JPH0240598A - Disposal method of radioactive waste - Google Patents

Abstract

PURPOSE:To hold the soundness of a waste body in the case where it is buried underground to dispose of by allowing a low viscosity solidifying material to permeate among the inner voids of a compressed substance to solidify. CONSTITUTION:At first a piece of inherent waste is compressed by a press 1 to reduce its volume and made a compressed substance 2. Next, since the compressed substance 2 has many voids in the inside thereof, it is put in a vessel 4 in a tank 3, the tank 4 is allowed to reduce pressure by a vacuum pump 5 and a low viscosity solidifying material is supplied from an upward nozzle 6 to permeate among the inner voids of the compressed substance 2. A vinyl system monomer such as styrene monomer and vinyl chloride is used as the low viscosity solidifying material. Next the compressed substance 2 is heated and pressurized in a tank 8 with a heater 7 to polymerize and solidify the solidifying material. Thereafter a plurality of the solidified compressed substances 2 are housed in the inside of a drum can 9 to fix the periphery of the compressed substance 2 by a fixing material 10 such as mortar and plastic.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for treating radioactive waste generated from nuclear power plants and the like.

(Prior art) Non-flammable radioactive waste generated from nuclear power facilities such as nuclear power plants is stored in sealed containers such as drums in storage warehouses, but in recent years, the storage capacity has reached its limit. It's approaching. For this reason, a method was developed to reduce the storage space by compressing and reducing the volume of non-flammable radioactive miscellaneous solid waste using a large press.
Many patent applications including No. 1-84599 have been filed.

On the other hand, a national basis for the disposal of radioactive waste generated from nuclear power plants, etc. is currently being considered, and land burial is scheduled to begin in 1986. In this case, the compressed waste is also planned to be buried in a container such as a drum in the form of a waste solidified with mortar or plastic. However, after burial, it is expected that underground water will corrode drums and water will enter the waste body. In particular, waste materials that absorb water, such as heat insulators and filters, will absorb water and generate swelling pressure within the waste body. Cracks may occur in the barrier layer and the integrity of the waste material may be significantly compromised.

As a result of tests, it was found that the reaction force associated with the swelling of the waste material reached more than 5 tons in a 2,000 ton compressed body of heat insulating material.High strength, Possible options include using a fixing material with high water impermeability and increasing the thickness of the fixing material, but problems such as an increase in the cost of the fixing material and a decrease in the effective capacity inside the container due to the increase in the thickness of the fixing material are considered. was there. In addition, in the case of compressed bodies such as filters, simply fixing them with mortar or plastic does not completely fix the powdered harmful substances that adhere to the filters, and when groundwater infiltrates into the waste, harmful substances and radioactivity are released into the container. It is possible that it may leak outside.

On the other hand, in the case of metal waste such as pipes and shaped steel, the voids in the compressed body after volume reduction treatment reach approximately 50%, and when the compressed body is fixed with conventional mortar or plastic, the viscosity of the fixing material is high. Complete entry into the void cannot be expected. As a result, voids remain inside the waste, which may become a channel for groundwater after burial, which is not desirable in terms of preventing notification of radioactivity.

(Problems to be Solved by the Invention) The present invention solves the conventional problems as described above, and provides a water absorption method that eliminates the risk of loss of integrity of the waste material due to intrusion of groundwater even when disposed of underground. This method was developed for the purpose of processing radioactive waste that has swelling properties.

(Means for solving the problem) The above problem is achieved by compressing and reducing the volume of radioactive solid waste, and then impregnating the internal voids of the compressed body with a low-viscosity solidifying material such as a vinyl monomer to solidify it. This is accomplished by storing the waste inside a drum and fixing the surrounding gap with a fixing material to create a stable waste product. In addition, this problem involves compressing and reducing the volume of radioactive solid waste, storing it inside a drum, filling the surrounding gaps with aggregate, and then applying a low-viscosity solidifying material such as vinyl monomer inside the compacted body. This can also be achieved by impregnating it into voids and between aggregates and solidifying it to form a stable waste.

The invention will now be explained in more detail with reference to concave surfaces.

Figures 1 to 4 are process diagrams of the first invention.
As shown in the figure, solid waste is compressed and reduced in volume by a press machine fil, and becomes a compressed body (2). Since this compressed body (2) has many voids inside it, next, as shown in FIG. 2, this compressed body (2) is placed in a container (4) in a tank (3), While reducing the pressure inside the tank (3) using a vacuum pump (5), a low-viscosity solidifying material is supplied from an upper nozzle (6) to impregnate the internal void of the compressed body (2). Typical low-viscosity solidifying materials used in the present invention include vinyl monomers such as styrene monomers, vinyl chloride monomers, and acrylic acid monomers. Other monomers can also be used as long as they can. However, in order to sufficiently impregnate the material into a dense compressed body such as a heat insulating compressed body, it is preferable to use an assimilated material having a viscosity of 1 void or less. Next, as shown in Fig. 3, this compressed body (2
) is heated and pressurized in a tank (8) equipped with a heater (7) to polymerize and solidify the assimilated material.

After that, as shown in Fig. 4, a plurality of solidified compressed bodies (2) are stored inside a drum can (9), and the periphery of the compressed bodies (2) is fixed with a fixing material Q [11] such as mortar or plastic. do. After the waste body is buried in such a state, groundwater etc. may corrode the outer drum (9) and reach the compacted body (2) through the fixing material QG+, but the internal voids may Since the compressed body (2) is completely filled with the solidified low-viscosity solidifying material, water does not penetrate into the inside of the compressed body (2). Therefore, there is no risk of leakage of radioactive substances due to intrusion of underground water after burial, or fracture of the waste body due to generation of swelling pressure, and it is possible to obtain a waste body with extremely excellent stability and soundness.

Figures 5 to 8 are process diagrams of the second invention.
As shown in the figure, radioactive solid waste is compressed and reduced in volume using a press (1) to form a compressed body (2). Next, this compressed body (2
) are stored in a drum can (9) as shown in Figure 6, and the gap around the compressed body (2) is filled with aggregate θυ such as sand or calcium carbonate, and then the vacuum pump (5 ) while reducing the internal pressure, a low-viscosity solidifying material such as a vinyl monomer is impregnated into the internal voids of the compressed body (2) and between the aggregates 00 from the nozzle (6). If this is heated by a heater (7) in a tank (8) as shown in FIG. 7 to polymerize the assimilated material and solidify the whole, a waste body as shown in FIG. 8 will be obtained. In this second invention, the reason why the impregnated surface is filled with aggregate αυ around the compressed body (2) in advance is to prevent the occurrence of cranks when the assimilated material solidifies and shrinks.

In addition, filling with aggregate (Ill) has the effect of improving the strength of the solidified material and reducing the amount of assimilated material by the amount of aggregate θD, making it economical. Like the waste obtained by the invention, this waste has excellent stability and soundness without the risk of swelling due to water absorption.

In addition to directly compressing insulation materials and filters,
It is also possible to compress and reduce the volume while stored in a container such as a drum. In this case, by making several holes in the outer skin of the compressed body after compression, it becomes possible to impregnate the inside with a low-viscosity solidifying material. . Further, if the radioactive waste is placed in a container or bag made of a material such as glass fiber or cloth that can be easily impregnated with the solidifying material and compressed, more reliable impregnation is possible. Furthermore, as shown in FIG. 9, if a spacer 03 is interposed between the compressed bodies (2), the injection and impregnation of the assimilating material can be carried out quickly and reliably.

(Example) Example 1 A silica-based heat insulating material with a specific gravity of 0.17 and a porosity of 92.5% was compressed and reduced in volume with a surface pressure of 9QOkg/cffl, and compressed to a bulk specific gravity of 1.18 and a porosity of 48%. I got a body. As a result of measuring the swelling pressure of this compressed body in water, 3. A swelling pressure of ITkg/self (7 tons when converted to a 2001 drum with a diameter of 530 mm) was generated.

Styrene monomer is added to this compressed body as a low-viscosity solidifying agent.
After vacuum impregnation with 50msl1g for 1 hour, 7kg/CA
It was polymerized and solidified by heating under a pressure of . This compressed body had a bulk specific gravity of 1.62 and a porosity of 1.7%, and the porosity was significantly reduced. No swelling pressure was observed even when the compressed body was placed in water after solidification. By storing a plurality of compressed bodies inside a drum and fixing them by pouring mortar around them, waste bodies with excellent stability and soundness were obtained.

Example 2 140 kg of metal waste such as pipes, steel molds, valves, etc.
The mixture was packed in a 01 drum and compressed and reduced in volume with a surface pressure of 900 kg/aJ to obtain a compressed body with a porosity of 49%. When this compressed body is placed in a container and fixed with mortar, there is little intrusion of mortar into the voids of the compressed body, and the porosity after solidification is 35%.
It was about. However, after impregnating and solidifying with styrene monomer, the porosity was 3% or less, and most of the pores in the compressed body were solidified by styrene monomer.

(Effects of the Invention) As explained above, the present invention impregnates and solidifies the internal voids of the compressed body with a low-viscosity solidifying material, thereby reducing the risk of swelling pressure due to water absorption even if groundwater etc. floods after burial. There is no possibility of cracks occurring in the waste body due to swelling pressure, and a waste body with extremely excellent stability and soundness can be obtained. Furthermore, in the case of compressed bodies such as filters, powdered harmful substances stuck to the filter can be reliably fixed, and leakage of harmful substances and radioactivity into the environment can be prevented when flooding with groundwater or the like. In addition, the voids inside the waste body can be reduced to a minimum, and a waste body with excellent soundness can be obtained. Therefore, the present invention greatly contributes to the development of industry as a radioactive waste disposal method that eliminates the problems of the conventional methods.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views explaining the first invention in detail,
FIGS. 5 to 8 are cross-sectional views explaining the second invention in detail,
FIG. 9 is a sectional view showing a modification thereof. (2): Compressed body, (9) Nidrum can, Al: Fixing material, Qll: Aggregate. fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig fig.

Claims (1)

[Claims] 1. After compressing and reducing the volume of radioactive solid waste, the internal voids of the compressed body are impregnated with a low-viscosity solidifying material such as a vinyl monomer to solidify it, and this is placed inside a drum. A method for disposing of radioactive waste characterized by storing it and fixing the surrounding gap with a fixing material to make a stable waste body. 2. After the radioactive solid waste is compressed and reduced in volume, it is stored inside a drum, the surrounding gaps are filled with aggregate, and a low-viscosity solidifying material such as vinyl monomer is applied to the internal voids of the compacted body and A method for disposing of radioactive waste characterized by impregnating it between aggregates and solidifying it to form a stable waste body.