KR101508957B1 - Concrete Composite for Shielding Radiation - Google Patents

Abstract

The present invention relates to a concrete composite for shielding radiation in order to block γ-ray and neutron ray which are in need of shielding as well as being difficult to shield. The present invention includes: water, a binding material, a thick aggregate, and a thin aggregate.

Description

{Concrete Composite for Shielding Radiation}

The present invention relates to a radiation-shielding concrete composition, and more particularly, to a functional concrete composition for shielding γ-rays and neutron rays which are highly shielded and difficult to shield.

Recently, there is a high public interest in the risk of radioactive materials in relation to the earthquake damage in Japan. However, compared to the interest in radiation, the technical development of the construction field for the protection facilities is insufficient, and technical studies on effective shielding concrete capable of shielding the alpha ray and the beta ray in the radiation as well as the gamma ray and the neutron ray in the radiation emission region Is still in its infancy.

In Korea, ICRP-60 was introduced in 1998 by Ministry of Science and Technology, Notice No. 98-12. After the introduction of the ICRP-60 in 2003, supervision and supervision of the ICRP-60 was carried out in accordance with the radiation protection regulations and optimized radiation shielding Since research and development has been started, radiation can be emitted not only in medical institutions such as hospitals but also in social infrastructures. Therefore, there is no room for installation of radiation shielding walls, and development research on these is also urgent.

The "radiation shield" at the center of the issue as described above can be defined as attenuating the intensity of the radiation field in a particular area. In other words, the intensity of the radiation field is attenuated by interacting with the constituent atoms of the substance during the passage of the substance. Using this phenomenon to physically attenuate the intensity of the radiation is called radiation shielding. It is called shielding.

In general, middle-earplugs such as nuclear fission fragments, α-rays, neutrons, and protons can be shielded by species or rubber gloves because their nodules are very short, and it is possible to know the thickness of shielding by calculating them non-formally. not. In addition, the β-ray is not larger than that of the middle-to-lower exposed person, but there is no big problem if you pay a little attention. The most important factor for shielding β rays is prevention of braking radiation. Therefore, in order to shield β rays, it is necessary to first shield the atomic number material (plastic, aluminum) to reduce the rate of braking radiation and to prevent the atomic number material (lead, iron, concrete, tungsten, It is necessary to perform secondary shielding.

On the other hand, in the case of X-ray or γ-ray shielding, two aspects should be considered. One is the shielding against the narrow beam that the radiation field is uniform and the physical phenomenon is easily represented by the formula, and the other is the shielding by the wide beam which composes the radiation field by combining the phenomenon by the actually occurring scattering. In general, shielding of X-rays and γ-rays with high permeability is shielded by materials with high density and high atomic number (lead, iron, concrete, tungsten, depleted uranium).

In addition, neutron shielding is achieved by the neutron beam's ability to lose its energy when it collides against a material containing a light atomic nucleus such as hydrogen. Since effective blocking of γ-rays and high-speed neutrons with large permeability are blocked automatically, the blocking of these radiation is fundamental to the actual shielding facility.

The shielding design of the radiation facility is designed in consideration of the stability to radiation and at the same time considering the economical efficiency, the minimum weight and the stability of the structure. The shielding system, the shielding material, the allowable dose outside the shield, the kind of radiation to be shielded, Evaluation of impact on scattering radiation in energy, strength, source geometry, thickness of shielding, test hole penetrating shielding, duct, trough construction, fire resistance, designed for shielded structure, earthquake resistance, durability, construction characteristics and maintenance The radiation shielding design considerations include shielding ability, physical and chemical properties, difficulty in obtaining, economical efficiency, construction characteristics, etc., It is to choose what meets the purpose. Shielding materials shall be those with effective shielding capability, depending on the type of radiation.

The thickness of the shielding material required for X-ray or γ-ray shielding is almost inversely proportional to the density of the material. In general, elements with large atomic numbers are effective in attenuating γ-rays, so heavy elements such as iron, lead, and uranium may be used as X-ray or γ-ray shields. However, it is necessary to meet the requirements of engineering strength, heat characteristics, construction characteristics, economical efficiency and the like.

In particular, when the space for the construction of the shielding structure is not limited, it is effective to use the general aggregate by increasing the wall thickness in view of workability, stability and economical efficiency, and there is little possibility of problems in purchasing or constructing the aggregate. However, when there is a limitation on the thickness of the shielding wall such as a multi-purpose research reactor or a reactor wall for a network of a laboratory reactor, it is not possible to shield the general aggregate. Therefore, a dense heavy concrete aggregate should be used. In addition, when it is necessary to satisfy the shielding performance with a limited wall thickness, it is necessary to use heavy aggregate because the specific gravity of the concrete must be increased.

As a prior art document related thereto, Korean Patent Laid-Open Publication No. 10-2011-0024136, entitled "Radioactive Shielding Concrete Composition for Replacing Concrete Aggregate ", discloses an invention for imparting a radioactive shielding function to concrete by including electric oxidation slag, A radiation shielding concrete composition comprising cement, coarse aggregate of 5 mm or more, aggregate of 5 mm or less, and unavoidable foreign matter, and an electric furnace slag for replacing the concrete fine aggregate, wherein the aggregate has a unit mass of 3500 kg / And at least one of the slag and the slag. The use of the electric furnace slag generated in the smelting and refining process of the iron ore as the building slab includes at least any one of the electric furnace slag and the magnetite having a unit mass mass of 3500 kg / m 3 or more as the coarse aggregate So that various incidental costs due to the reprocessing of the electric furnace oxidation slag can be reduced and the manufacturing cost of the concrete can be reduced.

However, since the radiation shielding is attempted by increasing the density of the concrete, the shielding ratio of the x-ray and the audit ray is high but it is not effective in shielding the neutron ray. And concrete production costs.

As a prior art, Korean Patent Laid-Open Publication No. 10-2014-0049049, entitled " Chemically bonded ceramic radiation shielding material and manufacturing method ", relates to a composition and a method of forming a radiation shielding member at ambient temperature, Chemically bonded oxide-phosphate ceramic cement matrix; And " cold-calcined " chemically bonded oxide-phosphate ceramic cement matrices.

However, it is hard to say that the low temperature calcination chemically bonded oxide phosphate ceramics satisfies the shielding of radiation with a certain thickness, and also the neutron shielding is not mentioned.

[Patent Document 1] Korean Patent Laid-Open No. 10-2012-0106191 entitled " Radioactive shielding concrete composition for replacing concrete aggregate, "2012.09.26. [Patent Document 2] Korean Patent Laid-Open Publication No. 10-2014-0049049 "Chemically bonded ceramic radiation shielding material and manufacturing method ", 2014.04.24.

It is an object of the present invention to develop a radiation shielding concrete composition which is effective in reducing the transmittance of gamma rays and neutron rays in a radiation emitting area on the basis of the above problem.

Particularly, there are many known materials that block or scatter radiation. However, it is very difficult for most materials to mix with concrete, or it tends to deteriorate the properties of concrete. Therefore, industrial byproducts, which have higher specific gravity than general aggregates, It is an object of the present invention to find an optimum mixing condition of a concrete composition capable of uniformly mixing a synthetic resin with concrete.

In order to solve the above problems, the present invention provides a concrete composition comprising water, a binder, a coarse aggregate and a fine aggregate, wherein the fine aggregate is mixed with steel making slag (SS) and high density polyethylene (HDPE) Composition ".

The present invention also aims to provide a radiation shielding concrete composition which is characterized in that the fine aggregate is composed of 75 to 85 wt% of steel making slag and 15 to 20 wt% of high density polyethylene.

The present invention also aims to provide a radiation shielding concrete composition which is characterized in that the high-density polyethylene is at least one of a powder type and a bead type.

The present invention also aims to provide a radiation shielding concrete composition which is characterized in that all or a part of the coarse aggregate is a steelmaking slag.

According to the shielded concrete composition according to the present invention, shielding performance effects of radiation such as gamma rays and neutron beams using industrial by-products are higher than those of existing concrete shields, which can contribute to formation of shielding walls of nuclear facilities, hospital facilities, It is eco-friendly and economical.

In addition, the steel slag of the present invention is replaced with coarse aggregate and fine aggregate, while keeping the strength of the shear resistance while keeping the unit weight high and shielding the radiation. The high density polyethylene contained as fine aggregate is well mixed with concrete, Thereby contributing to radiation shielding.

In particular, since the shielding wall using the concrete composition of the present invention has a higher shielding ratio than that of a general concrete composition, it is possible to reduce the thickness of the shielding wall while increasing the specific area while maintaining the same shielding effect.

The present invention provides a concrete composition comprising water, a binder, a coarse aggregate and a fine aggregate, wherein the fine aggregate is mixed with steel making slag (SS) and high density polyethylene (HDPE).

The present invention also provides a radiation shielding concrete composition, wherein the fine aggregate is composed of 75 to 85 wt% steel making slag and 15 to 20 wt% of high density polyethylene.

The present invention also provides a radiation shielding concrete composition wherein the high-density polyethylene is at least one of a powder type and a bead type.

The present invention also provides a " radiation shielding concrete composition characterized in that all or a part of the coarse aggregate is a steelmaking slag. &Quot;

Hereinafter, the radiation shielding concrete composition of the present invention will be described in detail with specific tests and examples.

The effective method of defending the human body from radiation is to adjust the dose so that the dose at the target point is less than the maximum allowable dose equivalent value by appropriately combining two or more of time, distance and shielding. ].

[Formula 1]

Exposure dose = dose rate × exposure time × (1 / multiple of distance 2) × shielding effect

The exposure dose is an amount of exposure that is received while staying in a certain radiation field for a certain period of time, which increases in proportion to the dose rate (radiation dose per unit time) and exposure time. In such a case, a proper shielding between the radiation source and the bombardment will reduce the radiation reaching the bombarder.

In the present invention, the focus is mainly focused on the shielding of the? -Ray and the neutron beam, because if the? -Ray and the high-speed neutron beam having large permeability are effectively blocked, the other is automatically blocked. Particularly, with respect to the? -Ray, an element having a large atomic number is effective for shielding. Therefore, in the present invention, heavy-weight concrete mixed with a heavy element for the purpose of radiation shielding is used.

For this purpose, in the concrete composition comprising water, binder, coarse aggregate and fine aggregate according to the present invention, the fine aggregate is mixed with steel making slag (SS) and high density polyethylene (HDPE) And to secure the shielding performance of radiation by using steel slag and high density polyethylene.

In general, in the binder represented by cement, it is necessary to prevent the occurrence of a portion which is a weak point of the blocking layer, so special care is required to prevent temperature cracking due to hydration heat. The cement used for radiation shielding concrete is usually based on the use of one type of Portland cement. It is also possible to use medium heat cement or fly ash cement with little hydration heat. Also, depending on the type of aggregate used, it reacts with alkali components (K ₂ O, Na ₂ O) in the cement to form an expandable component and causes expansion failure in concrete. Therefore, in reactors requiring reliability, It can also be used.

Particularly, the concrete composition of the present invention includes coarse aggregate and fine aggregate. When the structure for radiation shielding is not limited, it is preferable to use a general aggregate having a large wall thickness in terms of workability, stability and economy, If the thickness of the shielding wall is limited, such as the multi-purpose research reactor or the reactor wall of the experimental reactor network, the shielding performance should be satisfied with a limited wall thickness. In this case, since the shielding is not possible with the general aggregate, It is preferable to use aggregate for heavy concrete.

For this purpose, in the present invention, as a fine aggregate of aggregate, it is desired to use a mixture of steelmaking slag (SS) and high-density polyethylene (HDPE) as a substitute for sand used in the past. The steelmaking slag increases the density of the concrete and blocks the neutron beam. The high density polyethylene plays a role of shielding the radiation by elastically scattering the? -Ray or the neutron beam. In the present invention, it is also possible to provide a concrete composition in which weight is increased by using steelmaking slag (SS) as a coarse aggregate.

Generally, as a shielding material to be applied to the method of cutting the heavy wire by increasing the density of concrete by increasing the weight, olive rock and limestone aggregate have been used, or magnetite and refinery catalyst by-products have been used. It is difficult to maintain a certain level of strength while maintaining unit cost and economical efficiency. In the present invention, the steel making slag generated in the steel making process for smelting iron is used as a shielding material to improve the effect of radiation shielding because of its high unit weight and excellent shear resistance while being economical.

First, the steel making slag has chemical properties as shown in Table 1 below.

[Table 1]

The steel making slag has a high density, that is, a unit volume weight, which is effective for shielding gamma rays in radiation. Gamma rays are shielded in proportion to the thickness of the shielding material at the same density. However, the unit volume mass of the steel slag among the various materials that can be manufactured as heavy concrete is maintained at a rather higher level than that of the ordinary concrete in the unreinforced concrete state, effective.

Generally, in the case of chlorinated paraffin or oil catalyst by-product, the mini slump flow tends to decrease as the substitution rate increases, whereas in the case of steel slag, the mini slump is almost similar to that of ordinary concrete even by increasing the substitution rate. This is due to the increase in the viscosity of the mortar due to the difference in volume occupied by the paste in the mortar depending on the density.

In addition, the unit volume mass of other slags such as manganese slag and reduced slag is not maintained on the unreinforced concrete. The steel slag has a high unit volume mass and does not lower the compressive strength so that the utilization of steel slag is high .

According to Chae-Tae Chae, "A Study on Radiation Shielding of Architectural Structures - Concentrated Gamma Ray Shielding Based on Concrete Mixing, Chonnam National University, 1988", the radiation shielding rate of concrete exceeds the unit volume weight, ie, The amount of radiation to be irradiated is drastically reduced (see [Reference Figure 1]).

[Reference Figure 1]

The steel slag itself has a density of 3.81 as shown in Table 1, and when mixed with the concrete composition, the entire concrete composition is maintained at a high density to effectively shield the radiation. This will be described later with reference to the results of the test.

In the present invention, at least one of coarse aggregate or fine aggregate is replaced with steelmaking slag, and the coarse aggregate used as the coarse aggregate can be replaced with a steel slag having a predetermined size or larger, and the sand used as fine aggregate Of the steel slag powder.

At this time, when the steelmaking slag is substituted for the coarse aggregate, it is preferable that the steelmaking slag is substituted in the range of 50% to 100% of the coarse aggregate.

The fine aggregate of the present invention may incorporate high-density polyethylene together with the steelmaking slag. High-density polyethylene (HDPE) has chemical properties as shown in Table 2 below.

[Table 2]

In the concrete composition field, there is a problem that the conventional polyethylene powder is not rubbed due to the lightness of the conventional polyethylene powder, and the lightweight property of the conventional polyethylene powder is solved by using the material polymerized with the high density polyethylene, So that the required constant strength can be maintained.

The polyethylene powder has a higher neutron shielding effect than the other constituent materials under the same conditions as in the following [Reference Figure 2].

[Reference Figure 2]

That is, the high-speed neutron beam can increase the shielding rate by attenuating the velocity. The high-speed neutron beam collides with the polyethylene powder, and the elastic scattering occurs, so that the velocity of the fast neutron beam is attenuated. Particularly, by incorporating high density polyethylene powder, problems of lowered mixing and deterioration of concrete performance which may occur when ordinary polyethylene powder is mixed are solved.

The high-density polyethylene can be formed into a powder type and a bead type. The powder type is based on the fact that the high-speed neutron beam is more likely to have an elastic scattering probability by the polyethylene powder dispersed with high density. The bead type is a high density polyethylene powder, So that the high-speed neutron beam is elastically scattered and absorbed at the same time.

Particularly, the fine aggregate may be composed of 75 ~ 85% of steel making slag and 15 ~ 20% of high density polyethylene with respect to the weight of fine aggregate. In case of less than 15% of high density polyethylene, shielding effect of gamma ray and neutron beam is insufficient, It is preferable to mix high-density polyethylene in the range of 15 to 20%, since it does not rub well when mixed as a concrete composition.

[Reference Figure 3]

Referring to FIG. 3, it can be seen from the diagram that the flowability of the high density polyethylene is rapidly lowered when 20% or more of the high-density polyethylene is substituted, thereby making the concrete beam difficult.

Tests were carried out on the concrete composition of the present invention with respect to the shielding of the neutron beam and the? -Ray.

(1) Formulation of concrete composition

[Table 3]

[Table 4]

The comparative test was conducted using 10 types of blend as shown in [Table 3] and [Table 4] above. Formulation Nos. 1 to 8 contain 100% Portland cement as a cement, and 9 and 10 generally use Portland Cement (OPC): blast furnace slag fine powder (BFS) : Fly ash (FA): paraffin (Pa) was used in a ratio of 4: 4: 1: 1.

(2) γ ray shielding test

For γ ray shielding test, 300 × 300 × 5100 mm specimen shall be prepared and cured for 28 days at standard age. The dose can be measured using the Harwell Amber perspex Dosimeter, Batch VType 3042 from Harwell, UK. The shielding rate can be calculated from the irradiation dose of γ rays generated from the irradiation source (Co-60 Activity 360, 576Ci, average energy 1.25 MeV) The amount of γ-ray leakage detected by the detector, which is 3.25m away from the source, is divided into the case with and without the shield, and the ratio is calculated.

In particular, the breaking performance were verified by measuring the gamma dose installed transmitted through the test piece produced in front of the radiation-isotope ¹³⁷ C (cesium 137) source.

(3) Neutron Shielding Test

The neutron shielding test was carried out in accordance with KRISS calibration procedure C-26-4-0102 after standard curing for 28 days at the age of 300 × 300 × 1050 mm specimen.

① Neutron dose equivalent from the neutron source is installed at a distance of 1.5m and neutron dose equivalent (Model: LB6411) is installed to measure the neutron dose equivalent.

② Place the test sample in front of the neutron dose equivalent system and measure the equivalence of the neutron dose.

(3) To measure the effect of scattered neutrons, the same measurements as (1) and (2) were repeated after the shadow corn was installed, and the value obtained by subtracting the measured value was corrected by considering the scattered neutron effect.

Particularly, the evaluation of neutron source which is the most difficult to block was verified by using ²⁵² Cf (californium 252) element of colloidal silicon.

(4) Experimental results

In order to confirm the effect of the present invention, this experiment was conducted on the neutron beam, and tests were conducted on the numbers 1, 2, 5 and 6 in relation to the gamma ray.

[Table 5]

The results of tests No. 2, No. 5 and No. 6 corresponding to the concrete composition of the present invention show that the unit volume is higher than that of No. 1 (plain). Compression No. 2 containing high density polyethylene powder was found to have a higher compressive strength than that of No. 1 at the third day, and the strength at 7 days and 28 days is also within the effective range as compared with the first compressive strength.

Therefore, unlike other mixing conditions in which manganese slag, reduced slag, lecturer, etc. are mixed, the concrete composition of the present invention shows relatively high shielding ratio of gamma rays and neutrons without deteriorating the performance of the concrete itself.

Considering that the radiation shielding rate of the concrete sharply decreases when the unit volume weight, that is, the density, of the concrete exceeds 2.27 (g / cm ³ ) as in the above [Reference Fig. 1] And the density of No. 5 and No. 6 is higher than 2.4 (g / cm ³ ).

In addition, the radiation transmittance is exponentially decreased according to the thickness of the concrete. Based on the theory that the radiation dose rate decreases exponentially with the thickness of the concrete, the following formula [3] The shielding rate is calculated as follows.

[Formula 3]

Shielding rate = 1-e ^{(-μ x X)}

μ: coefficient according to concrete unit weight (0.117118 for neutron and 0.186433 for gamma ray)

X: Concrete thickness

[Table 6]

[Table 6] is a table showing the radiation shielding ratio of each concrete thickness based on the experimental result of the present invention by the above-mentioned [Equation 3]. According to the present invention, when the thickness of the concrete specimen is 10 cm, the thickness of the concrete is different from that of the concrete specimen. When the thickness of the concrete is 15 cm, the gamma ray is shielded by 90% or more. Shielding ratio. In particular, when the thickness of the concrete specimen is 25 cm, the shielding rate of the gamma ray reaches 99%. In contrast, in the case of general concrete, a blocking ratio of 99% can be secured only when the specimen thickness is 50 cm or more. It can be confirmed that a high shielding ratio is secured.

Generally, lead-free drywall is composed of 2mm thick lead, 4 gypsum boards and insulation (total thickness 160mm). In this case, existing technology that shows about 25% of gamma ray shielding performance, Compared with the shielded concrete developed as a method for reusing the used CRT glass, the radiation transmittance is less than 1% at a thickness of 50 cm, the present invention exhibits a gamma ray shielding performance of 85% even in a 10 cm thick concrete, , The gamma ray shielding rate of 99% is already noticeable.

In addition, the shielding effect of the neutron beam is already over 90% when the concrete specimen thickness is 20cm, 94% when it is 25cm, and 99% of the shielding rate is already calculated at 40cm. The concrete composition of the present invention can be used for installation of shielding walls of 25 to 40 cm in various facilities for radiation shielding.

The radiation shielding concrete composition according to the present invention has been described above with reference to concrete examples. However, modifications and variations falling within the scope of the present invention are possible in addition to the above embodiments. Accordingly, the claims of the present invention include modifications and variations that fall within the true scope of the present invention.

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Claims (4)

A concrete composition comprising water, a binder, a coarse aggregate and a fine aggregate so that a gamma ray shielding rate of 99% or more and a neutron shielding rate of 94% or more are secured when the wall thickness is 25 to 40 cm,
Wherein the fine aggregate comprises 80 to 85 wt% steel making slag (SS) and 15 to 20 wt% high density polyethylene (HDPE).
delete The method of claim 1,
Wherein the high-density polyethylene is at least one of a powder type and a bead type.
The method of claim 1,
In the coarse aggregate,
Wherein all or a part of the slag is steel-making slag.