the reactor. And then collecting the spent fuel containing zirconium. The method for treating spent fuel containing zirconium according to claim 12,
Zirconium is characterized by separating zirconium from the zirconium recovery part by reacting zirconium fluoride recovered with the zirconium recovery part to produce zirconium chloride and volatilizing the zirconium chloride at 350 ° C. or higher. Including spent fuel treatment methods. The method for treating spent fuel containing zirconium according to claim 12,
Zirconium in the fuel cladding tube and spent fuel are reacted with fluorine gas at a temperature of 300 to 600 ° C., and uranium in the spent fuel is recovered as UF ₆ ; A method for treating spent fuel, characterized in that a zirconium chloride gas is produced by reacting with a chloride gas, and the zirconium chloride gas is condensed and recovered in a zirconium recovery part installed inside the reactor. In the processing method of the spent fuel containing the zirconium according to claim 13-14,
A method for treating spent fuel containing zirconium, characterized in that boron chloride and silicon chloride gas are used as chloride gas.

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