KR101024102B1 - A preparation method of RE-rich U,RE4O9 and UO3 powder mixture with the large difference of magnetic susceptibility and the seperation method of U,RE4O9 and UO3 - Google Patents

Abstract

The present invention relates to the preparation of a mixed powder of high concentration rare earth element solid solution uranium oxide ((U, RE) ₄ O ₉ ) and uranium trioxide (UO ₃ ) having a large susceptibility difference, and more particularly, a rare earth of a complex component which is a neutron absorber Rare-earth: RE cation (U _1-x RE _x ) O ₂ Nuclear fuel solid solution _x solid solution (U _1-y RE _y ) ₄ O ₉ Phase Particles and U ₃ O ₈ Phase After preparing a mixed powder in which the particles are separated, ozone oxidation treatment is performed to selectively oxidize only U ₃ O ₈ phase particles to UO ₃ phase particles, which has high magnetization rate and high concentration of rare earth solid solution (U _1-y RE _y ) ₄ A method for producing a mixed powder of O ₉ phase particles and UO ₃ phase particles with very low susceptibility. The susceptibility of the (U _1-y RE _y ) ₄ O ₉ powder prepared according to the present invention can be produced UU ₃ powder or a powder having a much larger susceptibility difference than the conventional U ₃ O ₈ powder to recycle the UO ₃ powder Recovery rate can be improved. In addition, when the UO ₃ powder is reduced to UO ₂ nuclear fuel and burned in a nuclear reactor, the nuclear fission efficiency and the thermal conductivity of the UO ₂ substrate can be increased, which can be usefully used to increase power generation efficiency using nuclear power.

Description

Method for preparing triuranium trioxide and uranium trioxide mixed powder with high concentration of rare earth element with large susceptibility difference {A preparation method of RE-rich (U, RE) 4O9 and UO3 powder mixture with the large difference of magnetic susceptibility and the seperation method of (U, RE) 4O9 and UO3}

The present invention relates to a method for producing a high concentration of rare earth element solid solution of uranium trioxide and uranium trioxide mixed powder having a large susceptibility difference, and a method for separating triuranium citrate and uranium trioxide.

The present invention relates to a method for preparing a mixed powder of uranium oxide and uranium trioxide in which a high concentration of rare earth elements having a large susceptibility difference is dissolved. More specifically, (U _1-x RE _x ) in which x mol of a composite component rare earth element cation is dissolved. The O ₂ fuel solid solution was subjected to oxidation heat treatment and redox treatment to obtain a mixed powder in which (U _1-y RE _y ) O _{2 + z} phase particles and U ₃ O ₈ phase particles in which high concentrations of rare earth elements were dissolved were separated. After the ozone oxidation treatment, only U ₃ O ₈ phase particles are selectively oxidized to UO ₃ phase particles, which has high susceptibility and very high susceptibility to (U _1-y RE _y ) O _{2 + z} phase particles with high concentration of rare earth elements. A method for producing a mixed powder of low UO ₃ phase particles.

The rare earth elements of the composite component are the fission products that are produced when UO ₂ fuel is burned in the reactor and exist in the form of solid solution on the UO ₂ base. When the fuel is recycled to the oxide fuel by direct processing after the combustion, the rare earth element is As a neutron absorber, it reduces the fission efficiency of fissile material and is dissolved in the UO ₂ substrate, thereby lowering the thermal conductivity. Therefore, in order to increase nuclear fission efficiency and thermal conductivity in the recycling of nuclear fuel after combustion, a rare earth element separation study was conducted by using a dry method using a reactive gas and heat rather than a wet method dissolved in nitric acid.

As such, the rare earth element separation study is performed by oxidizing a (U _1-x RE _x ) O ₂ fuel solid solution containing x mol solid solution of a single component rare earth element into powder (U _1-x RE _x ) ₃ O ₈ . (U _1-y RE _y ) O _{2 + z} phase particles and U ₃ O ₈ phase particles produced by phase separation by oxidative heat treatment at 1150 to 1400 ° C. are combined with ultrasonic particles by injecting the particle powder into water. Or by redox reaction using reactive gas and heat. In general, the susceptibility of uranium oxide is U ₄ O ₉ > U ₃ O ₈ > UO _{3 in} order of (U _1-y RE _y ) O _{2 + z} {(U _1-y RE _y ) ₄ O ₉ } one increased when these rare earth elements are employed, because the magnetization rate of _{Pr 2 O 3, Nd 2 O} 3, Eu 2 O 3, in the case of Gd ₂ O _3, the magnetic susceptibility is higher than the U ₄ O ₉ in the rare-earth element, U ₄ O ₉ The lower susceptibility of Y ₂ O ₃ , CeO ₂ and La ₂ O _{3, which} is nonmagnetic, decreases when employed. In the burned nuclear fuel, rare earth elements with low susceptibility are employed at 41.4 mol% of the rare earth elements, and high temperature oxidative heat treatment results in (U _1-y RE _y ) O _{2 + z} phase particles. Because of the separation, there is a problem in that the magnetic separation efficiency is lowered because the difference in susceptibility is small when the magnetic separation.

Therefore, the present inventors have developed a method for producing a high concentration of rare earth element solid solution triuranium uranium trioxide and uranium trioxide mixed powder having a large susceptibility difference, and separates uranium trioxide and uranium trioxide by high gradient magnetic separation and recovers the recovered uranium dioxide. The present invention was completed by reducing (UO ₂ ) to prepare UO ₂ having high combustion degree.

An object of the present invention is to provide a method for preparing a powder mixture of high concentration rare earth element solid solution triuranium trioxide ((U _1-y RE _y ) ₄ O ₉ ) and uranium trioxide (UO ₃ ) having a large susceptibility difference.

Another object of the present invention is to provide a method for selectively separating triuranium citrate from the mixed powder prepared by the above method.

Another object of the present invention is to provide a method for producing uranium dioxide (UO ₂ ) nuclear fuel by reducing the uranium trioxide isolated from the uranium trioxide.

In order to achieve the above object, the present invention uses a (U _1-x RE _x ) O ₂ nuclear fuel solid solution in which x mol of a composite component rare earth element cation is dissolved to obtain a high concentration of rare earth element through an oxidation heat treatment process and an oxidation reduction process. After obtaining a mixed powder in which solid _-solution (U _1-y RE _y ) ₄ O ₉ phase particles and U ₃ O ₈ phase particles are separated, ozone oxidation is performed to selectively oxidize only U ₃ O ₈ phase particles to UO ₃ phase particles. The present invention provides a method for producing a mixed powder of (U _1-y RE _y ) ₄ O ₉ phase particles having high magnetization rate and high concentration of rare earth elements and UO ₃ phase particles having very low magnetization rate.

The present invention also provides a method for selectively separating (U _1-y RE _y ) ₄ O ₉ phase particles.

Furthermore, the present invention provides a method for producing UO ₂ nuclear fuel by reducing the UO ₃ phase particles in which the (U _1-y RE _y ) ₄ O ₉ phase particles are separated.

In the mixed powder prepared according to the present invention, (U _1-y RE _y ) ₄ O ₉ powder susceptibility can be obtained 60 ~ 100 times higher powder than UO ₃ powder at the heat treatment temperature, the conventional U ₃ O ₈ Since a powder having a much higher magnetization rate difference than that of the powder is obtained, the recovery rate by magnetic separation of the recycled UO ₃ powder can be increased.

In addition, when the UO ₃ powder is reduced to UO ₂ powder and then made into UO ₂ fuel according to a series of nuclear fuel processing procedures, and then burned in a nuclear reactor, the nuclear fission efficiency can be increased and the thermal conductivity of the UO ₂ substrate can be increased. It can be usefully used to increase power generation efficiency.

Hereinafter, the present invention will be described in detail.

In the present invention, the rare earth element (RE), a neutron absorber, is oxidized (U _1-x RE _x ) O ₂ nuclear fuel in which x mol is dissolved in an air atmosphere at 400 to 600 ° C. (U _1-x RE _x ) ₃ O ₈ Preparing a powder (step 1);

The (U _1-x RE _x ) ₃ O ₈ powder of step 1 was heated to 1150 to 1400 ° C. in an air atmosphere to obtain (U _1-y RE _y ) O _{2 + z} phase particles and U ₃ O ₈ phase particles. Preparing a chemically bound powder (step 2);

The (U _1-y RE _y ) O _{2 + z} phase particles and the U ₃ O ₈ phase particles of step 2 are combined with the reduced powder in a reducing atmosphere at 600 to 800 ° C. (U _1-y RE _y ) O ₂ Preparing a powder in which phase particles and UO ₂ phase particles are combined (step 3);

Of step _{3 (U 1-y RE y} ) O 2 phase particles and UO ₂ phase to the particles are oxidized to the combined mixture powder in an air atmosphere at 300 ~ 700 ℃ U ₃ O ₈ phase particles and the (U _1-y RE _y ) preparing a mixed powder in which ₄ O ₉ phase particles are separated (step 4);

The mixed powder in which the U ₃ O ₈ phase particles and the (U _1-y RE _y ) ₄ O ₉ phase particles of step 4 are separated is oxidized to the UO ₃ phase by oxidizing only the U ₃ O ₈ phase particles in an ozone atmosphere at 175 to 225 ° C. Of a mixture of uranium oxide and uranium trioxide mixed with a high concentration of rare earth elements having a large susceptibility difference, including a step (step 5) of preparing a mixed powder with (U _1-y RE _y ) ₄ O ₉ phase particles by making the particles. It provides a manufacturing method.

Hereinafter, with reference to the accompanying drawings it will be described in more detail each step of the method for producing a mixture of uranium citrate and uranium trioxide mixed with a high concentration of rare earth elements having a large susceptibility difference according to the present invention.

1 is a view showing each step of the method for producing a mixture of uranium citrate and uranium trioxide mixed with a high concentration of rare earth elements having a large susceptibility difference according to the present invention.

In the manufacturing method according to the present invention, step 1 is a rare earth element (RE) is a neutron absorber by oxidizing (U _1-x RE _x ) O ₂ nuclear fuel dissolved _x mol in the air atmosphere of 400 ~ 600 ℃ (U _1-x RE _x ) ₃ 0 ₈ to prepare a powder (S110).

Step 1 may oxidize the (U _1-x RE _x ) O ₂ solid solution in an air atmosphere to prepare a (U _1-x RE _x ) ₃ O ₈ phase powder in which rare earth element cations are unstable in solid solution.

At this time, the rare earth element is Praseodymium (Pr), neodymium (Nd, Neodymuim), Europium (Eu, Europium), Gd, (Gd, Gadolinium), yttrium (Y, Yttrium), lanthanum (La, Lanthanum) Preference is given to using cerium (Ce, Cerium), dysprosium (Dy, Dysprosium), erbium (Er, Erbium), semarium (Sm, Semarium) or mixtures thereof.

Furthermore, the (U _1-x RE _x ) O ₂ nuclear fuel contains (U, Nd) O ₂ fuel containing neodymium oxide (Nd ₂ O ₃ ), and (U, Nd) containing samarium oxide (Sm ₂ O ₃ ). Sm) O ₂ nuclear fuel, (U, Eu) O ₂ nuclear fuel containing europium oxide (Eu ₂ O ₃ ), (U, Dy) O ₂ nuclear fuel or dysium oxide (Er) containing dysprosium oxide (Dy ₂ O ₃ ) ₂ O ₃ ) (U, Er) O ₂ nuclear fuel may be used.

In this case, when the rare earth element is a composite component in step 1, x is 0.007 to 0.034, and in the case of a single component, x is preferably 0.06 to 0.18.

In the manufacturing method according to the present invention, step 2 is (U _1-y RE _y ) O ₂ by heating the (U _1-x RE _x ) ₃ O ₈ powder of step 1 in the air atmosphere at 1150 ~ 1400 ℃ _The step of preparing a powder in which the _{+ z} phase particles and the U ₃ O ₈ phase particles are chemically bonded (S120).

In step 2, the (U _1-x RE _x ) ₃ O ₈ phase powder is heated in an air atmosphere so that the rare earth element cation and the U cation are moved, and the high concentration (U _1-y RE _y ) O _{2 + z} phase particles and the rare earth element are moved. Separation into U ₃ O ₈ phase particles having no solubility of the cation.

At this time, the y is determined by the heat treatment temperature of step 2, the rare earth element cation and the U cation is moved in step 2, the numerical value is increased compared to the x of step 1, preferably has a value of 0.355 ~ 0.415 Can be.

In addition, z is a value representing an O / M ratio, which is a metal-to-oxygen ratio on (U _1-y RE _y ) O _{2 + z} formed in Step 2, and has the highest O / M ratio among cubic phases. . The phase having the highest O / M ratio while maintaining the cubic crystal in the UO ₂ -U ₃ O ₈ state is the U ₄ O ₉ phase and z is determined depending on y, and thus z may have a value of 2.0 to 2.25.

Next, in step 3 (U _1-y RE _y) of the phase ₂ O 2 _{+ z-shaped} particles and U ₃ O ₈ phase to the particles are reduced to the combined powders in a reducing atmosphere at 600 ~ 800 ℃ (U _{1- y} RE _y ) O ₂ phase particles and the UO ₂ phase particles to prepare a powder combined (S130).

The bonding of step 3 may be made of chemical bonding.

In the manufacturing method according to the present invention, step 4 is U by oxidizing the mixed powder of the (U _1-y RE _y ) O ₂ phase particles and UO ₂ phase particles of the step 3 in an air atmosphere of 300 ~ 700 ℃ _In step S140, a mixed powder in which ₃ O ₈ phase particles and (U _{1 -y} RE _y ) ₄ O ₉ phase particles are separated is prepared.

Step 4 is a U ₃ O ₈ phase and particles in which the (U _1-y RE _y ) O ₂ phase particles and the UO ₂ phase particles chemically bonded powder in step ₃ is oxidized in an air atmosphere To obtain a mixed powder in which (U _1-y RE _y ) ₄ O ₉ phase particles are not chemically separated.

Next, in step 5, the mixed powder in which the U ₃ O ₈ phase particles and the (U _1-y RE _y ) ₄ O ₉ phase particles of the step 4 are separated is U ₃ O ₈ phase particles in an ozone atmosphere of 175 ~ 225 ℃. It is a step of preparing a mixed powder with (O _1-y RE _y ) ₄ O ₉ phase particles by oxidizing only UO ₃ phase particles (S150).

The step 5 is selectively oxidizing only the U ₃ O ₈ particles, a powder mixture of the _{(U 1-y RE y)} 4 O 9 phase particles and U ₃ O ₈ phase grains separated by a chemical in an ozone atmosphere to UO ₃ phase particles This step is to obtain a mixed powder in which (U _1-y RE _y ) ₄ O ₉ phase particles having a high susceptibility and UO ₃ phase particles having a low susceptibility are mixed.

In addition, the present invention is a (U _1-y RE _y ) ₄ O ₉ phase particles by using a high gradient magnetic separation method from a mixture of uranium oxide and uranium trioxide mixed with a high concentration of rare earth elements with a high susceptibility difference prepared by the above method It provides a method for separating the uranium citrate, characterized in that to selectively recover the bay.

The uranium citrate prepared by the above method, that is, (U _1-y RE _y ) ₄ O ₉ phase particles have a susceptibility of 60 to 100 times larger than the susceptibility of the mixed UO ₃ phase particles, high gradient magnetic separation method Can be selectively separated using. Furthermore, the (U _1-y RE _y ) ₄ O ₉ phase particles have a susceptibility of 2 to 8 times larger than the susceptibility of the U ₃ O ₈ phase particles of step 4, and thus the U ₃ O ₈ phase particles and (U _1-y RE _y ) ₄ O ₉ It can be selectively separated even in the mixed powder in which the phase particles are mixed.

At this time, the high gradient magnetic separation method is preferably carried out in a magnetic field of 4,000 ~ 10,000 Gauss. If the magnetic field exceeds 10,000 Gauss, uranium trioxide or U ₃ O ₈ particles having a small susceptibility are also affected by the magnetic field and mixed with uranium citrate. If the magnetic field is less than 4,000 Gauss, the uranium oxide does not have a magnetic field. There is no problem.

Furthermore, the present invention provides a method for producing a UO ₂ fuel comprising the method for reducing the UO ₃ powder from which the uranium oxide is removed.

The UO ₂ nuclear fuel has a high combustion degree and is one of widely used nuclear fuels. Accordingly, the UO ₂ nuclear fuel having a high combustion degree can be recycled by a simple method of reducing the UO ₃ powder from which uranium oxide has been selectively removed through the separation method.

In this case, the reduction may be carried out by heat treatment at 600 ~ 800 ℃ under a reducing gas atmosphere, the reducing gas is preferably hydrogen (H2), argon (Ar) or a mixed gas thereof.

In the present invention, only a method for preparing a mixed powder of (U, RE) ₄ O ₉ phase particles and U ₃ O ₈ phase particles in which a high concentration of rare earth elements having a large susceptibility difference from a solid solution of (U, RE) O ₂ nuclear fuel is employed is described. In addition, the method for preparing a mixed powder having a large difference in susceptibility according to the present invention is equally applicable to a single component flammable absorber nuclear fuel having a similar phase separation behavior in heat treatment.

Hereinafter, the embodiment of the present invention will be described in more detail. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples.

Example 1 Preparation of Mixed Uranium Trioxide and Uranium Trioxide Powder

2 is a (U _0.966 RE _0.034 ) O ₂ solid solution in which 0.034 mol of rare earth element cations are dissolved by applying a method of preparing a mixed powder of uranium oxide and uranium trioxide in which a high concentration of rare earth elements having high susceptibility differences are employed. Is a diagram showing an example of manufacturing a powder of uranium citrate and uranium trioxide mixed with a high concentration of rare earth having a high susceptibility difference using solid solution.

Step 1. Preparation of (U _1-x RE _x ) ₃ O ₈ powder

The rare earth elements equivalent to 60,000 MWd / tU combustion fuel are Y = 0.0023, La = 0.004, Ce = 0.0077, Pr = 0.0036, Nd = 0.0129, Sm = 0.0024, Eu = 0.0005, Gd = 0.0005 mol. (U _0.966 RE _0.034 ) O ₂ solid solution containing 0.034 mol of cation solid solution was oxidized in an air atmosphere at 500 ° C. for 5 hours (S210) to prepare a (O _0.966 RE _0.034 ) ₃ O ₈ phase powder.

Step 2. Preparation of a powder chemically bonded to (U _1-y RE _y ) O _{2 + z} phase particles and U ₃ O ₈ phase particles

When (U _0.966 RE _0.034 ) ₃ O ₈ phase powder of step 1 is heated at 1400 ° C. for 4 hours in an air atmosphere (S220), (U _1-y RE _y ) O _{2 + z} phase particles and U ₃ O ₈ A powder mass made of phase particles was prepared.

At this time, the phase of the powders obtained can be confirmed by X-ray diffraction analysis, and the rare earth element concentration (U _1-y RE _y ) O _{2 + z} phase particles and U ₃ O ₈ phase generated by the oxidative heat treatment process 3 is a view illustrating a shape in which particles are bonded to each other.

In addition, electromagnet probe microanalyzer (EPMA) analysis was performed to determine the concentration of the multicomponent rare earth element cations dissolved in the (U _1-y RE _y ) O _{2 + z} and U ₃ O ₈ phase particles. (See Table 1).

As shown in Table 1, no rare earth element cations were dissolved in the U ₃ O ₈ phase particles, and 0.355 mol of rare earth element cations were dissolved in the (U _1-y RE _y ) O _{2 + z} phase particles. Therefore, it can be seen that the concentration of the rare earth element cations in the (U _1-y RE _y ) O _{2 + z} phase particles is about 11 times higher than the concentration of the rare earth element cations in the solid solution.

RE element concentration (y) in (U _1-y RE _y ) O _{2 + z} phases with initial element concentration (x) and heat treatment temperature element Initial composition
(x, mole) Composition according to heat treatment temperature (y, mole) 1150 ℃ 1200 ℃ 1300 ℃ 1400 ℃ U  0.9662  0.585 0.605 0.626 0.645 Y
La
Ce
Pr
Nd
Sm
Eu
Gd 0.0023
0.0040
0.0077
0.0036
0.0129
0.0024
0.0005
0.0005 0.027
0.062
0.061
0.056
0.113
0.037
0.028
0.030 0.026
0.052
0.063
0.051
0.112
0.038
0.024
0.028 0.026
0.042
0.065
0.045
0.111
0.039
0.021
0.027 0.031
0.042
0.058
0.038
0.096
0.034
0.026
0.029 Total (RE)  0.0338  0.415 0.395  0.374 0.355

Step 3. Preparation of the powder combined with the (U _1-y RE _y ) O ₂ phase particles and the UO ₂ phase particles

In order to separate the (U _0.645 RE _0.355 ) O _{2 + z} phase particles of the step 2 and the U ₃ O ₈ phase particles in which the rare earth element cation is not dissolved, reduction was carried out for 5 hours at 700 ° C. in a hydrogen gas atmosphere (S230). A mixed powder composed of (U _0.645 RE _0.355 ) O ₂ phase particles and UO ₂ phase particles was prepared.

Step 4. Preparation of a Mixed Powder Separated from U ₃ O ₈ Phase Particles and (U _1-y RE _y ) ₄ O ₉ Phase Particles

The agglomerated powder of step 3 was oxidized in an air atmosphere at 500 ° C. for 5 hours (S240) to mix the U ₃ O ₈ phase in which the particles were powdered and the U _{2 + z} phase particles that were not powdered (U _0.645 RE _0.355 ) O _{2 + z} Powder was prepared. The concentrated (U _0.645 RE _0.355 ) ₄ O ₉ phase particles and the U ₃ O ₈ phase particles were separated from each other by electron microscopy.

Step 5. Preparation of UO ₃ Phase Particles and (U _1-y RE _y ) ₄ O ₉ Phase Particle Mixed Powder

Rare earth element concentration from which the binding particles of step 4 were separated (U _0.645 RE _0.355 ) ₄ O ₉ phase The mixed powder of the particles and the U ₃ O ₈ phase particles were oxidized in an ozone atmosphere at 200 ° C. for 6 hours to prepare rare earth element concentrated particles (U _0.645 RE _0.355 ) ₄ O ₉ phase particles and UO ₃ phase particles.

Example 2 Preparation of (U _0.645 RE _0.355 ) ₄ O ₉ Powder

8 rare earth element oxides (RE ₂ O ₃ and REO ₂ ) and U ₃ O ₈ powder of Example 1 was mixed and prepared in the same manner as in Example 1 except that the oxidation heat treatment at 1400 ℃ for 4 hours. .

Example 3 Separation of (U _0.645 RE _0.355 ) ₄ O _{9 Phase}

In the mixed powder of UO _3- phase particles and (U _0.645 RE _0.355 ) ₄ O ₉ phase particles Highly gradient magnetic separation was performed using a 10,000 Gauss magnetic field to selectively separate only particles having a much higher magnetization rate (U _0.645 RE _0.355 ) ₄ O ₉ phase particles than UO ₃ phase particles.

Example 4 Preparation of UO ₂ Phase Particles by Reduction of UO ₃

In Example 3, the (U _0.645 RE _0.355 ) ₄ O ₉ phase particles are separated by UO by heat treatment at 1150 to 1400 ° C. under an argon (Ar) mixed gas atmosphere containing 4% hydrogen (H ₂ ). _2-phase particles were prepared.

Comparative Example 1

In Step 2 of Example 1, instead of the (U _0.966 RE _0.034 ) ₃ O ₈ phase powder of step 1 using pure pure U ₃ O ₈ powder to perform a heat treatment of step 4 to prepare a U ₃ O ₈ powder.

Comparative Example 2

Comparative Example 2 was subjected to ozone treatment of Step 5 of Example 1 to prepare a UO ₃ powder.

Experimental Example 1 Measurement of Susceptibility

Magnetic susceptibility of Example 2, Comparative Example 1 and Comparative Example 2 was shown in Figure 7 by measuring with a vibration sample magnetometer.

As shown in FIG. 7, the magnetization rate of Example 2 was 5 times larger than that of Comparative Example 1, and it was confirmed that powder mixing with a very large difference in susceptibility was obtained by performing ozone oxidation at 80 times as compared with Comparative Example 2.

Experimental Example 2 Crystal Structure Measurement According to Manufacturing Step

In order to confirm the phase change of the particles according to the preparation step, the powder prepared in step 4 of Example 1, the powder prepared in step 5 and X-ray diffraction analysis (MacScience MXP 3A-HF) of Comparative Example 2 Is shown in FIG. 6.

As shown in FIG. 6, it was confirmed that (U _0.645 RE _0.355 ) ₄ O ₉ phase particles did not react with ozone, but only U ₃ O ₈ phase particles reacted with ozone to produce a powder converted to UO ₃ phase particles. .

1 shows the preparation of a uranium citrate powder having a high concentration of rare earth elements with high magnetization and a uranium trioxide powder having a high susceptibility from a (U, RE) O ₂ nuclear fuel containing rare earth elements as neutron absorbers according to the present invention. A diagram showing each step of the method;

2 is a (U _0.966 RE _0.034 ) O ₂ fuel solid solution in which _0.034 mol of a rare earth element cation corresponding to a nuclear fuel of 60,000 MWd / tU combustion is employed by applying a powder manufacturing method having a large difference in susceptibility according to the present invention. FIG. 1 shows an example of preparing a uranium trioxide powder having a high concentration of rare earth element cation and a low uranium trioxide powder having a high susceptibility (Example 1);

FIG. 3 is a view showing the combination of rare earth element enriched (U _0.945 RE _0.355 ) O _{2 + z} phase particles and U ₃ O ₈ phase particles produced by phase separation by an oxidation heat treatment process;

4 is a rare earth element concentration (U _0.645 RE _0.355 ) ₄ O ₉ phase by reduction and oxidation treatment process The particle and U ₃ O ₈ phase particles are separated from each other;

5 is a rare earth element concentration by ozone oxidation process (U _0.645 RE _0.355 ) ₄ O ₉ phase A shape in which the particles and the UO ₃ phase particles remain unmodified and in shape;

6 is a view showing the results of X-ray diffraction analysis of powder before and after ozone oxidation; And

FIG. 7 is a graph showing the difference in magnetization between powder of rare earth element concentration (U _0.645 RE _0.355 ) ₄ O ₉ phase particles and powder of UO ₃ phase particles. FIG.

Claims (12)

A (U _1-x RE _x ) ₃ O ₈ powder was prepared by oxidizing a rare earth element (RE), a neutron absorber, with x mol of (U _1-x RE _x ) O ₂ nuclear fuel in an air atmosphere of 400 to 600 ° C. (Step 1); The (U _1-x RE _x ) ₃ O ₈ powder of step 1 was heated to 1150 to 1400 ° C. in an air atmosphere to obtain (U _1-y RE _y ) O _{2 + z} phase particles and U ₃ O ₈ phase particles. Preparing a chemically bound powder (step 2); The (U _1-y RE _y ) O _{2 + z} phase particles and the U ₃ O ₈ phase particles of step 2 are combined with the reduced powder in a reducing atmosphere at 600 to 800 ° C. (U _1-y RE _y ) O ₂ Preparing a powder in which phase particles and UO ₂ phase particles are combined (step 3); Of step _{3 (U 1-y RE y} ) O 2 phase particles and UO ₂ phase to the particles are oxidized to the combined mixture powder in an air atmosphere at 300 ~ 700 ℃ U ₃ O ₈ phase particles and the (U _1-y RE _y ) preparing a mixed powder in which ₄ O ₉ phase particles are separated (step 4); The mixed powder in which the U ₃ O ₈ phase particles and the (U _1-y RE _y ) ₄ O ₉ phase particles of step 4 are separated is oxidized to the UO ₃ phase by oxidizing only the U ₃ O ₈ phase particles in an ozone atmosphere at 175 to 225 ° C. Of a mixture of uranium oxide and uranium trioxide mixed with a high concentration of rare earth elements with a large susceptibility difference, including the step (step 5) of preparing a mixed powder with (U _1-y RE _y ) ₄ O ₉ phase particles by making the particles. Manufacturing method. According to claim 1, The rare earth element is Praseodymium (Pr, Praseodymium), Neodymium (Nd, Neodymuim), Europium (Eu, Europium), Gd (Gd, Gadolinium), Yttrium (Y, Yttrium), Lanthanum ( La, Lanthanum), Cerium (Ce, Cerium), Dysprosium (Dy, Dysprosium), Erbium (Er, Erbium) and semarium (Sm, Semarium), characterized in that any one or a mixture thereof characterized in that A method for producing a powder of uranium citrate and uranium trioxide mixed with a high concentration of rare earth elements with a large difference. According to claim 1, x is 0.007 ~ 0.034 when the rare earth element of the step 1 is a composite component, x is 0.007 ~ 0.18 when the single component is a high concentration rare earth element with a high concentration of the rare earth element, characterized in that solid solution Method for producing uranium and uranium trioxide mixed powder. The method of claim 1, wherein y in the step 2 is 0.355 to 0.415. The method for producing a powder of uranium citrate and uranium trioxide mixed with a high concentration of rare earth elements having a large susceptibility difference is employed. 2. The method of claim 1, wherein z in step 2 is 2.0 to 2.25. 4. The method of claim 1, wherein z is 2.0 to 2.25. Claim 1 (U _1-y RE using a high gradient magnetic separation method from a mixture of uranium citrate and uranium trioxide mixed with a high concentration of rare earth elements with a large susceptibility difference produced by any one of claims 1 to 5 _y) Gusan bright uranium separation method characterized in that the recovery of only the selective ₄ O ₉ phase particles. The method of claim 6, wherein the magnetization rate of the (U _1-y RE _y ) ₄ O ₉ phase particles are 60 to 100 times the magnetization rate of the UO ₃ phase particles of claim 1, characterized in that the uranium oxide separation method. The method of claim 6, wherein the susceptibility of the (U _1-y RE _y ) ₄ O ₉ phase particles is 2 to 8 times the magnetization rate of the U ₃ O ₈ phase particles of claim 1 characterized in that the separation of uranium oxide Way. 7. The method of claim 6, wherein the high gradient magnetic separation method is characterized in that the uranium oxide separation method is carried out with a magnetic field in the range of 4,000 ~ 10,000 Gauss. A method for producing a UO ₂ nuclear fuel, comprising the method of reducing the removed UO ₃ powder. The method of claim 10, wherein the reduction is under a reducing gas atmosphere, UO ₂ nuclear fuel production method characterized in that the heat treatment at 600 ~ 800 ℃. The method of claim 11 wherein the reducing gas is a process for producing UO ₂ fuel, characterized in that consisting of hydrogen (H _2), argon (Ar) or mixed gas thereof.

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