KR102711902B1 - Neutron and radiation shielding sheet, and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a neutron and proton shielding sheet and a method for manufacturing the same, and more particularly, to a sheet comprising a polymer binder and a filler, wherein the filler is a nanoparticle having a particle size of 40 to 1000 nm and comprises a boron compound and zinc borate. According to the present invention, the shielding effect for neutrons as well as protons is excellent, and since it can be manufactured into various shapes, it has the advantage of being usable as a film-type shielding material for protecting electronic products such as semiconductors as well as the nuclear power industry.

Description

Neutron and proton shielding sheet, and manufacturing method thereof {NEUTRON AND RADIATION SHIELDING SHEET, AND MANUFACTURING METHOD THEREOF}

The present invention relates to a neutron and proton shielding sheet and a method for manufacturing the same, and more particularly, to a neutron and proton shielding sheet having excellent neutron and proton shielding efficiency and excellent processability, thereby being capable of being manufactured into various shapes, and a method for manufacturing the same.

Nuclear reactors produce a large amount of radioactive elements. The areas where radiation exposure due to such radioactive materials can occur are divided into two systems, as shown in Figure 1. The primary system, which is the core area of the reactor, has very high levels of gamma ray and neutron ray emissions.

Gamma rays and neutron rays have completely different shielding methods. While gamma rays must be shielded using high-density lead, tungsten, bismuth, etc., neutron rays are shielded using materials made of elements such as hydrogen, boron, and carbon. That is, the neutron is absorbed by boron, and in order for boron to absorb the neutron, the neutron needs to be slowed down. Hydrogen is known to be the optimal material for slowing down neutrons, as hydrogen atoms collide with high-speed neutrons among neutrons and absorb energy, effectively slowing down neutrons. Therefore, neutron shielding can be more effective the more hydrogen and boron it contains.

Therefore, conventionally, neutron shielding is done by stacking HDPE blocks or block-shaped water tanks containing up to 20 to 30 wt% boron content to shield neutron rays.

However, these installations required a lot of time and manpower, and had the disadvantage of not being able to be utilized in appropriate locations or in various forms.

Meanwhile, cosmic radiation is divided into high-energy radiation generated outside the Earth and secondary radiation generated when that radiation collides with the Earth's atmosphere. Depending on the cause of generation, it is divided into galactic cosmic radiation (GCR) and solar cosmic radiation (SCR) generated by sunspot activity on the Sun.

Recently, interest in such cosmic radiation has been increasing. This is because the semiconductor industry is increasingly interested in minimizing the effects of external radiation on semiconductors as the standards for semiconductors in Part 11 of the ISO 26262:2018 (2ed) automotive electronic components standard have been strengthened, requiring evaluation of radiation impact tests on semiconductor reliability.

KR 10-2014-0032786 A KR 10-2122993 B1 KR 10-1589692 B1

Accordingly, the purpose of the present invention is to provide a neutron and proton shielding sheet having excellent neutron and proton shielding effects and being capable of being processed into a sheet form and thus being capable of being manufactured into various shapes, and a method for manufacturing the same.

Another object of the present invention is to provide a neutron and proton shielding sheet having excellent processability and usable as a film-type shielding material for protecting electronic products such as semiconductors as well as the nuclear power industry requiring shielding of neutrons and protons, and a method for manufacturing the same.

The neutron and proton shielding sheet of the present invention for achieving the above-mentioned purpose comprises a polymer binder and a filler, wherein the filler is a nanoparticle having a particle diameter of 40 to 1000 nm and comprises a boron compound and zinc borate.

The above polymer binder is characterized by being at least one of ethylene propylene rubber (EPDM), neoprene, chloroprene rubber (CR), natural rubber (NR), styrene butadiene rubber (SBR), nitrile rubber (NBR), urethane resin, ethylene vinyl acetate copolymer (EVA), and polyethylene (PE).

The above boron compound is characterized in that it is at least one of boron carbide (B ₄ C), boron oxide (B ₂ O ₃ ), and boric acid.

The above filler is characterized in that it further comprises boron-doped graphene oxide.

The above filler is surface-treated with a fatty acid, and the fatty acid is characterized by being at least one of oleic acid and stearic acid.

The above filler is characterized in that it further contains pentaerythritol.

The above sheet is characterized by a thickness of 0.5 to 3 mm.

The method for manufacturing a neutron and proton shielding sheet according to the present invention is characterized by including the steps of: sintering a filler including a boron compound and zinc borate at 200 to 350°C to remove crystal water; milling the filler from which the crystal water has been removed to manufacture nanoparticles having a size of 40 to 1000 nm; adding a fatty acid as a surfactant to treat the surface of the nanoparticles; mixing the surface-treated nanoparticles with a polymer binder; extruding and rolling the mixed mixture to form a sheet; and vulcanizing the formed sheet.

The above filler is characterized in that it further comprises boron-doped graphene oxide.

The above filler is characterized in that it further contains pentaerythritol.

The above fatty acid is characterized in that it is at least one of oleic acid and stearic acid.

The thickness of the above-mentioned molded sheet is characterized by being 0.5 to 3 mm.

According to the present invention, there is an advantage in that it has an excellent shielding effect for protons as well as neutrons, and can be manufactured in various forms, so that it can be used as a film-type shielding material for protecting electronic products such as semiconductors as well as the nuclear power industry.

Figure 1 is a diagram showing the system of a nuclear power plant.
Figure 2 is a drawing showing a manufacturing process of boron-doped graphene oxide according to the present invention.
Figure 3 is a manufacturing process diagram of a neutron and proton shielding sheet according to the present invention.

Hereinafter, the present invention will be described in detail.

The neutron and proton shielding sheet according to the present invention comprises a polymer binder and a filler, wherein the filler is a nanoparticle having a particle diameter of 40 to 1000 nm and comprises a boron compound and zinc borate.

Here, the polymer binder preferably uses an elastic rubber material or synthetic plastic material to facilitate the processability of the sheet and improve the overall physical properties of the sheet. Specifically, considering the processability, physical properties, etc., it is preferable to use at least one of ethylene propylene rubber (EPDM), neoprene, chloroprene rubber (CR), natural rubber (NR), styrene butadiene rubber (SBR), nitrile rubber (NBR), urethane resin, ethylene-vinyl acetate copolymer (EVA), and polyethylene (PE).

In the present invention, the polymer binder is included at 20 to 80 wt%. If the content is too high, the content of the filler is relatively low, which reduces the shielding effect of neutrons and protons, and if the content is too low, the processability is poor, making it difficult to manufacture into a sheet.

The above filler is for shielding neutrons and protons, and includes boron compounds and zinc borate.

At this time, it is preferable to use the filler as a nanoparticle having a particle size of 40 to 1000 nm for dispersion and mixing in the polymer binder, because if the particle size is outside the above range, dispersion and mixing are difficult.

The above filler is included at 20 to 80 wt%. If the content is too high, the processability deteriorates, and if the content is too low, the shielding effect of neutrons and protons decreases.

In the present invention, the boron compound used as the filler is at least one of boron carbide (B ₄ C), boron oxide (B ₂ O ₃ ), and boric acid. The boron compound serves to shield the central line by attenuating and slowing it down.

In addition, the above zinc borate (2ZnO·3B ₂ O ₃ ) significantly improves neutron shielding performance when applied together with boron compounds, and also acts as a flame retardant and improves the physical properties of the sheet.

That is, the present invention is characterized in that by using a boron compound and zinc borate together as the filler, not only is the neutron shielding effect further increased, but also the flame retardancy and physical properties of the sheet are improved.

In addition, it is preferable that the filler of the present invention further includes boron-doped graphene oxide.

The above boron-doped graphene oxide not only significantly increases the neutron and proton shielding efficiency, but also plays a role in improving the overall physical properties. The above boron-doped graphene oxide is doped with boron through a hydrothermal reaction, which reacts boric acid with the hydroxyl group (-OH) inside the graphene oxide. More specifically, as shown in Fig. 2, graphene oxide and boric acid are introduced into an Inconel batch reactor at a weight ratio of 1 to 2:2 to 3, and reacted at 250 to 300°C, thereby producing the graphene oxide.

At this time, it is also preferable to use the boron-doped graphene oxide as nanoparticles having a particle size of 40 to 1000 nm.

In addition, in the present invention, it is preferable to use the filler, boron compound, zinc borate and boron-doped graphene oxide, which are surface-treated with fatty acid.

The above filler is included in a high content in the sheet to play a role of surface activity through surface treatment. At this time, it is preferable to use at least one of oleic acid and stearic acid as the fatty acid, because oleic acid and stearic acid have excellent compatibility with the polymer binder used in the present invention.

And the above surface treatment is performed by adding 0.1 to 1 wt% of the fatty acid to 99 to 99.9 wt% of the filler and milling in a ball mill for 30 to 90 minutes. If the amount of fatty acid used is too little, miscibility is not improved, and if it is excessive, the overall physical properties are affected.

In addition, the mixing ratio between the boron compound used as the filler, typically boron carbide (B ₄ C), zinc borate, and boron-doped graphene oxide is most preferably 10:5 to 10:0.1 to 1 weight ratio when considering the shielding effect, but is not limited thereto, and if the use of boron-doped graphene oxide is omitted, the boron compound and zinc borate are used in a weight ratio of 10:5 to 10.

In addition, the filler may further include pentaerythritol (C ₅ H ₁₂ O ₄ ). The pentaerythritol is an organic flame retardant with a high hydrogen content, and is a material that has both a neutron attenuation effect and flame retardancy. In addition, it has a high melting point of 260.5°C, and by supplementing the hydrogen content, it increases the neutron shielding effect of the sheet, and also improves flame retardancy, processability, and overall physical properties.

It is preferable to use the above pentaerythritol so that the weight ratio of the boron compound and pentaerythritol is 10:1 to 5, and when the boron compound, zinc borate, boron-doped graphene oxide, and pentaerythritol are used together, the weight ratio is 10:5 to 10:0.1 to 1:1 to 5.

It is also desirable to use the above pentaerythritol in the form of nanoparticles of 40 to 1000 nm and by surface treatment with fatty acids, and further description thereof is omitted.

The neutron and proton shielding sheet of the present invention, configured as described above, has excellent neutron and proton shielding efficiency, and can be manufactured to a thickness of 0.5 to 3 mm, so it has excellent processability and can be used as a film-type shielding material for protecting electronic products such as semiconductors.

Hereinafter, a method for manufacturing a neutron and proton shielding sheet according to the present invention will be described in detail. However, in order to avoid redundant explanation, it is noted that previously described contents are omitted.

The method for manufacturing a neutron and proton shielding sheet according to the present invention is characterized by including, as shown in FIG. 3, a step of sintering a filler including a boron compound and zinc borate at 200 to 350°C to remove crystal water, a step of milling the filler from which the crystal water has been removed to manufacture nanoparticles having a size of 40 to 1000 nm, a step of treating the surface of the nanoparticles by adding a fatty acid as a surfactant, a step of mixing the surface-treated nanoparticles with a polymer binder, a step of forming the mixed mixture into a sheet by extruding and rolling, and a step of vulcanizing the formed sheet.

Below, each step is described in detail with reference to Fig. 3.

Step of removing crystal water by sintering a filler containing a boron compound and zinc borate at 200 to 350°C

First, a filler containing a boron compound and zinc borate is prepared. At this time, it is preferable that the filler is ground to a particle size of about 1 to 3 μm. This is in consideration of the subsequent ball mill process. Here, the boron compound is at least one of boron carbide (B ₄ C), boron oxide (B ₂ O ₃ ), and boric acid.

In addition, as explained above, it is natural that one or more of boron-doped graphene oxide and pentaerythritol may be further included as fillers. And since the mixing ratio between the fillers has been sufficiently explained above, further explanation thereon is omitted.

Next, the filler is sintered at 200 to 350°C to remove water of crystallization. However, when using pentaerythritol, it is natural to control the sintering temperature so as not to exceed its melting point.

A step of manufacturing nanoparticles of 40 to 1000 nm by milling the filler from which the above crystal number has been removed, and treating the surface of the filler nanoparticles by adding fatty acid, which is a surface active agent.

The filler from which the water of crystallization has been removed is placed in a milling container together with 5 to 10 mm tungsten carbide (WC) milling balls, and milled at 400 to 700 rpm for 30 to 90 minutes to produce nanoparticles of 40 to 1000 nm. Here, a weight ratio of the milling balls and the filler of about 1:0.5 to 2 is sufficient, and is not limited thereto.

However, in order to treat the surface, at least one fatty acid, such as oleic acid and stearic acid, is added as a surface-active agent to treat the surface of the filler nanoparticles. That is, the surface is treated by adding fatty acids during milling or at the initial stage of milling. Here, the amount of the fatty acid added is sufficient if it is 0.1 to 1 wt% with respect to 99 to 99.9 wt% of the filler.

A step of mixing the surface-treated nanoparticles and a polymer binder

And the surface-treated nanoparticles and the polymer binder are mixed at a temperature of 80 to 140°C at 30 to 40 rpm. At this time, the mixing ratio is 20 to 80 wt% of the surface-treated nanoparticles and 20 to 80 wt% of the polymer binder.

The above polymer binder is at least one of ethylene propylene rubber (EPDM), neoprene, chloroprene rubber (CR), natural rubber (NR), styrene butadiene rubber (SBR), nitrile rubber (NBR), urethane resin, ethylene vinyl acetate copolymer (EVA), and polyethylene (PE).

A step of forming the above-mentioned mixed mixture into a sheet by extruding and rolling it.

Next, the above-mentioned mixed mixture is extruded and rolled to form a sheet having a thickness of 0.5 to 3 mm. Here, the extrusion and rolling method is not particularly limited, and an extrusion and rolling method commonly used in the art can be selectively used.

Step of vulcanizing the above-mentioned molded sheet

And the above-mentioned molded sheet is cured by vulcanization to exhibit the mechanical properties of the sheet. At this time, the vulcanization method is not particularly limited, and a vulcanization method commonly used in the art can be selectively used.

Hereinafter, the present invention will be described in more detail through specific examples.

(Example 1)

Boron carbide with a particle size of 1 μm and zinc borate with a particle size of 1 μm were prepared as fillers and sintered at 200 to 350°C for 5 minutes to remove water of crystallization. Then, 10 kg of boron carbide and 5 kg of zinc borate from which water of crystallization was removed were milled at 100 rpm for 60 minutes with 150 g of oleic acid and 15 kg of 20 mm stainless steel milling balls to produce surface-treated nanoparticles with a particle size of 40 to 1000 nm.

Next, the surface-treated nanoparticles and chloroprene rubber were mixed using a high polymer hot mixing machine at 90 to 130°C and 15 RPM for 30 minutes.

And it was formed into a sheet by extrusion and rolling at 90℃, cross-linked and vulcanized at 80~90℃, and naturally dried for 24 hours.

Here, the mixing ratio of the surface-treated nanoparticles and chloroprene rubber and the sheet thickness were processed differently depending on the test example.

(Example 2)

The same procedure as in Example 1 was followed, but boron-doped graphene oxide having a particle size of 1 μm was additionally prepared as a filler, and after removing the water of crystallization, 10 kg of boron carbide from which the water of crystallization had been removed, 5 kg of zinc borate, and 100 g of boron-doped graphene oxide were surface-treated by milling.

At this time, the boron-doped graphene oxide was manufactured by putting graphene oxide and boric acid in a weight ratio of 1:2 into an Inconel batch reactor or an autoclave reactor and performing a hydrothermal reaction at 250 to 300°C for 20 minutes.

(Example 3)

The same procedure as in Example 2 was followed, except that pentaerythritol having a particle size of 1 μm was additionally prepared as a filler, and after removing the water of crystallization, 10 kg of boron carbide from which the water of crystallization had been removed, 5 kg of zinc borate, 100 g of boron-doped graphene oxide, and 5 kg of pentaerythritol were surface-treated by milling.

(Test Example 1) Neutron shielding effect by 40m neutron scattering device

To measure the neutron shielding effect and efficiency, tests were conducted in the irradiation environment of the 40m neutron scattering device of the Hanaro (Daejeon) research reactor, and the shielding rate was analyzed according to the temperature change of the measured sample.

A 40m neutron scattering device was used as the test equipment.

1) Device length (m): 40

2) Detector size (m ² ): 100×100

3) Detector resolution (cm ² ): 0.5×0.5

4) Neutron velocity selector maximum transmittance: 10%

5) Wavelength range (A): 4~20

6) Sample-to-detection interval (M): 1.1~19.8

7) Neutron induction tube cross-sectional area (cm): 5×5

7) Temperature control device: RT-300℃

At this time, the distance between the sample and the source or neutron generator was 19.8 m, and the distance between the sample and the detector or detector was approximately 2 m.

And the test specimens were prepared as shown in Table 1 below, and the results are shown in Tables 2 and 3 below (measured by increasing the sample temperature during measurement).

Test specimen of test example 1 division Surface-treated nanoparticles and chloroprene rubber
Mixing ratio (by weight) Sheet specifications Example 1 60:40 250×250×0.9(mm) Example 2 60:40 250×250×0.9(mm) Example 3 60:40 250×250×0.9(mm)

Neutron dose attenuation rate (%) at room temperature (20℃) division Example 1 Example 2 Example 3 Transmission
(D/F) 0.0003559505 1.1751×10 ^-5 3.4074×10 ^-6 Shielding rate
[1-(D/F)]×100
(%) 99.9644 99.9982 99.9997

Heating (40℃, 60℃) Neutron dose attenuation rate (%) division Example 2
(40℃) Example 3
(40℃) Example 2
(60℃) Example 3
(60℃) Transmission
(D/F) 1.8984*10 ^-5 3.7972*10 ^-6 2.0381*10 ^-5 4.5011*10 ^-5 Shielding rate
[1-(D/F)]×100
(%) 99.9981 99.9996 99.9980 99.9995

As shown in Tables 2 and 3 above, it was found that Examples 1 to 3 according to the present invention all had excellent neutron dose attenuation rates at room temperature and that there was no significant difference even in a heated state.

(Test Example 2) Neutron shielding effect by neutron penetration non-destructive testing device

To measure the neutron shielding effectiveness and efficiency, tests were conducted in the thermal neutron irradiation environment of the Hanaro (Daejeon) research reactor and the shielding rate was measured.

A neutron penetration non-destructive testing device was used as testing equipment.

1) Neutron flux: Up to 2×107n/ ^cm2 Sec

2) L(source-detector distance)/D(source aperture size) ratio: 267

3) Beam size: 350 × 450mm ²

4) Neutron imaging detector: 2048 × 2048 Andor CCD camera + 6LiF neutron scintillator (200um thick)

At this time, the distance between the sample and the source or neutron generator was about 6 m, and the distance between the sample and the detector or detector was about 2 cm.

And the test specimens were prepared as shown in Table 4 below, and the results are shown in Table 5 below.

Test specimen of test example 2 division Surface-treated nanoparticles and chloroprene rubber
Mixing ratio (by weight) Sheet thickness Example 1 50:50 10T Example 2 50:50 10T Example 3 50:50 10T

Neutron dose attenuation rate (%) division Example 1 Example 2 Example 3 1 95.33 96.13 96.63 2 95.40 96.14 96.62 3 95.85 96.49 96.95 4 95.49 96.17 96.67 5 95.58 96.30 96.71 6 95.59 96.27 96.71 7 95.66 96.32 96.76 8 95.68 96.32 96.79 9 96.00 96.53 96.95 10 95.77 96.35 96.84 average 95.64 96.30 96.76

As shown in Table 5 above, it was confirmed that Examples 1 to 3 according to the present invention all had excellent central beam attenuation rates.

(Experimental Example 3)_Proton shielding effect

To measure the proton shielding effect and efficiency, measurements were conducted in a 100 MeV proton beam irradiation environment.

TR-102 was used as the test equipment.

Energy: 30~100MeV

Beam Current: 2~5mA

Beam Fluence: 1E6~1E8#/㎠ (1.2mGy~0.12Gy)

Survey area (Irrad. Area): 100mm×100mm

Quality Standard (ISO9001): - Fluence: ±15%

-Uniformity: ±10%

-Energy: ±10%

Test environment

Proton beam energy: 100 MeV

Effective beam size: 10×7Cm ²

Uncertainty: 8.83%

Distance between shield and detector 10cm

The distance from the source is virtually negligible due to the nature of the proton beam.

And the test specimens were prepared as shown in Table 6 below, and the results are shown in Table 7 below.

Test specimen of test example 3 division Surface-treated nanoparticles and chloroprene rubber
Mixing ratio (by weight) Sheet thickness Example 1 25:75 3T Example 2 25:75 3T Example 3 25:75 3T

Proton shielding ratio division Before
(Monitor chamber with)(#/cm2) After
(Farmer IC) delta Pulse count start
hour end
hour Shielding rate Example 1 1.522E+09 1.518E+08 1.370E+09 30 17:11 17:12 90% Example 2 1.739E+09 1.594E+08 1.580E+09 30 17:13 17:13 91% Example 3 1.489E+09 1.441E+08 1.345E+09 29 17:14 17:14 90%

As shown in Table 7 above, it was confirmed that Examples 1 to 3 of the present invention had excellent proton shielding rates.

The above description of the present invention is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single component may be implemented in a distributed manner, and likewise, components described as distributed may be implemented in a combined manner.

The scope of the present invention is indicated by the claims described below, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims (11)

Including polymer binders and fillers,
The above filler is a nanoparticle having a particle size of 40 to 1000 nm and contains a boron compound and zinc borate.
The above filler further comprises boron-doped graphene oxide and pentaerythritol,
The above filler is surface-treated with fatty acid,
A neutron and proton shielding sheet characterized in that the weight ratio of the above boron compound, zinc borate, boron-doped graphene oxide, and pentaerythritol is 10:5 to 10:0.1 to 1:1 to 5.
In the first paragraph,
The above polymer binder,
At least one of ethylene propylene rubber (EPDM), neoprene, chloroprene rubber (CR), natural rubber (NR), styrene butadiene rubber (SBR), nitrile rubber (NBR), urethane resin, ethylene vinyl acetate copolymer (EVA), and polyethylene (PE).
The above boron compound is,
A neutron and proton shielding sheet characterized by comprising at least one of boron carbide (B ₄ C), boron oxide (B ₂ O ₃ ), and boric acid.
delete delete delete In the first paragraph,
A neutron and proton shielding sheet, characterized in that the thickness of the above sheet is 0.5 to 3 mm.
A step of removing crystal water by sintering a filler containing a boron compound and zinc borate at 200 to 350°C,
A step of manufacturing nanoparticles of 40 to 1000 nm by milling the filler from which the above crystal number has been removed, and treating the surface of the nanoparticles by adding fatty acid, which is a surfactant;
A step of mixing the surface-treated nanoparticles and a polymer binder,
A step of forming the above-mentioned mixed mixture into a sheet by extruding and rolling,
A step of vulcanizing the above-mentioned molded sheet is included,
The above filler further comprises boron-doped graphene oxide and pentaerythritol,
A method for manufacturing a neutron and proton shielding sheet, characterized in that the weight ratio of the boron compound, zinc borate, boron-doped graphene oxide, and pentaerythritol is 10:5 to 10:0.1 to 1:1 to 5.
delete delete In Article 7,
A method for manufacturing a neutron and proton shielding sheet, characterized in that the fatty acid is at least one of oleic acid and stearic acid.
In Article 7,
A method for manufacturing a neutron and proton shielding sheet, characterized in that the thickness of the above-mentioned molded sheet is 0.5 to 3 mm.