JP2006275645A - Radiation shielding material - Google Patents
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- JP2006275645A JP2006275645A JP2005092735A JP2005092735A JP2006275645A JP 2006275645 A JP2006275645 A JP 2006275645A JP 2005092735 A JP2005092735 A JP 2005092735A JP 2005092735 A JP2005092735 A JP 2005092735A JP 2006275645 A JP2006275645 A JP 2006275645A
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 15
- 229910052906 cristobalite Inorganic materials 0.000 claims description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 7
- 229910052735 hafnium Inorganic materials 0.000 claims description 7
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims description 7
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- 229910052796 boron Inorganic materials 0.000 claims description 6
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- 239000005909 Kieselgur Substances 0.000 claims description 4
- 150000001875 compounds Chemical class 0.000 claims description 2
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- 125000004429 atom Chemical group 0.000 description 16
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- 229910017052 cobalt Inorganic materials 0.000 description 5
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- 230000002285 radioactive effect Effects 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052693 Europium Inorganic materials 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 description 4
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- 229910052742 iron Inorganic materials 0.000 description 4
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- HGLDOAKPQXAFKI-UHFFFAOYSA-N californium atom Chemical compound [Cf] HGLDOAKPQXAFKI-UHFFFAOYSA-N 0.000 description 2
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- QSGNKXDSTRDWKA-UHFFFAOYSA-N zirconium dihydride Chemical compound [ZrH2] QSGNKXDSTRDWKA-UHFFFAOYSA-N 0.000 description 1
- 229910000568 zirconium hydride Inorganic materials 0.000 description 1
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 1
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F1/00—Shielding characterised by the composition of the materials
- G21F1/02—Selection of uniform shielding materials
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F1/00—Shielding characterised by the composition of the materials
- G21F1/02—Selection of uniform shielding materials
- G21F1/08—Metals; Alloys; Cermets, i.e. sintered mixtures of ceramics and metals
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Ceramic Engineering (AREA)
- Metallurgy (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
【課題】 本発明においては、原子力施設等の中性子及びガンマ線が混在する放射線場において、遮蔽材として耐熱性と耐酸性を有し、軽量で、また低放射化特性を有する放射線遮蔽材を提供することを目的とする。
【解決手段】 本発明においては、高エネルギー中性子線及びガンマ線に高い遮蔽効果を示す重金属、中性子遮蔽効果の大きい水素元素含有率の高い天然多孔質珪質素材、及び熱中性子吸収材を組み合わせることにより中性子線とガンマ線の両方に対し遮蔽効果を有し、多孔質珪質素材に対する重金属と熱中性子吸収材との配含比率を調整することにより任意に中性子遮蔽効率とガンマ線遮蔽効率とをコントロールすることが出来、原子炉のように核分裂線源を扱う施設等において実用的な遮蔽材としては最も高い遮蔽効果を実現出来る放射線遮蔽材を提供出来る。
【選択図】 図３
PROBLEM TO BE SOLVED: To provide a radiation shielding material that has heat resistance and acid resistance as a shielding material, is lightweight, and has a low radiation property in a radiation field in which neutrons and gamma rays are mixed, such as in a nuclear facility. For the purpose.
In the present invention, by combining a heavy metal having a high shielding effect against high-energy neutron rays and gamma rays, a natural porous siliceous material having a high hydrogen element content with a large neutron shielding effect, and a thermal neutron absorber. It has a shielding effect against both neutron rays and gamma rays, and arbitrarily controls the neutron shielding efficiency and gamma ray shielding efficiency by adjusting the inclusion ratio of heavy metal and thermal neutron absorber to the porous siliceous material It is possible to provide a radiation shielding material that can realize the highest shielding effect as a practical shielding material in a facility such as a nuclear reactor that handles a fission source.
[Selection] Figure 3
Description
本発明は、軽量の多孔質珪質素材をベースとし、中性子線とガンマ線を同時に遮蔽し、かつ優れた低放射化特性を有し、耐熱性及びフッ化水素酸以外の酸に対する耐酸性に優れる組成物の放射線遮蔽材に関するものである。 The present invention is based on a lightweight porous siliceous material, shields neutron rays and gamma rays at the same time, has excellent low radiation properties, and is excellent in heat resistance and acid resistance against acids other than hydrofluoric acid. The present invention relates to a radiation shielding material for the composition.
従来、放射線遮蔽材としては、放射線遮蔽効果を持つ素材を配合した合成樹脂、ゴム、コンクリート、セラミックス、ガラス、金属等が周知となっている。
原子炉や照射済み核燃料等の放射線源から放出される放射線にはガンマ線と（高エネルギーから熱エネルギーまでの）中性子が混在しており、これらの放射線を全て効果的に遮蔽することが必要である（特許文献１を参照）。
一般に、中性子遮蔽に対しては、従来水素が最も効果的な元素と考えられて使用されてきたが、中性子エネルギーが高くなると水素の遮蔽効果が減少するという間題がある。
原子炉等から出るエネルギーの高い中性子の遮蔽では、この水素の遮蔽効果が減少するエネルギー領域の中性子を遮蔽することも重要である。
水素の遮蔽効果の減少を補うものとして非弾性散乱により高エネルギー中性子を減速させる効果のある重金属があげられる。
一般的に放射線遮蔽材の重金属として鉛が使用されることが多いが、鉛は有害物質であるため、鉛を多量に含む放射線遮蔽材は、その生産において、鉛を含む原料がこぼれたり、飛散することによって環境汚染を引き起こしやすいという問題を有していた（特許文献２を参照）。
また、熱中性子等の中性子を吸収した場合には、通常エネルギーが極めて高く透過力の強い二次ガンマ線が発生する。
二次ガンマ線の発生を抑えるには熱中性子吸収材が必要であり、また、その透過を抑えるには比重の大きなジルコニウムやハフニウムのような重金属が必要である。
従来の放射線遮蔽材であるコンクリートに放射線が当たると、コンクリートに含まれている鉄、コバルト、ニッケル、ユウロピウムの元素が放射性同位元素に変化し、この放射性同位元素の放射壊変によって、コンクリートが放射線を発するようになる（特許文献３を参照）。
つまり、原子炉等の放射性発生源の稼動を停止しても、コンクリート製の遮蔽体中に放射能が残留し、放射線を発生し続けることになる。
このように放射線を発するに至ったコンクリートは、原子炉等の放射線発生源の保守、運転、解体等に携わる作業員に対して、放射線被ばくによる健康上の悪影響を及ぼす可能性がある。
原子炉施設の廃止措置等に伴う遮蔽材の使用終了時においては、放射化した遮蔽材はその保管や環境汚染の観点から間題が多い。
従って、それらが問題とならない程度の放射能しか発生しない低放射化遮蔽材の開発が望まれている。
Radiation emitted from radiation sources such as nuclear reactors and irradiated nuclear fuel is a mixture of gamma rays and neutrons (from high energy to thermal energy), all of which need to be effectively shielded. (See Patent Document 1).
In general, for neutron shielding, hydrogen has been conventionally considered to be the most effective element, but there is a problem that the shielding effect of hydrogen decreases as the neutron energy increases.
In shielding high-energy neutrons emitted from nuclear reactors and the like, it is also important to shield neutrons in the energy region where the hydrogen shielding effect is reduced.
To compensate for the decrease in the shielding effect of hydrogen, heavy metals that can decelerate high-energy neutrons by inelastic scattering can be mentioned.
In general, lead is often used as a heavy metal for radiation shielding materials. However, since lead is a harmful substance, radiation shielding materials containing a large amount of lead spill or scatter raw materials containing lead during production. By doing this, there was a problem that environmental pollution is likely to occur (see Patent Document 2).
In addition, when absorbing neutrons such as thermal neutrons, secondary gamma rays with extremely high energy and strong penetrating power are generated.
Thermal neutron absorbers are necessary to suppress the generation of secondary gamma rays, and heavy metals such as zirconium and hafnium, which have a large specific gravity, are required to suppress their transmission.
When radiation hits concrete, which is a conventional radiation shielding material, the elements of iron, cobalt, nickel, and europium contained in the concrete are changed to radioactive isotopes. (See Patent Document 3).
That is, even if the operation of a radioactive source such as a nuclear reactor is stopped, the radioactivity remains in the concrete shield and continues to generate radiation.
Such concrete that emits radiation may adversely affect health due to radiation exposure on workers engaged in maintenance, operation, and demolition of radiation sources such as nuclear reactors.
At the end of use of shielding materials due to decommissioning of nuclear reactor facilities, there are many problems with activated shielding materials from the viewpoint of storage and environmental pollution.
Therefore, it is desired to develop a low-activation shielding material that generates only a radioactivity that does not cause a problem.
以上のことから、本発明においては、原子力施設等の中性子及びガンマ線が混在する放射線場において、簡略な設備で作製できかつ実用的に使用出来る遮蔽材としての最高の遮蔽性能、実用的な耐熱性と耐酸性(フッ化水素酸を除く)を有し、軽量で、また低放射化特性を有する放射線遮蔽材を提供することを目的とする。
さらに詳しくは、原子炉施設及び核燃料サイクル施設等、並びに照射済み燃料、核燃料の再処理物質、放射性同位元素、放射性廃棄物等放射能を有する物質や放射線医療装置から放出される中性子とガンマ線とが混在した放射線を中性子吸収の結果発生する二次ガンマ線を含めて遮蔽でき、実用的な遮蔽物質の中では最も経済的で尚且つ遮蔽効果が高く、また、使用期間中あるいは使用後における生成放射能を無視できる程度に少なく出来る軽量耐熱耐酸性(フッ化水素酸を除く)の放射線遮蔽材を提供することを目的とする。
From the above, in the present invention, the best shielding performance and practical heat resistance as a shielding material that can be produced with simple equipment and can be used practically in a radiation field where neutrons and gamma rays are mixed, such as nuclear facilities. Another object of the present invention is to provide a radiation shielding material which has acid resistance and acid resistance (excluding hydrofluoric acid), is lightweight, and has low radiation characteristics.
More specifically, neutrons and gamma rays emitted from nuclear reactor facilities and nuclear fuel cycle facilities, radioactive materials such as irradiated fuel, nuclear fuel reprocessing materials, radioisotopes, radioactive waste, and radiological devices It can shield mixed radiation including secondary gamma rays generated as a result of neutron absorption, is the most economical and effective shielding material among practical shielding materials, and generates radioactivity during or after use. It is an object of the present invention to provide a light-weight, heat-resistant, acid-resistant (excluding hydrofluoric acid) radiation shielding material that can reduce the amount of water to a negligible level.
本発明の放射線遮蔽材は、中性子遮蔽効果の大きい水素元素含有率の高い多孔質珪質素材と、高エネルギー中性子線及びガンマ線に高い遮蔽効果を示す原子番号40以上の重金属と、熱中性子吸収材を組み合わせてなるものである。
本発明においては、前記多孔質珪質素材が珪藻土、クリストバル岩、硬質泥岩又は人工多孔質珪質素材よりなるものである。
本発明においては、前記重金属がジルコニウム又はハフニウムである。
本発明においては、前記熱中性子吸収材がリチウム又はホウ素を含む化含物である。
The radiation shielding material of the present invention is a porous siliceous material having a high hydrogen element content with a large neutron shielding effect, a heavy metal having an atomic number of 40 or more that exhibits a high shielding effect against high-energy neutron rays and gamma rays, and a thermal neutron absorber Are combined.
In the present invention, the porous siliceous material is made of diatomaceous earth, cristobalite, hard mudstone, or artificial porous siliceous material.
In the present invention, the heavy metal is zirconium or hafnium.
In the present invention, the thermal neutron absorber is a compound containing lithium or boron.
本発明においては、高エネルギー中性子線及びガンマ線に高い遮蔽効果を示す重金属、中性子遮蔽効果の大きい水素元素含有率の高い天然多孔質珪質素材、及び熱中性子吸収材を組み合わせることにより中性子線とガンマ線の両方に対し遮蔽効果を有し、多孔質珪質素材に対する重金属と熱中性子吸収材との配含比率を調整することにより任意に中性子遮蔽効率とガンマ線遮蔽効率とをコントロールすることが出来、原子炉のように核分裂線源を扱う施設等において実用的な遮蔽材としては最も高い遮蔽効果を実現出来る放射線遮蔽材を提供出来る。
本発明の放射線遮蔽材は、上述の構成よりなるので、中性子とガンマ線双方を考慮した実際的な遮蔽材として優れた遮蔽性能を示し、低放射化性、耐熱性及び耐酸性(フッ化水素酸を除く)を有し、非常に軽量である。
しかも、本発明の放射線遮蔽材は、コバルト、ニッケル、ユウロピウムを含んでおらず、鉄含有量もコンクリートよりも少なく、さらに、ケイ素を主成分としているため使用期間中及び使用後の廃棄の際に放射化が問題となる可能性は極めて少ない。
本発明によれば、容易な設備で複雑な形状や大型のサイズにも対応した成型体を提供することが出来る。
本発明の放射線遮蔽材は、本質的に鉛を含有しないため、その生産において、鉛を含む原料がこぼれたり、飛散することによって環境汚染を引き起こすことがない。
In the present invention, a neutron beam and a gamma ray are combined by combining a heavy metal having a high shielding effect against high energy neutron rays and gamma rays, a natural porous siliceous material having a high hydrogen element content with a large neutron shielding effect, and a thermal neutron absorber. It has a shielding effect on both, and by adjusting the inclusion ratio of heavy metal and thermal neutron absorber to the porous siliceous material, the neutron shielding efficiency and gamma ray shielding efficiency can be controlled arbitrarily, It is possible to provide a radiation shielding material that can achieve the highest shielding effect as a practical shielding material in a facility that handles a fission radiation source such as a furnace.
Since the radiation shielding material of the present invention has the above-described configuration, it exhibits excellent shielding performance as a practical shielding material considering both neutrons and gamma rays, and has low radiation, heat resistance, and acid resistance (hydrofluoric acid). And is very lightweight.
Moreover, the radiation shielding material of the present invention does not contain cobalt, nickel, or europium, and the iron content is less than that of concrete. Further, since it is mainly composed of silicon, it is used during and after use. Activation is very unlikely to be a problem.
ADVANTAGE OF THE INVENTION According to this invention, the molded object corresponding to a complicated shape and large size can be provided with an easy installation.
Since the radiation shielding material of the present invention essentially does not contain lead, the raw material containing lead does not spill or scatter during production of the radiation shielding material.
始めに、従来から知られている放射線遮蔽材としての利点と問題点をそれぞれ検討した結果を示す。
表１に、コンクリート、水、鉛、グラファイト（黒鉛）、鉄、ホウ素、ポリエチレン、水素化リチウム、水素化チタン／水素化ジルコニウムについて、遮蔽材の利点と問題点を示す。
First, the results of studying the advantages and problems of conventionally known radiation shielding materials are shown.
Table 1 shows the advantages and problems of shielding materials for concrete, water, lead, graphite (graphite), iron, boron, polyethylene, lithium hydride, titanium hydride / zirconium hydride.
この結果、一般に放射線遮蔽材として求められる特性は、１．できるだけ二次ガンマ線を発生させないこと、２．放射化しにくい元素で出来ていること、３．放射化した場合でも、出来るだけ半減期が短いか、極端に長い元素であること、４．放射性生体構成元素を生成しないこと、５．人体（生物）に有害な元素を使用しないこと、６．遮蔽材が放射線遮蔽で発生する高熱に耐えられること、７．再利用や副生成物の回収が容易であること、８．中性子による放射化で問題となるコバルト、ユウロピウムを含まないこと、である。
次に、秋田県の男鹿半島の女川層から採取した珪質頁岩（珪藻土、クリストバル岩）を構成する主要元素を表２及び微量元素を表３に示す。
As a result, the characteristics generally required as a radiation shielding material are: 1. Avoid secondary gamma rays as much as possible; 2. It must be made of an element that is difficult to activate. 3. Even when activated, it should be as short or half as long as possible. 4. Do not produce radioactive bioconstituent elements. 5. Do not use elements harmful to the human body (organisms). 6. The shielding material can withstand the high heat generated by radiation shielding. Easy to reuse and recover by-products, 8. It does not contain cobalt and europium, which is a problem in neutron activation.
Next, Table 2 shows the major elements that make up siliceous shale (diatomite, cristobalite) collected from the Onagawa Formation in the Oga Peninsula, Akita Prefecture, and Table 3 shows the trace elements.
そこで、前記珪質頁岩（珪藻土、クリストバル岩）を放射線遮蔽材として利用する。
前記珪質頁岩の特性は、１．資源として大変豊富である、２．ケイ素、アルミニウム等の放射化されにくい元素で構成されている、３、水素、リチウム、ホウ素、炭素等の中性子遮蔽効果のある元素を含んでいる、４．熱に強い、５．放射線損傷を受けても、結晶（クリストバル岩の場合）のため自己修復できる可能性がある、６．多孔体なので必要な元素の添加などの操作（機能改良）が容易である、７．放射性生体構成元素になりうる元素が少ない、８．人体（生物）に有害な元素が少ない、９．中性子による放射化で問題となるコバルト、ユウロピウムを含まない、等である。
Therefore, the siliceous shale (diatomaceous earth, cristobalite) is used as a radiation shielding material.
The characteristics of the siliceous shale are: 1. It is abundant as a resource. 3. It is composed of elements that are difficult to be activated such as silicon and aluminum, 3. It contains elements having a neutron shielding effect such as hydrogen, lithium, boron, and carbon. 4. Strong against heat 5. May be able to self-repair due to crystals (in the case of cristobalite) even after radiation damage. 6. Since it is a porous material, operations (function improvement) such as addition of necessary elements are easy. There are few elements that can become radioactive bioconstituent elements, 8. 8. There are few elements harmful to human body (living body). Does not contain cobalt or europium, which is a problem in neutron activation.
次に、放射線遮蔽材で問題となるのは、コンクリートと同様に放射化であり、クリストバル岩自身の放射化の問題について、図１で説明する。
まず、図１の縦軸は、上に行くと陽子数が増えて原子番号が増し、また下方向に行くと原子番号が減少する、すなわち、ケイ素を例にすると、一つ上はリンであり、下はアルミニウムになる。
横軸は、中性子の数であり、右に行くと同位体の中性子数が増え、左に行くと減少する。
次に、（ｎ，α）反応の場合、中性子が一つ吸収され、α線（中性子二個と陽子二個）を出す反応で、中性子は一つ減り、陽子が二個減り、結果として元の原子から一つ左で二個下の原子に変化する。
（ｎ，γ）反応の場合は、中性子が一つ吸収され、ガンマ線を出す反応で、元の原子から一つ右の同位体に変化する。
（ｎ，ｐ）反応の場合は、中性子を一つ吸収し、陽子を一つ出す反応で、右下の原子に変化する。
（γ，ｐ）反応の場合は、ガンマ線を吸収して陽子を一つ出す反応で、元の原子の一つ下の原子に変化する、すなわちケイ素の場合はアルミニウムに変化する。
（γ，ｎ）反応の場合は、ガンマ線を吸収して中性子を一つ出す反応で、元の原子の左側の同位体に変化する。
Next, the problem with the radiation shielding material is the activation as in the concrete, and the problem of activation of the cristobalite itself will be described with reference to FIG.
First, the vertical axis in FIG. 1 indicates that the number of protons increases and the atomic number increases when going upward, and the atomic number decreases when going downward. That is, when silicon is taken as an example, the upper one is phosphorus. The bottom is aluminum.
The horizontal axis is the number of neutrons. The number of neutrons in the isotope increases when going to the right and decreases when going to the left.
Next, in the case of the (n, α) reaction, one neutron is absorbed and emits α rays (two neutrons and two protons). One neutron is reduced and two protons are reduced. Changes from one atom to the next two atoms on the left.
In the case of the (n, γ) reaction, one neutron is absorbed and a gamma ray is emitted to change the original atom to the right isotope.
In the case of the (n, p) reaction, it is a reaction that absorbs one neutron and emits one proton, and changes to the lower right atom.
In the case of the (γ, p) reaction, it is a reaction that absorbs gamma rays and emits one proton, which changes to an atom one lower than the original atom, that is, in the case of silicon, changes to aluminum.
In the case of the (γ, n) reaction, it is a reaction that absorbs gamma rays and emits one neutron, and changes to the isotope on the left side of the original atom.
図１中のベクトルは、原子が崩壊する過程を意味し、α崩壊は中性子二個と陽子二個を放出するので、元の原子の左へ二個、下へ二個の位置にある原子に変化する。
β＋崩壊及び電子捕獲は、電子を一つ吸収するので、陽子が一つ中性子に変化し、その結果下へ一つ、右へ一つの場所にある原子に変化する。
β−崩壊は、逆に電子を一つ放出するので、中性子が一つ減り、陽子が一つ増え、つまり元の原子の左上の原子に変化する。
前記クリストバル岩は、中性子に関しては（ｎ，α）、（ｎ，γ）、（ｎ，ｐ）反応を考え、γ線に関しては（γ，ｐ）、（γ，ｎ）反応を考える。
The vector in Fig. 1 means the process of atom decay, and α decay emits two neutrons and two protons, so two atoms to the left of the original atom and two atoms down Change.
Since β + decay and electron capture absorb one electron, one proton changes to a neutron, resulting in one atom down and one atom to the right.
On the contrary, β - decay emits one electron, so one neutron is decreased and one proton is increased, that is, the atom changes to the upper left atom of the original atom.
The cristobalite considers (n, α), (n, γ), (n, p) reactions for neutrons and (γ, p), (γ, n) reactions for γ rays.
そして、本発明の放射線遮蔽材として、中性子遮蔽能を高いレベルに、また、ガンマ線及び中性子の減衰率を任意に設計出来るように、水素含有率の高い多孔質珪質素材、重金属、熱中性子吸収材等の使用を考慮する。
水素含有率の高い多孔質珪質素材として、珪質頁岩、すなわち珪藻土やクリストバル岩がある。
水素、リチウム、ホウ素、炭素の４元素は、元々珪質頁岩に含まれているが、ホウ素はホウ酸水を物理吸着させ、乾燥させることにより、必要量添加できる。
リチウムについても同様である。
熱中性子吸収材としては、低放射化の観点からリチウム、ホウ酸やハフニウムが好ましい。
ガンマ線及び高速中性子遮蔽材としては、例えばジルコニウム、ハフニウム等の原子番号40以上の重金属を使用する。
ジルコニウムとハフニウムは、ジルコン溶解液から化学吸着と物理吸着特性を利用して珪質頁岩に吸着させる。
両元素で高速中性子の減速とガンマ線遮蔽を行う、特にハフニウムはランタノイド収縮を起こしているため、電子密度が大きく、有効に高エネルギーガンマ線遮蔽が行える。
さらに、低エネルギーガンマ線については遮蔽能力が原子番号の４乗に比例するので、これらの両元素は共に有効に作用する。
中性子、（二次ガンマ線を含めた）ガンマ線を同時に効果的に遮蔽するためには多孔質珪質素材に対し重金属と熱中性子吸収素材を適切に配合する必要がある。
実際的には、多孔質珪質素材、重金属、熱中性子吸収素材の割合を変えながら放射線輸送計算を実施し、配合比率に関するデータを求め、決定する必要がある。
放射線源から大量の中性子が放出される場合、本発明の放射線遮蔽材を用いた場合でも不純物による放射化の可能性がある。
放射化物が生成されると、遮蔽材自体が放射線を出すので被ばくの原因となる、取扱いに支障が出る、あるいは廃棄の際放射化物として隔離保管をせねばならない、環境汚染の原因となる等の悪影響が生じる。
そこで、多孔質珪質素材は、出来るだけ純度が高いものを用いるようにする。
As a radiation shielding material of the present invention, a porous siliceous material having a high hydrogen content, heavy metal, thermal neutron absorption so that the neutron shielding ability can be designed to a high level and the attenuation rate of gamma rays and neutrons can be arbitrarily designed. Consider the use of materials.
Examples of porous siliceous materials having a high hydrogen content include siliceous shale, that is, diatomaceous earth and cristobalite.
The four elements of hydrogen, lithium, boron, and carbon are originally contained in siliceous shale, but boron can be added in a necessary amount by physically adsorbing boric acid water and drying.
The same applies to lithium.
As the thermal neutron absorber, lithium, boric acid and hafnium are preferable from the viewpoint of low radiation.
As the gamma ray and fast neutron shielding material, for example, heavy metals having an atomic number of 40 or more such as zirconium and hafnium are used.
Zirconium and hafnium are adsorbed on siliceous shale from zircon solution using chemical adsorption and physical adsorption characteristics.
Both elements decelerate fast neutrons and shield gamma rays, especially hafnium has lanthanide contraction, so it has high electron density and can effectively shield high-energy gamma rays.
Furthermore, for low energy gamma rays, the shielding ability is proportional to the fourth power of the atomic number, so both these elements work effectively.
In order to effectively shield neutrons and gamma rays (including secondary gamma rays) at the same time, it is necessary to appropriately mix heavy metals and thermal neutron absorbing materials with porous siliceous materials.
In practice, it is necessary to carry out radiation transport calculations while changing the proportions of porous siliceous materials, heavy metals, and thermal neutron absorbing materials to obtain and determine data on the blending ratio.
When a large amount of neutrons are emitted from the radiation source, there is a possibility of activation by impurities even when the radiation shielding material of the present invention is used.
If radioactive material is generated, the shielding material itself emits radiation, which may cause exposure, hinder handling, or must be kept isolated as radioactive material during disposal, or cause environmental pollution. An adverse effect occurs.
Therefore, the porous siliceous material should be as pure as possible.
男鹿半島の女川層から採取した珪質頁岩（クリストバル岩）を鉄蜂で砕き、２．３６ｍｍメッシュの篩で大きさを揃えたペレット状のものを、片面に和紙を貼った奥行き５ｃｍ、縦横３０ｃｍの木枠内に入れ、その後、残った一面を和紙で封じて実験試料を加工する。 A siliceous shale (cristobalite) collected from the Onagawa Formation in the Oga Peninsula is crushed with an iron bee, and a pellet-shaped one with a 2.36 mm mesh sieve and a Japanese paper on one side is 5 cm in depth and 30 cm in length and width. The sample is then put into a wooden frame and the remaining surface is sealed with Japanese paper to process the experimental sample.
前記実験試料を用いて、次の実験を行った。
実験１：線源にカリフォルニウム（２５２Ｃｆ）を用いた中性子遮蔽実験を行った。
図２に示すように、珪質頁岩、コンクリートについて、それぞれ３回測定を行った。
見掛上、珪質頁岩の中性子遮蔽効果は、普通コンクリートよりも劣るが、比重が約４分の１のため、コンクリートの比重と同程度に遮蔽材を充填することができれば普通コンクリートの２倍の遮蔽性能を持つ。
これは、珪質頁岩の表面に存在する水素によるものである。
The following experiment was performed using the experimental sample.
Experiment 1: A neutron shielding experiment using californium ( 252 Cf) as a radiation source was performed.
As shown in FIG. 2, the measurement was performed three times for each siliceous shale and concrete.
Apparently, the neutron shielding effect of siliceous shale is inferior to that of ordinary concrete, but because the specific gravity is about 1/4, if the shielding material can be filled to the same degree as the specific gravity of concrete, it is twice that of ordinary concrete. With shielding performance.
This is due to hydrogen present on the surface of siliceous shale.
図３に示すように、図２データの近似曲線で外挿してみると、普通コンクリートの２倍の厚さでコンクリートと同程度の中性子に対する遮蔽効果を得ることができることがわかる。
しかしながら、重量は普通コンクリートの約４分の１である。
As shown in FIG. 3, when extrapolated with the approximate curve of the data in FIG. 2, it can be seen that a shielding effect against neutrons similar to that of concrete can be obtained with twice the thickness of ordinary concrete.
However, the weight is about one-fourth that of ordinary concrete.
実験２：線源にカリフォルニウム（２５２Ｃｆ）を用いた二次ガンマ線遮蔽実験を行った。 Experiment 2: A secondary gamma ray shielding experiment using Californium ( 252 Cf) as a radiation source was performed.
実験３：線源にコバルト（６０Ｃｏ）を用いた場合のガンマ線遮蔽実験を行った。 Experiment 3 was performed the gamma ray shielding experiments when using cobalt (60 Co) to the source.
図４に示すように、珪質頁岩について、それぞれ６回測定を行った。
ガンマ線遮蔽効果は、物質の密度に依存するため、珪質頁岩だけではあまり遮蔽効果は期待できない。
しかしながら、ジルコニウム等の重金属を添加すれば十分にかつ容易にその遮蔽性能を改良できる。
As shown in FIG. 4, the measurement was performed 6 times for each siliceous shale.
Since the gamma ray shielding effect depends on the density of the material, silicic shale alone cannot be expected to provide a shielding effect.
However, if a heavy metal such as zirconium is added, the shielding performance can be improved sufficiently and easily.
図５に示すように、図４のデータの近似曲線を外挿してみると、珪質頁岩だけでガンマ線を遮蔽する場合、５０ｃｍ以上の厚さが必要であることがわかる。 As shown in FIG. 5, when extrapolating the approximate curve of the data of FIG.
まとめとして、珪質頁岩と普通コンクリートとを対比すると、
(１)珪質頁岩は普通コンクリートに比べ約２倍の中性子遮蔽性能がある。
(２)珪質頁岩は比重が小さい。クリストバル岩をブロック整形したものが１．２４、ペレット状にしたものが０．６７以上であるのに対して、普通コンクリートは２．３６である。
(３)珪質頁岩は中性子及びγ線による放射化のため問題となる核種の含有量が低い。
(４)珪質頁岩は熱に強い。
(５)珪質頁岩は酸性溶液に強い。
(６)珪質頁岩は他の放射線遮蔽材を添加して機能改良することが容易である。
したがって、珪質頁岩はコンクリートよりも優れた放射線遮蔽材となり、軽量・耐熱・耐酸性中性子遮蔽材として有効な素材である。
また、多孔質な特性を生かすことで、必要な元素の添加をすれば、さらに優れた放射線遮蔽材となる。
As a summary, when comparing siliceous shale and ordinary concrete,
(1) Siliceous shale has neutron shielding performance about twice that of ordinary concrete.
(2) The siliceous shale has a low specific gravity. The cristobalite rock-shaped block is 1.24, and the pelletized one is 0.67 or more, while the ordinary concrete is 2.36.
(3) The siliceous shale has a low content of nuclides that are problematic due to activation by neutrons and γ rays.
(4) Siliceous shale is resistant to heat.
(5) Siliceous shale is resistant to acidic solutions.
(6) It is easy to improve the function of siliceous shale by adding other radiation shielding materials.
Therefore, siliceous shale becomes a radiation shielding material superior to concrete, and is an effective material as a lightweight, heat-resistant and acid-resistant neutron shielding material.
Further, by taking advantage of the porous characteristics, if a necessary element is added, a more excellent radiation shielding material can be obtained.
本発明の放射線遮蔽材は、合成樹脂と混合し、鋳型に入れることにより自在な形状の成型体を実用的な大きさで作製できる。
それらの成型体を単独でもしくは成型体同士組み合わせて用いたり、放射線遮蔽材の小片を容器に充填して用いたり、また、枠等の各種部材で固定して用いたり、各種ゴム、各種コンクリート、各種金属、各種パテ等の複合材料用マトリックスで固定した形態で用いたりすることで、原子炉や原子炉利用施設、核燃料サイクル施設、使用済み燃料等放射性物質貯蔵・輸送容器、放射性同位元素、核融合炉、加速器等における各種放射線源等から放出される中性子やガンマ線を実用的に遮蔽できる。
本発明の放射線遮蔽材は多孔体であるため、必要に応じて水を添加吸着させ、この水（Ｈ2Ｏ）の水素原子によって、高エネルギーを有する放射線（中性子）を効果的に減速させることができる。
本発明の放射線遮蔽材は、中性子線及び/又はガンマ線の遮蔽に用いることができる。 本発明の放射線遮蔽材は、そのまま用いることもでき、小片を容器に充填したものを用いることもできる。
また、圧力を加えて成型し、ブロックとして使用できる他、合成樹脂等と混合し、任意の形状で用いることもできる。
本発明の放射線遮蔽材の小片を複合材料用マトリックスで固定した複合材料を中性子線
及び/又はガンマ線の遮蔽に用いてもよい。
The radiation shielding material of the present invention can be produced with a practical size by mixing it with a synthetic resin and placing it in a mold.
These moldings are used alone or in combination with one another, used by filling a small piece of radiation shielding material into a container, fixed by various members such as a frame, various rubber, various concrete, Reactor, reactor utilization facility, nuclear fuel cycle facility, radioactive fuel storage and transport container such as spent fuel, radioisotope, nuclear Neutrons and gamma rays emitted from various radiation sources in fusion reactors and accelerators can be practically shielded.
Since the radiation shielding material of the present invention is a porous body, water can be added and adsorbed as needed, and radiation (neutrons) having high energy can be effectively decelerated by hydrogen atoms of this water (H 2 O). Can do.
The radiation shielding material of the present invention can be used for shielding neutron rays and / or gamma rays. The radiation shielding material of the present invention can be used as it is, or a material obtained by filling a small piece into a container.
Moreover, it can be molded by applying pressure and used as a block, or it can be mixed with a synthetic resin and used in an arbitrary shape.
You may use the composite material which fixed the small piece of the radiation shielding material of this invention with the matrix for composite materials for shielding of a neutron beam and / or a gamma ray.
本発明の放射線遮蔽材は、医療関連施設に設置される医療用リニアックから発生する二次中性子の遮蔽、放射性廃棄物移送用貯蔵容器（キャスク）の放射線遮蔽材、核融合実験施設周辺の放射線遮蔽、可動型推進用原子炉（船舶及び惑星間有人ロケット等に搭載）の放射線遮蔽材、通常の原子力施設及び核燃料サイクル施設の放射線遮蔽材、原子炉火災時の放射線遮蔽材、火災作業用ヘリコプター自体の放射線遮蔽材、住宅の壁面用建材（原子力施設周辺の住宅向け）等に利用可能である。 The radiation shielding material of the present invention shields secondary neutrons generated from medical linacs installed in medical facilities, radiation shielding materials for radioactive waste transfer storage containers (casks), radiation shielding around fusion experimental facilities , Radiation shielding materials for mobile propulsion reactors (mounted on ships and interplanetary manned rockets, etc.), radiation shielding materials for ordinary nuclear facilities and nuclear fuel cycle facilities, radiation shielding materials for nuclear reactor fires, fire work helicopters themselves It can be used as a radiation shielding material for buildings, and building materials for residential walls (for housing around nuclear facilities).
Claims (4)
The radiation shielding material according to claim 1, wherein the thermal neutron absorber is a compound containing lithium or boron.
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| WO (1) | WO2006103793A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013137210A (en) * | 2011-12-28 | 2013-07-11 | Hiroshi Kokuta | Method of treating radiation contaminant using aqueous polymer inorganic compound |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109215274A (en) * | 2018-10-10 | 2019-01-15 | 江苏核电有限公司 | A kind of nuclear power station detector for fire alarm system shielding |
| CN111933323A (en) * | 2020-07-22 | 2020-11-13 | 上海核工程研究设计院有限公司 | Radiation protection structure of spent fuel transport ship |
| CN113539535B (en) * | 2021-07-06 | 2024-04-19 | 散裂中子源科学中心 | Neutron shielding element and method for manufacturing the same |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57207896A (en) * | 1981-06-17 | 1982-12-20 | Hitachi Ltd | Neutron absorbing material |
| JPS6161099A (en) * | 1984-09-03 | 1986-03-28 | 日本碍子株式会社 | Radiation shielding structural body |
| JP2868724B2 (en) * | 1996-04-08 | 1999-03-10 | 株式会社神谷匣鉢製造所 | Neutron traps and structures |
| JP4152562B2 (en) * | 2000-03-22 | 2008-09-17 | 電気化学工業株式会社 | Solidified material and neutron absorber of high concentration boric acid aqueous solution |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013137210A (en) * | 2011-12-28 | 2013-07-11 | Hiroshi Kokuta | Method of treating radiation contaminant using aqueous polymer inorganic compound |
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| Publication number | Publication date |
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| WO2006103793A1 (en) | 2006-10-05 |
| JP3926823B2 (en) | 2007-06-06 |
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