JP2004233210A

JP2004233210A - Flow rate response type reactor shutdown and drive element and nuclear reactor structure

Info

Publication number: JP2004233210A
Application number: JP2003022399A
Authority: JP
Inventors: Motohiko Nishimura; 元彦西村
Original assignee: Electric Power Development Co Ltd; Tohoku Electric Power Co Inc; Tokyo Electric Power Co Inc; Kyushu Electric Power Co Inc; Japan Atomic Power Co Ltd; Chugoku Electric Power Co Inc; Chubu Electric Power Co Inc; Hokuriku Electric Power Co; Kawasaki Heavy Industries Ltd
Current assignee: Electric Power Development Co Ltd; Tohoku Electric Power Co Inc; Kyushu Electric Power Co Inc; Japan Atomic Power Co Ltd; Chugoku Electric Power Co Inc; Chubu Electric Power Co Inc; Hokuriku Electric Power Co; Kawasaki Heavy Industries Ltd; Tokyo Electric Power Company Holdings Inc
Priority date: 2003-01-30
Filing date: 2003-01-30
Publication date: 2004-08-19
Anticipated expiration: 2023-01-30
Also published as: JP4006500B2

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a flow rate response type reactor shutdown and drive element capable of quicker operation than a magnetic self actuated shutdown mechanism (SASS) which makes control rods fall by holding the control rods by magnet, takes advantage of that coolant becomes high temperature in the case of core coolant performance degradation accidents and lowers holding force of the magnet, and a reactor structure loading the element. <P>SOLUTION: The flow rate response type reactor shutdown and drive element can automatically move neutron absorber to a position corresponding to core fuel region by the pressure difference between inlet and outlet quickly responding to lowering of coolant flow rate, and automatically move a neutron reflector to below and outside the position corresponding to the core fuel region. The invention includes a reactor structure in which the flow rate response type reactor shutdown and drive elements are dispersed in a certain array for loading in core fuel assemblies in a core of gas-cooled reactor so as to be surrounded by control rod assemblies and safety rod assemblies. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、原子力プラントにおいて、受動的炉停止機構（ＳＡＳＳ：ＳｅｌｆＡｃｔｕａｔｅｄＳｈｕｔｄｏｗｎＳｙｓｔｅｍ）に適応させる流量応答型炉停止駆動要素及びこの流量応答型炉停止駆動要素を分散装架した原子炉構造に関する。
【０００２】
【従来の技術】
一般に原子力プラントでは、冷却材循環機による炉心への冷却材の流量が低下することにより炉心冷却性能が低下する事故が発生した場合、これを検知し、制御棒を炉心に挿入して、原子炉出力を低下させ、原子炉を安全に停止させる設計としているが、万一の制御棒が炉心に挿入されない場合に対しても、炉心冷却性能低下事故が終息するように設計しなければならない。この対応として、炉心冷却性能低下による炉心状態及びこの炉心雰囲気の変化に基づき、受動的に制御棒が炉心に挿入される概念、即ち受動的炉停止機構（以下、ＳＡＳＳと称する）を採用する設計思想が有効とされている。
【０００３】
上記ＳＡＳＳは、ナトリウム冷却高速炉では、制御棒を磁石で保持し、炉心冷却性能低下事故等に冷却材が高温になることを利用して、磁石による保持力を低下して制御棒を落下させる概念が考えられている。この磁石式ＳＡＳＳの構造を、図８の炉心概念図によって説明すると、図中３１は炉心内に多数配列装架された炉心燃料集合体で、この炉心燃料集合体３１の群の中に一定配列に調整棒集合体３２が分散装架され、さらに同様に炉心燃料集合体３１の群の中に調整棒集合体３２に囲まれるように一定配列に安全棒集合体３３が分散装架されている。安全棒集合体３３の制御棒３４は電磁石３５により支持棒３６に保持されている。冷却材は下方から炉心燃料集合体３１に沿って上方へ矢印の如く流れる。
【０００４】
かかる構造の磁石式ＳＡＳＳにおいて、炉心燃料集合体３１内の燃料温度が上昇し、これに伴い燃料被覆管の温度も上昇すると、冷却材の温度も上昇する。この温度上昇した冷却材の上方への流れにより炉心中央部から安全棒集合体３３の制御棒３４を支持棒３６に保持している電磁石３５の部分に熱輸送され、電磁石３５の雰囲気温度が上昇し、電磁石３５の温度が上昇する。その結果、電磁石３５の制御棒保持力が低下し、制御棒３４が炉心中央部に落下し、炉が停止せしめられる。
【０００５】
ところで、ガス冷却炉のＳＡＳＳは、制御棒を下から支持して駆動しているため、単に磁石を切り離しても制御棒は落下しない。また、ガス冷却炉では、より高い温度状態で運転されるため、磁石による制御棒保持力が低下する。従って、磁石を大型化する必要がある。しかし、磁石を大型化すると、その熱容量が大きくなり、雰囲気温度の上昇に対する追従が鈍くなる。加えて、ガス冷却炉では冷却材であるガスの比熱および熱伝達率が小さいため、磁石自体の温度上昇はガスよりも遅れる。その結果、ＳＡＳＳの作動を遅らせることになり、早期に炉心冷却性能低下事故に対処できない可能性がある。先行技術文献として、特開平８−５０１８９号記載の原子炉停止装置がある。
【０００６】
【発明が解決しようとする課題】
そこで、本発明は、炉心の温度上昇が、炉心出力の割に冷却材流量が低下することにより生じることに着目し、冷却材流量の低下に反応させる方が磁石の温度上昇に依拠した方式よりも応答性の高いＳＡＳＳを構築できることから、差圧駆動式の流量応答型炉停止駆動要素を提供し、且つこの流量応答型炉停止駆動要素を炉心に挿入した原子炉構造を提供しようとするものである。
【０００７】
【課題を解決するための手段】
上記課題を解決するための本発明の流量応答型炉停止駆動要素の１つは、炉心燃料集合体の外管と同じ長さで上端板に炉心出口導圧孔を設けた外管内に、下端板を貫通して上端部まで内管を同心に配設し、内管内には外管の下方に突出する内管下端部の底板から上端部まで炉心入口導圧管を同心に配設し、外管内にて内管の下部に内・外管連通孔を設け、内・外管内に前記炉心入口導圧管の炉心入口圧力と前記炉心出口導圧孔の炉心出口圧力が等しい時、炉心燃料域の上端レベルとなる量の液体金属を装入し、且つ外管内の液体金属に炉心燃料域の範囲にわたる長さで中性子吸収体を装入し、前記炉心入口導圧管の炉心入口圧力が前記炉心出口導圧孔の炉心出口圧力よりも高い時、その差圧により液面が移動し前記中性子吸収体が炉心燃料域よりも上方に位置するように構成したことを特徴とするものである。
【０００８】
かかる構成の流量応答型炉停止駆動要素において、中性子吸収体は、多数の球体から成る場合と、円筒状の成形物から成る場合とがあり、その構成金属は例えば炭化ホウ素ボロン合金、カドミウム合金等である。
【０００９】
本発明の流量応答型炉停止駆動要素の他の１つは、炉心燃料集合体の外管と同じ長さで上端板に炉心出口導圧孔を設けた外管内に、下端板を貫通して上端部まで内管を同心に配設し、外管の下方に突出する内管下端部の底板から上端部まで内管内に炉心入口導圧管を同心に配設し、外管内にて内管の下部に内・外管連通孔を設け、内・外管内に前記炉心入口導圧管の炉心入口圧力と前記炉心出口導圧孔の炉心出口圧力が等しい時、炉心燃料域の下端以下のレベルとなる量の液体金属を装入し、且つ外管内の液体金属に炉心燃料域の範囲にわたる長さの中性子反射体を炉心燃料域の下方にて装入し、前記炉心入口導圧管の炉心入口圧力が前記炉心出口導圧孔の炉心出口圧力よりも高い時、その差圧により液面が移動し前記中性子反射体が炉心燃料域に位置するように構成したことを特徴とするものである。
【００１０】
かかる構成の流量応答型炉停止駆動要素において、中性子反射体は、円筒状の成形物から成り、その構成は重水、ベリリウム、黒鉛、ステンレススチールなどである。
【００１１】
本発明の原子炉構造は、ガス冷却炉の炉心内に炉心燃料集合体が多数配列装架され、この炉心燃料集合体の群の中に調整棒集合体と安全棒集合体が一定配列に分散装架された原子炉構造において、調整棒集合体と安全棒集合体とに囲まれるように炉心燃料集合体の群の中に上記構成の２つの流量応答型炉停止駆動要素のいずれかが一定配列に分散装架されていることを特徴とするものである。
【００１２】
【発明の実施の形態】
本発明の流量応答型炉停止駆動要素及び原子炉構造の実施形態について説明する。先ず、流量応答型炉停止駆動要素の１つの実施形態を図１，図２によって説明すると、１は炉心燃料集合体の外管と同じ長さの外管で、その外管１の上端板２に炉心出口導圧孔３が設けられている。外管１内には、下端板４を貫通して上端部まで内管５が同心に配設され、内管５内には、外管１の下方に突出する内管下端部の底板６を貫通して上端部まで炉心入口導圧管７が同心に配設されている。外管１内にて内管５の下部には内・外管連通孔８が設けられ、外管１及び内管５内に、前記炉心入口導圧管７の炉心入口圧力：Ｐ１と前記炉心出口導圧孔３の炉心出口圧力：Ｐ_０が等しい時、炉心燃料域Ｆの上端レベルとなる量の鉛ビスマス等の液体金属９が装入されている。さらに外管１内の液体金属９中に、図１に示すように炉心燃料域Ｆの範囲にわたる高さで、多数の球体、例えばボロン球からなる中性子吸収体１０が装入されて、前記炉心入口導圧管７の炉心入口圧力：Ｐ_１が前記炉心出口導圧孔３の炉心出口圧力：Ｐ_０よりも高い時、その差圧により図２に示すように前記中性子吸収体１０が炉心燃料域Ｆよりも上方に位置するようになっている。尚、多数のボロン球からなる中性子吸収体１０は、図３に示すように炉心燃料域Ｆの範囲にわたる長さで、外管１と内管５との間で上下し得る円筒状の成形物の中性子吸収体１０′に代替してもよいものである。
【００１３】
上記のように構成された流量応答型炉停止駆動要素１１は、ガス冷却炉のＳＡＳＳ（受動的炉停止機構）として採用される。即ち、図４に示すようにガス冷却炉の炉心１２内に、炉心燃料集合体１３が多数配列装架され、この炉心燃料集合体１３の群の中に、調整棒集合体１４と安全棒集合体１５が一定配列に分散装架された原子炉構造において、前記調整棒集合体１４と安全棒集合体１５とに囲まれるように炉心燃料集合体１３の群の中に流量応答型炉停止駆動要素１１が一定配列に分散装架される。図４中、Ｆは炉心燃料域を示す。
【００１４】
上記のように流量応答型炉停止駆動要素１１を、炉心１２内の炉心燃料集合体１３の群の中に分散装架したガス冷却炉において、冷却材であるヘリウムは、炉心１２の下部のプレナム室１６に矢印のように入り、下から燃料集合体１３に沿って矢印のように上昇し、炉心燃料域Ｆで燃料から熱が与えられて温度上昇し、炉心１２から出ていく。この冷却材が一定量流れ、ガス冷却炉が定格運転されている時は、流量応答型炉停止駆動要素１１における炉心入口導圧管７の炉心入口圧力：Ｐ_１が炉心出口導圧孔３の炉心出口圧力：Ｐ_０よりも高いので、その差圧により図２に示すように内管５内の液体金属９が内・外管連通孔８を通して外管１内に押し出されてそのレベルが下降し、外管１内の液体金属９のレベルが上昇し、それに伴い外管１内の中性子吸収体１０（又は１０′）が炉心燃料域Ｆよりも上方に位置している。
【００１５】
然して、ガス冷却炉の冷却材流量低下事故時には、炉心温度が上昇し、冷却材温度が上昇し、冷却材の流量が零となるため、流量応答型炉停止駆動要素１１における炉心入口導圧管７の炉心入口圧力：Ｐ_１と炉心出口導圧孔３の炉心出口圧力：Ｐ_０とが等しくなり、図１に示すように外管１内の液体金属９が内・外管連通孔８を通して内管５内に戻り、外管１の液体金属９のレベルが下がり、内管５の液体金属９のレベルが上がって、両レベルが同一となる。これに伴い外管１内の中性子吸収体１０（又は１０′）が下降し、炉心燃料域Ｆに位置する。その結果、炉心燃料域Ｆで核***によって生成された中性子は、中性子吸収体１０（又は１０′）に吸収されていき、中性子の連鎖反応が抑えられ、原子炉出力が低下せしめられ、原子炉の安全停止がなされる。勿論、ガス冷却炉の緊急停止事故時或いは冷却材流量低下事故時には、炉心燃料集合体１３の群の中に分散装架された制御棒集合体１４と安全棒集合体１５は、本来の機能を果たすべく炉心燃料域Ｆのレベルに挿入される。
【００１６】
次に、流量応答型炉停止駆動要素の他の１つの実施形態を図５、図６によって説明すると、１は炉心燃料集合体の外管と同じ長さの外管で、その外管１の上端板２に炉心出口導圧孔３が設けられている。外管１内には、下端板４を貫通して上端部まで内管５が同心に配設され、内管５内には、外管１の下方に突出する内管下端部の底板６を貫通して上端部まで炉心入口導圧管７が同心に配設されている。外管１内にて内管５の下部に内・外管連通孔８が設けられ、外管１及び内管５内に、前記炉心入口導圧管７の炉心入口圧力：Ｐ_１と前記炉心出口導圧孔３の炉心出口圧力：Ｐ_０が等しい時、炉心燃料域Ｆの下端以下のレベルとなる量の鉛ビスマス等の液体金属９が装入されている。さらに外管１内の液体金属９中に、図５に示すように炉心燃料域Ｆの範囲にわたる長さで、外管１と内管５との間で上下し得る重水、ベリリウム、黒鉛、ステンレススチールなどからなる円筒状の成形物の中性子反射体１８が炉心燃料域Ｆの下方にて装入され、前記炉心入口導圧管７の炉心入口圧力：Ｐ_１が前記炉心出口導圧孔３の炉心出口圧力：Ｐ_１よりも高い時、その差圧により図６に示すように前記中性子反射体１８が炉心燃料域Ｆに位置するようになっている。
【００１７】
上記のように構成された流量応答型炉停止駆動要素１９は、ガス冷却炉のＳＡＳＳ（受動的炉停止機構）として採用される。即ち、図７に示すようにガス冷却炉の炉心１２内に、炉心燃料集合体１３が多数配列装架され、この炉心燃料集合体１３の群の中に、調整棒集合体１４と安全棒集合体１５が一定配列に分散装架された原子炉構造において、前記調整棒集合体１４と安全棒集合体１５とに囲まれるように炉心燃料集合体１３の群の中に流量応答型炉停止駆動要素１９が一定配列に分散装架される。図７中、Ｆは炉心燃料域を示す。
【００１８】
上記のように流量応答型炉停止駆動要素１９を炉心１２内の炉心燃料燃料集合体１３の群の中に分散装架したガス冷却炉において、冷却材であるヘリウムは、炉心１２の下部のプレナム室１６に矢印のように入り、下から燃料集合体１３に沿って矢印のように上昇し、炉心燃料域Ｆで燃料から熱が与えられて温度上昇し、炉心１２から出ていく。この冷却材が一定量流れ、ガス冷却炉が定格運転されている時は、流量応答型炉停止駆動要素１９における炉心入口導圧管７の炉心入口圧力：Ｐ_１が炉心出口導圧孔３の炉心出口圧力：Ｐ_０よりも高いので、その差圧により図６に示すように内管５内の液体金属９が内・外管連通孔８を通して外管１内に押し出されてそのレベルが下降し、外管１内の液体金属９のレベルが上昇し、それに伴い外管１内の中性子反射体１８が炉心燃料域Ｆに位置するので、核***によって生成された中性子は中性子反射体１８に反射されて洩れが少なくなり連鎖反応が維持され、所定の原子炉出力が得られる。
【００１９】
然して、ガス冷却炉の冷却材流量低下事故時には、炉心温度が上昇し、冷却材温度が上昇するが、冷却材の流量が零となるため、流量応答型炉停止駆動要素１９における炉心入口導圧管７の炉心入口圧力：Ｐ_１と炉心出口導圧孔３の炉心出口圧力：Ｐ_０が等しくなり、図５に示すように外管１内の液体金属９が内・外管連通孔８を通して内管５内に戻り、外管１の液体金属９のレベルが下がり、内管５の液体金属９のレベルが上がって、両レベルが同一となる。これに伴い外管１内の中性子反射体１８が下降し、炉心燃料域Ｆの下方に位置する。その結果、炉心燃料域Ｆで核***によって生成された中性子は、中性子反射体１８がないため洩れていき、中性子の連鎖反応が減少し、原子炉出力が低下せしめられ、原子炉の安全停止がなされる。勿論、ガス冷却炉の緊急停止事故時或いは冷却材流量低下事故時には、炉心燃料集合体１３の群の中に分散装架された調整棒集合体１４と安全棒集合体１５は、本来の機能を果たすべく炉心燃料域Ｆのレベルに挿入される。
【００２０】
【発明の効果】
以上説明で判るように本発明の流量応答型炉停止駆動要素は、冷却材流量の低下に即応する入口圧力と出口圧力の差圧により、中性子吸収体を炉心燃料域に相当する位置に自動的に移動したり、或いは中性子反射体を炉心燃料域に相当する位置の外の下方に自動的に移動したりすることができるので、磁石の温度上昇に依拠した方式よりも敏速なＳＡＳＳの作動が可能である。また、磁石式のＳＡＳＳは低流量時に応答が遅くなるが、差圧は流量の２乗に比例するので、本発明の流量応答型炉停止駆動要素は、低流量でも有効に中性子吸収体或いは中性子反射体を所要の位置に移動できる。
【００２１】
また、本発明の原子炉構造は、上記の作用効果を奏する流量応答型炉停止駆動要素を、ガス冷却炉の炉心内における炉心燃料集合体の群の中に調整棒集合体と安全棒集合体に囲まれるように一定配列に分散装架したものであるから、ガス冷却炉の冷却材流量低下事故時に、流量応答型炉停止駆動要素における中性子吸収体を炉心燃料域に、或いは中性子反射体を炉心燃料域外に敏速に移動し、中性子の連鎖反応を減少して原子炉出力を低下することができるので、制御棒などの誤引き抜きがあっても事故に至らず、原子炉の安全停止を行うことができる。
【図面の簡単な説明】
【図１】本発明の流量応答型炉停止駆動要素の一実施形態で、中性子吸収体が炉心燃料域に位置している状態を示す縦断面図である。
【図２】図１における中性子吸収体が炉心燃料域外の上方に位置している状態を示す縦断面図である。
【図３】中性子吸収体の他の例を示す斜視図である。
【図４】図１の流量応答型炉停止駆動要素を炉心燃料集合体の群の中に分散装架したガス冷却炉の炉心概念図である。
【図５】本発明の流量応答型炉停止駆動要素の他の実施形態で、中性子反射体が炉心燃料域外の下方に位置している状態を示す縦断面図である。
【図６】図５における中性子反射体が炉心燃料域に位置している状態を示す縦断面図である。
【図７】図５の流量応答型炉停止駆動要素を炉心燃料集合体の群の中に分散装架したガス冷却炉の炉心概念図である。
【図８】磁石式ＳＡＳＳの構造を示すナトリウム冷却高速炉の炉心概念図である。
【符号の説明】
１外管
２上端板
３炉心出口導圧孔
４下端板
５内管
６底板
７炉心入口導圧管
８内・外管連通孔
９液体金属
１０中性子吸収体（ボロン球）
１０′中性子吸収体（円筒状の成形物）
１１流量応答型炉停止駆動要素
１２炉心
１３炉心燃料集合体
１４調整棒集合体
１５安全棒集合体
１６プレナム室
１８中性子反射体
１９流量応答型炉停止駆動要素
Ｆ炉心燃料域[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a flow response type reactor shutdown drive element adapted to a passive reactor shutdown system (SASS) in a nuclear power plant, and a nuclear reactor structure in which the flow response type reactor shutdown drive element is distributedly mounted.
[0002]
[Prior art]
Generally, in a nuclear power plant, when an accident occurs in which the cooling capacity of the core decreases due to a decrease in the flow rate of the coolant to the core by the coolant circulator, this is detected, and a control rod is inserted into the core and the reactor is inserted. Although the design is designed to lower the power and shut down the reactor safely, it must be designed so that even if the control rod is not inserted into the core, the core cooling performance deterioration accident will be terminated. As a countermeasure, a design in which a control rod is passively inserted into the core based on a change in the core state and the core atmosphere due to a decrease in the core cooling performance, that is, a design adopting a passive reactor shutdown mechanism (hereinafter referred to as SASS). Thought is valid.
[0003]
In the sodium-cooled fast reactor, the above-mentioned SASS uses magnets to hold the control rods and makes use of the fact that the coolant becomes hot in the event of core cooling performance deterioration, etc., and lowers the holding power of the magnets to drop the control rods. The concept is being considered. The structure of the magnet type SASS will be described with reference to the conceptual diagram of the core shown in FIG. 8. In the figure, reference numeral 31 denotes a core fuel assembly which is mounted and arranged in a large number in the core. The adjustment rod assemblies 32 are dispersedly mounted on the core rods, and the safety rod assemblies 33 are also distributed and mounted on the core fuel assemblies 31 in a fixed array so as to be surrounded by the adjustment rod assemblies 32. . The control rod 34 of the safety rod assembly 33 is held on a support rod 36 by an electromagnet 35. The coolant flows upward along the core fuel assembly 31 from below as shown by arrows.
[0004]
In the magnetic SASS having such a structure, when the temperature of the fuel in the core fuel assembly 31 rises and the temperature of the fuel cladding tube rises accordingly, the temperature of the coolant also rises. Due to the upward flow of the coolant whose temperature has increased, heat is transported from the central portion of the core to the portion of the electromagnet 35 holding the control rod 34 of the safety rod assembly 33 on the support rod 36, and the ambient temperature of the electromagnet 35 increases. Then, the temperature of the electromagnet 35 rises. As a result, the control rod holding force of the electromagnet 35 is reduced, the control rod 34 falls to the center of the core, and the furnace is stopped.
[0005]
By the way, since the SASS of the gas cooling furnace is driven while supporting the control rod from below, the control rod does not fall even if the magnet is simply cut off. Further, since the gas-cooled furnace is operated at a higher temperature, the control rod holding force by the magnet is reduced. Therefore, it is necessary to increase the size of the magnet. However, when the size of the magnet is increased, its heat capacity is increased, and the follow-up to the rise in the ambient temperature becomes slow. In addition, in a gas-cooled furnace, the temperature of the magnet itself rises later than the gas because the specific heat and the heat transfer coefficient of the gas as the coolant are small. As a result, the operation of the SASS is delayed, and there is a possibility that the core cooling performance deterioration accident cannot be dealt with early. As a prior art document, there is a reactor shutdown device described in JP-A-8-50189.
[0006]
[Problems to be solved by the invention]
Therefore, the present invention focuses on the fact that the temperature rise of the core is caused by a decrease in the coolant flow rate relative to the core output, and it is more preferable to react to the decrease in the coolant flow rate than a method that relies on the magnet temperature rise. To provide a differential pressure drive type flow rate responsive reactor stop drive element and to provide a nuclear reactor structure in which the flow rate responsive type reactor stop drive element is inserted into the core since a highly responsive SASS can be constructed. It is.
[0007]
[Means for Solving the Problems]
One of the flow response type reactor shutdown drive elements of the present invention for solving the above-mentioned problems is that a lower end is provided in an outer tube having the same length as the outer tube of the core fuel assembly and having a core outlet pressure introducing hole in an upper end plate. The inner pipe is arranged concentrically up to the upper end through the plate, and the core inlet pressure guide pipe is arranged concentrically from the bottom plate of the lower end of the inner pipe projecting below the outer pipe to the upper end inside the inner pipe. An inner / outer pipe communication hole is provided in the lower part of the inner pipe in the pipe, and when the core inlet pressure of the core inlet impulse tube and the core outlet pressure of the core outlet impulse hole are equal in the inner / outer pipe, the An amount of liquid metal at the upper end level is charged, and a neutron absorber is charged into the liquid metal in the outer tube with a length covering a range of the core fuel zone, and the core inlet pressure of the core inlet impulse line is set at the core outlet. When the pressure is higher than the core outlet pressure of the pressure guiding hole, the liquid level moves due to the pressure difference, and the neutron absorber moves into the core fuel zone. It is characterized in that it has configured to be positioned remote upward.
[0008]
In the flow response type reactor shutdown drive element having such a configuration, the neutron absorber may be composed of a large number of spheres or may be composed of a cylindrical molded product, and its constituent metals are, for example, boron carbide boron alloy, cadmium alloy and the like. It is.
[0009]
Another one of the flow response type reactor shutdown drive elements of the present invention is that the lower end plate is penetrated into an outer tube having the same length as the outer tube of the core fuel assembly and having an upper end plate provided with a core outlet pressure introducing hole. The inner pipe is arranged concentrically to the upper end, the core inlet impulse pipe is arranged concentrically within the inner pipe from the bottom plate of the lower end of the inner pipe protruding below the outer pipe to the upper end, and the inner pipe is placed inside the outer pipe. An inner / outer tube communication hole is provided in the lower portion, and when the core inlet pressure of the core inlet impulse tube and the core outlet pressure of the core outlet impulse hole are equal in the inner / outer tube, the level becomes lower than the lower end of the core fuel zone. Amount of liquid metal, and the liquid metal in the outer tube is charged with a neutron reflector having a length covering the range of the core fuel zone below the core fuel zone, and the core inlet pressure of the core inlet impulse line is reduced. When the core outlet pressure hole is higher than the core outlet pressure, the liquid level moves due to the pressure difference, and the neutron reflector becomes the core fuel. It is characterized in that it has configured to be positioned in frequency.
[0010]
In the flow-responsive furnace shutdown driving element having such a configuration, the neutron reflector is formed of a cylindrical molded product, and its configuration is heavy water, beryllium, graphite, stainless steel, or the like.
[0011]
In the reactor structure of the present invention, a large number of core fuel assemblies are arrayed and mounted in the core of the gas-cooled reactor, and the adjusting rod assemblies and the safety rod assemblies are divided into a fixed array in the core fuel assemblies. In the dispersed reactor structure, one of the two flow response type reactor shutdown drive elements having the above configuration is fixed in the group of core fuel assemblies so as to be surrounded by the adjustment rod assembly and the safety rod assembly. It is characterized by being distributedly mounted in an array.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a flow response type reactor shutdown drive element and a reactor structure of the present invention will be described. First, one embodiment of a flow response type reactor shutdown drive element will be described with reference to FIGS. 1 and 2. Reference numeral 1 denotes an outer pipe having the same length as the outer pipe of a core fuel assembly. Is provided with a core outlet pressure introducing hole 3. An inner tube 5 is concentrically arranged in the outer tube 1 through the lower end plate 4 to the upper end portion. A bottom plate 6 at the lower end portion of the inner tube projecting downward from the outer tube 1 is provided in the inner tube 5. A core inlet pressure guiding tube 7 is disposed concentrically therethrough to the upper end. An inner / outer tube communication hole 8 is provided below the inner tube 5 in the outer tube 1. In the outer tube 1 and the inner tube 5, the core inlet pressure of the core inlet pressure guiding tube 7: P1 and the core outlet When the core outlet pressure P _{0 of the} pressure introducing hole 3 is equal, the amount of the liquid metal 9 such as lead-bismuth which is at the upper end level of the core fuel zone F is charged. Further, a neutron absorber 10 composed of a number of spheres, for example, boron spheres, is inserted into the liquid metal 9 in the outer tube 1 at a height over the range of the core fuel zone F as shown in FIG. core inlet pressure at the inlet impulse line 7: P ₁ is the core outlet pressure guiding hole 3 of the core outlet pressure: when higher than P _0, the neutron absorber 10 is the core fuel zone as shown in FIG. 2 by the pressure difference It is located above F. The neutron absorber 10 composed of a large number of boron spheres has a length extending over the range of the core fuel region F as shown in FIG. 3 and can be moved up and down between the outer tube 1 and the inner tube 5. Neutron absorber 10 '.
[0013]
The flow response type furnace stop drive element 11 configured as described above is adopted as a SASS (passive furnace stop mechanism) of a gas cooling furnace. That is, as shown in FIG. 4, a large number of core fuel assemblies 13 are arrayed and mounted in a core 12 of a gas-cooled reactor, and a group of core fuel assemblies 13 includes an adjustment rod assembly 14 and a safety rod assembly. In a nuclear reactor structure in which the bodies 15 are distributed and mounted in a fixed arrangement, a flow response type reactor stop drive is provided in a group of core fuel assemblies 13 so as to be surrounded by the adjusting rod assemblies 14 and the safety rod assemblies 15. The elements 11 are distributed and mounted in a fixed array. In FIG. 4, F indicates a core fuel region.
[0014]
As described above, in the gas-cooled reactor in which the flow response type reactor shutdown drive element 11 is dispersedly mounted in the group of the core fuel assemblies 13 in the core 12, helium as a coolant is supplied to the plenum below the core 12. The fuel enters the chamber 16 as indicated by the arrow, rises from below along the fuel assembly 13 as indicated by the arrow, and is heated by fuel from the fuel in the core fuel zone F to rise in temperature. When a certain amount of this coolant flows and the gas-cooled furnace is in rated operation, the core inlet pressure P ₁ of the core inlet impulse line 7 in the flow response type furnace stop drive element 11 is the core of the core outlet impulse hole 3. Since the outlet pressure is higher than P ₀ , the pressure difference causes the liquid metal 9 in the inner tube 5 to be pushed out into the outer tube 1 through the inner / outer tube communication hole 8 as shown in FIG. As a result, the level of the liquid metal 9 in the outer tube 1 increases, and accordingly, the neutron absorber 10 (or 10 ′) in the outer tube 1 is located above the core fuel zone F.
[0015]
However, when the coolant flow rate of the gas-cooled reactor falls, the core temperature rises, the coolant temperature rises, and the coolant flow rate becomes zero. Core inlet pressure: P ₁ and the core outlet pressure: P ₀ of the core outlet pressure introducing hole 3 become equal, and the liquid metal 9 in the outer tube 1 passes through the inner / outer tube communication hole 8 as shown in FIG. Returning into the tube 5, the level of the liquid metal 9 in the outer tube 1 decreases, and the level of the liquid metal 9 in the inner tube 5 increases, so that both levels are the same. Accordingly, the neutron absorber 10 (or 10 ′) in the outer tube 1 descends and is located in the core fuel zone F. As a result, neutrons generated by fission in the core fuel region F are absorbed by the neutron absorber 10 (or 10 '), the neutron chain reaction is suppressed, the reactor power is reduced, and the reactor power is reduced. A safety stop is made. Needless to say, in the event of an emergency shutdown of the gas-cooled reactor or a decrease in the flow rate of the coolant, the control rod assemblies 14 and the safety rod assemblies 15 distributed and mounted in the group of the core fuel assemblies 13 have their original functions. It is inserted at the level of the core fuel zone F to fulfill.
[0016]
Next, another embodiment of the flow response type reactor stop drive element will be described with reference to FIGS. 5 and 6. Reference numeral 1 denotes an outer pipe having the same length as the outer pipe of the core fuel assembly. A core outlet pressure introducing hole 3 is provided in the upper end plate 2. An inner tube 5 is concentrically arranged in the outer tube 1 through the lower end plate 4 to the upper end portion. A bottom plate 6 at the lower end portion of the inner tube projecting downward from the outer tube 1 is provided in the inner tube 5. A core inlet pressure guiding tube 7 is disposed concentrically therethrough to the upper end. An inner / outer tube communication hole 8 is provided below the inner tube 5 in the outer tube 1, and the core inlet pressure of the core inlet pressure guiding tube 7: P ₁ and the core outlet in the outer tube 1 and the inner tube 5. When the core outlet pressure: P _{0 of the} pressure introducing hole 3 is equal, the amount of liquid metal 9 such as lead bismuth which is equal to or lower than the lower end of the core fuel zone F is charged. Further, heavy water, beryllium, graphite, stainless steel, which can move up and down between the outer tube 1 and the inner tube 5 in the liquid metal 9 in the outer tube 1 as shown in FIG. A cylindrical neutron reflector 18 made of steel or the like is charged below the core fuel zone F, and the core inlet pressure of the core inlet pressure pipe 7: P ₁ is the core of the core outlet pressure hole 3. outlet pressure: when higher than P _1, the neutron reflector 18, as shown in FIG. 6 is adapted to position the core fuel zone F by the pressure difference.
[0017]
The flow response type furnace stop drive element 19 configured as described above is employed as a SASS (passive furnace stop mechanism) of a gas cooling furnace. That is, as shown in FIG. 7, a large number of core fuel assemblies 13 are arrayed and mounted in a core 12 of a gas-cooled reactor, and an adjustment rod assembly 14 and a safety rod assembly are included in a group of the core fuel assemblies 13. In a nuclear reactor structure in which the bodies 15 are distributed and mounted in a fixed arrangement, a flow response type reactor stop drive is provided in a group of core fuel assemblies 13 so as to be surrounded by the adjusting rod assemblies 14 and the safety rod assemblies 15. Elements 19 are distributed and mounted in a fixed array. In FIG. 7, F indicates a core fuel region.
[0018]
As described above, in the gas-cooled reactor in which the flow response type reactor shutdown driving element 19 is dispersedly mounted in the group of the core fuel assemblies 13 in the core 12, the helium as a coolant is supplied to the plenum below the core 12. The fuel enters the chamber 16 as indicated by the arrow, rises from below along the fuel assembly 13 as indicated by the arrow, and is heated by fuel from the fuel in the core fuel zone F to rise in temperature. When a certain amount of this coolant flows and the gas-cooled furnace is in rated operation, the core inlet pressure of the core inlet pressure pipe 7 in the flow rate responsive furnace stop drive element 19: P ₁ is the core of the core outlet pressure hole 3. Since the outlet pressure is higher than P ₀ , the pressure difference causes the liquid metal 9 in the inner tube 5 to be pushed into the outer tube 1 through the inner / outer tube communication hole 8 as shown in FIG. Since the level of the liquid metal 9 in the outer tube 1 rises and the neutron reflector 18 in the outer tube 1 is located in the core fuel zone F, neutrons generated by fission are reflected by the neutron reflector 18. Leakage is reduced, the chain reaction is maintained, and a predetermined reactor output is obtained.
[0019]
However, when the coolant flow rate of the gas-cooled reactor falls, the core temperature rises and the coolant temperature rises, but the coolant flow rate becomes zero. 7 the core inlet pressure: P ₁ and the core outlet pressure guiding hole 3 of the core outlet pressure: P ₀ is equal, the inner through the liquid metal 9 the inner and outer tube communicating hole 8 of the outer tube 1 as shown in FIG. 5 Returning into the tube 5, the level of the liquid metal 9 in the outer tube 1 decreases, and the level of the liquid metal 9 in the inner tube 5 increases, so that both levels are the same. Accordingly, the neutron reflector 18 in the outer tube 1 descends and is located below the core fuel region F. As a result, neutrons generated by nuclear fission in the core fuel zone F leak due to the absence of the neutron reflector 18, the neutron chain reaction is reduced, the reactor power is reduced, and the reactor is safely shut down. You. Needless to say, in the event of an emergency shutdown of the gas-cooled reactor or an accident in which the coolant flow rate is reduced, the adjusting rod assemblies 14 and the safety rod assemblies 15 distributed and mounted in the core fuel assemblies 13 have their original functions. It is inserted at the level of the core fuel zone F to fulfill.
[0020]
【The invention's effect】
As can be seen from the above description, the flow response type reactor shutdown drive element of the present invention automatically moves the neutron absorber to a position corresponding to the core fuel zone by the differential pressure between the inlet pressure and the outlet pressure corresponding to the decrease in the coolant flow rate. Or the neutron reflector can be automatically moved below the position corresponding to the core fuel zone, so that the SASS operation can be performed more quickly than the method based on the temperature rise of the magnet. It is possible. In addition, although the response of the magnet type SASS is slow at a low flow rate, the differential pressure is proportional to the square of the flow rate. Therefore, the flow response type furnace stop drive element of the present invention can effectively use a neutron absorber or a neutron at a low flow rate. The reflector can be moved to a required position.
[0021]
Further, the reactor structure of the present invention includes a flow rate responsive reactor stop driving element having the above-described operation and effect, wherein an adjusting rod assembly and a safety rod assembly are arranged in a group of core fuel assemblies in the core of a gas-cooled reactor. The neutron absorber in the flow response type reactor shutdown drive element is placed in the core fuel area, or the neutron reflector is The reactor can be moved out of the core fuel area promptly and the neutron chain reaction can be reduced to reduce the reactor power, so even if a control rod is pulled out incorrectly, an accident does not occur and the reactor is safely shut down. be able to.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a state in which a neutron absorber is located in a core fuel region in one embodiment of a flow response type reactor shutdown drive element of the present invention.
FIG. 2 is a longitudinal sectional view showing a state in which the neutron absorber in FIG. 1 is located above the core fuel region.
FIG. 3 is a perspective view showing another example of the neutron absorber.
FIG. 4 is a conceptual view of a core of a gas-cooled reactor in which the flow response type reactor shutdown drive element of FIG. 1 is dispersedly mounted in a group of core fuel assemblies.
FIG. 5 is a longitudinal sectional view showing another embodiment of the flow response type reactor shutdown drive element according to the present invention, in which a neutron reflector is located below the core fuel region.
6 is a longitudinal sectional view showing a state where the neutron reflector in FIG. 5 is located in a core fuel region.
FIG. 7 is a conceptual view of a core of a gas-cooled reactor in which the flow response type reactor shutdown drive element of FIG. 5 is dispersedly mounted in a group of core fuel assemblies.
FIG. 8 is a conceptual view of a core of a sodium-cooled fast reactor showing the structure of a magnet type SASS.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Outer tube 2 Upper end plate 3 Core outlet pressure guiding hole 4 Lower end plate 5 Inner tube 6 Bottom plate 7 Core inlet pressure guiding tube 8 Inner / outer tube communication hole 9 Liquid metal 10 Neutron absorber (boron sphere)
10 'neutron absorber (cylindrical molded product)
Reference Signs List 11 Flow response type reactor shutdown drive element 12 Core 13 Core fuel assembly 14 Adjustment rod assembly 15 Safety rod assembly 16 Plenum chamber 18 Neutron reflector 19 Flow response type reactor shutdown drive element F Core fuel area

Claims

炉心燃料集合体の外管と同じ長さで上端板に炉心出口導圧孔を設けた外管内に、下端板を貫通して上端部まで内管を同心に配設し、内管内には外管の下方に突出する内管下端部の底板から上端部まで炉心入口導圧管を同心に配設し、外管内にて内管の下部に内・外管連通孔を設け、内・外管内に前記炉心入口導圧管の炉心入口圧力と前記炉心出口導圧孔の炉心出口圧力が等しい時、炉心燃料域の上端レベルとなる量の液体金属を装入し、且つ外管内の液体金属に炉心燃料域の範囲にわたる長さで中性子吸収体を装入し、前記炉心入口導圧管の炉心入口圧力が前記炉心出口導圧孔の炉心出口圧力よりも高い時、その差圧により液面が移動し前記中性子吸収体が炉心燃料域よりも上方に位置するように構成したことを特徴とする流量応答型炉停止駆動要素。In the outer tube with the same length as the outer tube of the core fuel assembly and the upper end plate provided with a core outlet pressure introducing hole, the inner tube is concentrically arranged to the upper end through the lower end plate, and the outer tube is A core inlet impulse line is concentrically arranged from the bottom plate at the lower end of the inner tube protruding below the tube to the upper end, and an inner / outer tube communication hole is provided at the lower part of the inner tube in the outer tube, and inside the outer tube. When the core inlet pressure of the core inlet impulse tube is equal to the core outlet pressure of the core outlet impulse hole, an amount of liquid metal which is at the upper end level of the core fuel region is charged, and the core metal is charged into the liquid metal in the outer tube. When the neutron absorber is charged with a length over the range of the region, and the core inlet pressure of the core inlet impulse line is higher than the core outlet pressure of the core outlet impulse hole, the liquid level moves due to the pressure difference. A flow-responsive reactor shutdown characterized in that the neutron absorber is located above the core fuel zone Dynamic element.

炉心燃料集合体の外管と同じ長さで上端板に炉心出口導圧孔を設けた外管内に、下端板を貫通して上端部まで内管を同心に配設し、内管内には外管の下方に突出する内管下端部の底板から上端部まで炉心出口導圧管を同心に配設し、外管内にて内管の下部に内・外管連通孔を設け、内・外管内に前記炉心入口導圧管の炉心入口圧力と前記炉心出口導圧孔の炉心出口圧力が等しい時、炉心燃料域の下端以下のレベルとなる量の液体金属を装入し、且つ外管内の液体金属に炉心燃料域の範囲にわたる長さの中性子反射体を炉心燃料域の下方に装入し、前記炉心入口導圧管の炉心入口圧力が前記炉心出口導圧孔の炉心出口圧力よりも高い時、その差圧により液面が移動し前記中性子反射体が炉心燃料域に位置するように構成したことを特徴とする流量応答型炉停止駆動要素。In the outer tube with the same length as the outer tube of the core fuel assembly and the upper end plate provided with a core outlet pressure introducing hole, the inner tube is concentrically arranged to the upper end through the lower end plate, and the outer tube is A core outlet impulse pressure tube is arranged concentrically from the bottom plate of the lower end of the inner tube protruding below the tube to the upper end, and a communication hole for the inner / outer tube is provided in the lower portion of the inner tube in the outer tube. When the core inlet pressure of the core inlet impulse tube is equal to the core outlet pressure of the core outlet impulse hole, an amount of liquid metal that is equal to or lower than the lower end of the core fuel region is charged, and the liquid metal in the outer tube is charged. A neutron reflector having a length extending over the core fuel zone is charged below the core fuel zone, and when the core inlet pressure of the core inlet impulse line is higher than the core outlet pressure of the core outlet impulse hole, the difference is determined. Wherein the liquid level is moved by pressure and the neutron reflector is located in the core fuel region. Responsive reactor shut down drive element.

ガス冷却炉の炉心内に炉心燃料集合体が多数配列装架され、この炉心燃料集合体の群の中に調整棒集合体と安全棒集合体が一定配列に分散装架された原子炉構造において、調整棒集合体と安全棒集合体とに囲まれるように炉心燃料集合体の群の中に請求項１又は２記載の流量応答型炉停止駆動要素が一定配列に分散装架されていることを特徴とする原子炉構造。In a nuclear reactor structure in which a large number of core fuel assemblies are arrayed and mounted in the core of a gas-cooled reactor, and adjustment rod assemblies and safety rod assemblies are distributed and mounted in a fixed array in the core fuel assemblies. 3. The flow response type reactor shutdown drive element according to claim 1 or 2, which is distributed and mounted in a fixed array within the group of core fuel assemblies so as to be surrounded by the adjustment rod assembly and the safety rod assembly. Reactor structure characterized by the following.