WO1994014167A1 - RADIATION-BARRIER MATERIAL CAPABLE OF SIMULTANEOUS SHIELDING AGAINST η-RAY, X-RAY AND NEUTRON BEAM - Google Patents

Abstract

A radiation-barrier material capable of simultaneous shielding against η-ray, X-ray and neutron beam, comprising 100 parts by weight of at least one thermosetting resin material selected from the group consisting of phenol, epoxy, cresol, xylene, urea and unsaturated polyester resins and 50-2,000 parts by weight of at least one inorganic substance selected from the group consisting of Pb, W, Cr, Co, Cu, Fe, Mn, Mo, Ag, Ta, Cd, Dy, Eu, Gd, Au, In, Hg, Re, Sm and U and compounds of these elements, and giving a molding with a density of 2.0 or above.

Description

 Specification

 Radiation shielding material capable of simultaneous shielding of X-rays, X-rays and neutrons

[Technical field]

 TECHNICAL FIELD The present invention relates to a radiation shielding material that simultaneously shields X-rays and neutron rays, and more particularly to a radiation facility, storage of radioactive waste, nuclear fuel, radioisotope (RI), etc., transport containers and related equipment. And other radiation shielding materials.

 [Background technology]

 Shielding of X-rays and X-rays in radiation does not differ much in the mass attenuation coefficient of any substance, and the higher the density of the substance, the larger the linear attenuation coefficient and the smaller the thickness of the shield. Generally, lead, iron, concrete, etc. are used.

 For shielding neutrons, high-molecular materials such as polyethylene, paraffin, and epoxy resin mixed with boron, and materials containing large amounts of hydrogen such as water are mainly used. Since concrete also contains hydrogen, it is used as a construction material that also serves as a shield.

 Hydrogen is very important for shielding neutrons.Fast neutrons irradiated into a substance lose their energy due to elastic scattering with hydrogen atoms in the substance and become thermal neutrons.Thermal neutrons are hydrogen and other elements Captured by nuclei. Thermal neutrons are more likely to be captured by nuclei with a larger thermal neutron capture cross section, but in this case secondary Ί rays may be emitted, so neutron beam shielding should include the shielding of this secondary y ray. There must be.

 Therefore, when shielding neutrons, or simultaneously shielding neutrons, a-rays, and X-rays, stack a neutron-shielding material such as polyethylene, paraffin, or water and an a-ray shielding material such as lead or iron. In particular, radiation facilities involving neutrons, shielding of waste, nuclear fuel, RI, etc., transport containers, and related equipment are constructed of high-density concrete, lead, iron, etc. The shield is made of polyethylene, paraffin, water, etc. as a completely different shield while being manufactured, or the shield is made of only a concrete structure.

When only concrete is used as a shield, its shielding ability is not sufficient. There is a problem that a considerable wall thickness is required and the usable area of the facility is reduced. In addition, concrete structures have the disadvantage of being very expensive, because they must absorb radioactive contaminated water due to their water absorption, and must be waterproof-coated or polymer-coated.

 In addition, when concrete, iron, lead, etc. are combined with polyethylene, paraffin, etc., it is difficult to construct and manufacture them due to poor adhesiveness. Furthermore, since the thermal expansion coefficients of the two are significantly different, cracks, warpage, desorption, etc. occur due to the difference in temperature, so considerable care must be taken in terms of construction and temperature control after production. Also, polyethylene and paraffin melt at a relatively low temperature, and varffin in particular tends to ignite, so careful attention must be paid to heat and fire resistance, resulting in extremely expensive facilities and products. When water is used to shield neutrons, the location and method of use are limited because of the liquid.

 The present invention eliminates the need for the above-mentioned drawback of a double structure by simultaneously shielding neutron rays, 7 rays, and X-rays, and has sufficient strength, excellent moldability, workability, and heat resistance. An object of the present invention is to provide a new type of low-cost radiation shielding material having excellent properties, hydrophobicity and chemical resistance.

 Conventionally, radiation shielding materials were generally considered separately for 7 wires, X-rays, and neutrons. A substance with a high density is effective for shielding materials for X-rays and X-rays, whereas a substance containing a large amount of hydrogen is more effective for neutrons, so it is conceptually a low-density substance. Was considered to be effective, and it was thought that the two shielding materials could not be shared because of inconsistency.

 In addition, the hydrogen content (% by weight) of the composition consisting of high-density inorganic material and synthetic resin is significantly lower than that of the molded product obtained from the resin alone, which is the base material. Was also thought to fall with it.

 [Disclosure of the Invention]

The present inventors have focused on the fact that what is important in neutron shielding is not simply the hydrogen content (% by weight), but the number of hydrogen atoms per unit volume (hydrogen atom density). The hydrogen atom density of the composition obtained by mixing the high-density inorganic substance in the thermosetting resin material is higher than the hydrogen content (weight ), The neutron shielding effect was not as high as that of the resin alone as the base material. Reached.

 According to the present invention, Pb, W, Cr, and Pb are added to 100 parts by weight of at least one kind of thermosetting resin material selected from a fuanol resin, an epoxy resin, a cresol resin, a xylene resin, a urea resin, and an unsaturated polyester. Co, Cu, Fe, Mn, Mo, Ag, Ta, Cd, Dy, Eu, Gd, Au, In, Hg, Re, Sm, U or at least one selected from these compounds A radiation shielding material capable of simultaneously shielding X-rays, X-rays, and neutrons, characterized by containing 50 to 2,000 parts by weight of various inorganic substances and having a molded article density of 2.0 or more is provided. You.

 It is desirable to use a thermosetting resin which contains a large amount of hydrogen and is strong against heat, for example, the radiation shielding material in the present invention. For example, fuynol resin, epoxy resin, cresol resin, xylene resin, urea resin, non- A saturated polyester resin or the like may be used alone or in combination of two or more. Thermosetting resins have sufficient strength, excellent moldability and addi- bility, and are relatively heat-resistant dogs. Depending on their selection, they can be used at 150 ° C or higher. The molecular weight range or the degree of polymerization of the thermosetting resin used in the present invention is not particularly limited.

 In addition, the use of a substance with as high a density as possible increases the shielding effect of 7 rays and X-rays, and an element with a large thermal neutron capture cross section or a substance containing a large amount of such elements is more effective in shielding neutron rays. By using or combining a high-density inorganic substance having these properties, it is possible to produce a more excellent radiation shielding material. The high-density inorganic substances used in the present invention include Pb, W, Cr, Co, Cu, Fe, Mn, Mo, Ag, Ta, Cd, Dy, Eu, Gd, Au, In , H g, Re, Sn and U, or at least one element selected from the group consisting of these compounds is used in a powder or pellet state. These compounds also include minerals such as, for example, iron ore, nickel ore, and copper ore.

The amount of the inorganic substance added to the thermosetting resin is preferably in the range of 50 to 2000 parts by weight of the inorganic substance per 100 parts by weight of the thermosetting resin. If it is less than 50 parts by weight, the shielding effect of a-rays and X-rays is inferior. In addition, the molded product becomes brittle and the mechanical strength of the molded product is deteriorated.

 For shielding in environments where various radiations such as neutrons and 7 rays coexist, the most effective shielding is performed by appropriately setting the mixing ratio within the above mixing ratio depending on the intensity and characteristics of various radiations. be able to. When the above composition is cured and molded, the density of the molded product must be 2.0 or more. Below this value, the ability to shield 7 rays and X-rays is inferior and unsuitable for simultaneous shielding. Since the density of concrete is usually 2.0 to 2.2, it must be larger than the shielding capacity of concrete.

 In the process of kneading high-density inorganic powders or granules in a thermosetting resin solution, air entrainment or volatile substances used as resin diluents remain in the composition and remain in the composition However, a molded article having a sufficient density may not be obtained. In order to prevent this phenomenon, defoaming kneading under reduced pressure and vacuum, and addition of an antifoaming agent that reduces surface tension and makes it easier for air bubbles to escape from the material will improve the density of molded products. It is valid. It was also confirmed that this operation was useful for improving the shielding performance of each radiation. Examples of the antifoaming agent used in the present invention include silicone-based and alcohol-based defoaming agents. In general, the amount of the defoamer added is preferably 1% by weight or less based on the total weight.

 Next, in the present invention, a high-density inorganic substance is added to the thermosetting resin, and a hydrogen storage alloy that has a relatively high dissociation temperature and combines and holds hydrogen up to a high temperature is added and mixed to maintain high density. As a result, it was found that the hydrogen atom density could be further increased. Hydrogen storage alloys have a hydrogen atom density equivalent to that of polymer compounds such as resins, but are considerably higher in density than polymer compounds, so they are very effective for simultaneous shielding of neutron rays, α rays, and X-rays.

Hydrogen storage alloys can store hydrogen as metal hydrides by reacting with hydrogen gas, and Ti, La (R), Mg, and Ca systems are known. However, for this purpose, an Mg system with a high hydrogen dissociation temperature at normal pressure is considered optimal. As the hydrogen storage alloy that can be used in the present invention, for example, M g H ₂ M g systems such _{as, M g. 2 M g- N} i system such as N i _2, M, such as M g C u Ho ₇ g- C u _{system, M g C a H 3 72} M g- C a system such as, and metal hydrides such as L a- M g system such as _{L a 2 M g 17 H 17} . The amount of hydrogen storage alloy added depends on product cost and cost. In consideration of the radiation shielding performance and the like, the range is preferably 1 to 50 parts by weight with respect to 100 parts by weight of the thermosetting resin.

 [Preferred embodiment of the present invention]

 Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.

In the test of the shielding performance, the thickness (1Z10 valence layer) of each test material for setting the dose equivalent rate of each radiation to 110 was determined, and the evaluation was performed based on the thickness. The ² C f as a neutron source in the test, was used ^6G Co as § ray source.

 [Test 1]

Bisphenol-based modified epoxy resin (epicon R-130A manufactured by Dainippon Ink and Chemicals, Inc., curing agent: Epicon R-130 BW manufactured by Dainippon Ink and Chemicals, Inc.) as a thermosetting resin and liquid Using phenolic resin (Regitop PL-4558, manufactured by Gunei Chemical Industry Co., Ltd., methanol-soluble), and metal lead powder, lead oxide (II) (specific gravity: 9.53), and tungsten oxide (VI) as high-density inorganic substances. Powders of wolframite (specific gravity: about 7.16) and iron pellets (specific gravity: 7.85), which are minerals whose main components are, are selected according to the mixing ratio shown in Table 1. , Deaeration kneading and addition of defoaming agent (1% by weight of silicone defoamer, KS-603, Shin-Etsu Chemical Co., Ltd.) Inject 60 x 60 x 2 cm Molded into One had to those of, measure the density and shielding performance, the hydrogen content (wt%) and was determined a hydrogen atom density. As comparative examples, epoxy resin alone (test number No. 1), polyethylene (low-density polyethylene manufactured by Sumitomo Bey-Kit Co., Ltd.), concrete, and carbon steel (SS41) were also used. Table 1 shows the obtained results. Table 1 Composition ratio (parts by weight) 7k 1 1 10-valent layer (cm) Content Density (X

 Epo fueno zulu

o. Metal iron oxide pellets (g / cm ³ ) lOVml) 252 Cf 60-Co

 Lead powder J Lead% neutron 7-line i fl 5

 Say

 1 100 0 0 0 0 0 1.35 8.04 6.478 15.8 33.0

2 100 0 50 0 0 0 2.05 5.38 6.547 15.6 22.5

3 100 0 0 100 0 0 2.23 4.05 5.394 15.4 20.0

4 100 0 0 0 100 0 2.33 4.05 5.638 15.2 18.2

5 100 0 0 150 0 0 2.53 3.25 4.917 16.0 17.2

6 100 0 0 0 150 0 2.74 3.25 5.326 15.8 15.7

7 Ι ϋϋ U U l ib 1 丄 b U 3.13 2.46 4.597 16.1 13.8

Q 丄 LMJ U U ΔΌΚ) U 3.81 1.66 3.785 16.3 11.8 q oU π U 1 io 1 丄 Ο π U 3.10 2.33 4.315 16.3 14.1

1 n 100 0 0 115 115 1200 5.64 0.54 1.806 27.3 8.1

1 1 100 0 0 200 200 1600 5.89 0.40 1.404 31.5 7.8

12 100 0 0 150 150 2000 The test material cannot be manufactured because it is brittle.

 13 50 50 0 115 115 1200 5.52 0.50 1.655 28.9 8.3

14 50 50 0 150 150 2000 The test material cannot be manufactured because it is brittle.

15 Polyethylene 0.92 14.40 7.912 13.0 44.5

16 concrete 2.10 '1.10 1.380 31.0 26.0

17 Carbon steel (SS41) 7.85 38.6 7.2 Table 1 shows that the test materials of Examples No. 2 to No. 9 have the same or higher neutron shielding ability than the case of the epoxy resin of No. 1 which is the comparative example alone. As the density increases, the 7-ray shielding capacity has also increased, and it is clear that the 7-ray, X-ray shielding ability and the neutron shielding ability have both high performance.

 Also, the examples of No. 10, No. 11, and No. 13 have the same or higher neutron shielding capacity than the concrete of No. 16, which is a comparative example. In addition, it shows excellent y-ray shielding ability close to that of No. 17 carbon steel (SS41), which also has high performance in both a-ray, X-ray shielding ability and neutron ray shielding ability. One thing is clear.

 As described above, in all the examples, when the 7-ray shielding ability and the neutron shielding ability were considered in an integrated manner, the superiority was clearly recognized as compared with any of the comparative examples, and by changing the mixing ratio, The X-ray and X-ray shielding performance and neutron shielding performance can be set arbitrarily, and it is possible to manufacture the most effective shielding material according to the situation at that site. In addition, the test materials of No. 12 and No. 14 were brittle and could not be manufactured, and the neutron shielding performance of the test material of No. 11 was lower than that of concrete. When the mixing ratio of the high-density inorganic substance to 200 parts by weight exceeds 2000 parts by weight, it is understood that a sufficient neutron beam shielding effect cannot be obtained and a molded article having sufficient strength cannot be obtained. .

 [Test 2]

The density and shielding ability of the test material No. 7 in Test 1 were compared when no antifoaming agent was added or deaeration kneading was performed, or when both were not performed. As a defoaming agent, 1% by weight of a silicon-based defoaming agent was added to the mixture of the resin and the inorganic substance, and deaeration and kneading were performed under reduced pressure. Table 2 shows the obtained results. Table 2

 From Table 2, it can be seen that in the production of high-density shielding materials, the addition of an antifoaming agent and deaeration and kneading have considerable effects, and not only increases the density, but also greatly affects the shielding performance of each. It is clear that.

 [Test 3]

Test 1 No. 5, to reduce the rate of in lead oxide and Uorufuramaito to No. 6, was mixed with M g- N i based alloy _{(M g 2 N i H 4} 2) as a hydrogen-absorbing alloy instead test The materials were evaluated for their density, hydrogen atom density, and shielding performance. The Mg-Ni-based hydrogen storage alloy can hold hydrogen up to a high temperature of 300 ° C or more in a normal state. The test materials of No. 21 and No. 22 were also deaerated and kneaded, and an antifoaming agent was added. Table 3 shows the obtained results.

 Table 3 Composition ratio (parts by weight) Density Hydrogen atom 1 Decavalent layer (cm) Epoxy dye Density (X

Hydrogen oxide storage (g / cm ³ ) 10 ²² / ml) 252-Cf 60-Co resin

 No. Lead alloy Neutron 7 wire

 Lamai

 5 100 150 0 0 2.53 4.917 16.0 17.2

21 100 125 0 25 2.50 5.391 15.7 17.2

6 100 0 150 0 2.74 5.326 15.8 15.7

22 100 0 125 25 2.69 5.801 15.3 15.7 From Table 3, it can be seen that No. 21 and No. 22 obtained by mixing the hydrogen storage alloy had the same line shielding performance as No. 5 and No. 6 not mixed with the hydrogen storage alloy. The neutron shielding ability has been improved while having power, and its superiority is clear.

 [The invention's effect]

 The radiation shielding material according to the present invention has a simultaneous shielding ability of X-rays, neutrons, and neutrons, which is much better than the conventional laminated type concrete, so that the shielding material can be made compact. By setting the mixing ratio of the raw materials appropriately, it is possible to design an optimal shielding material. Furthermore, by selecting the type of thermosetting resin or high-density inorganic substance, the production method, and the like, it is possible to produce a shielding material having sufficient mechanical strength and heat resistance for use. In addition, technologies related to molding of a thermosetting resin as a base material have already been established in various fields, and the present invention can be manufactured by utilizing those technologies and equipment. There are advantages such as being able to provide a cheap and stable shielding material.

Claims

The scope of the claims 1. Pb, W, Cr, Co, Cu, 100 parts by weight of at least one thermosetting resin material selected from phenolic resin, epoxy resin, cresol resin, xylene resin, urea resin and unsaturated polyester At least one inorganic substance selected from Fe, Mn, Mo, Ag, Ta, Cd, Dy, Eu, Gd, Au, In, Hg, Re, Sm, U, or a compound thereof Radiation shielding material for a-rays, X-rays, and neutrons, characterized by containing 50 to 2000 parts by weight of styrene and having a molded article density of 2.0 or more.  2. The radiation shielding material according to claim 1, wherein a hydrogen storage alloy is further added to the radiation shielding material.  3. The radiation shielding material according to claim 1, wherein an antifoaming agent is further added to the radiation shielding material.