JPH09281287A - Neutron capture member and structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to surely capture neutrons by solidifying a mixture which is prepd. by adding neutron capture particles formed by mixing boric acid with raw material earth and calcining the mixture to a solidifying material, thereby producing a neutron capture member. SOLUTION: The neutron capture member 1 is a combination of neutron capture particles 2 and the solidifying member 3 and is solidified in the state that the neutron capture particles 2 are nearly uniformly dispersed into the entire part in the solidifying member 3. The neutron capture particles 2 are produced by a method to work a slurry prepd. by mixing a satd. soln. of boric acid at ordinary temp. and clay, feldspar, etc., to calcined matter of a block form, then to pulverize the calcined matter to a desired grain size, etc. Cement is used as the solidifying member 3. Silica sand and the neutron capture particles 2 are added as aggregate to this member and after an admixture is further added thereto, water is added and the mixture is kneaded. The neutron capture particles 2 are set at nearly the same grain size as the grain size of the silica sand. The compounding rate of the solidifying member 3 and the aggregate contg. the neutron capture particles 2 is specified to nearly 1:1 by weight. The neutron capture member 1 formed in such a manner is of the same quality as the quality of the mortar used for the joints of tiles, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutron trap capable of effectively capturing neutrons generated in nuclear power generation, radiation therapy and the like and a structure having a neutron shielding function.

[0002]

2. Description of the Related Art The applicant of the present invention mixes a raw material soil of a burned material such as tile, roof tile, and brick with a saturated solution of boric acid at room temperature to prepare a sludge, and press-molds a powder made from the sludge and fires the powder. The method for producing a neutron trap thus formed was invented (JP-A-6-249997). This invention has made it possible to put tiles, bricks, and the like having neutron capture performance into practical use.

[0003]

In the above prior art, since the shape of the neutron trap is limited to a plate shape or a block shape, for example, when the neutron trap is used in a building, the appearance becomes a total tiled or brick-laid structure. I have no choice. Therefore, there is a problem that it is difficult to fully adopt the appearance of a pure Japanese style building.

Further, since tiles generally have joints when they are attached to a wall surface, there is a risk that neutrons will pass through the joints. To solve this problem, it is possible to shift the joints of the tile between the front and back of the wall surface, but the technique of reliably shifting the joints of the tile between the front and back of the wall surface is difficult, and the workability is prolonged and the construction period is prolonged. There was a problem. on the other hand,
Boric acid is added to the mortar that constitutes the joint, and a method of giving neutron capture performance to the joint itself is also possible, but in that case, the alkali of the cement that constitutes the mortar is neutralized by boric acid, making it brittle. There is a fatal problem that practical strength cannot be obtained.

[0005]

Means for Solving the Problems The present invention has been made in view of the above, and is a granular or powdery neutron capture grain obtained by mixing raw material soil with boric acid and firing, and a granular or powdery neutron capture grain separately. A neutron trap which is a combination with a solidifying member which is solidified by taking solidifying means, wherein at least neutron capture particles are added to and mixed with the solidifying member and the mixture is solidified. A typical example of the solidifying member is cement.

The neutron capture particles are, so to speak, in a state in which boric acid is trapped inside the fired product. Therefore, even if boric acid itself has a function of hindering the solidification of the solidification member, if it is mixed in the form of neutron capture particles, the solidification of the solidification member is hardly adversely affected. Examples of solidifying members include clay for soil walls and cement. In particular, cement has the property that when boric acid is added directly, the alkali is neutralized and it becomes brittle, but when boric acid is mixed in the state of neutron capture particles, it is possible to ensure that it is not affected by boric acid. Solidify into. Thus, in the neutron trap, since the neutron capture particles containing boric acid are dispersed throughout, the neutrons having a rectilinear collision collide with one of the neutron capture particles and are captured by the nuclear chemical reaction of the boron atom. It

Further, as in claim 3, a structure in which tiles or bricks having a neutron capture performance are arranged in a plane, and the joints of the tiles or bricks are filled with a neutron trap whose solidifying member is cement. Provide things.

As described above, even if neutron-capturing particles are mixed with cement, it solidifies without being influenced by boric acid. For example, the joint itself exhibits neutron capture performance. Therefore, the tile or brick and the joint make a structure capable of completely blocking the transmission of neutrons.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 is a partially enlarged vertical sectional view of the neutron trap.

As shown in FIG. 1, the neutron trap 1 of the present invention is a combination of the neutron trap particles 2 and the solidifying member 3, and the neutron trap particles 2 are substantially evenly distributed throughout the solidifying member 3. It is solidified in a dispersed state.

Therefore, first, the neutron capture particles 2 will be described. The neutron capture particles 2 are made into a block by mixing a saturated solution of boric acid at room temperature with clay, feldspar, porcelain stone, etc. to make a slurry, and processing this slurry in the order of dehydration / drying → pulverization → press → firing. The method of producing a calcined product of 1., crushing the calcined product to a desired particle size with a crusher such as a crusher, and extruding the sludge to an appropriate softness from a nozzle, cutting it into an appropriate length, and cutting it into a rotary kiln. There is a method of firing with. In any case, a firing temperature of about 900 ° C. is appropriate. The particle size of the neutron capture particle 2 is about 25 mm.
It can be adjusted in any way, from large particles of a degree (of course, more than that is possible) to fine powder particles having a particle diameter of about 1 mm or less, and may be set according to the purpose of use.

The mixing of clay or the like and boric acid is not limited to the method of making sludge using a saturated solution of boric acid at room temperature. You may employ | adopt the method of directly throwing in a slurry, the method of mixing boric acid with the raw material soil beforehand, etc.

By the way, in the sludge, combustible particles (for example, sawdust etc.) that are burned at a temperature lower than the firing temperature of the neutron capture particles 2 are added, and the combustible particles are burned in the firing process to make the porous neutron capture particles 2 It is also possible to manufacture

On the other hand, the solidifying member 3 is, for example, cement or clay, has a granular or powdery form in the state before solidifying, and has a solidifying means such as "drying by adding water" separately. Anything can be used as long as it has the property of solidifying by taking it.

As described above, since the solidifying member 3 is in the form of particles or powder in the state before solidifying, the neutron capture particles 2 are added to the solidifying member 3 before solidifying and uniformly mixed. Then, by solidifying the mixture by solidifying the solidifying member 3, the neutron trap 1 in which the neutron trapping particles 2 are almost uniformly dispersed in the entire solidifying member 3 is formed. When neutrons collide with the neutron capture particles 2 of the neutron capture body 1, the boron atom causes a nuclear chemical reaction to reliably capture the neutrons. Since the neutron capture particles 2 are almost evenly dispersed in the neutron capture body 1, neutrons having a straight traveling property are reliably captured. Therefore, there is almost no possibility that neutrons will pass through the neutron capture body 1.

[0016]

Example 1 Cement (Portland cement) is used as the solidifying member 3. Then, silica sand and neutron capture particles 2 as an aggregate are added to the solidifying member 3, and a known admixture is further added, and then water as a solidifying means is added and kneaded. The neutron capture grain 2 is set to be almost the same as the grain size of silica sand.
Further, the mixing ratio of the neutron capture particles 2 and silica sand is set by comprehensively taking into consideration each of the necessary capture ability of neutrons, the manufacturing cost, and the strength of the neutron capture body 1. Depending on the case, there is a possibility that the blending ratio of silica sand becomes zero. The mixing ratio of the solidifying member 3 and the aggregate containing the neutron capture particles 2 was approximately 1: 1 by weight.

The neutron trap 1 as described above is of the same quality as the mortar used for the joints and the base of the tile. Therefore, as shown in FIG. 2, a tile T having a neutron-capturing ability made by adding a saturated solution of boric acid is attached to the wall surface W of a structure such as a building or a wall, and the joint M portion of the tile T is the neutron. If it is filled with the trap 1, a structure in which neutrons do not penetrate at all can be formed. As a result, the wall surface W
There is no need to shift the joint M of the tile T between the front and back of
Reliable construction is possible in a short construction period.

If the neutron trap 1 is used as the base of the tile T, the roof is covered with a tile having a neutron capture performance, and a curtain, a blind, or a shutter having a neutron shielding function is provided at the window or entrance / exit. Higher neutron capture performance can be obtained. Curtains, blinds,
Lead (lead foil) may be used as a means of imparting a neutron shielding function to a shutter or the like, but the neutron capture particles are made into fine particles and coated with a chemical binder on the surface of a curtain, blind, shutter, etc. You may make it form the protective film of a capture particle.

[0019]

Example 2 Cement is used as the solidifying member 3. Then, coarse aggregate and fine aggregate containing the neutron capture particles 2 are added to the solidifying member 3, a known admixture is further added, and then water as a solidifying means is added and kneaded. Coarse aggregate has a particle size of about 5 mm
It is a mixture of 25 mm gravel and neutron capture particles 2 set to have a particle size almost equal to that of the gravel, and the fine aggregate has a particle size of about 4
It is a mixture of sand of mm or less and neutron capture grains 2 set to have almost the same grain size as the sand. The mixing ratio of the neutron capture particles 2 contained in the coarse aggregate and the fine aggregate is the same as in Example 1, and comprehensively takes into consideration each element of the necessary capture ability of neutrons, the manufacturing cost, and the strength of the neutron capture body 1. Set. Therefore, in some cases, it is conceivable that the coarse aggregate and the fine aggregate are all composed of the neutron capture particles 2. Alternatively, there is a possibility that the compounding ratio of the neutron capture particles 2 may be zero with respect to either the coarse aggregate or the fine aggregate. The mixing ratio of the solidified member 3 and the aggregate containing the neutron capture particles 2 (coarse aggregate + fine aggregate) is set to about 3: 7 by weight.

The neutron trap 1 thus constructed has the same quality as concrete generally used as a structural material for civil engineering and construction. By using this neutron trap 1, a structure such as a building having an excellent neutron shielding function can be easily constructed. Further, by replacing the concrete wall surrounding the radiation source in the nuclear power plant or the radiation treatment room with the neutron capture body 1, it becomes possible to dramatically reduce the thickness of the wall. Therefore, even if the cost of the neutron capturer 1 is higher than that of ordinary concrete, the total amount of the neutron capturer 1 can be reduced and the total cost is reduced.

Further, the neutron trap 1 is also useful for the purpose of urgently shielding a nuclear reactor that has leaked radiation in the event of an accident at a nuclear power plant. For such applications, a method of spraying or spraying the neutron capture particles together with a chemical binder onto a radiation source is also possible.

[0022]

Example 3 As the solidifying member 3, clay for earth wall is used. Then, the fine neutron capture particles 2 and straw are added to the solidifying member 3 and kneaded with water as a solidifying means. This neutron trap 1 is mainly used for the earth wall of a Japanese-style building. In addition, the surface of the wall made of this neutron trap 1 is
Higher neutron capture performance can be expected by overcoating with the neutron capture body 1 (mortar) including the wooden pole surface.

Further, the neutron capture particles 2 of the third embodiment are
It is more effective to use the above-mentioned porous type.
That is, it is possible to reduce the weight by making the neutron capture particles 2 porous, and since the fine pores have a water retaining function, it is possible to enhance the humidity control function peculiar to the soil wall.

[0024]

As described above, the neutron trap of the present invention is
Since the neutron capture particles containing boric acid are dispersed almost uniformly, neutrons collide with any neutron capture particles and are reliably captured. Further, since the neutron capture particles are in a state in which boric acid is confined inside the fired product, even if boric acid itself has an action of hindering the solidification of the solidified member, if it is mixed in the form of neutron capture particles. , Has almost no adverse effect on the solidification of the solidified member. Therefore, the solidifying member may be cement which is weak against boric acid, and the field of application of the useful neutron trapper is endlessly expanded.

Further, if a plurality of tiles or bricks having a neutron capture performance are arranged in a plane and the joints of the tiles or bricks are filled with a neutron capture body having a solidifying member as cement, a neutron shielding function is obtained. An excellent structure can be provided.

[Brief description of drawings]

FIG. 1 is a partially enlarged vertical sectional view of a neutron trap.

FIG. 2 is an enlarged front view of a main part showing a wall surface of a structure.

[Explanation of symbols]

 1 ... Neutron capture body 2 ... Neutron capture grain 3 ... Solidification member T ... Tile M ... Joint

Claims (3)

[Claims] 1. A combination of granular or powdery neutron capture particles obtained by mixing boric acid into raw material soil and firing, and a solidifying member which is granular or powdery and is solidified by taking a separate solidifying means. A neutron trap, characterized in that at least neutron capture particles are added to and mixed with the solidifying member and the mixture is solidified. 2. The neutron trap according to claim 1, wherein the solidifying member is cement. 3. A structure characterized in that a plurality of tiles or bricks having a neutron trapping ability are arranged in a plane, and joints of the tiles or bricks are filled with the neutron trapper according to claim 2. Stuff.