WO2008016053A1

WO2008016053A1 - Concrete for neutron shielding

Info

Publication number: WO2008016053A1
Application number: PCT/JP2007/064996
Authority: WO
Inventors: Koichi Okuno; Hitoshi Yamada; Masayoshi Kawai
Original assignee: Hazama Corporation; High Energy Accelerator Research Organization
Priority date: 2006-08-02
Filing date: 2007-07-31
Publication date: 2008-02-07
Also published as: JP4532447B2; JP2008039453A

Abstract

A concrete for neutron shielding which has the same compressive strength as concretes made with an ordinary aggregate and can have the excellent ability to block neutrons without the need of thickening the concrete wall. The concrete enables a wide range of space designs in constructing facilities necessitating neutron shielding. The concrete for neutron shielding is characterized in that it comprises cement, water, a coarse aggregate, and a fine aggregate, the coarse aggregate comprises crushed stones of peridotite, the fine aggregate comprises crushed peridotite sand and colemanite, and the content of the colemanite is 5-20 wt.% based on the whole concrete.

Description

Technical field

[0001] The present invention can be used mainly in a nuclear facility, an accelerator facility, an RI (radioisotope) research facility, a medical facility, etc., which can be used for a place requiring radiation shielding, particularly neutron shielding. Background art on neutron shielding concrete with both neutron shielding ability and strength

[0002] In radiation shielding in nuclear facilities and medical facilities, neutron shielding, which has been neglected in the past, is important as well as improving the performance of equipment used in the facility. Therefore, in order to improve such neutron shielding, for example, a method of increasing the wall thickness of concrete and a method of locally using a neutron shielding resin have been proposed. In addition, in the International Fusion Experimental Reactor ITER etc., expensive boron carbide (B C) is used for neutron shielding.

Concrete mixed with 4 is adopted.

However, in the method of increasing the wall thickness of the concrete, the occupied area of the wall becomes large, and it is difficult to design the facility efficiently. On the other hand, when using concrete mixed with neutron shielding resin or boron carbide, there is a problem in terms of cost, and there is also concern about the durability of the neutron shielding material.

[0003] JP-A-6-1645 discloses a boron-containing aggregate such as colemanite (apatite) and an oil admixture in which a surfactant that emulsifies the oil is mixed with an oil such as mineral oil. Neutron shielding concrete has been proposed in which each is mixed at a predetermined ratio. The scheelite used for the concrete has an excellent neutron shielding ability. However, there is a problem in that the strength of the obtained concrete does not appear when a large amount of borohydrite is mixed in the concrete. Therefore, when ashstone is used as an aggregate, it is difficult to achieve both desired neutron shielding ability and strength. In addition, the neutron shielding concrete uses a special mineral oil, which makes it difficult to use in the field.

On the other hand, in the compressive strength test of concrete blocks using limestone as coarse aggregate It has been reported that the strength could be maintained even when blended to some extent (Journal of Nuclear Materials 212-215 (1994), pl720-1723). However, it has been reported that when borohydrite is used as a fine bone agent, an excellent compressive strength cannot be obtained when the blending ratio is increased (Volkman, D. h.ana Bussolini). , PL, Journal or esting and bvaiuation, J¾ VA, Vol. 20, No. l, Jan. 1992, pp.92-96). In short, in order to give excellent neutron shielding ability, when it is used as fine bone so as to disperse the borohydrite throughout the concrete, the actual condition is that the desired strength is not obtained. Therefore, it is desired to develop concrete that combines excellent neutron shielding ability and strength.

Disclosure of the invention

Problems to be solved by the invention

[0004] An object of the present invention is to exhibit compressive strength comparable to that of concrete using ordinary aggregates, and to exhibit excellent neutron shielding ability without increasing the wall thickness of the concrete. The purpose is to provide concrete for neutron shielding that can be designed in a wide space during the construction of facilities that require a large amount of space. Means for solving the problem

[0005] As a result of intensive studies to solve the above problems, the present inventors have used peridotite quarry as coarse aggregate and peridotite crushed sand and peridotite as fine aggregate. In addition, the inventors have found that the above-mentioned problems can be solved by incorporating the above-mentioned borohydrite in a specific ratio with respect to the total amount of concrete, and have completed the present invention.

That is, according to the present invention, a neutron shielding concrete containing cement, water, coarse aggregate and fine aggregate, including peridotite quarry as coarse aggregate, and peridotite crushed sand as fine aggregate and A neutron shielding concrete is provided, characterized in that it contains a perovskite and the content ratio of the perovskite is 5 to 20% by weight based on the total amount of the concrete.

The invention's effect

[0006] The concrete for neutron shielding of the present invention includes peridotite quarry as coarse aggregate, includes peridotite crushed sand and peridotite as fine aggregates, and contains the perovskite at a specific ratio. It exhibits a compressive strength comparable to that of ordinary aggregates, and has excellent It can exhibit sexual barrier ability. For example, when evaluating with a ²⁵² c source that emits neutrons in the energy region that is important for exposure dose evaluation, it depends on the energy of the neutrons to be shielded and the thickness of the concrete compared to ordinary concrete of the same wall thickness. The difference in performance is a different force About 1.5 ~; 1. 7 times the shielding ability can be demonstrated, and the performance of secondary gamma ray generation can be less than about 1/2 to 1/10 Is possible.

Therefore, it can be suitably applied to facilities that require radiation shielding, particularly neutron shielding, in nuclear facilities, accelerator facilities, RI research facilities, medical facilities, and the like.

Brief Description of Drawings

[0007] FIG. 1 is a graph showing changes in compressive strength of concrete in Example 1 and Reference Example 1 with age.

FIG. 2 is a graph showing the calculation results of shielding performance of concrete in Example 1 and Reference Example 1 against a ²⁵² C inertial source.

FIG. 3 is a graph showing the calculation results of shielding performance of concrete in Example 1 and Reference Example 1 against a 14 MeV neutron source.

[Fig. 4] Changes in compressive strength with age of concrete in Examples 2 to 4 and Reference Example 2.

FIG. 5 is a graph showing the calculation results of shielding performance of concrete in Example 2 and Reference Example 2 against a ²⁵² C inertial source.

FIG. 6 is a graph showing the calculation results of shielding performance of concrete in Example 2 and Reference Example 2 against a 14 MeV neutron source.

BEST MODE FOR CARRYING OUT THE INVENTION

[0008] Hereinafter, the present invention will be described in more detail.

The neutron shielding concrete of the present invention includes cement, water, specific coarse aggregate, and specific fine aggregate.

As the cement, various Portland cements such as normal, early strength, super early strength, low heat, and moderate heat can be used.

In the neutron shielding concrete of the present invention, the amount of cement used and the water / cement ratio are appropriately selected according to the facility to be constructed, based on the conditions during normal concrete production. The power to do S. Similarly, the amount of aggregate can be selected as appropriate.

[0009] The peridotite (Olivine rock) used in the present invention has a slightly different composition depending on the place of origin, but usually contains SiO and MgO as main components and contains about 12% by weight of crystal water. In general, peridotite crushed stone used as coarse aggregate is usually crushed stone with a shortest diameter of about 5 mm that can pass through a 25 mm sieve. As the coarse aggregate, it is possible to contain other ordinary coarse aggregates other than peridotite crushed stone. However, in order to further improve the desired excellent neutron shielding ability of the present invention, the higher the content of peridotite crushed stone in the coarse aggregate, the better.

The content ratio of the coarse aggregate can be selected as appropriate, but is usually 40 45 wt%, preferably 41 42 wt%, based on the total amount of concrete.

[0010] In the present invention, the peridotite crushed sand used as the fine aggregate is usually crushed sand having a particle size of a size that can pass through a 10-mm sieve from the viewpoint of dispersibility in concrete. The blending ratio of the crushed rock is usually 17 36% by weight, preferably 17 26% by weight, based on the total amount of reinforced concrete that can be selected as appropriate considering the desired effect. If it exceeds 36% by weight, the desired neutron shielding ability may be reduced. On the other hand, if it is less than 17% by weight, the desired strength cannot be ensured! /.

[0011] In the present invention, the wollastonite used as the fine aggregate is a mineral containing 2Ca0.3B 0 · 5 主成分 0 as a main component, and preferably containing 43.49% by weight or more of Β0. In order to obtain the desired neutron shielding ability and strength, it is preferable that the boehmite has a particle size that normally passes through a 10 mm sieve, preferably a particle diameter that passes through a 5 mm sieve.

The content ratio of the borohydrite is about 520% by weight, preferably about 1018% by weight, based on the total amount of concrete, and may satisfy the condition of 0.4 to 22% by weight on the basis of the total amount of aggregate. This is preferable in that the desired effect can be further improved. If the content ratio of borohydrite to the total amount of concrete is less than 5% by weight, the desired neutron shielding ability cannot be obtained, while if it exceeds 20% by weight, the desired strength cannot be obtained! /.

[0012] In the present invention, the fine aggregate may be a general aggregate other than the peridotite crushed sand and the peridotite. It is also possible to include ordinary fine aggregate. However, in order to further improve the desired effect of the present invention, the content of other fine aggregates is low! /, And it is preferable!

In the present invention, the content of fine aggregate can be selected as appropriate, but is usually 27 to 41% by weight, preferably 27 to 36% by weight, more preferably 28 to 35% by weight, based on the total amount of concrete. . If it is less than 27% by weight, the desired neutron shielding ability may be reduced, while if it exceeds 41% by weight, the desired strength may not be ensured.

[0013] In the neutron shielding concrete of the present invention, the reason why both excellent compressive strength and neutron shielding ability can be achieved is considered to be due to the following actions.

In general, the interaction between neutrons and matter in radiation is complex, and the interaction changes depending on the difference in neutron energy. Neutron energy is divided into slow neutrons from OkeV to lkeV, medium neutrons from lkeV to 500 keV, and fast neutrons from 500 keV to 1 MeV.

There are roughly two types of neutron interaction: elastic scattering and inelastic scattering. Elastic scattering is caused by slow neutrons and medium neutrons. The interaction with light nuclei such as hydrogen reduces neutron energy. To do. In particular, since hydrogen atoms have the same mass as neutrons, neutron energy can be reduced efficiently. On the other hand, inelastic scattering is a phenomenon that occurs in fast neutrons, and the energy of neutrons decreases due to interaction with iron and the like.

The peridotite employed in the present invention contains a large amount of water, so that hydrogen atoms and neutrons in the water cause elastic scattering, and slow and medium speed neutrons are decelerated. In addition, iron is also included because it is a rock, and it is thought that this iron can also reduce the speed of fast neutrons.

[0014] The scheelite employed in the present invention is a natural rock and contains an average of 40% by weight or more of a boron component. Boron has been conventionally known to have the property of absorbing slow neutrons, and is a material used for nuclear reactor control rods. Therefore, in the neutron shielding concrete of the present invention, the neutrons decelerated by the peridotite are absorbed by the boron of the borohydrite, thereby efficiently shielding the neutrons. Can do. And since such an efficient neutron shielding ability is obtained, the desired neutron shielding ability can be achieved without increasing the content ratio of borohydrite as a fine aggregate that causes a decrease in strength. Degradation can be minimized. In addition, the use of peridotite as a coarse aggregate can further suppress the decrease in strength. In the present invention, it is considered that the desired effect can be achieved by the above-described action.

[0015] The neutron shielding concrete of the present invention can be manufactured by a method similar to that of ordinary concrete, and can therefore be easily constructed on site. At this time, if necessary, various additives and admixtures usually used for concrete are appropriately selected and used.

Example

[0016] Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.

The materials used in the examples are as follows.

Coarse aggregate (A): Peridotite quarry with a minimum diameter of 5 mm that passes through a 25 mm sieve

Coarse aggregate (B): j 11 gravel passing through a 25mm sieve (ordinary coarse aggregate)

Fine aggregate (A): Peridotite crushed sand passing through 10mm sieve

Fine Aggregate (B): Crushed calcite passing through 10mm sieve

Fine Aggregate (C): 1 J 11 sand passing through Omm sieve (ordinary fine aggregate)

Cement: Ordinary Portland cement

Admixture: AE water reducing agent

[0017] Example 1 and Reference Example 1

A concrete molding having a diameter of 100 mm and a height of 200 mm was prepared according to the composition shown in Table 1, and the compressive strength at the age of 7, 28, 56 and 91 days was measured according to JIS A 1108. The results are shown in Figure 1.

From Fig. 1, it was found that the concrete according to Example 1 has the same strength as the concrete of Reference Example 1 using ordinary aggregate.

[0018] [Table 1] Cement Coarse Aggregate (Weight ¾) Fine Aggregate (Heavy Aqueous Agent Water Cement Bone Shelving Fine Bone Agent (B) (Weight a¾ (B) (Weight Ratio (%) Ratio (Weight%) 3 3 5 2 0 9 8 2 0. 0 1 6 5. 0 7 9. 0 1 0. 0 mi 1 0 0-3 3 5 1 2 9 8 0. 0 1 6 5. 0 7 9. 0 0

Next, the neutron shielding performance of the concrete composition of Example 1 was compared with the concrete composition of Reference Example 1 by simulation calculation. The calculation code used is MCNP version 5, a neutron behavior simulation code developed at the Los Samos National Laboratory. The nuclear data used is JE NDL-3.3 maintained by the Japan Atomic Energy Agency. As input data, elemental analysis of concrete actually produced in Example 1 was performed, and the analysis result was used as input data for simulation calculation. Both of these calculation codes and nuclear data are widely used all over the world, and have a great track record as calculation codes that accurately reproduce experimental values.

The simulation calculation reproduces the energy range from slow neutrons to fast neutrons used in general nuclear facilities, so the shielding performance for ²⁵² Cf neutron sources (reproducible from slow neutrons to near lOMeV) and fusion facilities In order to reproduce the shielding performance of the 14 MeV neutron source, the shielding performance was calculated. The results are shown in Fig. 2 and Fig. 3.

Yes

From Fig. 2 and Fig. 3, the concrete of Example 1 composition is more than 1.7 times for the ²⁵² Cf neutron source and 1. It can be seen that the shielding performance is more than 5 times.

[0020] Examples 2 to 4 and Reference Example 2

A concrete molding having a diameter of 100 mm and a height of 200 mm was prepared according to the composition shown in Table 2, and the compressive strength at the age of 7, 28, 56 and 91 days was measured according to JIS A 1108. The results are shown in Fig. 4.

From Fig. 4, the concrete according to Examples 2 and 3 has the same strength as the concrete according to Reference Example 2 that does not use coarse aggregate (A) and fine aggregate (A), which are peridotite. The concrete in Example 4 was also slightly lower than the concrete in Reference Example 2.

[0021] [Table 2] Cement Coarse Aggregate (A) Fine Aggregate (Heavy Work Admixture Water Cement Skeleton Combined Fine Aggregate (?)

(Weight (Weight (A) <B) (Dragon ratio (wt%)

Difficult example 2 100 278 198 78 0. 01 55. 0 76. 6 10. 0

m 3 100 278 169 104 0. 01 55. 0 76. 6 13. 0

Example 4 100 278 141 129 0. 01 55. 0 76. 5 17. 0

Psalm 2 100 278 283-0. 01 55. 0 76. 9 0 Next, the neutron shielding performance of the concrete of the composition in Example 2 was compared with that of the concrete of the composition of Reference Example 2 and Example 1 and Reference Example. Comparison was made in the same way as 1. Figure 5 shows the calculation results of shielding performance for a ²⁵² C fertility source (reproducible from slow neutrons to around lOMeV), and Figure 6 shows the calculation results of shielding performance for a 14 MeV neutron source. From FIGS. 5 and 6, it can be seen that the concrete composition according to Example 2 has better shielding performance than the concrete composition according to Reference Example 2 that does not use peridotite as an aggregate.

Claims

The scope of the claims

[1] neutron shielding concrete containing cement, water, coarse aggregate and fine aggregate,

Peridotite quarry is included as coarse aggregate, peridotite crushed sand and peridotite are included as fine aggregate, and the content ratio of the perovskite is 5 to 20% by weight based on the total amount of concrete. Neutron shielding concrete.

[2] The neutron shielding concrete according to claim 1, wherein the content ratio of the borohydrite is 10 to 18% by weight based on the total amount of the concrete.

[3] The content of coarse aggregate is 41 to 42% by weight based on the total amount of concrete, the content rate of fine aggregate is 33 to 36% by weight based on the total amount of S concrete, and peridotite as fine aggregate The neutron shielding concrete according to claim 1 or 2, wherein the sand content is 17 to 26% by weight based on the total amount of concrete.

[4] Peridotite quarrying force as coarse aggregate A quarry with a minimum diameter of 5 mm that can pass through a 25 mm sieve, and a particle size that can pass through a 10 mm sieve peridotite used as fine aggregate The neutron shielding concrete according to any one of claims 1 to 3, wherein the neutron shielding concrete has a particle diameter that passes through a 10-mm sieve with a calcite strength used as a fine aggregate.