Shielding material for shielding radioactive ray and preparation method thereof

Abstract

A shielding material for shielding radioactive ray and preparation method thereof. The shielding material consists of water, a cementing material, a fine aggregate material, a coarse aggregate material and an additive, wherein the fine aggregate material consists of a borosilicate glass powder and a barite sand, and the coarse aggregate material consists of a barite. A content of boron element in the borosilicate glass powder accounts for 0.5%-1% of the total weight of the shielding material. A content of barium sulfate in the barite sand and the barite accounts for 71%-75% of the total weight of the shielding material. Other contents include water, the cementing material and the additive, and a sum of contents of all components is 100% total weight of the shielding material.

Claims

1. A shielding material for shielding radioactive ray consisting of: water; a cementing material; a fine aggregate consisting of a borosilicate glass powder and a barite sand, wherein a content of boron element in the borosilicate glass powder accounts for 0.5% to 1% of the total weight of the shielding material; a coarse aggregate consisting of a barite, and an additive selected from the group consisting of a water reducer, an early strength agent, a retarder, a pumping agent and an expanding agent, wherein a content of barium sulfate in the barite sand and the barite accounts for 71% to 75% of the total weight of the shielding material, a sum of contents of all the components is 100% total weight of the shielding material.

2. The shielding material for shielding radioactive ray according to claim 1, wherein the cementing material is P.II 52.5 Portland cement.

3. The shielding material for shielding radioactive ray according to claim 1, wherein a range of density of the shielding material is 3.46 g/cm.sup.3 to 3.55 g/cm.sup.3.

4. The shielding material for shielding radioactive ray according to claim 1, wherein the additive is a polycarboxylic water reducer.

5. The shielding material for shielding radioactive ray according to claim 1, wherein the shielding material is applicable to radioactive sources for neutron capture therapy that contain neutron and Gamma ray.

6. A preparation method for the shielding material for shielding radioactive ray according to claim 1, wherein the preparation method includes the following steps: crushing and screening a barite ore, so that the barite sand for fine aggregate, the grain size of which is less than 4.75 mm but not less than 75 m, is obtained; crushing and screening a barite ore, so that the barite for coarse aggregate, the grain size of which is not less than 4.75 mm, is obtained; crushing and screening a borosilicate glass, so that the borosilicate glass powder for the fine aggregate, the grain size of which is less than 4.75 mm but not less than 75 m, is obtained; pouring the cement, the coarse aggregate and the fine aggregate into a container to form a partially mixed material; pouring the water and the additive into the container; premixing along with the partially mixed material for a preset time t, wherein 30 st60 s; and mixing the partially mixed material by a mixer and then discharging.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is energy spectra of neutron and Gamma ray in a radioactive source coming out of a beam outlet for neutron capture therapy used in embodiments of the present disclosure.

(2) FIG. 2 is neutron shielding effects of embodiments 1 to 3 of the present disclosure and comparative examples under different thicknesses.

(3) FIG. 3 is Gamma ray shielding effects of the embodiments 1 to 3 of the present disclosure and the comparative examples under the different thicknesses.

(4) The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

(5) In accordance with specific embodiments, a shielding material for shielding radioactive ray in the present disclosure will be further elaborated hereinafter, so that its composition and effect can be understood more clearly, but the protection scope of the present invention should not be limited thereby.

(6) The following embodiments adopt a radioactive source for neutron capture therapy that contains neutron and Gamma ray, and thus, the neutron and Gamma ray shielding effect of the following embodiments of the shielding material for shielding radioactive ray in the present disclosure can be highlighted. For details, please refer to FIG. 1. It shows energy spectra of neutron and Gamma ray in a radioactive source coming out of a beam outlet for neutron capture therapy. Taking the intensity of the neutron and Gamma ray 4.5 meters away from the beam outlet into consideration, most of neutrons fall into an epithermal neutron energy region (0.5 eV-10 eV), while the energy of the Gamma ray is distributed uniformly in a range from 0.1 MeV to 10 MeV. The embodiments of the present disclosure only take this radioactive source as an example, but do not limit the variety of radioactive sources thereby. As wellknown by those skilled in the art, according to the teaching and suggestion of the embodiments of the present disclosure, the shielding material for shielding radioactive ray in the embodiments of the present disclosure is also applicable to other radioactive sources with different energy spectra that contain neutron and Gamma ray.

(7) The shielding material in the following embodiments is composed of water, a cementing material, fine aggregate, coarse aggregate and an additive, wherein the fine aggregate is composed of borosilicate glass powder and barite sand, and the coarse aggregate is composed of galena and barite; boron element content in the borosilicate glass powder accounts for 0.5 to 1 percent of the total weight of the shielding material; barium sulfate content in the barite sand and the barite accounts for 71 to 75 percent of the total weight of the shielding material; the other contents are the water, the cementing material and the additive, and a sum of contents of all the components is 100 percent total weight of the shielding material.

(8) The cementing material chosen for the shielding material is P.II 52.5 Portland cement, the additive is one or more of a water reducer, an early strength agent, a retarder, a pumping agent and an expanding agent, the density of a first type of shielding material is 3.46 g/cm.sup.3 to 3.55 g/cm.sup.3, and the density of a second type of shielding material is 3.73 g/cm.sup.3 to 4.01 g/cm.sup.3. As wellknown by those skilled in the art, other types of cementing materials can also be chosen for implementation; the additive can be determined according to the specific embodiments, and as a preference, a polycarboxylic water reducer is chosen as the additive in the embodiments. The embodiments will be described in detail hereinafter.

Embodiment 1

(9) Please refer to table 1. The shielding material is composed of water, a cementing material, fine aggregate, coarse aggregate and an additive. The weight of the water accounts for 2.48 percent of the total weight of the shielding material, P.II 52.5 Portland cement is chosen as the cementing material, the fine aggregate is composed of borosilicate glass powder and barite sand, and the coarse aggregate is composed of barite, a polycarboxylic water reducer is chosen as the additive, wherein the weight of boron element accounts for 0.51 percent of the total weight of the shielding material, the content of barium sulfate accounts for 75.33 percent of the total weight of the shielding material, the other contents are the cementing material and the additive, and a sum of contents of all the components is 100 percent total weight of the shielding material.

(10) A preparation process mainly includes the following steps: (1) crushing and screening a barite ore, so that the barite sand for the fine aggregate, the grain size of which is less than 4.75 mm but not less than 75 m, is obtained; (2) crushing and screening a barite ore, so that the barite for the coarse aggregate, the grain size of which is not less than 4.75 mm, is obtained; (3) crushing and screening a borosilicate glass, so that the borosilicate glass powder for the fine aggregate, the grain size of which is less than 4.75 mm but not less than 75 m, is obtained; (4) pouring the cement, the coarse aggregate and the fine aggregate into a container to form a partially mixed material; (5) pouring the the water and the additive into the container and premixing along with the partially mixed material for a preset time t, wherein 30 st60 s; and (6) mixing the partially mixed material by a mixer and then discharging.

(11) In some cases requiring outside transportation, two types of transportation means, a mixer truck and a tipper truck, can be chosen to be adopted, but the range of application should be taken into consideration. It is crucial that the shielding material should be transported and poured almost in a state at the completion of mixing as much as possible. Transportation must be quick, and the time from the beginning of mixing to arrival at a site should be controlled. According to the provisions of the current national standard Standard for Quality Control of Concrete GB 50164, when outside air temperature is lower than 25 C., the mixer truck is adopted for transportation, and the transportation time should not be longer than 90 minutes for concrete greater than or equal to C30; and when outside air temperature exceeds 25 C., the transportation time should not be longer than 60 minutes for the concrete greater than or equal to C30. According to the provisions of the current national standard Premixed Concrete GB/T 14902, concrete which is transported by adopting the mixer truck should be unloaded within 1.5 hours; concrete which is transported by adopting the tipper truck should be unloaded within 1.0 hours; and when the highest air temperature is lower than 25 C., the transportation time can be prolonged by 0.5 hour. The reason why 90 minutes is specified is that the longer the time is, the slump loss of concrete will be greater, and as a result, the workability of the concrete cannot be guaranteed. During practical application, when properties cannot meet requirements, an additive can be added for regulation on the basis of experimental verification, and water is not allowed to be added. Normally, technical measures, such as adding an additive with a retarding effect to prolong the solidification time of concrete, are adopted.

(12) The strength grade of the shielding material is C30 or C40, the standard axial compressive strength value of the shielding material should reach 17.1 N/mm.sup.2 to 22.8 N/mm.sup.2 or be higher, and the standard axial tensile strength value of the shielding material should reach 1.70 N/mm.sup.2 to 2.05 N/mm.sup.2 or be higher.

(13) P.II 52.5 Portland cement is chosen as the variety of the cement, that is, the contents of clinker and gypsum is greater than or equal to 95 percent of the total weight of the cement, the content of granulated blast-furnace slag is less than or equal to 5 percent of the total weight of the cement, or the content of limestone is less than or equal to 5 percent of the total weight of the cement. The clinker mainly contains raw materials of CaO, SiO.sub.2, Al.sub.2O.sub.3 and Fe.sub.2O.sub.3, which are ground into fine powder according to appropriate proportions and are burnt to be fused partially, so that a hydraulic cementing substance with calcium silicate as a main mineral component is obtained. The calcium silicate mineral is not less than 66 percent, and the mass ratio of calcium oxide to silicon oxide is not less than 2.0. With regard to the choice of gypsum, if natural gypsum is chosen, it should be gypsum or mixed gypsum that is grade II or above in category G or category M, as specified in GB/T 5483; if gypsum which is an industrial byproduct is chosen, it should be an industrial byproduct with calcium sulfate as a main component, and before adoption, an experiment should be carried out to prove that cement properties are not impaired. Among the chemical indexes of the P.II 52.5 Portland cement, insoluble substances (parts by mass) should be less than or equal to 1.50 percent, loss on ignition (parts by mass) should be less than or equal to 3.5 percent, sulfur trioxide (parts by mass) should be less than or equal to 3.5 percent, magnesium oxide (parts by mass) should be less than or equal to 6.0 percent, and chloridion (parts by mass) should be less than or equal to 0.06 percent. The grade of the Portland cement is 52.5; 3 days after shaping, the compressive strength is greater than or equal to 23.0 Mpa, and the bending strength is greater than or equal to 4.0 MPa; 28 days after shaping, the compressive strength is greater than or equal to 52.5 Mpa, and the bending strength is greater than or equal to 7.0 MPa.

(14) In the shielding material prepared according to the proportions and the preparation method, the borosilicate glass powder accounts for 17 percent of the weight of the fine aggregate, and the barite sand accounts for 83 percent of the weight of the fine aggregate. The volumetric weight (i.e., density) of the shielding material is 3554 kg/m.sup.3, and the sand ratio is 32.1 percent. The water-cement ratio is 0.37, and the amount of the added additive is 1.80 percent. Calculated according to a total amount of 500 tons in demand, the weights of the various needed substances are listed in table 1 below.

(15) TABLE-US-00001 TABLE 1 Weight Proportions in Embodiment 1 Composition Water Cement Fine Aggregate Coarse Aggregate Additive (Unit: kg/m.sup.3) Apparent Density (g/cm.sup.3) 1.00 3.12 2.23 4.34 3.98 4.34 4.34 1.20 Strength Cement Additive Borosilicate Barite Volumetric Sand Grade Variety Variety Water Cement glass powder sand Total Barite Total Additive weight ratio C30 or P.II Poly- 142 400 164 802 966 2046 2046 7.20 3554 32.1% C40 52.5 carboxylic water reducer Mass 17% 83% 100% 100% 100% Ratio Volumes 73.5 184.8 471.4 6.0 Substances Contents (L) 141.7 128 242.7 471.4 H.sub.2O 2.48% Water- Volume Total Borosilicate Total cement Sand Amount glass Barite Amount Water Ratio Additive Ratio in Demand powder sand Barite Cement Additive B 0.51% B W W/B % AD % s/a % 500 tons 20.5 100.3 255.8 50 9.0 BaSO.sub.4 75.33% 400 148 0.37 1.80% 34%

(16) For the same materials, conditions or method used in embodiment 1, please refer to the description in embodiment 1, which will not be repeated in embodiments 2-3.

Embodiment 2

(17) Please refer to table 2. The shielding material is composed of water, a cementing material, fine aggregate, coarse aggregate and an additive. The weight of the water accounts for 2.51 percent of the total weight of the shielding material, P.II 52.5 Portland cement is chosen as the cementing material, the fine aggregate is composed of borosilicate glass powder and barite sand, the coarse aggregate is composed of barite, and a polycarboxylic water reducer is chosen as the additive, wherein the weight of boron accounts for 0.75 percent of the total weight of the shielding material, the content of barium sulfate accounts for 73.07 percent of the total weight of the shielding material, the other contents are the cementing material and the additive, and a sum of contents of all the components is 100 percent total weight of the shielding material.

(18) Its preparation method is the same as that of embodiment 1. In the shielding material produced according to the proportions and the preparation method, the borosilicate glass powder accounts for 26 percent of the weight of the fine aggregate, and the barite sand accounts for 74 percent of the weight of the fine aggregate. The volumetric weight (i.e., density) of the shielding material is 3508 kg/m.sup.3, and the sand ratio is 31.0 percent. The water-cement ratio is 0.37, and the amount of the added additive is 1.80 percent. Calculated according to a total amount of 500 tons in demand, the weights of the various needed substances are listed in table 2 below.

(19) TABLE-US-00002 TABLE 2 Weight Proportions in Embodiment 2 Composition Water Cement Fine Aggregate Coarse Aggregate Additive (Unit: kg/m.sup.3) Apparent Density (g/cm.sup.3) 1.00 3.12 2.23 4.34 3.79 4.34 4.34 1.20 Strength Cement Additive Borosilicate Barite Volumetric Sand Grade Variety Variety Water Cement glass powder sand Total Barite Total Additive weight ratio C30 or P.II Poly- 142 400 239 681 921 2046 2046 7.20 3508 32.0% C40 52.5 carboxylic water reducer Mass 26% 74% 100% 100% 100% Ratio Volumes 107.3 157.0 471.4 6.0 Substances Contents (L) 141.7 128 243.0 471.4 H.sub.2O 2.51% Water- Volume Total Borosilicate Total cement Sand Amount glass Barite Amount Water Ratio Additive Ratio in Demand powder sand Barite Cement Additive B 0.75% B W W/B % AD % s/a % 500 tons 29.9 85.2 255.8 50 9.0 BaSO.sub.4 73.07% 400 148 0.37 1.80% 34%

Embodiment 3

(20) Please refer to table 3. The shielding material is composed of water, a cementing material, fine aggregate, coarse aggregate and an additive. The weight of the water accounts for 2.55 percent of the total weight of the shielding material, P.II 52.5 Portland cement is chosen as the cementing material, the fine aggregate is composed of borosilicate glass powder and barite sand, and the coarse aggregate is composed of barite, and a polycarboxylic water reducer is chosen as the additive, wherein the weight of boron element accounts for 1.00 percent of the total weight of the shielding material, the content of barium sulfate accounts for 70.76 percent of the total weight of the shielding material, the other contents are the cementing material and the additive, and a sum of contents of all the components is 100 percent total weight of the shielding material.

(21) Its preparation method is the same as that of embodiment 1. In the shielding material prepared according to the proportions and the preparation method, the borosilicate glass powder accounts for 36 percent of the weight of the fine aggregate, and the barite sand accounts for 64 percent of the weight of the fine aggregate. The volumetric weight (i.e., density) of the shielding material is 3457 kg/m.sup.3, and the sand ratio is 29.8 percent. The water-cement ratio is 0.37, and the amount of the added additive is 1.80 percent. Calculated according to a total amount of 500 tons in demand, the weights of the various needed substances are listed in table 3 below.

(22) TABLE-US-00003 TABLE 3 Weight Proportions in Embodiment 3 Composition Water Cement Fine Aggregate Coarse Aggregate Additive (Unit: kg/m.sup.3) Apparent Density (g/cm.sup.3) 1.00 3.12 2.23 4.34 3.58 4.34 4.34 1.20 Strength Cement Additive Borosilicate Barite Volumetric Sand Grade Variety Variety Water Cement glass powder sand Total Barite Total Additive weight ratio C30 or P.II Poly- 142 400 313 556 869 2046 2046 7.20 3457 29.8% C40 52.5 carboxylic water reducer Mass 36% 64% 100% 100% 100% Ratio Volumes 140.3 128.2 471.3 6.0 Substances Contents (L) 141.7 128 242.8 471.3 H.sub.2O 2.55% Water- Volume Total Borosilicate Total cement Sand Amount glass Barite Amount Water Ratio Additive Ratio in Demand powder sand Barite Cement Additive B 1.00% B W W/B % AD % s/a % 500 tons 39.1 69.5 255.7 50 9.0 BaSO.sub.4 70.76% 400 148 0.37 1.80% 34%

(23) Two shielding materials for shielding radioactive ray which are common in the market are introduced hereinafter to be compared with the shielding material for shielding radioactive ray in the embodiments of the present disclosure.

Comparative Example 1

(24) Comparative example 1 is a radiation-shielding material which is common in the market, and the percentages by weight of elements contained in it are listed in table 4 below:

(25) TABLE-US-00004 TABLE 4 Elements and Contents thereof in Comparative Example 1 Elements H B O Al Si S Fe Ca Ba Na Pb Mg C K Contents 0.8% 47.3% 3.6% 14.5% 0.3% 1.1% 24.7% 2.4% 5.0% 0.2%

Comparative Example 2

(26) Comparative example 2 is another barite radiation-shielding material, and its weight proportions are listed in table 5 below:

(27) TABLE-US-00005 TABLE 5 Substances and Weight Proportions thereof in Comparative Example 2 Composition Water Cement Fine Aggregate Coarse Aggregate Additive (Unit: kg/m.sup.3) Apparent Density (g/cm.sup.3) 1.00 3.12 2.23 4.34 4.34 4.34 4.34 1.20 Strength Cement Additive Borosilicate Barite Volumetric Sand Grade Variety Variety Water Cement glass powder sand Total Barite Total Additive weight ratio C30 or P.II 52.5 Polycarboxylic 142 400 0 1054 1054 2046 2046 7.20 3641 34.0% C40 water reducer Mass 0% 100% 100% 100% 100% Ratio Volumes 0.0 242.8 471.3 6.0 Substances Contents (L) 141.7 128 242.8 471.3 H.sub.2O 2.42% Volume Total Water-cement Sand Amount Water Ratio Additive Ratio B 0.00% B W W/B % AD % s/a % BaSO.sub.4 80.02% 400 148 0.37 1.80% 34%

(28) For the elements contained in the shielding material in each of the above-mentioned embodiments and comparative examples and the percentage of each element accounting for the total weight of the shielding material, please refer to table 6 below:

(29) TABLE-US-00006 TABLE 6 Elements and Contents thereof in Embodiments and Comparative Examples Comparative Comparative Example 1 Example 2 Embodiment 1 Embodiment 2 Embodiment 3 H 0.8% 0.3% 0.3% 0.3% 0.3% B 0.5% 0.8% 1.0% O 47.3% 29.6% 31.0% 32.1% 32.3% Al 3.6% 0.4% 0.4% 0.4% 0.4% Si 14.5% 1.1% 2.4% 3.2% 3.7% S 0.3% 11.8% 11.1% 10.8% 10.5% Fe 1.1% 0.3% 0.3% 0.3% 0.3% Ca 24.7% 5.0% 5.2% 5.2% 5.3% Ba 50.1% 47.2% 46.6% 44.3% Na 0.2% 0.3% 0.4% Pb Mg 2.4% C 5.0% K 0.2% Density 2.36 3.64 3.55 3.51 3.46 (g/cm.sup.3)

(30) For the radiation-shielding property indexes of the shielding material in each of the embodiments and the comparative examples, please refer to table 7, and it can be seen therefrom that under the condition of the same thickness of 50 cm, both the neutron-shielding property and photon-shielding property of the shielding materials in embodiments 1-5 are far better than those in comparative examples 1-2.

(31) TABLE-US-00007 TABLE 7 Radiation-shielding Property Indexes of Embodiments and Comparative Examples Neutron Photon Density Attenuation Attenuation Thickness (cm) (g/cm.sup.3) Coefficient Coefficient Comparative 50 2.36 0.104 0.042 Example 1 Comparative 50 3.64 0.100 0.058 Example 2 Embodiment 1 50 3.55 0.161 0.084 Embodiment 2 50 3.51 0.166 0.084 Embodiment 3 50 3.46 0.175 0.083

(32) Considering from the thickness and price factors of the shielding materials, especially the thicknesses of the various shielding materials required to attenuate the radioactive source for neutron capture therapy to an ambient dose equivalent rate of 2.5 Sv/h (as a suggestion for reference), please see table 8, although the shielding material in comparative example 1 is very cheap, the material is required to be very thick in order to achieve the requirement of the standard; although the shielding material in comparative example 2 is cheap, the required thickness is also large; and although the shielding material of boron-containing polyethylene+lead bricks can come up to the requirement of the standard with very small thickness, its price is very high. Whereas, under the precondition of meeting the standard, the shielding materials in embodiments 1-3 not only are moderate in thicknesses, but also are cheap.

(33) TABLE-US-00008 TABLE 8 Thicknesses and Prices of Shielding Materials Thickness of Thickness of Total Shielding Material 1 Material 2 Thicknesses Materials (cm) (cm) (cm) Prices Comparative 180 Very Example 1 cheap Comparative 130 Cheap Example 2 Boron-containing 12 18 30 Very high polyethylene + lead bricks Embodiment 1 80 Cheap Embodiment 2 80 Cheap Embodiment 3 80 Cheap

(34) Please see FIG. 2 and FIG. 3 below to evaluate the effective dose performances of the various shielding materials under different thicknesses.

(35) It can be seen from FIG. 2 and FIG. 3 that the shielding materials in the embodiments have obvious advantages in comparison with the comparative examples in terms of shielding both neutrons and , and with an increase in thicknesses, their effect will become more remarkable.

(36) Because the capture cross section of .sup.10B for neutrons complies with the characteristic of 1/v within a range that energy is lower than 500 keV, as neutron energy decreases, the reaction cross section increases as well, for example, there are about 3866 barns of capture cross section for neutrons of 0.025 eV, and therefore a large number of epithermal neutrons will be absorbed by the .sup.10B element after the epithermal neutrons are decelerated into slow neutrons by the concrete. That is, 0.5 percent of boron content in embodiment 1 can exert a good neutron shielding effect, there is no obvious difference between comparative examples 1 and 2 in terms of neutron shielding, and the neutron shielding effect of the ordinary barite concrete in comparative example 2 is even poorer. This shows that for a mixed radiation field for neutron capture therapy, it is very necessary to add at least 0.5 percent of boron into concrete.

(37) It can be seen clearly from the two comparative examples in FIG. 3 that the barite concrete has a good shielding effect. This is mainly because barium sulfate in barite increases the apparent density of the concrete, that is, the higher the content of barium sulfate is and the higher the apparent density is, the better the shielding effect is. On the basis of barite, the concrete developed by our company varies in three different types of boron contents, which highlights the necessity of adding at least 0.5 percent of boron in the concrete. Although the ordinary barite concrete in comparative example 2 is improved obviously in comparison with the ordinary concrete in comparative example 1, the effect is greatly improved after 0.5 percent of boron is added in embodiment 1.

(38) After being mixed uniformly, the concrete is transported to a construction site by a concrete transportation truck, a property test is carried out in reference to the following method: GB/T50557-2010 Technical Code for Barite Concrete Against Radiation and GB/T50081-2002 Standard for Test Methods of Mechanical Properties of Ordinary Concrete, and a test result is shown in table 9:

(39) TABLE-US-00009 TABLE 9 Property Parameters of Concrete in Each Embodiment Of the Present Disclosure Embodiment Embodi- Property Indexes 1 Embodiment 2 ment 3 Slump/ Slumps 196 198 203 Extension Extensions 486 475 492 (mm) Compressive 3 d 39.8 40.5 36.6 Strength (MPa) 7 d 48.7 49.6 44.8 28 d 52.2 53.1 48.0 Axial Compressive Strength 36.1 34.9 37.4 (MPa) Compressive Elastic Modulus 38.6 32.7 40.5 (GPa)

(40) The above illustrates and describes basic principles, main features and advantages of the present disclosure. Those skilled in the art should appreciate that the above embodiments do not limit the present disclosure in any form. Technical solutions obtained by equivalent substitution or equivalent variations all fall within the scope of the present disclosure.