KR100910260B1 - A Method of Reinforce of Radiation Shilding Ability by the way of Shilding the Low Energy Photons - Google Patents

Abstract

The present invention relates to supplementing the shielding performance of the shielding wall inside the 'nuclear power facility', which is currently being used and used, and in particular, a radiation worker required by the revised nuclear energy law, with an emphasis on low-energy radiation shielding such as scattered radiation and characteristic X-rays. It is a low-cost shielding technology to satisfy the dose limit of the product, and it provides technology that complements the shielding performance of the shielding wall by using plastering and masonry, based on barite, which is harmless to the human body and easily available.

Scattered radiation, characteristic X-rays, shielding, barite (BaSO4), plastering, masonry

Description

A method of reinforce of Radiation Shilding Ability by the way of Shilding the Low Energy Photons}

1 is a block diagram for easily explaining the present invention.

2 is a diagram for explaining the principle of generating characteristic X-rays by scattered radiation and photoelectric effect due to interaction between radiation and materials

3 is a diagram showing that low-energy electromagnetic radiation is particularly dangerous to bones among human body components.

FIG. 4 is a diagram showing that the shielding effect in the low energy region is increased when the shield is composed of a material having a large atomic number even if the shield is the same density.

FIG. 5 is a diagram showing that the spatial dose rate is increased when the space dose rate due to the radiation of the same flux density is 0.08 mega electron volt as the minimum point, and is increased or decreased based on this.

FIG. 6 is a diagram showing that the exposure amount due to low energy radiation such as scattered radiation and characteristic X-rays is increased when the space is shielded by a shield.

7 is a concave-convex shielding brick for use when a large amount of radiation is leaked and sufficient shielding is not realized only by simple plastering work using shielding mortar.

The present invention relates to a shielding mortar using barite (BaSO4, specific gravity: 4.48) as a substitute for sand and a concave-convex shielding brick using the same for supplementing shielding performance of a shielding wall in a 'nuclear power facility'.

Radiation shielding technology in the law means' nuclear reactor ',' fuel cycle facility ',' nuclear material use facility ',' radioactive isotope use facility ',' radiation generating device use facility ',' Technology applied to the design of shielding walls for 'radioactive waste treatment and storage facilities' and 'related facilities'. These facilities are already designed for shielding in the early stages of construction, so You can think that no serious problems will occur. However, due to the recent amendment of the Atomic Energy Act, as recommended by the International Commission on Radiological Protection, from January 1, 2003, the annual exposure dose limit for radiation workers working at nuclear facilities is from 50 milliverts (mSv) to 20 milliverts. As a result of the lowering, there is a problem of compensating the shielding performance of the barrier against these facilities in use. In the existing 'nuclear power facility', the area that needs reinforcement of shielding is mainly used facility that frequents workers' access, so the specific gravity composed of 'lead plate', 'lead brick' or 'steel and cement' currently on the market is about 3.5 In the case of supplementing the shielding performance with 'high density shielding brick', it may be said that there is a problem in safety such as fear of damage to the shield due to expansion due to harmful lead and oxidation. Therefore, in order to supplement the shielding performance of the shielding wall of the existing 'nuclear power facility' due to the revision of the Atomic Energy Act, it is necessary to introduce a new technology that can achieve the desired purpose while maintaining the safety of the human body and physically. have.

The technical problem to be solved by the present invention is to find out which area of the radiation generated in the 'nuclear power facility' which is currently in operation, which radiation has a high contribution rate to the exposure dose, and the radiation shielding for the energy section. The ability is to find a stable form of ceramic material that is excellent and readily available in nature. Through this, it is possible to maximize the shielding effect from the point of view of the radiation dose to the radiation worker and to develop a shielding technology that is convenient to use.

Radiation in the energy region with a high contribution to the exposure dose among the radiations generated at the 'nuclear power facility' currently in operation can be referred to as scattered radiation and characteristic X-rays in the 0.01 to 0.1 mega electron volt (MeV) region. . The reason for this is that ① the energy range of scattered radiation and characteristic X-rays (Fig. 2) emitted by increasing the thickness and density of the shielding wall is 0.1 mega electron volt or less, and ② radiation in this energy region is applied to the bones that make up the human body. The risk is about 4 times higher than that in the high energy range (Fig. 3), but it is easy to shield (Fig. 4), and the flux density of radiation that generates a spatial dose rate of 10 microsieverts (μSv) is low energy at high energy. It tends to increase as it goes down, but when it goes down to the area with 0.08 mega electron volt as the highest point, it decreases inversely and contributes to the increase in dose rate (Fig. 5). This is because the exposure by X-ray takes up a large part of the total exposure dose (Fig. 6). Also, as shown in Table 1, nuclear fission products and the industry And radioisotopes that emit low energy used by the medical community.

Nuclear fission products and other radioisotopes that emit low-energy radiation Nuclide Half-life Fission generation ratio Energy (KeV) Remarks Nuclide Half-life Emission Ratio (%) Energy (KeV) Remarks Kr-85m 4.4h 0.0133 151 γ-ray Tc-99m 6.02h 89 141 γ-ray kr-85 10.76y 0.00285 2.11 " Co-50 270d 86 122 " Xe-133m 2.26d - 326 " Tl-201 3.044 46 70.8 X-ray, K Xe-133 5.27d 0.0677 30 " " " 47 10 X-ray, L

Barite (BaSO4, specific gravity: 4.3 ~ 4.7), which is not harmful to the human body, is not corroded by oxidation like iron, and is easily available among metal oxides with high atomic number and density, was selected as the main raw material. After molding by mixing gypsum and sodium silicate binder, the shielding performance of scattered radiation and characteristic X-rays in the range of 0.01 to 0.1 mega electron volt was examined. For reference, barite is a colorless, tasteless, odorless and stable substance with a melting point of 1,600 ° C, which is widely distributed in nature. The main ingredient, barium sulfate, is a safe substance used as an internal medicine for X-ray imaging of organs in a hospital.

In order to compare the performances of the shielding bricks composed mainly of barite and the existing iron-based shielding bricks according to the present invention, the energy absorption coefficients and shielding relations of the previously published radiations were applied at 0.02. The shielding effect calculation results in the range of 0.10 mega electron volt are classified into 'Inventive solids', 'High density shielding bricks' and 'General concrete', and are listed in Table 2.
Comparison of Shielding Performance by Solid Formation for Low Energy Radiation and X-rays (Reference: Nuclear Engineering VOL.28 No.5 1982) division Density (g / cm 3) Thickness (mm) Shielding effect by energy (MeV) of radiation (%) 0.02 0.03 0.03 0.05 0.06 0.07 0.08 0.09 0.10 The present invention solid (main ingredient: barite) 3.0 3 100 100 100 86 75 63 50 39 32 50 100 100 100 100 100 100 100 100 100 High Density Shielding Brick (Main ingredient: Iron) 3.5 3 100 99 86 68 63 53 41 35 29 50 100 100 100 100 100 100 100 99 98 General Concrete (Main Ingredient: Sand) 2.3 3 79 56 34 24 18 16 14 13 12 50 100 100 99 95 89 85 79 77 74

Shielding mortar for applying the present invention, barium (Ba-137) is added, which has a lower density but higher photoelectric effect than iron (Fe-56), which is the main raw material of the existing 'high density shielding brick' As the main barite is used as the main raw material, the 'inventive solidified body', which has a density of 3.0, has a shielding performance, compared to the existing 'high density shielding brick,' which is composed of iron with a density of 3.5, as shown in Table 2. It can be seen that it is excellent in terms of, and specifically, when the shielding thickness is 3mm construction, it can be seen that the shielding performance of the present invention solids is 1% to 21% higher than the 'high density shielding brick'. However, when the 50mm thickness is applied, the present invention solids and high density shielding bricks can be almost completely shielded against radiation in the range of 0.02 to 0.10 mega electron volts, but at 0.10 mega electron volts. It was confirmed that about 2% difference appeared. Of course, these calculations are based on theory and may vary depending on the measurement and the error of solidification. When supplementing the shielding wall for the 'nuclear power facility', the shielding mortar corresponding to the present invention may be immersed in water and applied to the existing shielding wall surface in the form of a plastering operation. It is possible to use a method of construction with the uneven shield brick (Fig. 7).

Embodiments for using the present invention in the field of the 'nuclear facility' are as follows, the present invention is not limited thereto. The manufacturing process of the shielding mortar using the barite (BaSO4) and the binder as the main raw material or the step of the uneven shielding brick using the same, and the step of overlaying the existing shielding wall in the form of plastering or attaching it in parallel with the shielding wall and stacking it in the form of masonry Complement the shielding performance through, but if it is enough to apply only 1mm to 5mm to the existing shielding wall, prepare a shielding mortar mixed with a cement ratio of 50 to 80 weight ratio cement 20 to 50 weight ratio binder, and then water 10 To 40 weight ratio is added and it mixes uniformly, and is used. If more shielding is required, mortar composed of 50 to 80 weight ratio of barite powder and 20 to 50 weight ratio of cement, or 50 to 70 weight ratio of barite powder, 10 to 30 weight ratio of gypsum, 10 to 30 weight ratio of sodium silicate, and 10 to 30 weight ratio of cement The binders are mixed, but the mixture is mixed with 10 to 40 parts by weight of water in a mortar mixed so that the total weight ratio of each component does not exceed 100. Then, the mixture is poured into a molding mold to produce a solid in the form of 'Fig. 7'. do.

In order to solidify the barite powder, in the present invention, gypsum, sodium silicate and cement were used alone or as a mixture, and insoluble calcium silicate hydrate was obtained when a mixture of gypsum (CaSO4) and sodium silicate (Na2nSiO2xH2O) was used as the binder. The resulting principle was described by chemical reaction.

As a result of analyzing the shielding effect when applying the shield fabricated as described above to the 'nuclear power facility', as shown in 'Table 2', the radiation of 0.02 to 0.10 mega electron volt region is generated by the 5 cm-thick 'inventive solids'. As it can be seen that 100% shielding is performed, a radiation worker working at a workplace constructed with an existing shielded wall designed based on the annual allowable exposure dose of 50 milli-sieverts is 50 millimeters per year through the exposure path as shown in Figure 6. Assuming that the Sibert is exposed, and also 80% of the total dose is due to scattered radiation and characteristic X-rays, of which 75% represents an energy range of 0.01 to 0.10 mega electron volts showing 100% shielding performance by the present invention solids. Assuming that is at, it is possible to shield radiation equivalent to 30 milliverts (50 * 0.8 * 0.75), resulting in 20 milliverts corresponding to the revised annual allowable dose. It can be concluded that the possible. This result, of course, corresponds to the assumptions made in the assumptions to simplify the calculations, so the results may vary with varying conditions in the field.

 Due to the use of the present invention, using a raw material that is harmless to the human body, physicochemically stable, and easily available, supplements the shielding performance of the shielding wall for the existing 'nuclear facility' by simple methods such as plastering and masonry. This allows the radiation dose to radiation workers to be maintained within the dose limits set by the revised nuclear law.

Claims (4)

In the method of reinforcing shielding performance for 'nuclear power facility', 50 to 80 weight ratio of barite (BaSO4) powder is added to 20 to 50 weight ratio of cement uniformly mixed to make a shielding mortar, uniformly mixed (Mixing) by adding water to the shielding mortar 10 to 40 weight ratio Shielding performance reinforcement method for 'nuclear power facility', characterized by hardening by coating the shielding wall in the form of plastering In the method of reinforcing shielding performance for the 'nuclear power facility', the step of uniformly mixing 10-30 weight ratio of gypsum, 10-30 weight ratio of sodium silicate, and 10-30 weight ratio of cement to 50-70 weight ratio of barite powder, water to the mixture 10 to 40 weight ratio is added to mix uniformly and then poured into a molding mold to produce a concave-convex shielding brick, attaching the concave-convex shielding brick in parallel with the shielding wall and stacked in the form of 'nuclear power facility, characterized in that Method for reinforcing shielding performance Mortar for reinforcing the shielding performance of claim 1, the mortar for shielding, characterized in that evenly mixed by adding 50 to 80% by weight of the cement corresponding to the binder to 50 to 80% by weight of barite powder. In the concave-convex shielding brick used for reinforcing the shielding performance of claim 2, a binder corresponding to 50 to 70 weight ratio of barite powder, 10 to 30 weight ratio of gypsum, 10 to 30 weight ratio of sodium silicate, and 10 to 30 weight ratio of cement is uniformly mixed. After the addition of 10 to 40 weight ratio of water and then evenly mixed and then poured into a molding mold for uneven shielding brick

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