JPH0611601B2 - Waste treatment container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a container for treating and disposing of waste, particularly radioactive waste and industrial waste (hereinafter simply referred to as treatment), which is lined with dense concrete or mortar.

[Conventional technology and its problems]

In recent years, the amount of wastes, especially various radioactive wastes emitted from nuclear facilities such as nuclear power plants and nuclear power plants, and industrial wastes such as harmful heavy metal sludges emitted from chemical plants have increased. I have a hard time processing it.

Unlike heavy metals, radioactive materials decay and decay with individual nuclides with a unique half-life, so the period of time that must be kept separate from our environment is finite. The long-lived wastes in the current nuclear fission system are mainly generated from nuclear fuel reprocessing plants. The lifetime is calculated to be several hundred years if the radiation performance of β- and γ such as 90Sr and 137Cs is focused, and it is calculated to be several hundred thousand years if the α-activity of transuranium element having an atomic number of 93 or more is focused. At present, the most problematic emission amount is low-concentration low- and medium-level waste.
It is said that it can be considered as less than about 100 years. In other words, a land storage container ideally lasts about 100 years.

By the way, at present, the main body of processing containers for low- and middle-level radioactive waste is basically stainless steel drums. For example, a drum or a multi-layered container in which concrete is lined with about 5 cm inside the drum is uniformly solidified with cement or asphalt. Drum cans are simple and relatively inexpensive and have a good track record of use, but they are unsuitable for long-term storage because they corrode in about 10 years. If stored indoors, not only will it be difficult to handle after corrosion and handling, but it will also cause workers to be exposed to radiation and eventually cause environmental pollution. However, if it is made of stainless steel, it is not practical because it is not only expensive but also gradually deteriorates in the long term.

Recently, as the storage facilities of each nuclear power plant have become too small,
The asphalt solidification method, which enables volume reduction and solidification at relatively low cost, is in the limelight. However, the solidified asphalt easily burns in a fire, which is not preferable, and is more dangerous when the drum can is corroded. Furthermore, in Japan, where the land is small,
It is impossible to permanently store radioactive waste. Ideally, such wastes that have been stored for a long period of time and have reduced radioactivity should be disposed of by ocean dumping or underground dumping so that the storage site can be effectively used. Therefore, containers for land storage or land treatment / disposal based on drums are not preferable. In addition, methyl methacrylate (MM
A) A polymer-impregnated concrete container that is impregnated and polymerized with monomers such as A) is a superior container that has high strength and long-term durability and can prevent the leaching of radioactive substances. However, compared with ordinary concrete, impact resistance is not improved so much and fire resistance is reduced. For this reason, there is concern about impact accidents such as falling during transportation, disasters such as earthquakes, and fire, and it is not suitable as a land treatment / disposal container.

By the way, when ordinary concrete is reinforced with steel fiber, impact resistance, toughness, shear strength, fatigue resistance, etc. are remarkably improved, but there is a problem in corrosion deterioration of steel fiber such as seawater and acidic water. In addition, it is difficult to use as a radioactive waste container because of the drawbacks such as non-uniformity of fiber and lack of solidity of concrete resulting in variations in product due to the characteristics during manufacturing.

Further, in order to solve the above problems, a treatment container for radioactive waste and industrial waste produced by impregnating a preformed steel fiber reinforced concrete container with an impregnating agent such as a polymerizable monomer and then polymerizing and solidifying in concrete. However, there are many practical problems in terms of economic efficiency and quality stability. The container for solidification of radioactive waste cement,
Conventionally, waste is solidified by stirring it with a solidifying agent such as cement in a container. However, in the case of conventional stirred vessels,
When the stirring blade is taken out after completion of stirring, a space corresponding to the volume of the stirring blade is formed in the upper part of the container. Therefore, it is necessary to fill the space with asphalt, mortar and the like.

[Problems to be solved by the invention]

The main object of the present invention is to provide a land treatment container for radioactive waste and industrial waste, which is excellent in strength, impact resistance, chemical resistance, fire resistance, corrosion resistance, economical efficiency, and quality stability.

[Means for solving problems]

That is, the present invention is to line the inner surface of the container with a cementitious material, ultrafine powder having an average particle size at least one order lower than that of the cementitious material, a high-performance water reducing agent, an aggregate, and concrete or mortar containing water as a main component. This is a waste treatment container.

Hereinafter, the present invention will be described in detail.

The cementitious material referred to in the present invention is usually, early early super early early strength,
Various types of portland cement such as white or sulfate resistant, further, mixed cement obtained by mixing admixtures such as blast furnace slag and fly ash, and mixed cement obtained by pulverizing mixed material and / or mixed cement are generally used.

The ultrafine powder used in the present invention has an average particle size lower than that of the above-mentioned cementitious material by at least one order, and in particular, an average particle size lower by 2 orders is preferable from the viewpoint of the flow characteristics of the kneaded product. Specifically, silica dust (silica fume) and siliceous dust produced as a by-product during the production of silicon, silicon-containing alloys, and zirconia are particularly suitable. In addition, calcium carbonate, silica gel, opalaceous silica, fly ash, and slag. Ultra fine powders such as titanium oxide and aluminum oxide can also be used. In particular, the use of ultrafine powder obtained by crushing opalaceous silica, fly ash, and slag with a jet mill equipped with a classifier is effective in improving curing shrinkage.

The amount of ultrafine powder used is preferably a cementitious substance 60-9.
5 to 40 parts by weight, more preferably 6
It is 10 to 35 parts by weight with respect to 5 to 90 parts by weight, and if it is less than 5 parts by weight, it is difficult to obtain high strength (fastness), and if it exceeds 40 parts by weight, the fluidity of the kneaded product is remarkable. And the strength becomes insufficient, and the strength development becomes insufficient.

The high-performance water reducing agent used in the present invention (hereinafter referred to as a water reducing agent) is also called a superplasticizer, and is an admixture that remarkably enhances the fluidity of concrete, while maintaining the same workability as ordinary concrete. , Unit water volume 15-25%
And, it can be greatly reduced.

Normal water reducing agents have the effect of delaying the setting time of cement, but the high-performance water reducing agent used in the present invention does not cause excessive delay of setting or excessive air entrainment even when added in large amounts to cement. Surfactants having a large dispersibility include those containing naphthalene sulfonic acid formaldehyde condensate salts, melamine sulfonic acid formaldehyde condensate salts, high molecular weight lignin sulfonates, polycarboxylates, etc. as main components. . The water reducing agent is necessary for obtaining a kneaded product at a low water ratio, and the conventional amount used is 0.3 to 1% by weight as solid content with respect to the cementitious substance, but in the present invention, However, it is preferable to add a larger amount than that. Specifically, it is used up to about 10 parts by weight as a solid content with respect to 100 parts by weight of a mixture of a cementitious substance and ultrafine powder, and if added in a larger amount than that, the curing reaction is adversely affected. A particularly preferred amount of addition is 1 to 5 parts by weight. When the water reducing agent is used in such an amount in combination with the ultrafine powder, it is possible to obtain a fluidized kneaded product which can be molded by a usual method even when the ratio of the water cementitious substance and the ultrafine powder is 25% or less.

The water used in preparing the mixture in the present invention is necessary for molding, but it is preferable to make it as small as possible in order to obtain a high-strength cured product, and 100% by weight of the mixture of cementitious substance and ultrafine powder. The amount is preferably 12.5 to 30 parts by weight, more preferably 15 to 28 parts by weight. The amount of water is 3
If it is more than 0 parts by weight, it is difficult to obtain a high-strength cured product, and if it is less than 12.5 parts by weight, ordinary molding such as casting becomes difficult.

The aggregate used in the present invention may be one that is usually used, but it is desirable that it is hard and has a large specific gravity. Mohs hardness is 6 or more, preferably 7 or more or Knoop indenter hardness is 700 kg.
Those selected according to any of the criteria of / mm ² or more are preferable. Examples that meet this criterion include silica, pyrite, hematite, magnetite, yellow jade, lawsonite, emery, corundum, phenasite, spinel, beryl, algae,
There are tourmaline, granite, beryl, cruciate, zircon, calcined bauxite, charcoal silicon, fused silica, fused magnesia, silicon carbide, cubic boron nitride, etc., especially in the case of radioactive waste containers, It is preferable to secure the specific gravity of concrete to 3.2 or more by using iron powder or the like.

In addition to the above materials, a chemical admixture used for ordinary concrete or mortar can be used in combination as required.

A method for mixing and kneading the above materials is not particularly limited, and a usual method can be applied.

Further, the lining method is usually performed, and includes, for example, centrifugal lining, injection lining using an inner mold, and spray lining.

The shape of the processing container according to the present invention is generally a drum, but is not limited to this.

As a specific example, the present invention will be further described based on an example using a drum can.

The drum used in the present invention is a 200 steel drum JI.
Using SZ1600-1977H class (1.6 mm) as a standard, reinforcing reinforcing bars are embedded in the inner surface of the drum as shown in FIG. 1 and a dense concrete of the above composition having a thickness of 30 to 70 mm is lined. The concrete lining method is based on injection molding, in which densely kneaded and dense concrete is poured into a gap between a predetermined inner mold and a drum can by pouring with a head pressure, pouring with a pump, pouring, or the like. At this time, if the kneaded dense concrete is degassed in vacuum to remove air bubbles contained in the concrete, the denseness of the hardened material can be further improved.

Further, as the inner formwork, a plastic molded product or a stainless wire mesh may be used to be buried.
It can be appropriately selected in consideration of economy and practicality.

The container of the present invention, as shown in FIG.
It is composed of a body portion 2 and a bottom portion 3, and the body portion and the bottom portion are integrally molded in advance, and a predetermined waste is filled therein, and solidified by cement or the like, and then a canopy portion is molded to complete.

When molding the body and bottom, the rebar to be embedded in the canopy is installed in advance, and when molding the canopy, the solid concrete is integrated on the solidified waste without using an internal formwork. Cast. That is, according to the present invention, the upper space formed after the stirring blade is taken out after the stirring is completed when the drum can is packed with the radioactive waste with cement,
It is replaced by dense concrete when molding the canopy.

〔Example〕

 The present invention will be further described in the following examples.

Example 1 200 steel drum [JIS Z1600 H class (1.6 m
m)], the inner mold was set so that the lining thickness was 50 mm.

Reinforcing bars with a diameter of 6 m / m are installed at intervals of 20 cm as shown in the drawing.

Concrete having the composition shown in Table 1 was prepared and pumped.

Steam curing was carried out at 50 ° C. for 12 hours. After that, the physical properties were evaluated. Based on the evaluation criteria of Japan Atomic Energy Research Institute, the impact test and airtight test of the lined drum tube were performed.

As a result, there was no problem.

Example 2 Using the concrete, resin concrete, heavy concrete, and ordinary concrete having the composition used in Example 1, lining as in Example 1 to produce a container,
A heat resistance test was carried out one month later.

In the heat resistance test, the sample was heated at a temperature rising rate of 5 ° C./1 minute, reached 900 ° C., then held at a temperature of 900 ± 10 ° C. for 1 hour, and then naturally left to cool.

After confirming that the container temperature was 30 ° C. or lower, an impact test and an airtight test were carried out in the same manner as in Example 1.

The mix of resin concrete, heavy concrete, and ordinary concrete is as follows.

(1) Resin concrete binder Unsaturated polyester 71 parts by weight Shrinkage reducer 28 parts by weight Cobalt octenoate curing accelerator 0.28 parts by weight Methyl ethyl ketone catalyst 0.30 parts by weight Silane coupling agent 1.0 parts by weight Binder: calcium carbonate: fine bone Material: Coarse aggregate weight ratio =
1: 1: 2.8: 4.2 (2) Heavy concrete Water: Normal cement: Fine aggregate: Coarse aggregate: AE Unit amount of water reducing agent
(kg / m ³ ) ＝ 182: 365: 835: 1025: 0.91 AE The water reducing agent is Pozzolith No. 70, a trade name, manufactured by Pozoris Bussan Co., Ltd. (3) Normal concrete As a fine aggregate, Himekawa produced sand is used as coarse aggregate. Same as heavy concrete except that Himekawa river gravel is used.

As a result, compressive strength and bending strength are shown in Table-2.

In addition, none of the containers other than the container of the present invention could meet the evaluation criteria of the Japan Atomic Energy Research Institute.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY According to the present invention, a container having sufficient performance as a treatment container for medium to low level radioactive waste and other industrial wastes was obtained.

[Brief description of drawings]

The drawing is a cross-sectional view of a lined drum tube showing an embodiment of the present invention. Reference numeral 1 ... Canopy portion, 4 ... Steel 2 ... Body portion, 5 ... Dense concrete 3 ... Bottom portion, 6 ... Reinforcing bar

Claims (1)

[Claims] 1. An inner surface of a container is lined with a cementitious substance, ultrafine powder having an average particle size at least one order lower than that of the cementitious substance, a high-performance water reducing agent, an aggregate, and concrete or mortar containing water as a main component. Waste treatment container.