JPS58182598A - Device and method for volume-decreasing and solidifying radioactive solid waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to volume reduction and solidification treatment of radioactive solid waste containing tritium by hot isostatic press (hereinafter abbreviated as HIP).

Nowadays, it is expected that fossil fuels such as oil will run out early, and the use of INN energy as an alternative energy source is being developed, but in the process of nuclear energy production, many radioactive wastes with long half-lives are generated. Therefore, the establishment of technology to safely store such radioactive waste is important for preventing environmental pollution. For example, used burner pull poison, which suppresses and controls the burnup of new fuel in the Toyo reactor (for power fuel) and maintains a uniform burnup throughout the reactor, is irradiated with neutrons in the reactor. Metal waste such as spent fuel cladding tubes after shear melting, upper and lower end members of fuel assemblies, spacers, streaks 1°, etc. that generate notium or are generated from cars in the pretreatment process of reprocessing plants (see below)
・Not only does it absorb J-thium and become a high-level radioactive solid waste, but it is also a special waste material due to the risk of spontaneous combustion of its material, namely Zircaloy.
Nod 1 nonk° and storage technology are strongly required.

Conventionally, such radioactive solid waste has been stored in drums and submerged in stainless steel-lined water tanks due to the difficulty of handling.

However, this method requires a huge amount of storage space because the hull has a low density of about 1.1 to 9/l, and there are problems such as the structure is not strong enough to withstand external disturbances. have.

Therefore, more compact and stable storage formats are being investigated in various fields. For example, in the case of metal waste, a method has been proposed in which it is melted and solidified in a heating furnace to form a dense block. In addition, in the case of radioactive incineration ash generated by incinerating combustible waste, a method has been proposed in which this is melted and solidified using micro-melting means.

All of these methods have achieved some success in terms of volume reduction, but they have the disadvantage of generating secondary waste disposal problems such as radioactive gas during melting and radioactivity of furnace refractories.

Recently, attention has been paid to the use of H-P to reduce the volume and solidify radioactive solid waste as a way to compensate for the above-mentioned difficulties.

H engineering pH Originally inert gas such as argon gas or heat resistant non-condensing fluid such as heat resistant grease and molten glass.

A three-dimensional static paddy field is added to the object to be processed under high temperature using heat-resistant powder such as BN powder, pyroferrite, talc, zirconium oxide, magnesium oxide, etc. as a field force medium, and the process is isostatically contracted, sintered, and diffused. This is a method for joining, removing defects in cast products, etc.

The present applicant has followed this technological trend and has been conducting research on volume reduction and solidification methods for radioactive solid waste using HIF treatment, and has already proposed some of them. For example, in order to prevent the capsule housing the hull etc. from being locally deformed and damaged during compression, metal powder or ceramic powder may be filled into the capsule space, or the hull etc. may be pre-compressed by mechanical pressing. We proposed that the material be placed in a highly ductile capsule and subjected to HIF treatment. In addition, in these methods, T is added to the capsule to prevent spontaneous combustion of Zircaloy, which constitutes the hull etc.
Considerations have been taken, such as adding an oxygen getter such as 1 or Zr, or degassing the capsule before sealing it. Only the use of less permeable materials, such as Ou or kl, is disclosed. However, Hull etc.
When processing, the temperature rises to about 60% of the melting point temperature of the hull, etc., so the tritium becomes significantly activated, and it is still difficult to completely confine it within the capsule and securely immobilize it using the previously proposed methods. Not only is this insufficient, but it also cannot completely prevent the leakage of radionuclides other than tritium, and there is a risk of secondary waste generation.

The present invention is the result of intensive research to solve the above-mentioned problems, and its purpose is to completely release radionuclides such as tritium in order to make it suitable for long-term safe storage. The object of the present invention is to provide a block of radioactive solid waste which is immobilized and has a significantly reduced volume. Another purpose is to prevent the leakage of radioactive substances such as tritium to the outside of the thread through the radioactive solid waste volume reduction treatment process for forming such blocks, and to prevent the generation of secondary waste. Yet another objective is to provide a device that can be effectively applied to achieve the above objectives. Other purposes will become clear from the description below.

The feature of the method of the present invention for achieving the above object is that a pre-compressed body formed by compressing radioactive solid waste with a compression press is housed in a metal capsule, degassed and sealed, and then subjected to HIP treatment. In this method, prior to degassing and sealing the metal capsule, the tritium gas released from the pre-compressed body is heated by the action of an oxidizing agent placed inside the metal capsule, and the necessary The process involves oxidizing and converting it to water with the help of an oxidation catalyst, and then degassing and sealing the metal capsule with the water trapped inside. In addition, an apparatus invented to suitably apply the method of the present invention includes a metal capsule formed of a composite metal plate whose inner surface is made of copper or aluminum and whose outer surface is made of stainless steel; A layer consisting of an oxidizing agent or an oxidizing catalyst is added to the inner surface of the capsule to cover at least the conduit leading to the degassing pipe, and a moisture adsorbent is loaded into the degassing pipe, which is used to heat the metal capsule. and a cooling means for cooling the degassing pipe.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The basic steps of the method of the present invention are as follows.

(]) Mixing the oxidizing agent or oxidizing catalyst powder or pellets into a radioactive solid waste such as a hull so as to be substantially uniformly dispersed therein.

(2) Preliminarily compressing the above mixture using a compression press,
The pre-compressed body contains an oxidizing agent or an oxidizing catalyst substantially uniformly dispersed therein.

(3) Storing the pre-compressed body in a metal capsule.

(4) Weld the lid with the degassing pipe installed upright.

(5) Raise the temperature of the metal capsule.

(6) Degas the metal inside the metal capsule through the degassing pipe.

(7) Seal the degassing tube.

(8) Subject the metal capsule to HIP treatment.

FIG. 1 is a system diagram showing each step of the method of the present invention. First, radioactive solid waste (1) such as a hull cut into appropriate lengths is converted into powder or pellets of an oxidizing agent or oxidation catalyst (
2) while substantially uniformly mixing the press molding machine (3).
and compressed at a temperature around room temperature to form a pre-compressed body (4).
shall be. As the oxidizing agent, in addition to metal oxides that easily release oxygen such as copper oxide and silver oxide, metal peroxides such as Na2O2 and PbO2, oxyacid salts, etc. can also be used.
Copper oxide and silver oxide are most suitable.

Regardless of such an oxidizing agent, when using oxygen in the air as the oxidizing agent, an oxidizing medium such as platinum or palladium is dispersed and mixed in order to promote the oxidizing reaction with the help of an oxidizing catalyst.
. Thus, the oxidizing agent or oxidizing catalyst is contained in a substantially uniformly dispersed state during precompression. The main purpose of such pre-compression is to improve the apparent density when charging into the H-P process.If the apparent density is low, it will be densified in the H-P process. There is a risk of damage to the metal capsule when doing so. Therefore, in order to prevent this damage, the molded product is compressed in advance to have a density of 60% or more of the true density.

In addition, heat-resistant grease, incompressible fluids such as molten glass, or B
N powder, talc, gdefite, Noguiro 7 Elite,
In the case of the HIP method, which uses a fluid powder such as molybdenum disulfide as a pressure medium and is compressed by a mechanical press, a lower density is sufficient.

Next, a plurality of pre-compressed bodies (4) formed into disk shapes by the compression press are housed in metal capsules (5) made of a metal material.

In this case, the materials used for the capsule include Ou,
Using single At or double pipes combined with stainless steel, or composite boards such as plywood clad with these,
In the case of a composite plate, Ou, At, etc. are used such that stainless steel is placed on the inner surface of the capsule and stainless steel is placed on the outer surface.

By doing this, tritium (3H) absorbed in the nozzle, etc. is prevented as much as possible from leaking out of the capsule during the subsequent heat treatment, and it also prevents oxidation and corrosion resistance during long-term storage. It is valid. This is because Ou and AL are generally considered to be materials that are difficult for tritium to pass through, and stainless steel has a high permeation of tritium but is resistant to oxidation and corrosion.

Next, a metal capsule (
5) Weld the lid (7) with the double degassing pipe (6) upright. When welding, weld the welded area as much as possible so that the heat during welding does not activate the tritium absorbed by the nozzles, etc. It is preferable to position it away from the hull etc. In addition, in consideration of handling of the metal capsule, it is also a suitable means to weld a magnetic stainless steel plate to the lid to facilitate handling such as lifting and transportation using a magnet.

In this way, the pre-compression body (4) is stored inside and the degassing pipe (6) is opened.
The metal capsule (5) is welded with a lid (7) that is erected.
Next, it is subjected to a temperature raising treatment. In other words, when the metal capsule (5) is heated and heated by a heating means (8) such as electric heating, in the case of a pre-compressed body mixed with an oxidation catalyst, tritium gas activated by heating and released from the hull etc. Under the action of a catalyst, it reacts with oxygen in the air inside the capsule and converts it into water. If the amount of tritium gas is large, the air necessary for oxidation is supplied from the degassing pipe (6).

Further, in the case of a pre-compressed body mixed with an oxidizing agent, tritium gas generated by heating similarly reacts with the oxidizing agent and becomes tritiated water. In this case, the degassing can be carried out while degassing by connecting the degassing pipe (6) to the vacuum device (9).

In either case, it is important to heat the inside of the metal capsule (5) to a degree that does not reach a temperature above the boiling point of water.
When the temperature rises, the generated tritiated water becomes water vapor and is discharged from the degassing pipe, potentially causing secondary pollution.

After converting the tritium gas inside the metal capsule into water as described above, the vacuum device (9) connected to the degassing pipe (6) is operated to degas the inside of the metal capsule (5), and then the degassing pipe Press or press 00) and seal. The metal capsule degassed and sealed in this manner is free from the risk of damage to the genus A capsule due to internal rise during heating during the subsequent H-P treatment, and is also effective in preventing ignition of Zircaloy.

A sealed metal capsule (5) containing the pre-compressed body (4)
) is then subjected to HIP treatment. As mentioned above, during the H/P treatment, it is necessary to raise the temperature to approximately 60% of the melting point temperature of the solid waste, for example, in the case of a hull made of Zircaloy, it is necessary to raise the temperature to approximately 900°C. At this time, the tritium water inside the capsule turns into water vapor, so that king moss is generated inside the capsule. However, in reality, the amount of tritium water is extremely small, and is large enough to destroy the capsule.
It is not enough to generate mosquitoes.

For example, the dimensions of the capsule after H-P treatment are φ3oo1.
．． Calculations for the case of X6ooH■ are as follows.

Hull weight = 7X302X60X65X10-3 = 27
5 Kg Amount of tritium in hull = 300 N1000μ 4 *
=0.3~1°X9 *Note: The Ommunity's R&D
Programmeon Radioactive
Waste Management andSt
By orage.

Amount of tritium in capsule = 8.25 to 2'7501 Volume of tritium gas = 0.37 7. . , Amount of tritium gas in the capsule = 31 ~ 102 Ncc31 ~ 102 Amount of tritium water in the capsule = 22400 × 18
=0.02~0.08S' Capsule internal gas volume at 900°C 273-1-900 -(31~102) x273+25=122~4
00cc (latm) = 3-6~12 cc (30
atm)=1~3cc (130atm)
In other words, there are only 1 to 2 drops of tritium water inside the capsule, and when heated to 900°C, an external pressure of, for example, 1 OOOatm is applied at the same time due to the H-P treatment, so there is no fear that the capsule will break. do not have. Furthermore, when the temperature of the treated body decreases after the HIP treatment, the water vapor within the capsule condenses again to become water and remains within the capsule.

The H-P treatment uses a conventionally known H-P device, and employs a known method in which the solid waste is heated to a temperature that causes plastic deformation, and the solid waste is held at high pressure for 30 minutes or more using an inert gas as a pressure medium. It can be compacted and densified into a molded body with approximately true density.

On the other hand, such HIP processing concerns the introduction of inert gas into the H-P equipment, the mechanism for discharging it from the H-P equipment, the safety aspects of compressible gas, and the installation and maintenance under the High Pressure Gas Control Act. This method is not necessarily the best method because it is complicated to handle, has problems such as a long processing cycle time due to temperature rise and rise time, and low production efficiency. Therefore, recently, pressurized media that do not rely on inert gas, such as granular materials such as BN powder, graphite, pyroferrite, talc, molybdenum disulfide, zirconium oxide, and magnesium oxide powder, or non-curing materials such as molten glass and heat-resistant grease, have been developed. A method of compressing metal capsules embedded in a raw cotton device consisting of a high-pressure cylinder and a reciprocating stem using a fluid through the medium (hereinafter referred to as semi-H-processing). It has been adopted. The quasi-HIP treatment can also be advantageously applied in the method of the present invention, and the process will be explained with reference to FIG. 1. The sealed metal capsule is sent to a heating process and heated in an electric furnace or the like (11).

Heating is carried out to a temperature suitable for the subsequent semi-H-work P treatment, and usually varies depending on the type of pressure medium used during the semi-H-work P treatment. , below 2300℃ for magnesium oxide, etc., above the melting point of the salt for molten salt, and 1250℃ for heat-resistant grease.
An appropriate temperature below ℃ is selected.

After the heat treatment is completed, the sealed metal capsule (+2) is semi-H engineering P
It is sent to a processing step and subjected to the required compression process.

In semi-H engineering P processing, a pressure medium 05) is placed in a compression device consisting of a high-pressure cylinder 03) and a reciprocating stem 0→.
The heated sealed capsule (b) is buried in the pressure medium, and the stem 0 is moved to compress it through the pressure medium.

Here, the conditions that the pressure medium should satisfy in the semi-H-work P process in the method of the present invention include the following points.

(1) Can be used repeatedly.

That is, since pressure is applied through the capsule, the pressure medium will not be contaminated in the first place, but if the capsule is damaged or tritium permeates, the pressure medium may be contaminated. Therefore, in that case, repeated use is required to prevent generation of secondary waste.

(2) It must have heat insulation properties.

The pressure medium preferably has heat insulating properties so that the heat of the capsule does not transfer to the high-pressure cylinder and reduce the strength of the cylinder.

(3) It must have lubricity.

It is desirable that the cylinder has low frictional resistance when moving in response to the entry of the stem into the cylinder.

(4) Low deformation resistance.

In order to apply equal pressure to the capsule, low deformation resistance is required.

(5) Do not become a sintered body.

If it becomes a sintered body, its isotropic compressibility will be hindered.

(6) No decomposition occurs due to heat.

(7) Do not damage the inner wall of the cylinder.

As a material satisfying the above conditions, BN and graphite are selected according to the temperature during the treatment.

Possible materials include powders or pellets of pyroferrite, talc, molybdenum disulfide, etc. In addition to molten salt, heat-resistant grease is one of the preferred pressure media when the processing temperature is low.
However, it has some problems in terms of deterioration due to repeated use. However, heat-resistant grease is extremely practical due to its fluidity, mold releasability, and consistency.

The pressure exerted on the sealed capsule due to the use of these pressure media is different from that of the gas king, and can sufficiently handle up to about 20,000 kita, but if the life of the compression device is taken into account, the pressure exerted on the sealed capsule is 1 O,000.
It is usually carried out in the range of 1,000 to 10°,000 ki.

In this case, the high pressure holding time during the semi-HIP treatment is generally relatively short after raising the pressure, and while conventional HIP treatment required more than 30 minutes, the pressure was maintained for several minutes using the pressure medium. IW for about 1 minute is sufficient.

Through each of the above steps, the radioactive solid waste is densified and reduced in volume while the tritium is converted into tritium water and confined inside, and has a strong binding force. Can be compacted into blocks.

Note that if a heat insulating layer is provided on the inner wall of the high pressure cylinder (13) or on the outer periphery of the sealed metal capsule (b), the retention time of the sealed capsule in the compression device can be extended, so that pressure media such as heat-resistant grease can be used. It is suitable when used.

Further, each of the above steps is a basic processing step of the method of the present invention, but various modifications can be made within the scope of the present invention.

That is, instead of dispersing and mixing the oxidizing agent or oxidizing catalyst uniformly in the pre-compressed body, the oxidizing agent or oxidizing catalyst is placed on the inner surface of the metal capsule (5) as shown in FIG. The same effect can be obtained by adding a layer 06) made of a sintered catalyst to cover at least the guide hole θ7) leading to the degassing pipe (6).

Furthermore, when using the method shown in the basic process and the apparatus shown in Figure 2, if the conditions are incorrect when heating or degassing the metal capsule containing the pre-compressed body, trace amounts of tritium gas or tritium water vapor may be emitted. It cannot be said that there is no risk of Therefore, preferred embodiments of the present invention for completely eliminating these risks will be described below.

FIG. 3 is a schematic explanatory diagram of an apparatus used in a preferable embodiment of the method of the present invention, in which water is adsorbed inside the degassing tube (6) of the apparatus shown in FIG. Agent (+8) is filled. The adsorbent 08) functions to trap moisture generated in the subsequent heating step, and for example, molecular sieves are preferably used.

In addition, the tip of the degassing pipe (6) is left unfilled with adsorbent in case it becomes blocked due to forging or the like.

A cooling means such as a cooling coil 09) is provided around the degassing pipe (6), and a heating means such as an electric heater (A) is provided around the metal capsule (5).

When a pre-compressed body is stored in such a device and heated by applying electricity to the electric value (a), tritium gas released from the pre-compressed body enters the layer (16) of the oxidation agent or oxidation catalyst. At the same time, it is converted to water and vaporized by high temperature to become water vapor. The water vapor is further conducted into the degassing tube (6), reaches the cooling zone, condenses, becomes water again and is captured by the adsorbent (6). After that, the inside of the metal capsule (5) is degassed by a vacuum device (9) connected to deaeration-f (61),
Seal as described above.

According to this device, even if the generated tritiated water is vaporized due to high temperature or reduced pressure, it becomes recondensed water or mist and is completely collected by the adsorbent, so that leakage to the outside can be prevented.

FIG. 4 is a schematic explanatory diagram showing an improved version of the device shown in FIG. 3, in which a carrier gas introduction pipe (22) is provided at the bottom opening toward the internal space O of the metal capsule (5).

In such a device, a carrier gas flow path is formed that sequentially starts from the carrier gas inlet pipe (22), passes through the inner space of the metal capsule, passes through the layer (16) made of an oxidizing agent or oxidation catalyst, and then leads to the degassing pipe (6). .

The pre-compressed body is housed in the above device in which the layer (16) is an oxidizing agent, and a carrier gas made of an inert gas such as helium is introduced while heating, and the generated tritium gas is transferred to the oxidizing agent layer (16). ), the tritium water vapor vaporized due to the high heat is further led to the cooling zone of the degassing pipe (6), condensed, and captured by the adsorbent (+8).

In addition, when the layer 06) is an oxidation catalyst, by introducing air from the carrier gas introduction pipe (221), it is possible to supply a sufficient amount of air to completely oxidize the tritium gas.

If such a device is used, tritium gas will not remain in the precompression body, but will contact and react with the oxidizing agent or oxidation catalyst one after another, and the generated water will also be efficiently captured by the adsorbent.

FIGS. 5 and 6 are schematic explanatory diagrams showing improved versions of FIGS. 3 and 4, respectively.

In Fig. 5, an inverted cup-shaped copper or aluminum inner capsule (23) having an outer diameter and height smaller than the inner diameter and height of the metal capsule (5) is installed concentrically inside the metal capsule (5). Thus, a mantle-shaped part is formed between the metal capsule (5) and the inner capsule, and the lower end of the inner capsule is either separated from the bottom surface or when in close contact with the bottom surface. A through hole provided near the lower end forms a flow path between the interior space of the capsule and the mantle. Also, in the mantle,
A layer of oxidizing agent or oxidizing catalyst is loaded. According to this device, the inner capsule uses copper or aluminum that is difficult for tritium gas to pass through, so when heated, it is released from the hull, etc., and the tritium gas passes through the entire length of the oxidizer or oxidation catalyst layer loaded in the mantle. The tritium gas inside the capsule is completely converted to tritium water without remaining, and this is adsorbed, so that hetritium does not leak outside the capsule.

Fig. 6 shows a device shown in Fig. 5 in which a carrier gas introduction pipe (22) is further inserted into the degassing pipe, and its operation is similar to that shown in Fig. 4, but the effect is similar to that shown in Fig. 5. It goes without saying that this method is much superior to that using the apparatus shown in the figure.

The effects of the present invention detailed above are as follows.

(1) Tritium (tritium gas or tritium water) will not leak out of the capsule during the volume reduction treatment (H Engineering P treatment or semi-H Engineering P treatment) of hulls, etc. (2) Inside the capsule after treatment Since it remains in the form of tritiated water, there is no leakage to the outside due to permeation through the capsule wall.

(a)) Nuclides other than +J thium are also captured by the oxidizing agent and adsorbent, and do not leak out of the capsule.

That is, since powder or a sintered body of powder is used as the oxidizing agent and adsorbent, it acts as a filter, and dusty radionuclides are collected. Furthermore, the nuclide that has become fume-like due to heating is cooled in the cooling zone, becomes guest-like, and is collected by an adsorbent. In other words, no secondary waste is generated.

(4) In the method of collecting and processing tritium outside the capsule, separate immobilization processing is required to store the collected tritium, such as absorption into titanium, etc., and hardening with cement after conversion to tritium water. A waste treatment body will be generated separately from the waste treatment body.

In the present invention, since tritium is sealed in the same capsule as the waste to be treated, the number of solidified bodies to be treated is minimized.

Next, specific examples of the method of the present invention are listed.

Example 1 Waste obtained by shearing spent nuclear fuel cladding in a power fuel reactor, outer diameter 12 rtrm, thickness 0.8 m
A short Zircaloy tube with a length of 30 to 50 g is loaded into a mechanical press while uniformly spreading and mixing copper oxide powder thereto, and is screened with a pressure of 3''/m to a diameter of approximately 80111111 mm and a thickness of approx. It was preformed into a disk shape of 50 ran.The apparent density of this preshrinkage material was 3.2ζg, and the tritium content was about 800 μl, or 0.601 per disc. The six compressed bodies were then housed in a capsule container made of stainless steel with an internal diameter of 85 mm and a height of 310 mm, the inner surface of which was clad with a copper plate, and a lid with a degassing pipe was welded. The capsule was connected to a vacuum device, the temperature of the capsule was raised to about 80° C., and the inside of the capsule was vacuum degassed to 10 −1 or more through the degassing tube. In this state, the degassing tube was forge welded and the capsule was sealed.

During vacuum aspiration, virtually no tritium gas emissions into the vacuum apparatus were detected.

The thus-formed sealed capsule container was placed in a normal HIP device and heated at 900°C using argon gas as a pressure medium.
The H-P treatment was carried out under the conditions of 1000% X I Hr (temperature increase, maintenance time after EE). As a result, although the sealed capsule container had a significant volume reduction compared to the HIP treatment, the capsule did not break and was a solid block with no voids, and its density was 5.2 mm. It showed a value close to the theoretical density.

Example 2 A disc-shaped pre-compressed body was produced in the same manner as in Example 1 except that the copper oxide powder was not mixed by scattering. Three such pre-compressed bodies were housed in a metal capsule of the type shown in FIG. 5 having an inner diameter of 85 fi and a height of 155 fi, and a lid having a degassing tube with a length of 75 fins was welded to the capsule. aluminum inner capsule and stainless steel on the peripheral wall and top wall of the metal capsule,
The mantle-shaped part formed between the steel outer capsule α5) was filled with silver oxide particles, and the inside of the degassing tube was filled with molecular sieves, leaving a tip portion of 45 m. A cooling coil was installed around the deaeration tube while the deaeration tube was connected to a vacuum device, and an electric heating device was further provided around the metal capsule container. The electric heating device is energized to heat the capsule container to approximately 500°C. At the same time, the cooling coil cools the degassing tube part, and the vacuum device is activated to evacuate the inside of the container to a depth of 10". The degassing tube was forged and the capsule was sealed. During the vacuum degassing operation, virtually no leakage of tritium gas or tritium water vapor outside the container was detected.

The sealed capsule container thus formed was embedded in heat-resistant grease filled in a compression device consisting of a high-pressure cylinder and a reciprocating stem, and heated until the temperature reached 1200°C. Using heat-resistant grease as a pressure medium 5
The fabric was subjected to HJp treatment under conditions of ,000% jX l rm. As a result, compared to before semi-HIP treatment, the sealed capsule container was a #i hard block body with remarkable integrity in appearance and no voids, and its density had reached the theoretical density. Also,
No leakage of radioactivity outside the container was detected.

Example 8 The 1000-pound compact obtained in Example 2 of II was housed in a metal capsule container of the type shown in FIG. 4 using a sintered plate of platinum and palladium particles as the layer (16), electric heating device ff
At the same time as heating the capsule container to 500℃ by applying electricity to
Air was introduced into the capsule through the carrier gas introduction tube (2a) while cooling the degassing tube part with a cooling coil. During this time, no tritium or tritium water vapor was detected from the degassing tube.

Thereafter, the carrier gas introduction tube (221) was forged welded, a vacuum device was connected to the degassing tube, and the vacuum device was activated to vacuum evacuate the inside of the container to 10 - yen to seal the capsule. Semi-H engineering P treatment was carried out in exactly the same manner as described above. A stable and strong hull block having a density extremely close to the true density was molded. No leakage of radioactivity from this block was detected at all.

The density of the dense block body obtained by the present invention described above is almost the true density or close to the true density. Therefore, the volume of the original radioactive solid waste is significantly reduced by pre-compression and HIP treatment or semi-HIP treatment, and it can be easily stored inside a drum can or the like as a volume-reduced and solidified block. It can be stored stably as is. As a result, the storage space aM can be used more efficiently than conventional storage methods, and radioactive waste can be stored stably for a long period of time and rationally in a relatively small space. Furthermore, since densification progresses through plastic deformation and diffusion bonding within an airtightly sealed container, there is no need to worry about the generation of secondary waste such as radioactive gas.

As described above, the present invention is extremely useful and significant from the viewpoint of the safety of radioactive waste, which will be necessary in the future as the use of nuclear energy increases.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the steps in the method of the present invention, and FIGS. 2 to 6 are schematic diagrams showing different embodiments of the metal capsule used in the method of the present invention. (])・・・・・・Radioactive solid waste. (2)...Oxidizing agent or &''i oxidation catalyst. (3)...Press molded product, (4)...
...Pre-compressed body. (5)...Metal capsule, (6)...
・Deaeration pipe. (7)...-Lid, (8)...Heating means. (9)...Vacuum equipment, (11)...
···Electric furnace. (12)... Sealed metal capsule. 'θ3)...-High pressure cylinder, 04I...
..., stem. (15)...-Pressure medium, 06)...
- Layer of sintered body. (17)・・・・・Guiding hole, (18)・・・・・・−
1 Moisture adsorbent. (19)... Cooling coil, (a)...
...Electric heat. (2υ・・・・・・internal space, (22・・・・・・
Carrier gas introduction pipe. @・・・−・・・・Inner capsule. Patent applicant: Kobe Steel, Ltd. Certain Z-eye rod 30$4 diagram

Claims (1)

[Claims] ■ A pre-compressed body formed by compressing radioactive solid waste using a compression press is housed in a metal capsule, degassed and sealed, and then subjected to hot isostatic press treatment to form a dense unit. In the method, the metal capsule is subjected to a heating treatment prior to being degassed and sealed, and the tritium gas released from the pre-compressed body is placed in the gold capsule and is inevitably oxidized by the action of an oxidizing agent. A method for volume reduction and solidification of radioactive solid waste, characterized by oxidizing it into water with the help of an oxidation catalyst, and then deaerating and sealing a metal capsule with water trapped inside it. . 2. The method for volume reduction and solidification of radioactive solid waste according to claim 1, wherein the metal capsule is made of copper, aluminum, or a composite material of these and stainless steel. 8. The method for volume reduction and assimilation of radioactive solid waste according to claim 1 or 2, wherein warming is performed by the action of an oxidizing agent made of oxidized steel or silver oxide. 4. The oxidation is carried out using oxygen in the air as an oxidizing agent and by the action of an oxidation catalyst.
Method for volume reduction and solidification of radioactive solid waste as described in Section 1. 5. The method for volume reduction and solidification of radioactive solid waste according to claim 4, wherein the oxidation catalyst is platinum or palladium powder or pellets. 6. After uniformly dispersing and mixing the oxidizing agent or oxidizing catalyst into the radioactive solid waste, the oxidizing agent or oxidizing catalyst is compressed using a compression press to form a pre-compressed body, thereby making the oxidizing agent or oxidizing catalyst into a pre-compressed body housed in a metal capsule. A method for volume reduction and solidification of radioactive solid waste according to any one of the preceding claims, wherein the radioactive solid waste is arranged in a compressed body in a uniformly dispersed state. 7. Tritium gas released from the pre-compression body is guided into a layer made of an oxidizing agent or an oxidizing catalyst in a metal capsule and converted into water, and the water vapor produced by vaporization due to temperature rise is further guided to a cooling area where it is condensed. 6. A method for volume reduction and solidification of radioactive solid waste according to any one of claims 1 to 5, wherein the solid waste is captured by an adsorbent and then the metal capsule is degassed and sealed. 8. The method for volume reduction and solidification of radioactive solid waste according to claim 7, wherein the adsorbent is molecular sieves. 9. The radioactive material according to claim 7 or 8, in which a carrier gas is introduced into a pre-compressed body within a metal capsule to guide tritium gas to an oxidizing agent layer, and to introduce water vapor into a cooling region. Volume reduction and solidification method of solid waste. 10. The method for volume reduction and solidification of radioactive solid waste according to claim 9, wherein the carrier gas is an inert gas. 11. Radioactive solid waste according to claim 7 or 8, in which air is fed into the pre-compressed body within the metal capsule to guide tritium gas to the oxidation catalyst layer and further lead water vapor to the cooling zone. Volume reduction solidification method. 12. A hot isostatic pressing device and a metal capsule that can be inserted into the device and is formed of a composite metal plate with an inner surface of copper or aluminum and an outer surface of stainless steel; The capsule includes a degassing pipe protruding from the top thereof, a layer of an oxidizing agent or an oxidizing catalyst loaded on the inner surface of the metal capsule to cover at least the conduit leading to the degassing pipe, and a layer loaded in the degassing pipe. Has a moisture adsorbent,
An apparatus for use in a method for volume reduction and solidification of radioactive solid waste, characterized in that the apparatus comprises a heating means for heating a metal capsule and a cooling means for cooling a degassing tube. 18. An inverted cup made of copper or aluminum, which has an outer diameter and height smaller than the inner diameter and height of the metal capsule, and is installed inside the metal capsule concentrically and with a flow path formed at the lower end. An fji comprising an inner capsule, and a layer made of an oxidizing agent or an oxidation catalyst is loaded into a mantle-shaped part formed between a metal capsule and the inner capsule.
The device according to claim 12. 14. A carrier gas introduction pipe is provided that opens toward the interior space of the metal capsule, and a carrier gas flow path is formed that leads from the carrier gas introduction pipe sequentially through the interior space of the metal capsule, the oxidizing agent or the oxidation catalyst layer, and the degassing pipe. An apparatus according to claim 12 or 13, comprising: 15/Claim 1, wherein the layer consisting of an oxidizing agent or an oxidizing catalyst is a sintered body of powder or granules of a metal or metal oxide
The device according to any one of items 2 to 14. 16. The device according to any one of claims 12 to 15, wherein the moisture adsorbent is molecular sieves. 17. The device according to any one of claims 12 to 16, wherein the oxidizing agent is copper oxide or silver oxide. 18. The apparatus according to any one of claims 12 to 16, wherein the oxidation catalyst is platinum or palladium.