JP4082179B2

JP4082179B2 - Spent nuclear fuel storage container

Info

Publication number: JP4082179B2
Application number: JP2002322505A
Authority: JP
Inventors: 公紀伊賀; 清水　　仁; 生剛堂守; 眞琴林
Original assignee: Hitachi GE Nuclear Energy Ltd
Current assignee: Hitachi GE Nuclear Energy Ltd
Priority date: 2002-11-06
Filing date: 2002-11-06
Publication date: 2008-04-30
Anticipated expiration: 2022-11-06
Also published as: JP2004156997A

Description

【０００１】
【発明の属する技術分野】
本発明は原子力発電所から発生する使用済核燃料を輸送用または輸送貯蔵兼用として用いられる使用済核燃料収納容器に関する。
【０００２】
【従来の技術】
【特許文献１】
特開２００１―３１８１８７号公報
原子力発電所の原子炉炉心で一定期間使用された核燃料（燃料）は、炉心より取出されて使用済核燃料プール等に一次保管される。所定の冷却期間が終了した燃料は燃料プール中でキャスク（収納容器）に収納され、燃料再処理施設もしくは中間貯蔵施設などに運搬される。中間貯蔵施設では燃料をキャスクに収納した状態で長期間に亘り貯蔵するようにしている。
【０００３】
キャスクの内筒は上部開口の円筒形状容器であり、使用済核燃料が発生するγ線を遮蔽できる厚さに構成されている。使用済核燃料が発する中性子は内筒の外周面及び底面に設けた中性子遮蔽材（中性子遮蔽体）で遮蔽する。中性子遮蔽体の外周には二次γ線の遮蔽と中性子遮蔽体の保護のために円筒形状の外筒が配置される。内筒と外筒は、通常ステンレス鋼や炭素鋼で構成される。
【０００４】
使用済核燃料が発生する崩壊熱を効率よく除去するためにキャスク内筒と外筒の間には熱伝導体で作られた十数枚の伝熱フィンが取付けられている。伝熱フィンは内筒、外筒の両方もしくは片方に溶接によって固着されており、事故時等に外筒が外れないように保持している。伝熱フィンには内筒及び外筒と溶接が容易で、かつ外筒を保持する十分な強度を持った炭素鋼もしくはステンレス鋼が用いられる。
【０００５】
キャスクの内筒と外筒の間に設けられる中性子遮蔽体は、十分に混練された液状の中性子遮蔽材をキャスクを立てた状態にして、内筒、外筒および伝熱フィンで区切られた空間（中性子遮蔽空間と称する）に上部開口から注入して充填固化して形成している。
【０００６】
上述したようなキャスクについては、例えば、上述した特許文献１に記載されている。
【０００７】
ところで、中性子遮蔽材が注入される中性子遮蔽空間を形成する面の一部には固化した中性子遮蔽体の割れを防止するため剥離剤を塗布し、中性子遮蔽材を注入している。中性子遮蔽材を注入する中性子遮蔽空間は高さが４〜５m程度あり、また、上部開口は一辺が１０〜２０cm程の略角形である。したがって、剥離剤の塗布は専用の機械を使用して行われる。
【０００８】
一方、使用済燃料の長期間の貯蔵中には中性子遮蔽体より水蒸気を主成分としたガスが放出される。通常、中性子遮蔽空間の圧力上昇を抑えるためにガス抜き穴が設けられている。使用済燃料のキャスクへの収納は燃料プール中で行われるため、ガス抜き穴には中性子遮蔽体に水が入らないよう逆止弁などが取り付けられる。この逆止弁は貯蔵期間中動作することを確認する必要がある。
【０００９】
【発明が解決しようとする課題】
従来技術は、伝熱フィンに外筒を保持するのに必要な強度を持った炭素鋼、ステンレス鋼等の金属材料を用いると、崩壊熱を除熱するためには外筒を保持するのに必要以上の伝熱フィンを必要とする。また、中性子遮蔽空間を形成する面に剥離剤を塗布するのに専用の機械を必要としている。
【００１０】
このように、従来技術はキャスクの重量が重く製造期間が長期間になり、ガス抜き穴の逆止弁の保守が大きな負担になるという問題点を有する。
【００１１】
本発明の目的は、内筒と外筒間の伝熱性能向上させて軽量化でき、かつ製造期間の短縮可能でガス抜き穴の逆止弁の保守を不要にできる使用済核燃料収納容器を提供することにある。
【００１２】
【課題を解決するための手段】
本発明の特徴とするところは、内筒の外周面に一端を固着され外方に突出して配設されている複数の外筒支持部材の他端を外筒の内周面を固着し、伝熱部材は断面略コ字型で１つの脚にガス溜部として長手方向のガス溜空間が形成されると共に断面略コ字型内部に中性子遮蔽材を充填固化され、中性子遮蔽材を固着された伝熱部材が、一方脚の外面が内筒の外周面、他方脚の外面が外筒の内周面にそれぞれ対向するように、内筒、外筒および外筒支持部材によって形成される中性子遮蔽材配置領域に配置されることにある。
【００１３】
本発明は伝熱部材で外筒を支持する必要がなくなり伝熱部材として軽く熱伝導度の高い材料を使用でき、また、外筒支持部材を外筒の支持に必要な量だけ使用すればよいので、伝熱性能の向上と軽量化を図ることができる。また、中性子遮蔽体（伝熱部材と中性子遮蔽材）はキャスク本体とは別に製作できるためキャスクの製造期間を短縮することができる。さらに、伝熱部材にガス溜空間を形成しているのでガス溜空間容積を大きくできるためガス抜き穴と逆止弁を設ける必要が無く逆止弁の保守を不要にできる。
【００１４】
【発明の実施の形態】
図１に本発明の一実施例を示す。
図１において、内筒１は上部が開口している炭素鋼製の円筒形状容器であり、図示しない使用済核燃料が発生するγ線を遮蔽できる厚さに構成されている。使用済核燃料が発生する中性子は内筒１の外周面に設けた中性子遮蔽体２で遮蔽する。以後、中性子遮蔽体２は中性子吸収材とも称する。中性子遮蔽体２は図３に示すように、断面略コ字型の伝熱部材４の断面略コ字型内部に固化充填されている。中性子遮蔽体２としては、通常エポキシ樹脂又はシリコンゴムなどの高分子化合物に粉末状の中性子吸収材及び耐火材といった添加物を加えた樹脂が使用されている。なお、中性子遮蔽体２は内筒１の底面にも設けられるが図示を省略している。
【００１５】
伝熱部材４は図３に示すように略断面コ字型に形成され、腹部４１に脚４２、４３を備えている。一方脚４２の先端は内側に略９０度折曲された後に外方（他方脚４３と平行方向）に略９０度折曲されたＬ字型の鍵部４４を形成している。鍵部４４の外側の窪み４５がガス溜空間となる。鍵部４４は伝熱部材４のガス溜部となる。
【００１６】
伝熱部材４は図５に示すように断面略コ字型の開放端を図示しない平板で密閉され、長手方向の一端も平板４６で密閉される。また、伝熱部材４の長手方向の他端に液状の中性子吸収材２を注入する注入機具４７が取付けられる。注入機具４７から中性子吸収材２を注入し固化させる。伝熱部材４は中性子遮蔽体２を製作する場合において中性子吸収材２を受ける容器として使用される。
【００１７】
中性子吸収材２が固化したら断面略コ字型の開放端を図示しない平板、平板４６および注入機具４７を取外し、注入機具４７側の中性子吸収材２を平坦に研磨する。このようにして伝熱部材４の断面略コ字型内部には中性子吸収材２が充填固化される。
【００１８】
さて、内筒１の外周面には図２に示すように複数の外筒支持板（外筒支持部材）１３の一端が溶接によって固着されている。複数の外筒支持板１３の他端は外方に放射状に突出している。複数の外筒支持板１３は内筒１の外周面に、例えば、４５度の等角度で固定されている。
【００１９】
内筒１、外筒３および外筒支持板１３で形成される空間（中性子遮蔽材配置領域）１７には図２に示すように３個の伝熱部材４が配置されている。中性子遮蔽空間１７は内筒1、外筒３、外筒支持板１３の他に上端板１２、下端板１４によって形成される。
【００２０】
伝熱部材４は脚４２の外面が内筒１の内周面に対向し、脚４３の外面が外筒３の内周面に対向している。脚４２の外面を内筒１の外周面に当接させ、脚４３の外面を外筒３の内周面の当接させるようにしてもよい。このようにそれぞれが当接されることによって、内筒１から脚４２への伝熱特性、および脚４３から外筒３への伝熱特性を向上させることができる。
【００２１】
また、伝熱部材４の脚４２の先端（鍵部４４）は図２に示すように外筒支持板１３あるいは他の伝熱部材４の腹部４１の外面に対向して配置される。鍵部４４は外筒支持板１３あるいは他の伝熱部材４の腹部４１の外面に当接されてもよい。伝熱部材４の鍵部４４の窪み４５はガス溜空間１５を形成する。鍵部４４の窪み４５は外筒支持板１３の内筒１との溶接部分の肉盛りとの干渉を排除する。
【００２２】
外筒３を保持する外筒支持板１３は内筒１と外筒３に溶接が容易に行える部材、例えば炭素鋼もしくはステンレス鋼で構成されている。また、伝熱部材４は炭素鋼よりも伝熱性能の良いアルミもしくはアルミ合金で構成されている。
【００２３】
二次γ線の遮蔽と中性子遮蔽体２の保護のために炭素鋼製の円筒形状の外筒３が配置される。外筒３は周方向に複数に分割して構成され、分割された長手方向の端が外筒支持板１３の他端に位置するように配置される。分割された外筒３は外筒支持板１３の他端に隣接する他の分割外筒３と共に溶接して固着される。
【００２４】
内筒１の内部にはバスケット５が配置され、バスケット５に使用済核燃料（図示せず）が格子状に配置される。バスケット５はいかなる場合においても使用済核燃料が臨界になるのを防止するように構成されている。キャスク本体蓋部は、一次蓋６と二次蓋７の二重構造となっており、キャスク本体内部の放射能を確実に閉じ込める構造となっている。一次蓋６にも中性子遮蔽体１６が設けられている。
【００２５】
図１には図示が複雑になるので省略しているが、図４に示すように内筒１に上端板１２と下端板１４が取付けられている。上端板１２と下端板１４は中空円盤状に構成され、内筒１の全周に取付けられている。また、キャスクの外側には吊下ろし等の取扱い時に使用するトラニオン８が設けられている。
【００２６】
なお、キャスクは４メートル程度の長さの使用済核燃料を収納するため、その高さは5メートル程度、直径は2.5メートル程度であり、使用済核燃料集合体を収納した時の全重量は100から150トン程度となる。
【００２７】
このような構成のキャスクは次のような手順で製作される。この製作手順を図６、図７を参照して説明する。
【００２８】
工程Ａにおいて伝熱部材４を製作する。伝熱部材４としてアルミもしくはアルミ合金を使用する場合には、押出成型により製作することで同一形状の物を短期間に製作することが可能となる。工程Ｂでは製作した伝熱部材４の必要な面に剥離剤を塗布する。伝熱部材４は断面略コ字型形状であり、長手方向の一面が開放されているので、特別な専用機器を用いることなく剥離剤を簡単に塗布することができる。
【００２９】
次に、工程Ｃでは図５のようにして上述したようにして伝熱部材４の内部に中性子遮蔽材２を鋳込む作業を実施する。すなわち、伝熱部材４は図５に示すように略断面コ字型の開放端を図示しない平板で密閉され、長手方向の一端も平板４６で密閉される。また、伝熱部材４の長手方向の他端に液状の中性子吸収材２を注入する注入機具４７が取付けられる。注入機具４７から中性子吸収材２を注入し固化させる。伝熱部材４は中性子遮蔽体２を製作する場合において中性子吸収材２を受ける容器として使用される。工程Ｄに移り伝熱部材４に中性子遮蔽体２を固化充填した状態で外観検査などによって検査を行う。
【００３０】
一方、工程Ｅでは別ルートで図７（ａ）のようなキャスク内筒１を製作する。工程Ｆに移行して図７（ｂ）に示すように、内筒１を横置きにして複数の内筒支持板１３を溶接により固定する。工程Ｇでは図７（ｃ）に示すように内筒１に上端板１２と下端板１４を溶接によって取付ける。
【００３１】
工程Ｈでは図７（ｄ）に示すように複数の内筒支持板１３と上端板１２、下端板１４を取付固定された内筒１に上述の要領で製造された中性子遮蔽体２を固化充填された伝熱部材４を外筒支持部材１３の間に配置する。中性子遮蔽体２を固化充填された伝熱部材４は内筒１の長手方向に沿って複数個配置される。
【００３２】
工程Ｉでは図７（ｅ）のように分割製作された外筒３を中性子遮蔽体２（伝熱部材４）を覆うように取付け、外筒支持部材１３に溶接する。
【００３３】
以上の作業を内筒１の全周に亘って行うことによって中性子遮蔽体２を固化充填されている伝熱部材４の取付けが完了する。
【００３４】
このような構成のキャスクは、伝熱部材４で外筒を支持する必要がなくなり伝熱部材４として軽く熱伝導度の高い材料を使用でき、また、外筒支持部材１３を外筒３の支持に必要な量だけ使用すればよいので、伝熱性能の向上と軽量化を図ることができる。また、中性子遮蔽体（伝熱部材４と中性子遮蔽材２）はキャスク本体とは別に製作できるためキャスクの製造期間を短縮することができる。
【００３５】
また、長期間の貯蔵中に中性子遮蔽体２より図４に矢印で示すように水蒸気を主成分としたガスが放出される。このガスは伝熱部材４の鍵部４４によって形成されるガス溜空間１５に貯留される。ガス溜空間１５は容量が大きいので中性子遮蔽空間１７からガスを抜く必要がなくなる。したがって、ガス抜き穴と逆止弁を設ける必要が無く逆止弁の保守を不要にできる。
【００３６】
なお、中性子遮蔽体２を取付けるには、図８に示すように、内筒１、外筒支持部材１３、外筒３を溶接しキャスク底部の遮蔽体カバー１８を取付、キャスクを縦置きにし中性子遮蔽体２を内筒１、外筒３および外筒支持部材１３によって形成される中性子遮蔽空間１７に伝熱部材４を挿入し、その後に上端板１２を溶接するようにしても行える。
【００３７】
図９に断面略コ字型伝熱部材４の配置の他の例を示す。
図９は内筒１と外筒３の間隔の間隔方向に２個の伝熱部材４を重ねて配置している。２個の伝熱部材４はそれぞれ断面略コ字型内部に中性子遮蔽材２を固化充填されている。図９の構成においても上述の実施例と同様な効果を奏し得る。
【００３８】
図１０に伝熱部材４の他の例を示す。図１０の伝熱部材４は脚４３に溝４８を設け、溝４８でガス溜空間１５を形成するようにしたものである。
【００３９】
図１０に伝熱部材４でも図３の伝熱部材と同様にガス溜空間の容積を大きくでき、上述の実施例と同様な効果を奏し得る。
【００４０】
以上説明したように、本発明の使用済核燃料収納容器は伝熱部材で外筒を支持する必要がなくなり伝熱部材として軽く熱伝導度の高い材料を使用でき、また、外筒支持部材を外筒の支持に必要な量だけ使用すればよいので、伝熱性能の向上と軽量化を図ることができる。また、中性子遮蔽体（伝熱部材と中性子遮蔽材）はキャスク本体とは別に製作できるためキャスクの製造期間を短縮することができる。さらに、伝熱部材にガス溜空間を形成しているのでガス溜空間容積を大きくできるためガス抜き穴と逆止弁を設ける必要が無く逆止弁の保守を不要にできる。
【００４１】
また、上述の実施例は伝熱部材が断面略コ字型であり、開放端から剥離剤の塗布及び塗布状態の確認が容易となる。さらに、キャスクとは別に中性子遮蔽体を製作するため中性子遮蔽体の外観の全数検査が可能となる。
【００４２】
【発明の効果】
本発明は伝熱部材で外筒を支持する必要がなくなり伝熱部材として軽く熱伝導度の高い材料を使用でき、また、外筒支持部材を外筒の支持に必要な量だけ使用すればよいので、伝熱性能の向上と軽量化を図ることができる。
また、中性子遮蔽体（伝熱部材と中性子遮蔽材）はキャスク本体とは別に製作できるためキャスクの製造期間を短縮することができる。
さらに、伝熱部材にガス溜空間を形成しているのでガス溜空間容積を大きくできるためガス抜き穴と逆止弁を設ける必要が無く逆止弁の保守を不要にできる。
【図面の簡単な説明】
【図１】本発明の一実施例を示す構成図である。
【図２】本発明の一実施例の要部を示す拡大断面図である。
【図３】本発明の伝熱部材の一例を示す構成図である。
【図４】本発明を説明するための部分拡大図である。
【図５】本発明による伝熱部材の説明図である。
【図６】本発明による実施例の一例製作工程図である。
【図７】本発明による実施例の製作工程の一例説明図である。
【図８】本発明による実施例の製作工程の説明図である。
【図９】本発明の伝熱部材配置の他の例を示す構成図である。
【図１０】本発明の伝熱部材の他の例を示す構成図である。
【符号の説明】
１…内筒、２…中性子遮蔽体、３…外筒、４…伝熱部材、５…バスケット、６…一次蓋、７…二次蓋、８…トラニオン、１２…上端板、１３…外筒支持部材、１４…下端板、１７…中性子遮蔽空間、１５…ガス溜空間。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spent nuclear fuel storage container that is used for transportation or transportation and storage of spent nuclear fuel generated from a nuclear power plant.
[0002]
[Prior art]
[Patent Document 1]
JP, 2001-318187, A Nuclear fuel (fuel) used for a certain period in the reactor core of a nuclear power plant is taken out from a core, and is primarily stored in a spent nuclear fuel pool. The fuel whose predetermined cooling period has ended is stored in a cask (storage container) in the fuel pool and transported to a fuel reprocessing facility or an intermediate storage facility. In the intermediate storage facility, the fuel is stored for a long time in a state of being stored in the cask.
[0003]
The inner cylinder of the cask is a cylindrical container with an upper opening, and is configured to have a thickness that can shield γ rays generated by spent nuclear fuel. Neutrons emitted from the spent nuclear fuel are shielded by neutron shielding materials (neutron shields) provided on the outer and bottom surfaces of the inner cylinder. A cylindrical outer cylinder is disposed on the outer periphery of the neutron shield for shielding secondary γ rays and protecting the neutron shield. The inner and outer cylinders are usually made of stainless steel or carbon steel.
[0004]
In order to efficiently remove the decay heat generated by the spent nuclear fuel, dozens of heat transfer fins made of a heat conductor are attached between the cask inner cylinder and the outer cylinder. The heat transfer fin is fixed to both or one of the inner cylinder and the outer cylinder by welding, and is held so that the outer cylinder does not come off during an accident or the like. The heat transfer fin is made of carbon steel or stainless steel that is easily welded to the inner cylinder and the outer cylinder and has sufficient strength to hold the outer cylinder.
[0005]
The neutron shield provided between the inner and outer cylinders of the cask is a space partitioned by the inner cylinder, the outer cylinder and the heat transfer fins, with the kneaded liquid neutron shielding material in a state where the cask is raised. It is formed by injecting into a neutron shielding space (filled and solidified) through an upper opening.
[0006]
The cask as described above is described in Patent Document 1 described above, for example.
[0007]
By the way, a part of the surface forming the neutron shielding space into which the neutron shielding material is injected is coated with a release agent in order to prevent cracking of the solidified neutron shielding body, and the neutron shielding material is injected. The neutron shielding space for injecting the neutron shielding material has a height of about 4 to 5 m, and the upper opening has a substantially square shape with a side of about 10 to 20 cm. Therefore, the release agent is applied using a dedicated machine.
[0008]
On the other hand, during the long-term storage of spent fuel, a gas mainly composed of water vapor is released from the neutron shield. Usually, a vent hole is provided to suppress an increase in pressure in the neutron shielding space. Since spent fuel is stored in the cask, a check valve or the like is installed in the vent hole to prevent water from entering the neutron shield. This check valve must be verified to operate during storage.
[0009]
[Problems to be solved by the invention]
In the prior art, when using a metal material such as carbon steel or stainless steel having the strength required to hold the outer cylinder on the heat transfer fin, the outer cylinder is held to remove the decay heat. More heat transfer fins are needed. In addition, a special machine is required to apply the release agent to the surface forming the neutron shielding space.
[0010]
As described above, the prior art has a problem that the weight of the cask is heavy and the manufacturing period becomes long, and maintenance of the check valve for the gas vent hole becomes a heavy burden.
[0011]
An object of the present invention is to provide a spent nuclear fuel storage container that can improve the heat transfer performance between the inner cylinder and the outer cylinder, reduce the weight, and can reduce the manufacturing period and eliminate the need for maintenance of the check valve of the gas vent hole. There is to do.
[0012]
[Means for Solving the Problems]
A feature of the present invention is that one end is fixed to the outer peripheral surface of the inner cylinder and the other outer ends of a plurality of outer cylinder support members disposed so as to protrude outward are fixed to the inner peripheral surface of the outer cylinder. The heat member has a substantially U-shaped cross section, a gas reservoir space in the longitudinal direction is formed as a gas reservoir in one leg, and the neutron shielding material is filled and solidified inside the substantially U-shaped cross section , and the neutron shielding material is fixed. The heat transfer member is formed by the inner cylinder, the outer cylinder, and the outer cylinder support member so that the outer surface of the one leg faces the outer circumferential surface of the inner cylinder and the outer surface of the other leg faces the inner circumferential surface of the outer cylinder. It is to be arranged in the material arrangement area.
[0013]
The present invention eliminates the need to support the outer cylinder with the heat transfer member, and can use a light and high thermal conductivity material as the heat transfer member, and only use the outer cylinder support member in an amount necessary for supporting the outer cylinder. Therefore, the heat transfer performance can be improved and the weight can be reduced. Further, since the neutron shield (heat transfer member and neutron shield) can be manufactured separately from the cask body, the cask manufacturing period can be shortened. Furthermore, since the gas reservoir space is formed in the heat transfer member, the gas reservoir space volume can be increased, so that it is not necessary to provide a gas vent hole and a check valve, and maintenance of the check valve can be eliminated.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of the present invention.
In FIG. 1, an inner cylinder 1 is a cylindrical container made of carbon steel that is open at the top, and has a thickness that can shield γ rays generated by spent nuclear fuel (not shown). Neutrons generated from the spent nuclear fuel are shielded by a neutron shield 2 provided on the outer peripheral surface of the inner cylinder 1. Hereinafter, the neutron shield 2 is also referred to as a neutron absorber. Neutron shield 2, as shown in FIG. 3, and is solidified filled with a substantially U-shaped cross-section substantially U-shaped heat transfer member 4. As the neutron shield 2, a resin obtained by adding additives such as a powdered neutron absorber and a refractory material to a polymer compound such as epoxy resin or silicon rubber is usually used. The neutron shield 2 is also provided on the bottom surface of the inner cylinder 1 but is not shown.
[0015]
As shown in FIG. 3, the heat transfer member 4 is formed in a substantially U-shaped cross section, and includes legs 42 and 43 on the abdomen 41. On the other hand, the tip of the leg 42 forms an L-shaped key portion 44 that is bent approximately 90 degrees inward and then bent outward (parallel to the other leg 43) by approximately 90 degrees. A recess 45 on the outer side of the key portion 44 becomes a gas reservoir space. The key portion 44 serves as a gas reservoir for the heat transfer member 4.
[0016]
As shown in FIG. 5, the heat transfer member 4 has an open end with a substantially U-shaped cross section sealed with a flat plate (not shown), and one end in the longitudinal direction is also sealed with a flat plate 46. An injection device 47 for injecting the liquid neutron absorber 2 is attached to the other end in the longitudinal direction of the heat transfer member 4. The neutron absorber 2 is injected from the injector 47 and solidified. The heat transfer member 4 is used as a container for receiving the neutron absorber 2 when the neutron shield 2 is manufactured.
[0017]
When the neutron absorber 2 is solidified, the open end having a substantially U-shaped cross section is removed from the flat plate 46, the flat plate 46, and the injector 47, and the neutron absorber 2 on the injector 47 side is polished flat. In this way, the neutron absorber 2 is filled and solidified inside the substantially U-shaped cross section of the heat transfer member 4.
[0018]
Now, as shown in FIG. 2, one end of a plurality of outer cylinder support plates (outer cylinder support members) 13 is fixed to the outer peripheral surface of the inner cylinder 1 by welding. The other ends of the plurality of outer cylinder support plates 13 project radially outward. The plurality of outer cylinder support plates 13 are fixed to the outer peripheral surface of the inner cylinder 1 at an equal angle of 45 degrees, for example.
[0019]
As shown in FIG. 2, three heat transfer members 4 are arranged in a space (neutron shielding material arrangement region) 17 formed by the inner cylinder 1, the outer cylinder 3 and the outer cylinder support plate 13. The neutron shielding space 17 is formed by an upper end plate 12 and a lower end plate 14 in addition to the inner cylinder 1, the outer cylinder 3, and the outer cylinder support plate 13.
[0020]
In the heat transfer member 4, the outer surface of the leg 42 faces the inner peripheral surface of the inner cylinder 1, and the outer surface of the leg 43 faces the inner peripheral surface of the outer cylinder 3. The outer surface of the leg 42 may be brought into contact with the outer peripheral surface of the inner cylinder 1, and the outer surface of the leg 43 may be brought into contact with the inner peripheral surface of the outer cylinder 3. By contacting each other in this way, the heat transfer characteristics from the inner cylinder 1 to the legs 42 and the heat transfer characteristics from the legs 43 to the outer cylinder 3 can be improved.
[0021]
Further, the distal ends (key portions 44) of the legs 42 of the heat transfer member 4 are arranged to face the outer surface of the outer cylinder support plate 13 or the abdomen 41 of the other heat transfer member 4 as shown in FIG. The key portion 44 may abut on the outer surface of the abdomen 41 of the outer cylinder support plate 13 or other heat transfer member 4. The recess 45 of the key portion 44 of the heat transfer member 4 forms a gas reservoir space 15. The depression 45 of the key portion 44 eliminates interference with the build-up of the welded portion with the inner cylinder 1 of the outer cylinder support plate 13.
[0022]
The outer cylinder support plate 13 that holds the outer cylinder 3 is made of a member that can be easily welded to the inner cylinder 1 and the outer cylinder 3, for example, carbon steel or stainless steel. The heat transfer member 4 is made of aluminum or aluminum alloy having better heat transfer performance than carbon steel.
[0023]
A cylindrical outer cylinder 3 made of carbon steel is arranged for shielding secondary γ rays and protecting the neutron shield 2. The outer cylinder 3 is divided into a plurality in the circumferential direction, and is arranged so that the divided end in the longitudinal direction is located at the other end of the outer cylinder support plate 13. The divided outer cylinder 3 is welded and fixed together with another divided outer cylinder 3 adjacent to the other end of the outer cylinder support plate 13.
[0024]
A basket 5 is arranged inside the inner cylinder 1, and spent nuclear fuel (not shown) is arranged in a lattice shape in the basket 5. The basket 5 is configured to prevent the spent nuclear fuel from becoming critical in any case. The cask main body lid portion has a double structure of the primary lid 6 and the secondary lid 7, and has a structure that reliably confines the radioactivity inside the cask main body. The primary lid 6 is also provided with a neutron shield 16.
[0025]
Although not shown in FIG. 1 because the illustration is complicated, an upper end plate 12 and a lower end plate 14 are attached to the inner cylinder 1 as shown in FIG. The upper end plate 12 and the lower end plate 14 are formed in a hollow disk shape and are attached to the entire circumference of the inner cylinder 1. Moreover, the trunnion 8 used at the time of handling, such as hanging, is provided in the outer side of a cask.
[0026]
Since the cask contains about 4 meters of spent nuclear fuel, its height is about 5 meters and its diameter is about 2.5 meters. The total weight when the spent nuclear fuel assembly is stored is 100 About 150 tons.
[0027]
The cask having such a configuration is manufactured by the following procedure. This manufacturing procedure will be described with reference to FIGS.
[0028]
In step A, the heat transfer member 4 is manufactured. When aluminum or an aluminum alloy is used as the heat transfer member 4, it is possible to manufacture a product having the same shape in a short time by manufacturing by extrusion molding. In step B, a release agent is applied to a necessary surface of the manufactured heat transfer member 4. Since the heat transfer member 4 has a substantially U-shaped cross section and one surface in the longitudinal direction is open, it is possible to easily apply the release agent without using a special dedicated device.
[0029]
Next, in step C, the operation of casting the neutron shielding material 2 into the heat transfer member 4 is performed as described above with reference to FIG. That is, as shown in FIG. 5, the heat transfer member 4 is sealed with a flat plate (not shown) at an open end having a substantially U-shaped cross section , and one end in the longitudinal direction is also sealed with a flat plate 46. An injection device 47 for injecting the liquid neutron absorber 2 is attached to the other end in the longitudinal direction of the heat transfer member 4. The neutron absorber 2 is injected from the injector 47 and solidified. The heat transfer member 4 is used as a container for receiving the neutron absorber 2 when the neutron shield 2 is manufactured. It moves to the process D and inspect | inspects by appearance inspection etc. in the state which solidified and filled the heat-transfer member 4 with the neutron shield 2. FIG.
[0030]
On the other hand, in the process E, the cask inner cylinder 1 as shown in FIG. As shown in FIG. 7B, the process moves to step F, and the inner cylinder 1 is placed horizontally, and the plurality of inner cylinder support plates 13 are fixed by welding. In step G, as shown in FIG. 7C, the upper end plate 12 and the lower end plate 14 are attached to the inner cylinder 1 by welding.
[0031]
In Step H, as shown in FIG. 7 (d), the inner cylinder 1 to which the plurality of inner cylinder support plates 13, the upper end plates 12 and the lower end plates 14 are fixedly attached is solidified and filled with the neutron shield 2 manufactured as described above. The heat transfer member 4 is disposed between the outer cylinder support members 13. A plurality of heat transfer members 4 solidified and filled with the neutron shield 2 are arranged along the longitudinal direction of the inner cylinder 1.
[0032]
In step I, the outer cylinder 3 divided and manufactured as shown in FIG. 7 (e) is attached so as to cover the neutron shield 2 (heat transfer member 4) and welded to the outer cylinder support member 13.
[0033]
By performing the above operation over the entire circumference of the inner cylinder 1, the attachment of the heat transfer member 4 solidified and filled with the neutron shield 2 is completed.
[0034]
The cask having such a configuration eliminates the need to support the outer cylinder with the heat transfer member 4 and can use a light and high thermal conductivity material as the heat transfer member 4, and also supports the outer cylinder support member 13 to support the outer cylinder 3. Therefore, the heat transfer performance can be improved and the weight can be reduced. Moreover, since the neutron shield (the heat transfer member 4 and the neutron shield 2) can be manufactured separately from the cask main body, the manufacturing time of the cask can be shortened.
[0035]
Further, during the long-term storage, a gas containing water vapor as a main component is released from the neutron shield 2 as indicated by an arrow in FIG. This gas is stored in the gas storage space 15 formed by the key portion 44 of the heat transfer member 4. Since the gas reservoir space 15 has a large capacity, it is not necessary to extract gas from the neutron shielding space 17. Therefore, it is not necessary to provide a gas vent hole and a check valve, and maintenance of the check valve can be made unnecessary.
[0036]
In order to attach the neutron shield 2, as shown in FIG. 8, the inner cylinder 1, the outer cylinder support member 13 and the outer cylinder 3 are welded, and the shield cover 18 at the bottom of the cask is attached, and the cask is placed vertically and the neutron shield is installed. The shield 2 may be inserted into the neutron shielding space 17 formed by the inner cylinder 1, the outer cylinder 3, and the outer cylinder support member 13, and then the upper end plate 12 may be welded.
[0037]
FIG. 9 shows another example of the arrangement of the substantially U-shaped heat transfer member 4 in cross section .
In FIG. 9, two heat transfer members 4 are stacked in the direction of the interval between the inner cylinder 1 and the outer cylinder 3. Each of the two heat transfer members 4 is solidified and filled with a neutron shielding material 2 inside a substantially U-shaped cross section . 9 can achieve the same effects as those of the above-described embodiment.
[0038]
FIG. 10 shows another example of the heat transfer member 4. The heat transfer member 4 of FIG. 10 is provided with a groove 48 in the leg 43 and the gas reservoir space 15 is formed by the groove 48.
[0039]
In the heat transfer member 4 shown in FIG. 10, the volume of the gas reservoir space can be increased similarly to the heat transfer member in FIG. 3, and the same effect as in the above-described embodiment can be obtained.
[0040]
As described above, the spent nuclear fuel storage container according to the present invention does not need to support the outer cylinder with the heat transfer member, and can use a light and high thermal conductivity material as the heat transfer member. Since it is sufficient to use only the amount necessary for supporting the cylinder, the heat transfer performance can be improved and the weight can be reduced. Further, since the neutron shield (heat transfer member and neutron shield) can be manufactured separately from the cask body, the cask manufacturing period can be shortened. Furthermore, since the gas reservoir space is formed in the heat transfer member, the gas reservoir space volume can be increased, so that it is not necessary to provide a gas vent hole and a check valve, and maintenance of the check valve can be eliminated.
[0041]
In the above-described embodiment, the heat transfer member has a substantially U-shaped cross section , and it becomes easy to apply the release agent and confirm the application state from the open end. Furthermore, since the neutron shield is manufactured separately from the cask, 100% inspection of the appearance of the neutron shield is possible.
[0042]
【The invention's effect】
The present invention eliminates the need to support the outer cylinder with the heat transfer member, and can use a light and high thermal conductivity material as the heat transfer member, and only use the outer cylinder support member in an amount necessary for supporting the outer cylinder. Therefore, the heat transfer performance can be improved and the weight can be reduced.
Further, since the neutron shield (heat transfer member and neutron shield) can be manufactured separately from the cask body, the cask manufacturing period can be shortened.
Furthermore, since the gas reservoir space is formed in the heat transfer member, the gas reservoir space volume can be increased, so that it is not necessary to provide a gas vent hole and a check valve, and maintenance of the check valve can be eliminated.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is an enlarged sectional view showing a main part of one embodiment of the present invention.
FIG. 3 is a configuration diagram showing an example of a heat transfer member of the present invention.
FIG. 4 is a partially enlarged view for explaining the present invention.
FIG. 5 is an explanatory diagram of a heat transfer member according to the present invention.
FIG. 6 is an example manufacturing process diagram of an embodiment according to the present invention.
FIG. 7 is an explanatory diagram showing an example of a manufacturing process of the embodiment according to the present invention.
FIG. 8 is an explanatory diagram of a manufacturing process of an embodiment according to the present invention.
FIG. 9 is a configuration diagram showing another example of the heat transfer member arrangement of the present invention.
FIG. 10 is a configuration diagram showing another example of the heat transfer member of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Inner cylinder, 2 ... Neutron shield, 3 ... Outer cylinder, 4 ... Heat-transfer member, 5 ... Basket, 6 ... Primary lid, 7 ... Secondary lid, 8 ... Trunnion, 12 ... Upper end plate, 13 ... Outer cylinder Support member, 14 ... lower end plate, 17 ... neutron shielding space, 15 ... gas reservoir space.

Claims

An inner cylinder that forms an internal space for storing spent nuclear fuel, a plurality of outer cylinder support members that are fixed to an outer peripheral surface of the inner cylinder and project outward, and the plurality of outer cylinder supports An outer cylinder having an inner peripheral surface fixed to the other end of the member, a heat transfer member having a substantially U-shaped cross section, and a gas reservoir space in the longitudinal direction formed as a gas reservoir on one leg ; , the heat transfer member comprises a neutron shielding material which is solidified filled with a substantially U-shaped, wherein the neutron shielding member is secured to said heat transfer member, whereas the outer circumference of the outer surface of the legs the inner tube Characterized in that it is arranged in a neutron shielding material arrangement region formed by the inner cylinder, the outer cylinder and the outer cylinder support member such that the outer surface of the other leg faces the inner peripheral surface of the outer cylinder. Used nuclear fuel storage container.

An inner cylinder in which a basket for storing spent nuclear fuel is disposed in each of a plurality of lattices, and a plurality of outer cylinder support plates that are fixed to one outer periphery of the inner cylinder and project outward. And an outer cylinder having an inner peripheral surface fixed to the other end of each of the plurality of outer cylinder support plates, and a substantially U-shaped cross section, and the tip of one leg is bent in an L shape inside. comprising a heat transfer member which is longitudinal direction of the gas reservoir space is formed as a gas reservoir, and a neutron shielding material which is solidified filled with a substantially U-shaped of the heat transfer member, the neutron shielding material The fixed heat transfer member includes the inner cylinder, the outer cylinder, and the outer cylinder so that the outer surface of one leg is in contact with the outer peripheral surface of the inner cylinder and the outer surface of the other leg is in contact with the inner peripheral surface of the outer cylinder. Spent nuclear fuel storage characterized in that it is placed in the neutron shielding material placement region formed by the tube support plate container.

3. The spent nuclear fuel storage container according to claim 1, wherein a plurality of the heat transfer members are arranged in the neutron shielding material arrangement region along the longitudinal direction of the inner cylinder.

3. The spent nuclear fuel storage container according to claim 1, wherein a plurality of the heat transfer members are arranged in the neutron shielding material arrangement region along the circumferential direction of the inner cylinder.

3. The outer cylinder support member or the outer cylinder support plate according to claim 1, wherein the outer cylinder support member or the outer cylinder support plate is made of the same kind of metal material as the inner cylinder and the outer cylinder, and the heat transfer member constitutes the inner cylinder and the outer cylinder. A spent nuclear fuel storage container characterized in that it is made of a metal material that is lighter and has a higher thermal conductivity than the metal material to be used.

The gas reservoir space may be formed by a recess formed by bending one leg of the substantially U-shaped heat transfer member into an L shape and an outer surface of the outer cylinder support plate or another heat transfer member. Characterized spent nuclear fuel storage container.