JPH01147399A - Fiber-reinforced neutron shielding mortar concrete - Google Patents

Abstract

PURPOSE:To improve moldability, durability and economic efficiency by adding a cement hardener and reinforcing fibers to cement so that a large amt. of boron compds. can be added to the cement. CONSTITUTION:Powders of colemanite, borocalcite, boric acid, borax, titanium boron, zirconium boron, molybdenum boron, etc., are added at 5-200wt.% as the boron compd. to the cement and lithium hydroxide, potassium aluminate, calcium acetate, etc., are added at compounding ratio (%) of the boron compd.X0.1 as the hardening accelerator to the cement. The reinforcing fibers such as bundled filament and alkali resistant glass fibers formed by bundling monofilaments of filaments of polyvinyl alcohol synthetic fibers, polyacrylonitrile synthetic fibers, carbon fibers, aramid fibers and polyarylate fibers are added at 0.3-5% thereto. The flash setting and delayed hardening of the cement by the boron ions are thereby prevented and the installation characteristic, durability and economic efficiency improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a fiber-reinforced neutron shielding mortar for the purpose of biological protection to prevent radiation damage such as neutron beams and tertiary gamma rays exerted on the human body from a neutron source. Concerning concrete.

<Prior art and problems to be solved by the invention> The fundamental principle in the design of radiation shields is to convert radiation energy into thermal energy through the interaction between radiation and matter. Of the radiation types, radiation has a large interaction with matter and is easily shielded, but gamma rays and neutrons have a large ability to penetrate materials, and some of their energy is transmitted to other radiation due to scattering. Handling is complicated as there are many cases of conversion. Therefore, it is mainly gamma rays and neutrons that pose problems in radiation shielding. The basic idea behind these shields is that when the energy is small, the probability of absorption by a substance increases, so the energy is lowered and absorbed.

Steel is the best material for shielding structures.

Iron has a large absorption cross section for fast neutrons, thermal neutrons, and gamma rays, and it can withstand high temperatures and is hardly affected by radiation (111). However, when iron captures neutrons, it emits high-energy gamma rays. Therefore, note α is required.

The next most commonly used material is concrete.

This is because it is inexpensive, has excellent strength, stability, moldability, and uniformity, and is hardly susceptible to radiation damage. Furthermore, it has a large absorption of gamma rays and slows down neutrons to a T effect. However, the drawback is that it has poor thermal conductivity, which poses a problem in high-power nuclear reactors because it is difficult to remove the heat generated by shielding. Portland cement is generally used for shielding concrete, but moderate heat Portland cement is superior because it generates less heat and shrinks less.

As for the aggregate, heavy concrete is preferable because the higher the specificity, the greater the gamma ray shielding effect. Heavy concrete uses Portland cement as cement and barite (Ba5O,), S9, iron ore, etc. as aggregate.

Now, the problem with neutron shielding is that high-energy gamma rays are emitted when neutrons are captured. Therefore, the most ideal thing would be to decelerate with a material that does not emit strong secondary gamma rays and then shoot with a material that does not emit strong secondary gamma rays.

This is caused by the Ilλ
The accelerated neutrons are further slowed down by a substance (e.g., paraffin, polyethylene, water, etc.) that contains hydrogen atoms (with a very large neutron scattering cross section), and then are bombarded by a substance containing a large amount of boron atoms (absorption).・Extinction) method is often used.

Concrete has features such as low cost, mechanical strength, stability, formability, uniformity, and resistance to radiation deterioration, so by adding compounds containing hydrogen atoms and boron compounds to the concrete mix, it can be made optimal as a neutron shielding material. What is obtained is easily boiled. Particularly effective hydrogen atoms include bound water in hardened cement, capillary water, and the like. However, the biggest drawback is that when a boron compound is added to cement, an abnormal reaction occurs, and the hardened material shrinks and deforms significantly, becoming like a sun-dried brick. That is, the workability of ordinary cement concrete cannot be obtained, and the compressive and bending strengths of the concrete are significantly reduced, so boron compounds cannot be easily used as is or as additives in concrete.

As a neutron shielding material, a method of mixing a boron compound into a polymer resin such as polyethylene has been adopted as described in Japanese Patent Publication No. 62-493os+; Publication No. 62-49306; However, problems remain in terms of nonflammability, moldability, and economic efficiency.

JP-A-58-86496 describes that the above-mentioned problems can be solved by making boron concrete into a sandwich structure with heavy concrete, but this technique has problems in terms of workability, formability, and illegality. It is not satisfactory in terms of strength. In addition, examples of concrete using volcalzite and colemanite are also described in "Atomic Industrial Materials," but poor coagulation occurs due to dissolved boric acid during construction, and the strength of the mortar cement of the molded product is not satisfactory. do not have.

Means for Solving the Problems〉 An object of the present invention is to use an AI material for the purpose of protecting living organisms, so that it can be easily formed and formed to shield equipment and structures that are sources of neutron generation, and it can be formed at high cost. The object of the present invention is to provide fiber-reinforced neutron-shielding mortar concrete that has mechanical strength and toughness in bending, compression, etc., and is highly durable and economical.

This purpose is to create fibers containing 5 to 200 rIim% of a boron compound (all blending ratios are expressed in weight percent based on the hydraulic substance), 0.3 to 5% of reinforcing fibers, and 40% or less of a cement hardening accelerator. The solution is reinforced neutron shielding mortar concrete.

The features of the present invention are as follows: Firstly, by using a curing accelerator, cement is improved in workability by reducing both the instantaneous setting of cement at the initial stage due to the abnormal reaction of boron compounds and the poor curing during curing due to the influence thereof. The mechanical properties of mortar concrete should be improved, and secondly, it should be a neutron-shielding mortar concrete that has excellent formability without deteriorating workability by blending hli strong fibers, and has increased bending and compressive strength and toughness. There are two points.

The key point of the present invention is that a combination of cement and a boron compound, which was previously thought to be suitable, and a cement hardening accelerator is used.
This makes it possible to provide a mortar molded body with remarkable neutron shielding.

This cement hardening accelerator mixes cement with boron compounds, especially compounds such as boric acid, borax, and calcium borate, which easily dissolve in water and release borate ions. This makes it possible to prevent delayed effects and keep it within a range that can be handled in the same way as the hardening reaction of cement.

Specific examples of the curing accelerator used in the present invention include lithium hydroxide, calcium aluminate, and calcium acetate. The effect of the addition of such a hardening accelerator is to reduce the large amount of boric acid ions that are generated when a large amount of boron compounds such as boric acid, colemanite, and polocalcite are added, that is, when they are added in an amount of 35% or more based on the hydraulic material. It is remarkable that
In this case, a hardened cement product cannot be obtained unless a hardening accelerator is added. The amount of curing accelerator added at this time requires a boron compound blending ratio (%) of XO, 1 or more. In order to obtain hardening accelerator properties of cement mortar, high mechanical properties and high neutron shielding properties of the cured product, it is effective to add the curing accelerator in an amount of 40% or less. If it is added in an amount exceeding 40%, the cement mortar generates a large amount of heat during hardening, and the volume changes drastically during hardening, which is not preferable.

More preferably it is 30% or less.

The boron compound used in the present invention is colemanite (ColcmaniLe 2CaO・3BtOs) as a natural mineral.
・511*O), Borocalci
It is preferable to use powder with a nominal sieve size of 5 mm or less. As a synthetic product, boric acid,
Powders of borax, titanium boron, zirconium boron, molybdenum boron are preferred, and boric acid, borax, etc. may be used after being dissolved in water.

The addition rate of boron compound is effective at 5 to 200%, but
Preferably 10-100%, more preferably 25-10
It is 0%. If the addition rate is less than 5%, the neutron absorption ability will be poor, and if it exceeds 200%, the heat generation during /i'Al41 will be intense, and the volume change of the molded product will be large, resulting in uneven thickness,
This is undesirable as it causes cracks to occur due to residual strain.

Concrete is generally strong against compressive forces, but is very weak against tensile and bending forces, and has the disadvantage of being brittle due to its low elongation.

In order to compensate for these shortcomings, the current situation is to provide hli strength by arranging reinforcing bars and steel frames.

The present invention can be used without impairing workability. By adding strong fibers, the disadvantages of mortar concrete, such as tensile strength, bending strength, and impact strength, are improved. The binding fibers uC include polyvinyl alcohol (hereinafter abbreviated as PVΔ)-based synthetic fibers, polyacrylonitrile (hereinafter abbreviated as PΔN)-based synthetic fibers, carbon fibers, aramid fibers U[, and monofilaments of polyarylate fibers or bundled filaments made by focusing filaments. It is preferable to use rod-shaped articles or chopped strands of each of the following. Alkali-resistant glass fiber IF and steel fiber may be used in combination, and one or more fibers may be mixed.

Furthermore, it is effective to use it in combination with reinforcing bars and steel structures.

In particular, PVA-based synthetic fibers have good adhesion to cement.
．． In addition, PVA compounds have excellent long-term alkali resistance and chemical resistance against boron compounds in cement, and because PVA compounds contain large amounts of hydrogen atoms, they have high neutron absorption performance and are also excellent against radiation deterioration. Reinforcement ta
It is the most effective fiber.

Fiber e (1°
Physical properties include mechanical properties such as a tensile strength of 90 kg/mm' or more and a Young's modulus of 1700 kg/mm' or more. When the tensile strength is less than 90 kg/n+m'' and the Young's modulus is less than 1700 kg/mm'', a sufficient hli strength effect of mortar concrete cannot be obtained.

tM t (U shape p is fineness of 6 denier or more and aspect ratio (tJ! t (the value obtained by dividing the length (L) by the diameter (D) of the circle corresponding to its cross-sectional area) or 30 to 300. The cut surface of the fiber may be a circular or oblate shape, and it may be a monofilament or a monofilament made of melamine resin, formalin resin, urea resin, epoxy resin, polyvinyl acetate resin, PVA resin, etc. It may be a chopped strand obtained by cutting the bundled fibers <4t.The aspect ratio (L/D) in the case of the bundle $a i (t) is the circular diameter (D ).Thin fibers with a fineness of less than 6 deniers increase the number of fibers added, impairing the fluidity of mortar concrete and causing problems during mixing and construction.The preferred fineness is 100. ~10000
denier, more preferably 350 to 5000 denier.

The aspect ratio is a measure of the morphology of the fibers, and if the aspect ratio is less than 30, the mixing and dispersibility in mortar concrete is good, but the tensile strength after hardening of mortar concrete is
The fibers eft are pulled out due to bending stress, and no reinforcing effect can be obtained. On the other hand, if it exceeds 300, the fibers become entangled, and even if added to mortar concrete, uniform dispersion of fibers f(i) cannot be obtained, so no reinforcing effect can be obtained.A more preferable range is 40 to +00. .

The addition rate of fiber is 0.3 to 5%, more preferably 0.
．． It is 5-2%. If the addition rate of fiber is less than 0.3%, sufficient reinforcing performance for tensile bending and toughness cannot be obtained.1.
If it exceeds 5%, the fluidity of the mortar during kneading will be impaired due to the amount of fibers being too large, and problems will occur in workability as uniform dispersion of fibers cannot be obtained, and of course sufficient hli strength performance will not be obtained. I can't. Mortar concrete using reinforcing fibers meeting these conditions can be as good as conventional mortar concrete in handling properties during kneading and molding, as well as formability and workability.

In addition, by specifying the strength and Young's modulus of ta t (m), dispersibility in mortar concrete, and addition rate, the reinforcing performance is excellent, and when the economical efficiency of fibers is included, the reinforcing effect is better than ever. You can get what you want.

Cement as a hydraulic substance is ordinary Portland cement, moderate heat Portland cement, blast furnace cement (class C), and fly ash cement! - (Class C), Nunka cement, MO cement lj, etc. Other early strength Portland cement, super J11-strong Boltland cement, alumina cement, white Portland cement,
Examples include commonly used cements such as expanded cement.

As the aggregate, polymer resin powder, aggregate for heavy concrete, etc. can be used. The polymer resin powder is a hydrogen atom-containing polymer compound, preferably polyethylene, polypropylene, or PVA, which are paraffinic polymers with a high hydrogen atom content per mole. (Also Borisdylene, polymethyl methacrylate, polyaccuronitrile, cellulose, etc.) can be used, and from the viewpoint of workability, powders whose maximum particle diameter is 211I+1 or less are preferred, and if necessary, usually 30% or less It can be used within the range of

In addition, as aggregate for heavy concrete, magnetite, magnetite, iron sand, barite, iron powder, iron phosphorus, blast furnace slag, etc. can be used, and one or more of these types can be used in combination as required. Usually, it can be added in a range of 200% or less.

Next, the kneading method is to knead the boron compound, polymer resin powder if necessary, bone phase for heavy concrete, and cement using a mortar mixer, a two-socket mixer, an auger mixer, a tilting mixer, an omni mixer, an Eirich type mixer, etc. Dry kneading is carried out using a mixing device such as a mixer or a batcher plant.
Further, water and a cement hardening accelerator are added to the mixture, and finally, reinforcing fibers are added to avoid forming fiber balls to obtain a uniform mortar base.

The molding is performed by pouring the mortar paste into a predetermined mold, or by vibration molding, press molding, centrifugal molding, or the like, if necessary. It can be used for pre-packed concrete, and it can also be poured into formwork with reinforcing bars such as reinforcing bars. Curing is done at room temperature or with steam curing at about 40-80℃ to avoid hardening, then demolding, followed by curing in air or water, resulting in a compressive strength of 150 kg/c after 2 weeks.
It is possible to obtain a cured product having a bending strength of 40 kg/cm" or more.

As is clear from the bending stress vs. bending curve shown in Figure 1, the cured product is reinforced with fibers, so the maximum breaking strength is of course higher than that of the unreinforced one, and the breakage is rapid. This does not occur, and the deflection increases, indicating high toughness. This will be explained below using Examples and Comparative Examples.

Examples 1 to 7, Comparative Examples 1 to 4 When using colemanite, crushed colemanite (passed through a sieve with a nominal size of 1.2 mm), lithium hydroxide, ferrous oxide, PVA powder (average particle size 1 m + a )
A predetermined amount of , and ordinary Portland cement were put into an omni mixer, and the mixer was dry-kneaded for 1 minute, and then a predetermined amount of water was added and kneaded for 5 minutes.

After that, vinylon fiber (RF 35002 manufactured by Kuraray Co., Ltd.)
x 17, fineness 350 denier, tensile strength and Young's modulus 93 kg/+m'' and 3100 kg/mm' respectively, fiber length 17 mm, aspect ratio 85) were added to the mortar paste while loosening so as not to form fiber balls, and A homogeneous fiber-mixed mortar was obtained by kneading for a minute.
As shown.

Next, when using boric acid, put a predetermined amount of boric acid, PVA powder, and ordinary Portland cement into an omni mixer, dry mix for 1 minute, and then add a pre-dissolved lithium hydroxide aqueous solution with a predetermined amount of water. Insert 5
Knead for a minute. After that, vinylon fiber It F 35
002x17 was added so as not to form fiber balls and kneaded for 5 minutes to obtain a uniform fiber-mixed mortar. The formulations are as shown in Example 6.7 and Comparative Example 4 in Table 2.

The mortars obtained in Examples 1 to 7 and Comparative Examples 1 to 4 were immediately poured into predetermined molds (for compression, bending strength measurement, and neutron shielding test) and molded. Demoulding was carried out after being left to dry overnight at room temperature and cured, and curing was also carried out under the same conditions for 4 weeks.

The materials used in the formulation were boron compounds (boric acid: manufactured by Borax Co., Ltd., Colemanite manufactured by Nikinboshi Kogyo Co., Ltd.), curing accelerator (lithium hydroxide: manufactured by Wako Pure Chemical Industries, Ltd.), polymer resin powder (fully saponified PVA fine powder: Kuraray) aggregate (ferrous oxide: hematite manufactured by Kawasaki Steel), aggregate for heavy concrete (ferrous oxide: hematite manufactured by Kawasaki Steel),
Cement (ordinary Portland cement manufactured by Onoda Corporation) and water (Asahikawa tap water) were used.

Observations regarding moldability and molding were performed using the following method.

(1) Moldability: The flow value of mortar was measured according to JIS 5201.

(2) Dispersibility of reinforcing fibers: According to the mortar washing test method according to JIS ^1103, mortar was collected on a wire mesh and washed with water to remove the mortar, and the dispersibility of the fibers was visually judged. Dispersibility is judged as ◎ when it is uniform, × when there are fiber balls, and ○ when it is in the middle.
And so.

(3) Heat generation of mortar during curing: A thermometer was embedded in the mortar and the temperature rise was measured. When the temperature rise was 10°C or more, it was marked as x, and when it was lower, it was marked as ○.

(4) Regarding hardenability: After pouring into a mold and leaving it at room temperature for a day and night, a hardness that allows removal from the mold is rated as ◎, a hardness that is so uncured that it cannot be removed is rated as ×, and a hardness in between is rated as O.

(5) Deformation of the molded product: After pouring into the mold and leaving it at room temperature for a day and night, observe the surface of the molded product for bulges, dents, and cracks. was set to 0.

Measurement of mechanical properties of cured products The specimen for measuring bending strength and compressive strength was 5 cm thick.

+113se+m, poured into a 25cm long formwork, and after curing it became 5cm thick, 115cm long, 15cm long.
A piece cut into lengths of m was used.

(1) Bending strength Using Cointron TTCM, the distance between the supporting points is 10 cm, the loading speed is 0.2 c++/min, the center loading method is used, and the initial fracture strength (Lo
P), the maximum breaking strength (MOR), and the amount of deflection at that time were determined as 411. The bending stress was determined from 3PL/(2bt"). (P is the load kg, SL is the measurement span 10cm, and b and t are the thickness and width of the specimen, respectively) (2
) Compressive strength: The specimen was molded using the same method as the bending strength measurement, and had a thickness of 5 cm+, a medium diameter of 5 cm, and a length of 15 cm. In the measurement, the maximum compressive strength was determined using a universal testing machine manufactured by Shimadzu Corporation at a compression cross-sectional area of 5 cm x 5 cm and a loading rate of 0.2 c*/it. Tables 1 and 2 also show the moldability and mechanical properties during mortar molding.

In the case of using colemanite shown in Table 1 below, when the addition rate of colemanite is 40% or less, a curing accelerator is not added. Looking at the results, from Examples 1 to 3 and Comparative Examples 1 to 3, As the addition rate of colemanite increases, the hardening performance of the mortar decreases, and the compressive strength also decreases.

In particular, in Comparative Example 3, when the colemanite content was 40%, the mortar did not harden. Example 4.5 and Comparative Example 2
shows that the addition of 10% curing accelerator improved the curability of the mortar and also improved the compressive strength.

The effect of adding reinforcing fibers is clear from Example 4 and Comparative Example 2, in which the four reinforcing fibers did not generate cracks and improved bending, compressive strength, and toughness. In particular, with regard to bending strength, the MOR increases, the deflection also increases, and the toughness is significantly improved.

When boric acid shown in Table 2 is used, when comparing Example 6.7 and Comparative Example 4, the mortar of Comparative Example 4 without the addition of a curing accelerator does not harden, but the mortar with 20% curing accelerator added is found. This indicates that the mortar has hardened. Furthermore, the bending and compressive strengths of Examples 6 and 7 were both high, and good molded bodies could be obtained. Example 7 shows that the addition of a hardening accelerator increased both the bending and compressive strengths and improved the toughness compared to Comparative Example 1 in which no boron compound was added.

A typical example of the bending stress-deflection curve is shown in FIG.

Neutron Shielding Effect The neutron shielding concrete of the present invention is intended to shield living organisms from slow neutrons moderated by various moderators and secondary gamma rays generated by their capture. Since neutrons have a large ability to penetrate through substances, not only can brain concrete not only be unable to sufficiently shield neutrons, but also produce secondary gamma rays when reacting with concrete, so it cannot be used as a biological shielding material. The concrete of the present invention is designed to effectively block neutrons by incorporating a boron compound and a hydrogen compound. In other words, neutrons that are scattered in all directions by hydrogen nuclei and are easily captured are absorbed by boron nuclei. The reaction between neutrons and boron nuclei is “B + 'n =
7Li + 1dle + 2.79
It is expressed in MeV and emits charged particles (α particles) and gamma rays. The gamma rays generated at this time do not have much energy, so they can be effectively shielded with ordinary brane concrete. Further, since the α particles ('l1a) are easily shielded, there is no problem. However, gamma rays produced by the reaction between plain concrete and neutrons have relatively high energy, so concrete of the thickness used in this experiment cannot effectively shield them. Therefore, the neutron shielding effect can be determined by detecting captured gamma rays generated by neutron capture.

FIG. 2 is a layout diagram for a measurement experiment of neutron shielding effect, and FIG. 3 is a detailed layout diagram of concrete blocks for measurement. This measurement was conducted at the High Energy Physics Research Institute Neutron Scattering Facility (
KENS). A pulse beam from a 500 MeV proton synchrotron (booster) is irradiated onto a target (uranium-238), and the fast neutrons generated are speeded up by a moderator (solid methane at 238) placed on the target (the neutron intensity at this time is The distribution is shown in Figure 4)
Thereafter, the neutrons were guided to a location behind 29I11 with a low background using a neutron conduit, and were used as incident neutrons for measurement. The intensity of the incident neutrons was measured by a helium-3 counter installed at the outlet of the conduit, and time analyzer (TΔ) 2
was recorded as a pulse waveform.

The samples are Example 1.2.3.6.7 of the present invention and Comparative Example 1
The molded body was made into blocks of a predetermined size, and the arrangement was as shown in FIGS. 2 and 3. The incident neutron is 5
Irradiation was performed within an area of cm x 15 cm.

Measurement of captured gamma rays was performed using six incident neutrons with energy lower than 5 MeV shown in FIG.

That is, a gamma ray scintillator (BGO) is attached to the window of the photomultiply tube, and the detector 3, which is completely shielded from light with black tape, is placed behind (X+) and above (X,) the measurement concrete, respectively, and the emission intensity is measured. It was measured and recorded in a pulse waveform using Time Analyzer 4. Measure!
The measurement was carried out for several minutes to 20 minutes.

Experiment 1 Test mortar concrete used to measure the shielding effect of mortar concrete with different effectiveness rates of colemanite and boric acid was prepared using the formulations of Example 1.2.3.7 and Comparative Example 1 as shown in Figures 5 and 6, respectively. It was molded into the shape shown. Thickness 5c+ of the formulations of Examples 1.2.3 and 7 on the side closer to the neutron source
Comparative example 1 was placed behind m mortar concrete.
The mortar concrete was made to have a thickness of 10 cm, and the overall size was made into a molded body with a thickness of 15 cm and a height of 25 cm, and the intensity of secondary gamma rays at the rear (xl) was measured. The results are shown in Table 3. Also, test N of incident neutron spectrum and detected gamma ray spectrum.
Examples of ol, 5 are shown in Figures 11-14.

Since the maximum intensity of the incident neutron spectrum changes in the margin-normalized values below, test Nos. 2 to 5 are calculated by proportional calculation so that the maximum intensity of test No. (t'1) of the detected secondary gamma ray was determined from the value when .

Experiment I was a measurement of the shielding effect when the colemanite addition rate was varied from 10 to 30%, and the values were normalized to the Blen mortar concrete of Comparative Example 1. Example 2
The detected secondary gamma rays could be reduced to 0.083, and Example 2.3 was also found to have a sufficient neutron shielding effect. The formulation of Example 7 further reduced the normalized secondary gamma ray value to 0.048, and the neutron shielding effect of this formulation was remarkable. This seems to be due to the effect of lithium in the curing accelerator.

Experiment 2 Position of shielding mortar concrete Test No. 7 of the test sample used in the experiment
5 (Figure 6) and molded with the same formulation as in Figure 7, the formulation of Comparative Example I with a thickness of 10 cm was placed on the side closer to the neutron beam source, and then the formulation of Example 7 was molded with a thickness of 5 cm at the rear ( xl) was measured for the intensity of the second-order gamma ray. The results are shown in Table 4.

When the shielding mortar is placed behind the brane mortar concrete as in Test No. 6, the normalized value of the secondary gamma rays only decreases to 0.9, and the shielding effect is small. From this, is the neutron shielding mortar a neutron source? It can be seen that it is effective to place the neutrons close to each other and slow down the neutrons.

Experiment 3 The test mortar concrete used to measure the shielding effect on the side surface of shielding mortar concrete was a block (20 cm thick .

The intensity of secondary gamma rays was measured from the upper side (X-axis).

The results are shown in Table 5.

Hereinafter, as in Margin Experiment I, the shielding effect on the lateral side of the Example 117 formulation was reduced to about 175 to 1/10 compared to the Comparative Example I formulation, and the shielding effect was remarkable.

<Effects of the Invention> The fiber-reinforced neutron-shielding mortar concrete according to the present invention protects against neutron rays and gamma rays (especially secondary gamma rays) that are harmful to the human body and are generated from nuclear reactors, fusion reactors, accelerators, atomic bombs, neutron bombs, etc. It can be used as a shielding material to protect living organisms from radiation), radioactive elements, radioactive isotopes, and radioactive waste containing them. Also, background that affects the accuracy of nuclear reactor facilities, fusion reactor facilities, accelerator facilities, radioactive elements, radioactive isotopes, disposal facilities and storage facilities containing radioactive elements, facilities for experimental research, and various measurement and automatic control devices. It can also be used as a shielding material to maintain low levels of For example, walls of constructions,
It can be used as a mortar concrete member for construction such as floors, ceilings, roofs, Beskow mirrors, piping, ducts, manholes, etc., and as pre-formed objects such as plates, pillars, block pipes, etc.

[Brief explanation of the drawing]

Figure 1 shows the bending stress-deflection curves of the concrete of the present invention (Examples!, 6) and other concretes (Comparative Examples 1.2), and Figure 2 shows the neutron shielding effect measurement experimental equipment used in the examples. Figure 3 is the layout of the sample used to measure the neutron shielding effect using the device, Figure 4 is the layout of the sample used to measure the neutron shielding effect.
Fig. 11 is a time-of-flight spectrum diagram of cold neutrons emitted from a methane cooling moderator at 0, Figs. Figure 12 is the incident neutron spectrum of concrete test No. 1, Figure 12 is the detected secondary gamma ray spectrum of the same test, and Figure 13 is the incident neutron spectrum of test No. 5 of mixed concrete coat of Example 7. 14 are diagrams of detected secondary gamma ray spectra of the same test. Patent applicant RiRa Shi Co., Ltd.

Claims (1)

[Claims] 1. The boron compound has a 5 to 2
A fiber-reinforced neutron-shielding mortar concrete consisting of 0.00% by weight (all blending ratios hereinafter are expressed as weight percentages based on the hydraulic substance), 0.3 to 5% of reinforcing fibers, and 40% or less of a cement hardening accelerator. However, when the blending ratio of the boron compound is 35% or more, the blending ratio (%) of the curing accelerator satisfies the formula of the boron compound blending ratio (%) x 0.1 or more. 2. The fiber reinforcement according to claim 1, wherein the boron compound is a mixture of one or more selected from colemanite, volcalcite, boric acid, borax, titanium boron, zirconium boron, and molybdenum boron. Neutron shielding mortar concrete. 3. The reinforcing fiber has a tensile strength of 90 kg/mm^2 or more,
It has a Young's modulus of 1700 kg/mm^2 or more, a fineness of 6 denier or more, and an aspect ratio (ratio of fiber length l to circle equivalent diameter D, that is, l/D) of 30 to 30.
0, one or two selected from polyvinyl alcohol synthetic fibers, polyacrylonitrile synthetic fibers, aramid synthetic fibers, polyarylate synthetic fibers, and carbon fibers.
The fiber-reinforced neutron-shielding mortar concrete according to claim 1 or 2, which comprises a combination of more than one species. 4. The cement hardening accelerator is one or two selected from calcium aluminate, lithium hydroxide, and calcium acetate.
The fiber-reinforced neutron-shielding mortar concrete according to any one of claims 1 to 4, which comprises a combination of more than one type. 5. The fiber-reinforced neutron-shielding mortar concrete according to any one of claims 1 to 5, wherein the reinforcing fibers are polyvinyl alcohol fibers.