KR20090010591A

KR20090010591A - Radioactive ray shield

Info

Publication number: KR20090010591A
Application number: KR1020070073838A
Authority: KR
Inventors: 지상협
Original assignee: 지상협
Priority date: 2007-07-24
Filing date: 2007-07-24
Publication date: 2009-01-30

Abstract

A radiation shielding material capable of improving feeling of wearing of shielding garment by removing lead component is provided to expand selection range by controlling thickness of a neutron shielding layer and a non-permeability resin layer according to radiation neutron energy strength. A radiation shielding material comprises a first and a second radiation shielding layers(1) and a neutron shielding layer(2). The first and the second radiation shielding layers are made of polyolefin resin including polyolefin resin or inorganic material. The neutron shielding layer is a gel type sheet. The sheet is formed through mixing/extrusion/foaming thermoplastic polyolefin of 100 weight%, foam of 0.1~10 weight%, sub foam and sub cross-linking agent of 0.5~50 weight%. A meshed air bubble is formed through an extension of the sheet. The sheet having the meshed air bubble structure is dipped into melting paraffin, and is sealed between non-permeability resin layers.

Description

Radiation shield {radioactive ray shield}

Places where there is a lot of radiation, or where there is a lot of radiation, for example, those working in the radiation zones of nuclear power plants or in industrial sites handling radiation transmission test equipment are always at risk of exposure to radiation.

It is well known that radiation, such as x-rays and gamma rays, causes many serious diseases and disorders, including carcinogenesis, genetic disorders, and cataracts. Accordingly, in 1934, the International Commission on Radiation Protection was launched to limit the use of radiation (0.2 R / day), and in 1977 the International Recommendation on Radiation Protection (ICRP-26) was adopted, followed by X-ray diagnosis, treatment and nuclear Guidelines for reducing the exposure of patients, workers and carers to medicine have been published, and countries have enacted laws on the use of radiation.

As such, exposure to radiation is very harmful to the human body, so it should be made as limited as possible. However, people who directly or indirectly deal with radiation, such as radiologists, doctors, and nuclear power personnel in hospitals, may be exposed to radiation continuously because of their work characteristics. Should be

Therefore, in order to protect the workforce when working in places with high radiation such as repair or inspection of nuclear power plants, radiation shielding suits are worn to protect from the danger of exposure.

The present invention relates to a shield for preventing radiation exposure as above.

As a method for shielding the radiation exposure, it is common to wear a sheet-like gown formed by dispersing lead components in a rubber and then extruding them. However, gowns made in this way are effective for radiation shielding, but are very heavy, such as 5-10 kg, and have a poor fit.

As a lighter shielding suit, US Patent No. 3,194,239 discloses a method of manufacturing radiation absorbing fibers using an alloy wire for radiation absorption, but this has a problem of poor flexibility and radiation shielding properties.

On the other hand, a method for shielding the neutron is also used by filling the jacket with water, but the water is concentrated down, the thickness of the jacket is not uniform, there is a risk of water leakage, it was inconvenient to wear.

Conventionally, workers have been exposed to radiation exposures more than necessary because they have not been able to develop work clothes necessary for shielding radiation workers from nuclear power plants or nuclear facilities.

Since neutrons have a wide energy distribution (O.OleV ~ 1000MeV) from thermal neutrons to genus neutrons, it is difficult to shield them.When selecting a shield, the neutron must select the type of shield depending on the conditions. When it hits the concrete wall, it protrudes again (Albed phenomenon), so the lead and concrete walls did not have a great effect on shielding.

The present invention is to prevent radiation and / or neutron exposure by providing a radiation shielding material injected with paraffin during the maintenance work and work of the radiation neutron generating zone in a nuclear power plant or nuclear facilities.

The present invention is to solve the above problems, by using a polyolefin resin and a blowing agent to prepare a sheet formed with fine and uniform pores, injecting paraffin oil into the sheet and interposed between the impermeable polyolefin resin to form a neutron shielding layer It is. The neutron shielding layer is sealed between the impermeable polyolefin resin layers to prevent leakage of oil. In the present invention, the radiation shielding material may increase the selection width by adjusting the thicknesses of the neutron shielding layer and the impermeable resin layer according to the radiation neutron energy intensity.

Specifically,

The present invention is the first impermeable resin layer (1); Neutron shielding layer 2; And a second impermeable resin layer 1,

The first and second impermeable resin layers are composed of a polyolefin resin or a polyolefin resin containing an inorganic material,

The neutron shielding layer is mixed with 0.1 to 10 parts by weight of a blowing agent, 0.5 to 50 parts by weight of a foaming aid and a crosslinking aid with respect to 100 parts by weight of thermoplastic polyolefin, and foamed after extrusion to prepare a sheet, and the sheet is stretched to form network pores. After the molten paraffin is injected / impregnated and interposed between the first and second impermeable resin layers, the sheet is characterized in that the porosity is 30 to 90%.

In addition, the present invention is characterized in that the impermeable resin layer is a polyolefin resin containing at least one or more elements of gadolinium, boron, lithium having an average particle size of less than 10㎛ diameter.

It is possible to prevent neutron exposure of equipment operation and maintenance workers by radiation workers occurring during operation of nuclear power plants or nuclear facilities, and to secure safety for nuclear workers by reducing health hazards.

Detailed embodiments of the invention are disclosed herein. It should be understood, however, that the disclosed embodiments may be practiced in various forms only as illustrations of the invention. Accordingly, the detailed description disclosed herein should not be construed as limiting, but merely as a basis for teaching those skilled in the art to the basis of the claims and how to make and / or use the invention.

The thermoplastic polyolefin of the present invention is a crystalline homopolymer or copolymer obtained by polymerizing ethylene, propylene, 1-butene, 4-methylpentene, 1hexene, and the like, and polyolefins such as copolymers thereof, vinyl chloride resin, vinyl acetate resin, and polystyrene. , Fluorine resin, polyamide resin, polyacetal resin, polycarbonate, thermoplastic polyimide, thermoplastic polyurethane, polyphenylene salpide, polyvinyl alcohol and the like. Among these, polyolefins, such as polyethylene and a polypropylene, are preferable from a moldability and economical viewpoint.

Specifically, the neutron shielding layer 2 of the present invention is prepared by impregnating a solvent in a polyolefin resin in which pores are formed using a blowing agent, and in this case, any solvent can be used as long as it has a neutron shielding ability. Volatile solvents are preferred.

As the blowing agent, a decomposition type is used. Specific examples thereof include azodicarbonamide, azodicarboxylic acid metal salt, dinitrosopentamethylenetetramine, hydrazodicarbonamide, p-toluene sulfonyl semicarbazide, s-trihydrazinotriazine, and the like. have.

The addition amount of these blowing agents is about 0.1-10 weight part with respect to 100 weight part of thermoplastic resins normally. In addition, in order to adjust the decomposition behavior of the blowing agent, a foaming aid or a crosslinking aid for adjusting the bubble size can be appropriately added. The addition amount of the said foaming aid and crosslinking adjuvant is about 0.5-50 weight part with respect to 100 weight part of thermoplastic resins normally.

By adding a blowing agent to the thermoplastic resin to form bubbles, in addition to the method of extruding the die temperature above the decomposition temperature of the blowing agent, for example, by heating under pressure in a mold to decompose the blowing agent, decompressing and expanding, After molding in the mold, take out, reheat and cause decomposition to cause expansion. In addition, in order to maintain the bubble shape of the thermoplastic foam, it is preferable to crosslink the resin. As a crosslinking method, the method of using chemical crosslinking agents, such as an organic peroxide, and the method of irradiating radiation, such as an electron beam, can be used.

The macro formation of bubbles by the above-described methods can take various forms under the formation method and the molding conditions. Any of the bubbles may be an independent closed type, an open type connected to each other, or a mixed type thereof. Among these, a close type is preferable.

In addition, although the boundary of foam | bubble may be any of surface shape, columnar shape, or fiber shape, a surface shape is especially preferable. As the microstructure constituting the boundary of the bubble, any one of the polymer lamellar crystals or the laminate thereof is grown in one dimension in a fibrous or columnar shape, in two-dimensional growth in a planar shape, or in three-dimensional growth in a spherical shape. It may be made.

It is preferable that the porosity of the gel-like sheet after foaming is 30 to 90%. If the porosity is less than 30%, the radiation shielding effect is inferior. If the porosity is 90% or more, the durability of the sheet is deteriorated.

In the present invention, it is necessary to break the bubble boundary of the bubble. The foam boundary itself plastically deforms by applying a tensile stress exceeding an internal bubble shape deformation or a compressive stress and then applying a tensile stress to the foam. Specifically, the film is drawn after stretching or stretching. Stretching is performed at a predetermined magnification by the usual tenter method, roll method, inflation method, rolling method, or a combination of these methods.

The bubble boundary is broken as described above, the sheet having the network pore structure is impregnated in the molten paraffin and interposed between the impermeable polyolefin resin, and the adhesion between the sheet and the impermeable resin layer uses a conventional bonding method. The sheet sealed with an impermeable resin layer is cooled to below the melting point (47-65 ° C.) of the paraffin to solidify the paraffin to prepare a neutron shielding layer.

Hereinafter, the present invention will be described using specific examples.

High Density Polyethylene (HDPE) Density 0.955g / cm ³ , Melt Index (MI, 190 ° C, 2.16Kg Load) 9g / 10min 90 parts by weight with Polybutene-1 (PB-1) (M8340, Mitsui Sekiyu Chemical Industries Azodicarbonamide (Aiwa Kagaku Co., Ltd.) as a foaming agent with respect to 100 weight part of resin components which mix | blended 10g weight part of 4 g / 10min (O) Ltd. melt index (MI, 190 degreeC, 2.16Kg load) 5 parts by weight, 1.0 parts by weight of trimethol propane trimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.), 1.0 parts by weight of antioxidant, and a Henschel mixer at 30 ° C, After mixing for 2 minutes at 500 rpm, it was fed to an extruder having a T die of 50 mm phi and length / diameter (L / D) = 28, extruded at an extrusion temperature of 150 deg. C, and a sheet having a thickness of 1 mm was prepared.

Next, the sheet was irradiated with an electron beam of 750 KV at a dose of 8 Mrad and crosslinked. Thereafter, the foaming agent was decomposed in a 250 ° C. air oven for 1.0 minute and foamed about 5 times. The apparent density after foaming was 0.19 g / cm ² .

As a result of observing the cross section of this sheet with a scanning electron microscope, it turned out that the foam which the polymer composition comprises a bubble boundary is formed. In addition, as a result of observing a very thinly sliced piece of this sample wrapped with an epoxy resin with a transmission electron microscope, it was found that the microstructure of the bubble boundary consisted of a spherical crystal. This pore size was 28.2 μm and the space ratio was 80.1%.

Next, the sheet was stretched 3 × 3 times to break the bubble boundary to form a sheet having a thickness of 1.8 mm to 5 mm. Melt paraffin is injected / impregnated into a sheet having a network structure by breaking up the bubble boundary on the pressure reducing conveyor belt to prepare a sheet impregnated with oil, and interposed between the impermeable polyethylene resin layers 1 on a cooling roll at 20 ° C. The neutron shielding layer 2 of the form which solidified paraffin was produced.

The impermeable polyethylene resin was used in thicknesses from 0.2 mm to 10 mm. The impermeable resin is for preventing leakage of oil or the like from the neutron shielding layer.

In this case, the impermeable resin may include at least one element of polyolefin resin or gadolinium, boron, lithium having an average particle size of less than 10 μm, in particular less than 5 μm in diameter. Substances containing the above elements include gadolinium oxide Gd ₂ O ₃ , gadolinium gallium and garnet Gd ₃ Ga ₅ O ₁₂ , gadolinium ferrite GdFeO ₃ , Gd ₃ Fe ₅ O ₁₂ , gadolinium hydroxide Gd (OH) ₃ , and cerium Activated gadolinium silicate Gd ₂ SiO ₅ : Ce, europium activated borate Gadolinium GdBO ₃ : Eu, europium activated gadolinium oxide Gd ₂ O ₃ : Eu, europium activated gadolinium sulfate Gd ₂ O ₂ S : Eu, europium-activated gadolinium Gd ₃ Al ₅ O ₁₂ : Eu, europium-activated gallium acid gadolinium Gd ₃ Ga ₅ O ₁₂ : Eu, europium-activated vanadium acid gadolinium GdVO ₄ : Eu And gallium gadolinium Gd ₃ Ga ₅ O ₁₂ : Ce, Cr, terbium-activated gadolinium oxide Gd ₂ O ₃ : Tb, terbium-activated gadolinium sulfate Gd ₂ O ₂ S: Tb, Gadolinium Sulfate Gd ₂ O ₂ S Activated with Furaseom: Pr, terbium-activated gallium gadolinium Gd ₃ Ga ₅ O ₁₂ : Tb, terbium-activated gadolinium Gd ₃ Al ₅ O ₁₂ : Tb, boron carbide B ₄ C, boron nitride BN, boron phosphide BP, boron sulfide B ₂ S ₃ , boron phosphate BPO ₄ , boron oxide B ₂ O ₃ , lithium oxide Li ₂ O, lithium peroxide Li ₂ O ₂ , lithium aluminate LiAlO ₂ , lithium metaborate LiBO ₂ , lithium tetraborate Li ₂ B ₄ O ₇ , Lithium germanium Li ₂ GeO ₃ , lithium molybdate Li ₂ MoO ₄ , lithium niobate LiNbO ₃ , lithium metasilicate Li ₂ SiO ₃ , lithium titanate LiTaO ₃ , lithium titanate Li ₂ TiO ₃ , lithium vanadate LiVO ₃ , lithium tungstate LiWO ₄ , lithium zirconate Li ₂ ZrO ₃ , lithium nitride Li ₃ N, lithium hydroxide LiOH.H ₂ O, methoxy lithium LiOCH ₃ .

It is the result of the shielding test performed with the shielding material manufactured by this invention. A neutron beam outlet of a certain size was made, and a detector capable of measuring the intensity of the neutron was placed at a certain distance (5 cm) from the outlet, and the intensity of the neutron penetrating the shielding material was measured. At this time, it measured with the detector, changing the thickness of a shielding material. The measured intensity was calculated as the neutron absorption cross-sectional area factor.

The method of calculating the neutron absorption cross section coefficient is as follows.

I / I ₀ = L ^-μx or μ = [log (I ₀ / I)] / x

(I ₀ : incident beam, I: transmission beam, x: transmission thickness, μ: suction area coefficient)

Test result

Thickness (cm) count μ (cm ^-1 ) 0.3 30,149 7.042 0.4 16,347 6,911 0.5 9,033 6.812 0.7 3,356 6.624 1.0 1,579 6.533 1.5 615 5.318 2.0 471 4.239 2.5 395 3.582

The reason why the radiation shielding material with uniform pores increases the radiation shielding ability compared to the non-porous phase is not known exactly. However, the shielding effect appears to increase due to energy attenuation due to scattering of radiation in the voids.

1 is a cross-sectional view for explaining the structure of the radiation shielding material of the present invention.

Figure 2 is a cross-sectional view for explaining the pore structure of the radiation shielding material of the present invention.

* Explanation of reference marks *

A: pore B: polyolefin resin layer

Claims

1st impermeable resin layer 1;

Neutron shielding layer 2; And

It is comprised by the 2nd impermeable resin layer 1,

The neutron shielding layer is mixed with 0.1 to 10 parts by weight of a blowing agent, 0.5 to 50 parts by weight of a foaming aid and a crosslinking aid with respect to 100 parts by weight of a thermoplastic polyolefin, and foamed after extrusion to prepare a sheet, and the sheet is stretched to form network pores. And then impregnated / cooled in molten paraffin and sealed between the impermeable resin layers, wherein the sheet has a porosity of 30 to 90%.

The radiation shielding material according to claim 1, wherein the impermeable resin layer is a polyolefin resin containing at least one element of gadolinium, boron and lithium having an average particle size of less than 10 µm in diameter.