JPH04359193A - Shielding body - Google Patents

Abstract

PURPOSE:To reduce the disposal cost of wastes by effectively utilizing the wastes generated when a nuclear power-related facility is decommissioned. CONSTITUTION:At least one selected among a group of reinforcing bar wastes in the reinforced concrete wastes generated when the concrete of a nuclear power-related facility is demolished and reclaimed aggregates reclaimed from the concrete wastes is put into a preset shuttering, and cement paste or cement mortar is put in it to form a shielding body.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shield that makes effective use of reinforced concrete waste generated from the demolition of concrete at nuclear power related facilities.

0002

[Background of the Invention] The peaceful use of nuclear energy has been in use in Japan for more than 30 years, and today it is attracting worldwide attention. Nuclear power generation is one of the peaceful uses of nuclear energy.
Today, nuclear power generation plays a major role as a stable source of electricity supply. By the way, just as all things have a lifespan, nuclear power plants cannot avoid their lifespan. If this is a normal facility, there would not be much of a problem with how to dispose of it after dismantling the facility, but the treatment and disposal of dismantled waste from nuclear power plant facilities will need to be considered in the future, including economic considerations.

[0003] Furthermore, it is estimated that hundreds of thousands of tons of waste will be generated when nuclear power plant facilities are dismantled. Currently, disposing of a large amount of waste at a general industrial waste disposal site may become a problem in the future due to location issues at the general industrial waste disposal site, but disposing of it at a radioactive waste disposal site is However, there is a problem from an economic point of view, and there is a need to reuse demolition waste.

[0004] A method is being considered in which the reinforcing bar waste generated from reinforced concrete is reprocessed into reinforcing bars by putting it into a melting furnace installed in a nuclear facility, but this method requires large-scale equipment. .

[0005]

[Disclosure of the invention] By the way, 90% of the hundreds of thousands of tons of waste generated by dismantling nuclear power plant facilities
The remainder is believed to be concrete and rebar scrap. Moreover, it is estimated that most of the concrete has a low radioactivity level of less than 10-4 curies/ton. Although it is thought that such low-level waste does not need to be transported to a radioactive waste disposal site, a more rational disposal method is expected.

[0006] Furthermore, in Japan, the basic policy of the country is to dismantle nuclear power plant facilities that have reached the end of their service life and to utilize the sites. On the other hand, the construction of nuclear power plants requires large amounts of concrete materials. Therefore, if the reinforced concrete waste generated from demolition as described above is effectively used in the construction of new nuclear power plants, it will be possible to eliminate the waste of concrete materials, and it will be possible to dispose of it more rationally. It was revealed that the disposal cost would be low, and this led to the completion of the present invention.

[0007] That is, an object of the present invention is to provide a technology for effectively utilizing waste generated by dismantling nuclear power related facilities and reducing waste disposal costs. The purpose of the present invention is to place at least one material selected from the group consisting of reinforcing bar scraps in reinforced concrete waste generated from the demolition of concrete in nuclear power related facilities and recycled aggregate recycled from concrete waste into a predetermined formwork. This is achieved by a shield characterized by containing cement paste or cement mortar.

That is, according to the present invention, reinforced concrete waste generated from the concrete demolition of nuclear power related facilities can be effectively used as a shield for the nuclear power related facility being constructed, and moreover, this shield can be constructed at a location where radiation is generated. Therefore, there is no problem even if concrete waste from nuclear facilities, which has a low radioactivity level at most, is used as the material for constructing this shield, and the waste material should be used effectively. The cost of waste disposal becomes low.

The present invention will be explained in more detail. Various materials are generated as waste materials from nuclear power related facilities, and in order to effectively utilize them as shields for nuclear power related facilities, it is preferable to use concrete with a high specific gravity or thick concrete. One possible example of such concrete is heavy concrete in which reinforcing steel scraps are cut into chips, for example, and are used as heavy aggregate. In addition, for thick concrete, there is a method of using recycled aggregate from waste materials generated from the demolition of concrete of nuclear power related facilities as aggregate.

[0010] That is, heavy aggregate obtained by cutting reinforcing bar scraps from waste materials generated from the demolition of concrete in nuclear power related facilities and recycled aggregate from concrete can be effectively used as shields for nuclear power related facilities. In order to construct shields for nuclear power related facilities, cement as a binding material is required in addition to the above-mentioned rebar scraps and recycled aggregates.

[0011] Examples of this cement include ordinary Portland cement, early strength Portland cement, ultra early strength Portland cement, moderate heat Portland cement, sulfate-resistant Portland cement, blast furnace cement, silica cement, and fly ash cement. Cement or the like that substantially does not contain calcium oxide may be used, but it is most preferable to use a type of cement that incorporates a large amount of water of crystallization into the solidified material, which is effective in shielding neutrons.

[0012] Examples of cements containing polycrystalline water in the solidified cement include 3CaO.3Al2 O3.
CaSO4, CaO・Al2O3, 12CaO・
A calcium sulfoaluminate compound such as 7Al2O3 whose CaO/Al2O3 (molar ratio) is less than 3, or a clinker or cement whose main component is a calcium aluminate compound, is 3 to 20 in terms of the calcium sulfoaluminate compound or calcium aluminate compound. The first raw material, which can be expressed as % by weight, and the tricalcium silicate (3CaO
・SiO2 ) or dicalcium silicate (2CaO・Si
A second raw material that can be made from clinker or cement whose main component is 3 to 20% by weight in terms of a calcium silicate compound, and gypsum such as anhydrite or dihydrate as a calcium silicate compound.
A third raw material that can be made in an amount of 6 to 40% by weight in terms of SO4,
A fourth raw material containing 20 to 88% by weight of blast furnace water slag and a fifth raw material containing 0.1 to 1.5% by weight of oxycarboxylic acids such as sodium citrate and malic acid are mixed. (3Al2O3 +1.5SiO2)/(C
There are some in which the molar ratio (aO-SO3) is 1 or more.

[0013] Furthermore, when the above-mentioned composition is used as a cement source for cement paste or cement mortar constituting a shield, the shield is less likely to suffer damage such as cracking or peeling, and is highly durable and safe. It gets expensive. The reason for this is explained from the viewpoint of hydration reaction in an example using calcium sulfoaluminate clinker whose main component is calcium sulfoaluminate compound 3CaO.3Al2 O3.CaSO4, Portland cement, and blast furnace water slag. That's right.

The calcium sulfoaluminate compound is
As roughly shown in the following equation, ettringite is formed by reacting with calcium hydroxide and gypsum at the initial stage of the hydration reaction, and 32 moles of crystal water are taken in. 3CaO・3Al2 O3 ・CaSO4 +8CaS
O4 +6Ca(OH)2 +90H2 O→3(3C
aO・Al2 O3 ・3CaSO4 ・32H2 O
) This reaction begins immediately after contact with water and ends approximately 24 hours later. During this period, the cement hydrate structure is in a relatively loose state, so the generated ettringite does not cause any adverse effects on the structure.

On the other hand, in the case of ordinary Portland cement, only 3 to 6 moles of crystallization water are incorporated, as roughly shown in the following equation. 2(3CaO・SiO2)+6H2O→3Ca(O
H)2 +3CaO・2SiO2・3H2 O2(2
CaO・SiO2 )+4H2 O→Ca(OH)2
+3CaO・2SiO2 ・3H2 O3CaO・Al
2 O3 +6H2 O→3CaO・Al2 O3 ・
6H2 O 4CaO・Al2 O3 ・Fe2 O3 +2Ca(
OH)2 +10H2 O→3CaO・Al2 O3
・6H2 O+3CaO・Fe2 O3 ・6H2 O Therefore, since the above cement has more water of crystallization than ordinary Portland cement, it has a lower neutron shielding effect when used as a material for shielding bodies related to nuclear facilities. It is expected to be high, and from this point of view it is extremely preferable.

[0016]

[Example] At least one selected from the group of reinforcing bar scraps and recycled aggregates generated by demolition of buildings instead of concrete demolition of nuclear power related facilities, such as reinforcing bar scraps, reinforcing bar chips, recycled aggregates, and reinforcing bar scraps. By filling recycled aggregate, rebar scrap chips, recycled aggregate, and cement paste or cement mortar with high crystallization water simultaneously or sequentially, solidifying, curing, and demolding, it is possible to create blocks of precast concrete. A shield is obtained.

[0017] Here, regarding the shielding material using reinforcing bar scraps or reinforcing bar scrap chips, since the specific gravity is large, the shielding effect of γ rays is increased, and the cement used is of a type containing a large amount of crystallized water. High neutron shielding effect. In addition, the shielding bodies made of recycled aggregate are not inferior in properties to those made with ordinary aggregates, and the cement used is of a type with a high content of crystallized water. It has a high neutron shielding effect.

[0018]

[Effects] The shield according to the present invention uses at least one material selected from the group consisting of reinforcing bar scraps in reinforced concrete waste material generated from concrete demolition of nuclear power-related facilities and recycled aggregate recycled from concrete waste materials, into a predetermined formwork. Since it is constructed by putting cement paste or cement mortar into the interior, the waste materials generated from the concrete demolition of nuclear power related facilities can be effectively used as a shield for the nuclear power related facilities being constructed. Since it is constructed at the location where it is generated, it has the advantage of making effective use of waste materials and reducing the cost of processing reinforced concrete waste.

Claims (1)

[Claims] Claim 1: Putting at least one material selected from the group consisting of reinforcing bar scraps in reinforced concrete waste generated from concrete demolition of nuclear power-related facilities and recycled aggregate recycled from concrete waste into a predetermined formwork; A shield characterized by containing paste or cement mortar.