JP2001027694A - Solidified body of radioactive condensed waste substance and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a large filling amount of sodium salt of a solidified body and make it insoluble in water by adding the compound of elements selected from alkali earth metal, transition metal, metalloid or the like to a vitrification base material, and forming to heat and melt them. SOLUTION: In a preprocessing process, radioactive waste liquid containing sodium compound is dried to become powder, and in a storing process, the powder is stored in a storage tank. In a first mixing process, the dried powder is weighed to supply the powder of SiO2 so as to be mixed at a constant rate. In a second mixing process, about 2-22 mol.% of one oxide out of CaO, B2O3, Al2O3, Fe2O3, TiO2 or the like is added to the mixed powder, and sodium oxide in a vitrified and solidified body is made about 26-35 wt.% to be mixed and agitated. In a heating melting process, the heating and melting temperature of a furnace is set at 850-1100 deg.C, and a mixture is put into a crucible to be heated or continuously heated in a cylindrical furnace. In a cooling and solidifying process, it is preferably forcedly cooled at about 500-600 deg.C by furnace outside air cooling, fan air cooling, water cooling or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solidified radioactively concentrated waste material containing sodium nitrate generated in a spent nuclear fuel reprocessing facility or the like, especially a vitrified solidified material and a method for producing the solidified material. About.

[0002]

2. Description of the Related Art Conventionally, the treatment of radioactive waste liquid generated in a spent nuclear fuel reprocessing facility or the like is performed by a wet treatment method such as the so-called Purex method. It dissolves and recovers nuclear fuel materials such as uranium and plutonium from the solution by solvent extraction.In this process, high-level waste liquid containing fission products and medium-low level It has been established that waste liquid is generated and high-level waste liquid is dissolved in molten borosilicate glass and solidified.On the other hand, medium- and low-level waste liquid that is generated in large quantities is conventionally treated by asphalt solidification or cement solidification. Used. However, sodium nitrate (NaNO ₃ ) and sodium nitrite (NaN
O ₂ ) is used as an explosive, an oxidizing agent, etc., and is therefore designated as a first-class dangerous substance by the Fire Service Law, and is easily dissolved in water.

[0003] Therefore, in the asphalt solidification method, there is a danger of fire or explosion due to a chemical reaction between the sodium nitrate or the like and asphalt in a hot-melt state. Also, in the cement solidification method, when exposed to rainwater, the waste liquid elutes, and secondary contamination cannot always be prevented. In order to solve the drawbacks of the prior art, in recent years, the above-mentioned medium-to-low level waste liquid has been dried, and a vitrification aid containing SiO ₂ as a main component is mixed with the dried substance, and the mixture is heated and melted to form a vitrification reaction. A technique has been proposed in which after cooling, the solidified material is cooled and solidified to enclose and solidify an oxide of a radiation component in glass. (JP 6
0-146199, JP-A-61-82200, JP-A-61-61200
-132898, JP-A-61-200500, JP-A-62
-12499, JP-A-62-284298, JP-A-63
-300999)

[0004]

However, Japanese Unexamined Patent Publication No.
No. 0-146199 discloses that the vitrified base material is made of SiO.
₂Questions about stability at high temperatures
Not only that, as is clear from the description of Example 1,
Using multiple types of boron and calcium silicate
Therefore, the compounding ratio becomes complicated. Also radioactive
Sodium oxide Na₂O exchange
About 25% by weight is still not enough.

In Japanese Patent Application Laid-Open No. 61-82200,
SiO for vitrification matrix₂Also used as an additive
Addition of three kinds of acid, aluminum hydroxide and calcium carbonate
Agents are required, and the adjustment of the compounding ratio becomes complicated. Again
The melting temperature is as high as 1100-1200 ° C
Equipment must have high heat resistance. Also sodium oxide Na ₂
The amount of enclosed vitrified waste material in O conversion is around 20% by weight.
Low.

In Japanese Patent Application Laid-Open No. 61-132898,
Similarly, the vitrification matrix is made of SiO ₂Also use
Boron compounds, aluminum compounds, alkalis
Three kinds of additives of earth compounds are necessary, and the
Adjustment is complicated. Heating and melting temperature is as high as 1200 ° C
Therefore, high heat resistance is required for the melting equipment.

In Japanese Patent Application Laid-Open No. 61-200500, vitrification is carried out using a vitrification base material containing SiO ₂ as a main component such as silica sand, sand or clay. However,
For vitrification using silica sand, etc., the heating and melting temperature is 12
A high temperature of over 00 ° C is required, which not only makes the melting equipment expensive, but also makes the soda-silicate glass made of silica sand, sand, etc. extremely poor in water resistance if it contains 20% by weight or more of sodium oxide. Secondary contamination such as elution of radioactive waste.

Japanese Patent Application Laid-Open No. 62-12499 discloses that the standard for disposing of the radioactively concentrated waste material as described above has not been determined at this stage, so that it can be reprocessed at the stage when it is established. As described above, the dried body is 400 to 800
It is mixed with low-melting glass of ℃. For this reason, a problem arises in the present technology in terms of glass stability and cross-contamination.

Japanese Patent Application Laid-Open No. 62-284298 discloses a method in which a high-concentration solidified material is embedded in a rock raw material and hydrothermally synthesized, and is basically different from the vitrification technique.

Japanese Patent Application Laid-Open No. 63-300999 also discloses a technique in which aluminum hydroxide or iron hydroxide is added to the above-mentioned medium-to-low level radioactive substances to heat and denitrate sodium nitrate and sodium nitrite in the radioactively concentrated waste substances. Yes, different from vitrification technology.

In view of the above prior art, the present invention provides a solidified material, particularly a vitrified material, which is one of the final treatment forms of waste materials mainly containing middle and low levels of sodium nitrate generated in a nuclear fuel reprocessing facility or the like. In producing, during the solidification,
It is an object of the present invention to increase the filling amount of the solidified sodium salt as much as possible and to produce a vitrified solid that does not elute in water. Furthermore, another object of the present invention is to reduce the load on the device as the melting temperature during the production of the solidified body is lower. The present invention is to provide a vitrified radioactive waste material capable of stably retaining sodium and a method for producing the solidified product.

[0012]

According to the present invention, in order to solve the above-mentioned problems, a low-level radioactive waste material containing sodium nitrate and other sodium compounds (hereinafter referred to as waste material) is required. Represents both a waste liquid and a waste solid.) And a waste material vitrified body using SiO ₂ as a base material, in addition to a vitrified base material other than the above, magnesium magnesium, calcium Ca, etc. Alkaline earth metals, transition metals such as titanium Ti and iron Fe, metalloids such as boron B or aluminum Al (As, S
b, Bi, Ge, B, except that SiO ₂ is included together with the base material. ), More specifically, iron Fe, titanium Ti, boron B, calcium C
a, a waste material vitrified material characterized by being formed by adding a compound containing one element selected from a, aluminum Al, or magnesium Mg and heating and melting the compound.

That is, when an attempt is made to produce a vitrified product using only the dried waste material and SiO ₂ , the melting temperature becomes high and uniform glass is hardly produced. For this reason, it is necessary to add an additive for lowering the melting temperature and the viscosity of the glass to the two kinds of base materials, but when there are a plurality of such additives, not only the adjustment of the mixing ratio becomes complicated, but also , The amount of vitrification of radioactive condensed waste material is sodium oxide Na ₂ O
It is still less than 25% by weight in conversion. On the other hand, in the present invention, one element selected from titanium Ti, boron B, calcium Ca, aluminum Al, iron Fe, or magnesium Mg in addition to the dried substance of the waste substance and the vitrified base material composed of SiO _2. , Not only facilitates the adjustment of the compounding ratio, but also the amount of vitrification of the radioactive condensed waste material is reduced to sodium oxide Na ₂
26% by weight or more in terms of O, more specifically, the upper limit is 30 to
The content can be about 35% by weight.

The invention of claim 4 specifies this point, and claims that the waste material vitrified product contains 26 to 35% by weight of sodium oxide.
The reason why the upper limit is set to 35% by weight in the invention according to claim 4 is that if the amount is 35% by weight or more, vitrification does not occur stably.

In the invention described in claims 1, 3 and 4, if the selected elements are the same element, the compound may be, for example, a combination or complex of an oxide and a hydroxide of the one element. Included in the present invention. And preferably, as described in claim 2, the ion compound of 1, CaO _system, B 2 _{O 3} system, _Al 2 _{O 3} system, _Fe 2 _{O 3}
It is preferably an oxide compound of any one of a system, an FeO ₂ system and a TiO ₂ system. Among them, especially C
aO system and TiO ₂ system and MgO-based and _Fe 2 _{O 3} system is advantageous.

The invention according to claim 3 is characterized in that the addition amount of the one compound is about 2 to 22 mol%. By setting the temperature within the above range, the vitrification melting temperature can be reduced to 1000 ° C. or less, and the Na elution rate can be reduced to 10%.
% By weight or less, and the amount of the radioactive concentrated waste material enclosed in the vitrified body can be increased to 30% by weight or more in terms of sodium oxide Na ₂ O. When the melting temperature is set to 900 ° C. or lower, the amount of the compound to be added is preferably set to 4 to 18 mol%. More specifically, when the additive is a B ₂ O ₃ system and the melting temperature is set to 900 ° C. or less, the amount of the B ₂ O ₃ based compound added is 4 to
In order to reduce the vitrification melting temperature to 12% by mol or less to 1000 ° C. or less, the amount of the B ₂ O ₃ based compound added is 2
It is good to set to ~ 22 mol%.

The additive is CaO-based and the melting temperature is 900 ° C.
When set below, the addition amount of the CaO-based compound is 4 to 18 mol%, and when the vitrification melting temperature is reduced to 1000 ° C. or less, the addition amount of the CaO-based compound is 3 to 22 mol%. It is good to set to. Further, the additive is A
When the melting temperature is set to 900 ° C. or less in the l ₂ O ₃ system, the amount of the Al ₂ O ₃ compound added is 4 to 16 mol%.
When the vitrification melting temperature is reduced to 1000 ° C. or lower, the amount of the Al ₂ O ₃ compound is preferably set to 2 to 22 mol%. Further, when the additive is TiO ₂ and the melting temperature is set to 900 ° C. or less,
_In order to reduce the addition amount of the di-based compound to 5 to 19 mol%, and to reduce the vitrification melting temperature to 1000 ° C. or less,
The addition amount of the O ₂ -based compound is preferably set to _{2 to} 22 mol%.

Further, when the additive is Fe ₂ O ₃ type and the melting temperature is set at 900 ° C. or lower, the amount of the Fe ₂ O ₃ type compound is 4 to 16 mol% and the vitrification melting temperature is When the temperature is reduced to 1000 ° C. or lower, the amount of the Fe ₂ O ₃ compound to be added is preferably set to 2 to 22 mol%.

Further, the additive is MgO-based and has a melting temperature of 90.
When the temperature is set to 0 ° C. or lower, the addition amount of the MgO-based compound is 5 to 19 mol%, and the vitrification melting temperature is 1000
When the temperature is reduced to not more than ℃, the amount of the MgO-based compound to be added is preferably set to 2 to 22 mol%.

The content of SiO ₂ as a vitrification base material contained in the waste material vitrified product is 50 to 7%.
By setting the content to 2% by weight, more preferably from 60 to 72% by weight, vitrification is further promoted, and it becomes possible to reduce the radioactive concentration waste material and the melting temperature.

The invention according to claim 6 relates to a manufacturing method for effectively manufacturing such an invention, wherein low levels of sodium nitrate and other sodium compounds generated in a spent nuclear fuel reprocessing facility or the like are contained. The radioactive concentrated waste material (waste material indicates both waste liquid and waste solid) is dried, and the dried material and SiO ₂ are dried together with magnesium M.
g, alkaline earth metals such as calcium Ca, titanium T
i, one element selected from transition metals such as iron Fe, and metalloids such as boron B or aluminum Al;
More specifically, iron Fe, titanium Ti, boron B, calcium Ca, aluminum Al, or magnesium M
g, a mixture comprising three components of a compound containing one element selected from g is heated and melted, vitrified, and then cooled and solidified to produce a vitrified body.

The invention according to claim 7 is characterized in that the heating and melting temperature of the mixture comprising the three components is approximately 850 to 1100 ° C. The reason for limiting the temperature to 850 ° C. or higher is that the radioactive concentrated waste material contains a small amount of sodium carbonate and sodium sulfate in addition to sodium nitrate and sodium nitrite, and their melting points are around 850 ° C. It depends.

The invention according to claim 8 is characterized in that the dried product and Si
It is characterized in that about 2 to 22 mol% of the one ionic compound is added to a glass base material made of O ₂ and then heated and melted.

According to a ninth aspect of the present invention, the cooling and solidifying performed after heating and melting the mixture to vitrify the mixture are performed by cooling means other than natural cooling in the furnace, such as cooling outside the furnace, fan cooling, water cooling, and the like. Forcibly cooling to at least about 500 ° C. Here, the transition point of the vitrified material is set to 500 ° C. at around 500 to 600 ° C., and the elution of Na is reduced by forcibly cooling until passing through this transition point. After passing the temperature of about 500 to 600 ° C., either natural cooling or forced air cooling may be used. In any case, it is necessary to perform cooling at such a cooling rate that cracks do not enter the vitrified body.

According to a tenth aspect of the present invention, there is provided a dried product of a low-level radioactively concentrated waste material (waste material indicates both waste liquid and waste solid) while containing sodium nitrate and other sodium compounds. In the vitrified waste material whose base material is SiO ₂ and SiO ₂ , in addition to the vitrified base materials other than the above, alkaline earth metals such as magnesium Mg and calcium Ca, transition metals such as titanium Ti and iron Fe, and boron B or a compound containing one element selected from metalloids such as aluminum Al (including the case where the compound is a combination or complex of an oxide and a hydroxide of the element) is added and heated and melted. It is characterized in that the cooling and solidification performed after vitrification is performed in a shape in which the difference between the center temperature and the surface layer temperature is 100 ° C. or less.

The same effect as in the ninth aspect of the present invention can be obtained by setting the difference between the center temperature and the surface layer temperature to 100 ° C. or less, for example, a small diameter or a hollow diameter in relation to the cooling energy. Can be obtained.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the invention, but are merely illustrative examples.

FIG. 1 is a flow chart showing the procedure for producing a vitrified low concentration radioactive waste material (waste material includes waste liquid and waste solid) according to the embodiment of the present invention. This flow chart shows a pretreatment step (S1) of drying and pulverizing a low-level radioactive concentrated waste liquid containing sodium nitrate and other sodium compounds generated in a spent nuclear fuel reprocessing facility or the like, A storage step (S2) for storing the dried powder obtained in the processing step (S1) and discharging a weighed amount; a dry powder and a silica SiO ₂ powder discharged quantitatively from the storage step (S2) The mixture is mixed in a first mixing step (S3) in which the body is mixed in a ratio of about 3: 7 to 4: 6 (% by weight) in “Na ₂ O: SiO ₂ conversion”, and in the first mixing step (S3). CaO and B ₂ are added to the “Na ₂ O + SiO ₂ ” mixed powder.
O ₃ , Al ₂ O ₃ , Fe ₂ O ₃ , FeO ₂ or Ti
A second mixing step (S5) of adding and mixing approximately 2 to 22% by weight of any one of the oxidized compounds of O ₂ , and a mixture of the dried product, silica SiO _2, and one oxidized compound A heating and melting step (S6) of heating and melting; and a cooling and solidifying step (S7) of cooling and solidifying the melt vitrified in the heating and melting step (S6) to produce a vitrified body.
A step (S8) of treating off-gas such as NO _X discharged in the heating and melting step (S6), and a transport step (S9) of transporting the waste material vitrified product obtained in the cooling and solidifying step (S7) to a storage. ). However, the step (S8) of treating the off-gas is included as needed.

The pretreatment step (S1) comprises a drying apparatus for drying and pulverizing the radioactive concentrated waste liquid. Storage process
(S2) comprises a storage tank for storing the powder and a fixed amount discharge section provided at the bottom of the storage tank. The first mixing step (S
3) is a method in which the weighed dry powder is mixed with silica SiO ₂
A mixing device that supplies a fixed amount of powder and mixes the powder in the ratio described above.
For example, it comprises a screw mixer or a rotary mixer.

Similarly, the second mixing step (S5) also includes, for example, a screw mixer or a rotary mixer, and adds “Na ₂ O + SiO ₂ ” mixed powder to CaO, B ₂
O ₃ , Al ₂ O ₃ , Fe ₂ O ₃ , FeO ₂ or Ti
About ₂ to 22 mol% of any one of the oxidized compounds of O ₂ is added so that the sodium oxide contained in the vitrified waste material becomes 26 to 35 wt%, and then the above-mentioned mixer is used. Stir and mix using.

The heating and melting step (S6), the heating melting temperature can be set at approximately 850 to 1100 ° C., it is composed of an electric furnace or a high-frequency heating furnace or the like, the dried product and silica SiO ₂
The mixture comprising the three components of the above-mentioned oxide compounds may be placed in a crucible and heated batchwise, or may be continuously heated and melted using a cylindrical electric furnace.

In the cooling and solidifying step (S7), the crucible may be naturally cooled in the heating furnace, or the crucible may be drawn out at room temperature and cooled outside the furnace. It is preferable to perform forced cooling to at least approximately 500 to 600 ° C. by fan cooling or water cooling. After passing the temperature of about 500 to 600 ° C., either natural cooling or forced air cooling may be used. In any case, it is necessary to perform cooling at such a cooling rate that cracks do not enter the vitrified body.

FIG. 2 shows a heating and melting step (S6) and a cooling and solidifying step.
In the heating / cooling temperature diagram of (S7), the dried product and silica Si
A mixture consisting of three components of O ₂ and one oxide compound is placed in a crucible and heated in an electric heating furnace, and the mixture is mixed in batches of 1000.
After heating at 3 ° C. for 3 hours, the crucible was taken out and allowed to cool outside the furnace at room temperature (B). After being forcedly cooled by a fan until the center temperature reached 500 ° C., the crucible was released outside the furnace at room temperature. The Na elution rate was examined for two types (A) which were cooled. As a result, “Na ₂ O: SiO ₂ : B ₂ O ₃ =
Also in the first sample 1 of “30:60:10”, the Na elution rate was changed from 2.7% (sample 1B) to 1.6% (sample 1A), and “Na ₂ O: SiO ₂ : TiO ₂ = Also in the second sample 2 of “30:60:10”, the Na elution rate was 0.5% (sample 2).
From B), it is understood that the Na elution rate is reduced to 0.3% (sample 2A). The crucible was taken out of the furnace and cooled outside the furnace at room temperature (B).

Next, the case of melting by heating using a cylindrical electric furnace will be described. FIG. 8 shows an electric furnace 40 in which a heating element 46 is bent around a crucible and “Na ₂ O: SiO ₂ : B ₂ O ₃ = 3”.
0:60:10 "shows a glass body 43 which was eluted from the bottom hole 41 after heating the first sample 1 at 1000 ° C. for 3 hours and cooled and solidified. (B is about 15 cm) and naturally cooled, B is naturally cooled by setting the bottom hole diameter 41 to a small diameter (about 3 cm) of 1/5 or less of A, and C is forced air cooling of B by a fan 47 Things. The sectional shape of the bottom hole diameter 41 is arbitrary, and may be, for example, a hollow thin wall.

When examining the cooling rate of this embodiment,
As shown in FIG. 9, the embodiment A has two layers in the surface layer and the central portion.
While the temperature difference is 100 ° C or more up to around 00 ° C, B
No difference in temperature between the central portion and the surface portion is observed in both the embodiment of Example 1 and the embodiment of Example C. As shown in FIG. 10, the influence of the temperature difference between the surface layer portion and the central portion on the Na elution rate showed a significant difference in the elution rate in the example of A in which the temperature difference was 100 ° C. or more.

Returning to FIG. 1, the off-gas treatment step (S8) in FIG. 1 is for removing NO _X generated in the heating and melting furnace.
It oxidizes combustible gas remaining without being completely oxidized, and removes dust and radioactivity contained therein from high-temperature gas. However, the step (S8) of processing the off-gas is inserted as needed.

Now, the vitrified waste material according to the present invention is:
Although manufactured according to the above-mentioned process procedure, the effects of the present invention were confirmed by a simulation at a laboratory stage as shown below. First, as a medium- or low-level radioactive concentrated waste liquid similar to a dry powder, sodium carbonate (preferably sodium nitrate is used,
a ₂ CO ₃ was used. ) And silica are used as silica, and the powders are mixed in a mortar in such a manner that they are mixed in a ratio of about 3: 7 (% by weight) in terms of Na ₂ O and SiO _2. It was a powder.

To this raw material powder, 0 mol% (no addition) of B ₂ O ₃ as an additive, 2 mol%, 5 mol%, 10 mol%,
Each of the three-component mixed powder to which 15 mol% and 20 mol% are added is uniformly mixed in a mortar, and each is poured into a platinum crucible so as to be about 50 g. Next, the platinum crucible into which the three-component mixed powder was charged at the respective addition ratios was charged into an electric heating furnace, and then the temperature was changed from room temperature to a predetermined temperature (900 or 1000 ° C.).
) At a heating rate of 300 ° C / h, and then maintained at a heating temperature of 900 or 1000 ° C for 3 hours. Thereafter, the electric heating furnace was opened, the crucible was taken out, and the core was forcibly cooled with a fan until the center temperature reached 500 ° C., and then the furnace was allowed to cool outside at room temperature.

As a result, as shown in FIG. 3A, when the heating temperature is 1000 ° C., the amount of B ₂ O ₃ that can reduce the Na elution rate to 10% by weight or less is _{2 to} 22 mol%. When the melting temperature is 900 ° C., the Na elution rate is 1
The amount of B ₂ O ₃ that can be reduced to 0% by weight or less is 4
１２12 mol%. In addition, the Na elution rate evaluation was performed by grinding the vitrified material obtained in the above experimental procedure into a lump having a diameter of about 5 mm or less on a mortar, collecting 5 g of the pulverized powder, and measuring 100 g of the powder.
1 of pure water. Then, the water temperature was raised until boiling, and immersion was performed for 90 minutes. Thereafter, the mixture was cooled to room temperature, filtered through a bore filter, and the Na concentration in the filtrate was measured by flame photometry. Finally, the ratio of the amount of Na eluted into the filtrate to the amount of Na contained in the solid
The elution rate is calculated and performed.

Next, FIG. 3B shows the result of a similar experiment conducted by changing the B ₂ O ₃ to CaO. In this figure, when the heating temperature is 1000 ° C., the Na elution rate is 10% by weight.
The amount of CaO that can be reduced below is 3 to 22 mol%, and when the melting temperature is 900 ° C., the Na elution rate is 1%.
The amount of CaO that can be reduced to 0% by weight or less is 4 to
It was 18 mol%.

Next, FIG. 4A shows the result of a similar experiment conducted by changing B ₂ O ₃ to Al ₂ O ₃ . In this figure,
When the heating temperature is 1000 ° C., the amount of Al ₂ O ₃ that can reduce the Na elution rate to 10% by weight or less is 2 to 2.
When the melting temperature is 22 ° C. and the melting temperature is 900 ° C., Al ₂ can reduce the Na elution rate to 10% by weight or less.
O ₃ content was 4-16 mol%.

Next, FIG. 4B shows the result of a similar experiment conducted by changing B ₂ O ₃ to TiO ₂ . In this figure, when the heating temperature is 1000 ° C., the amount of TiO ₂ that can reduce the Na elution rate to 10% by weight or less is 3 to 22%.
When the melting temperature was 900 ° C., the amount of TiO ₂ capable of reducing the Na elution rate to 10% by weight or less was 5 to 20 mol%.

Next, FIG. 5A shows the result of a similar experiment conducted by changing B ₂ O ₃ to Fe ₂ O ₃ . In this figure,
When the heating temperature is 1000 ° C., the amount of Fe ₂ O ₃ that can reduce the Na elution rate to 10% by weight or less is 2 to 2.
22 mol%, and, if the melting temperature is 900 ° C., Fe ₂ capable of reducing the Na dissolution rate in 10 wt% or less
O ₃ content was 4-16 mol%. The addition amount of the gO ₂ compound is preferably set to _{2 to} 22 mol%.

Next, FIG. 5B shows the result of a similar experiment conducted by changing B ₂ O ₃ to MgO. In this figure, when the heating temperature is 1000 ° C., the Na elution rate is 10% by weight.
The amount of MgO that can be reduced below is 3 to 22 mol%, and when the melting temperature is 900 ° C., the Na elution rate is 1%.
The amount of TiO ₂ that can be reduced to 0% by weight or less is 5%
１９19 mol%.

Next, the vitrified product was observed for its appearance (visually confirming the transparency and residual crystals of the vitrified product) and evaluated for crystallinity (by X-ray diffraction, it was confirmed that it was an amorphous substance). 6) and 7), the vitrified material whose Na elution rate could be reduced to 10% by weight or less has transparency, has no residual crystals and the like, and is amorphous. It was confirmed that the material was vitrified. Therefore, according to the present embodiment, Na is converted to Na ₂
O content of 30% by weight or more and melting temperature of 100
It has become possible to produce a stable solidified glass of Na having a low temperature of 0 ° C. or less and a reduced Na elution rate of 10% by weight or less.

[0046]

According to the present invention as described above, wherein, according to the present invention, radioactive concentration waste material medium low level terms of Na 2 _O, conventionally can contain 5 wt% often 30 wt% or more and (the melting temperature of 1000 To 900 ° C. or lower, and a stable vitrified body whose Na elution rate at the time of secondary contamination is reduced to 10% by weight or less can be provided.

[Brief description of the drawings]

FIG. 1 is a flow chart showing a manufacturing procedure of a vitrified body of a low-level radioactive concentrated waste material (waste material includes a waste liquid and a waste solid) according to an embodiment of the present invention.

FIG. 2 shows a temperature distribution diagram in a heating-melting step and a cooling-solidification step in FIG. 1, and a Na elution rate in each sample performed at the temperature distribution.

FIG. 3 shows a glass base material composed of Na ₂ O and SiO ₂ ,
FIG. 5 is a graph showing the relationship between the Na elution rate and an appropriate amount of any one of B ₂ O ₃ and CaO,
(A) is an additive compound of B ₂ O ₃ , (B) is an additive compound of Ca
The case of O is shown.

FIG. 4 Na₂O, SiO₂The glass base material consisting of
Al₂O₃Or TiO₂Any one of the acids
Was added in an appropriate amount to determine the relationship with the Na elution rate
In the graph, (A) shows that the additive compound is Al₂O₃, (B) is attached
Addition of TiO ₂The case of is shown.

FIG. 5 shows a glass base material composed of Na ₂ O and SiO ₂ ,
Fe 2 _{O 3,} or any one of the oxide compounds of the MgO appropriately added amount graph of examining the relationship between Na dissolution rate, (A) additive compound is Fe 2 _{O 3,} (B) Indicates the case where the additive compound is MgO.

[6] the addition compounds of Figures 3 and 4 are _B 2 _O 3, Ca
O, an Al 2 _{O 3,} TiO ₂ respectively The test results showing the relationship of glass load of selected external observation conducted on some and the crystal evaluation and Na dissolution rate.

7 is a test result showing the relationship between the observation of appearance, the evaluation of crystallinity, and the Na elution rate performed on selected glass bodies of each of the additive compounds of Fe ₂ O ₃ and MgO in FIG. 5.

FIG. 8 shows a glass body eluted from a bottom hole of an electric furnace surrounding a heating element 46 around a crucible and cooled and solidified, and the bottom hole diameter is set to a large diameter (about 15 cm) and naturally cooled A; A sample B having the bottom hole diameter reduced to a small diameter (about 3 cm) and naturally cooled, and a sample C obtained by forcibly cooling the B with a fan are shown.

FIG. 9 is a graph showing the cooling rates of Examples A, B, and C shown in FIG.

FIG. 10 is a table showing the Na elution rate of the surface layer portion and the central portion of Examples A, B, and C shown in FIG.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Miyake 2-1-1, Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside the Takasago Research Laboratories, Mitsubishi Heavy Industries, Ltd. No. 1 Inside Mitsubishi Heavy Industries, Ltd. Takasago Research Laboratory (72) Inventor Yoshikatsu Kawase 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Heavy Industries, Ltd.

Claims (10)

[Claims] 1. A dried product of a low-level radioactively concentrated waste material (waste material includes both waste liquid and waste solid) containing sodium nitrate and other sodium compounds;
In the waste material vitrified body using iO ₂ as a base material, in addition to the vitrified base material other than the above, alkaline earth metals such as magnesium Mg, calcium Ca, titanium Ti, iron F
transition metal such as e, a compound containing one element selected from metalloids such as boron B or aluminum Al (including when the compound is, for example, a combination or complex of an oxide and a hydroxide of the element). A solidified radioactively concentrated waste material formed by adding, heating and melting. 2. The compound according to claim 1, wherein the compound is MgO-based, CaO-based,
₂O₃System, Al₂O ₃System, Fe₂O₃System, FeO₂Descent
Or TiO₂An oxidizing compound of any one of the systems
2. The radioactively concentrated waste material according to claim 1,
Solidified body. 3. The compound is added in an amount of about 2 to 22 mol%.
The solidified radioactively concentrated waste material according to claim 1, wherein: 4. The solidified waste of radioactively concentrated waste according to claim 1, wherein the amount of sodium oxide contained in the solidified waste of the waste is 26 to 40% by weight. 5. The solidified radioactively concentrated waste material according to claim 1, wherein the content of SiO ₂ as a vitrification base material contained in the waste material vitrified material is 50 to 72% by weight. 6. A low-level radioactive enriched waste material (waste liquid indicates both waste liquid and waste solid) while containing sodium nitrate and other sodium compounds generated in a spent nuclear fuel reprocessing facility or the like. Dry, together with the dried product and SiO ₂ , alkaline earth metals such as magnesium Mg, calcium Ca, titanium Ti, iron Fe
A mixture consisting of three components of a compound containing one element selected from transition metals such as transition metals such as boron B or aluminum Al is heated and melted, vitrified, and then cooled and solidified to produce a solidified body. A method for producing a solidified radioactively concentrated waste material. 7. The method for producing a solidified radioactively concentrated waste material according to claim 5, wherein the heating and melting temperature of the mixture of the three components is approximately 850 to 1100 ° C. 8. The radioactive waste according to claim 5, wherein about ₂ to 22 mol% of the one ionic compound is added to the glass base material composed of the dried product and SiO ₂ and heated and melted. A method for producing a solidified substance. 9. The cooling and solidifying performed after heating and melting the mixture to vitrify the mixture is forcibly cooled to at least about 500 ° C. by cooling means other than natural cooling in the furnace. A method for producing a solidified radioactively concentrated waste material according to the above. 10. A dried product of a low-level radioactively concentrated waste material (waste material indicates both a waste liquid and a waste solid material) containing sodium nitrate and other sodium compounds;
In a waste material vitrified body using SiO ₂ as a base material,
In addition to the vitrified base material other than the above, magnesium Mg,
Alkaline earth metals such as calcium Ca, transition metals such as titanium Ti and iron Fe, boron B or aluminum Al
A compound containing one element selected from metalloids such as (including the case where the compound is, for example, a combination or complex of an oxide and a hydroxide of the element) was added, heated and melted, and vitrified. A solidified radioactive waste material, wherein the solidification by cooling is performed in such a manner that the difference between the center temperature and the surface layer temperature is 100 ° C. or less.