JP4489046B2 - How to start a natural circulation furnace - Google Patents

How to start a natural circulation furnace Download PDF

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JP4489046B2
JP4489046B2 JP2006087792A JP2006087792A JP4489046B2 JP 4489046 B2 JP4489046 B2 JP 4489046B2 JP 2006087792 A JP2006087792 A JP 2006087792A JP 2006087792 A JP2006087792 A JP 2006087792A JP 4489046 B2 JP4489046 B2 JP 4489046B2
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natural circulation
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誠一 横堀
信明 安部
昭 村瀬
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Description

本発明は、自然循環型沸騰水型原子炉の起動初期に現れる不安定流動現象を防止または緩和し、起動安定化を図った自然循環炉の起動方法に関するものである。   The present invention relates to a startup method for a natural circulation reactor that prevents or alleviates an unstable flow phenomenon that appears in the early stage of startup of a natural circulation boiling water nuclear reactor and stabilizes the startup.

従来、軽水からなる冷却材を自然循環させる自然循環型沸騰水型原子炉（自然循環型ＢＷＲ）が開発され、例えばオランダのドッドワード炉（原子炉熱出力１８３ＭＷ、既に閉鎖）や、現在開発中の大型自然循環炉などが知られている。このような自然循環炉の起動方法は、再循環ポンプを有する強制循環式の沸騰水型原子炉（ＢＷＲ）の起動方法とは異なる。   Conventionally, a natural circulation boiling water reactor (natural circulation type BWR) that naturally circulates a coolant made of light water has been developed, such as the Dutch Doddword reactor (reactor thermal output 183 MW, already closed), and currently under development Large natural circulation furnaces are known. Such a method for starting a natural circulation reactor is different from a method for starting a forced circulation boiling water reactor (BWR) having a recirculation pump.

上述のドッドワード炉の起動方法では、非特許文献１に示すように、まず起動に先立ち停止時冷却系（Reactor Shutdown Cooling System）により冷却材温度が調整され、原子炉水位が維持される。冷却材温度が約９５℃に達すると、制御棒が引き抜かれて原子炉は臨界となる。その後は核加熱により毎時４５〜５５℃の昇温率で冷却材温度が上昇され、タービンとバイパス弁とが閉鎖されて主蒸気ラインの小さなベントラインを使用した原子炉の圧力調整が行われる。   In the above-described method for starting a Dodward reactor, as shown in Non-Patent Document 1, first, the coolant temperature is adjusted by a Reactor Shutdown Cooling System to maintain the reactor water level. When the coolant temperature reaches about 95 ° C., the control rod is withdrawn and the reactor becomes critical. Thereafter, the temperature of the coolant is increased by a heating rate of 45 to 55 ° C. per hour by nuclear heating, the turbine and the bypass valve are closed, and the pressure adjustment of the reactor using the small vent line of the main steam line is performed.

原子炉圧力が４気圧に達すると、バイパス弁が開放され、さらに原子炉圧力の調整が行われる。原子炉圧力が増加してくると、原子炉浄化系（Reactor Water Cleanup System）が立ち上げられ、原子炉水位が調整される。なお、現在開発中の大型自然循環炉の起動方法はドッドワード炉にて確立された方法と同様である。   When the reactor pressure reaches 4 atm, the bypass valve is opened and the reactor pressure is adjusted. When the reactor pressure increases, the Reactor Water Cleanup System is started and the reactor water level is adjusted. The start-up method for the large-scale natural circulation reactor currently under development is the same as that established in the Doddward furnace.

非特許文献２には、起動過程の各段階が示されている。この文献に示された起動過程を図５のグラフにより説明する。図５に示すように、脱気期間（Ａ）では主蒸気隔離弁「ＭＳＩＶ」が開とされ、蒸気ドレンラインを開放したまま冷却材が脱気される。冷却材は冷却材浄化系／停止時冷却系（Reactor Water Cleanup/Shutdown Cooling System）の補助ヒータや崩壊熱を用いて、８０〜９０℃まで昇温される。この時点での原子炉圧力は５０〜６０ｋＰａである。   Non-Patent Document 2 shows each stage of the startup process. The starting process shown in this document will be described with reference to the graph of FIG. As shown in FIG. 5, in the deaeration period (A), the main steam isolation valve “MSIV” is opened, and the coolant is deaerated while the steam drain line is open. The coolant is heated up to 80-90 ° C. using an auxiliary heater or decay heat of a coolant purification system / cooling system at shutdown (Reactor Water Cleanup / Shutdown Cooling System). The reactor pressure at this point is 50-60 kPa.

脱気後には主蒸気隔離弁（ＭＳＩＶ）が閉鎖され、制御棒引き抜き（Ｂ）により臨界となって起動が開始される。原子炉水位をセパレータ頂部近くに（主蒸気ラインよりも十分に低く）維持したまま、核加熱により冷却材は加熱される。水位近傍の蒸発により原子炉圧力容器内は加圧される。炉心部はチムニーやセパレータの大きなヘッドにより、十分にサブクール状態を維持される。原子炉が昇温加圧されるにつれて、冷却材浄化系／停止時冷却系はダウンカマの温度調整、冷却材流量の増加、下部プレナム層状化防止用に用いられる。主蒸気隔離弁は、原子炉圧力が６．３ＭＰａとなる起動過程の最後で再度開放される。これ以降は、タービンバイパス弁が原子炉圧力調整に用いられる。そして、原子炉出力が増加し、タービンの準備が行われる。   After deaeration, the main steam isolation valve (MSIV) is closed, and the control rod is pulled out (B) to start critical operation. The coolant is heated by nuclear heating while maintaining the reactor water level near the top of the separator (which is well below the main steam line). The inside of the reactor pressure vessel is pressurized by evaporation near the water level. The core is sufficiently subcooled by the chimney and the large separator head. As the reactor is heated and pressurized, the coolant purification / stop cooling system is used for downcomer temperature adjustment, coolant flow rate increase, and lower plenum stratification prevention. The main steam isolation valve is opened again at the end of the start-up process when the reactor pressure is 6.3 MPa. Thereafter, the turbine bypass valve is used for reactor pressure adjustment. The reactor power is then increased and the turbine is prepared.

一方、最近では自然循環型ＢＷＲを模擬した試験装置において、低圧低温の起動時に不安定流動現象が観測されており、低圧時に２つの不安定な流動挙動が発生する可能性があることがわかった。   On the other hand, recently, in a test apparatus simulating a natural circulation type BWR, an unstable flow phenomenon was observed at the start of low pressure and low temperature, and it was found that two unstable flow behaviors may occur at low pressure. .

非特許文献３および非特許文献４には、第１の不安定流動現象が示されている。この現象を図６によって説明する。図６（ａ）に示すように、チムニー部１０１を流れる冷却材に対し、図６（ｂ）〜（ｄ）に順次に示すように、炉心出口で発生したボイド１０３がサブクール状態のチムニー部１０１で成長および凝縮する結果、冷却材１０２としての冷水が充満することによって炉心流量が振動するガイセリング流量振動が発生する。このガイセリング流量振動現象は、炉心でのボイド１０３の発生および消滅が繰返されることにより発生するものとされる。なお、ガイセリング流量振動はドッドワード炉では２２回の起動の際に一度も経験していない。しかしながら、もしこのようなガイセリング流量振動が発生するなら、炉心でボイド１０３の発生および消滅が繰返されることから、核熱フィードバックを介して大きな流量振動に至る可能性があると想定される。   Non-Patent Document 3 and Non-Patent Document 4 show the first unstable flow phenomenon. This phenomenon will be described with reference to FIG. As shown in FIG. 6A, with respect to the coolant flowing through the chimney unit 101, as shown in FIGS. 6B to 6D sequentially, the void 103 generated at the core outlet is in the subcooled state. As a result of growing and condensing in this case, a Geisling flow rate vibration in which the core flow rate vibrates due to the filling of the cold water as the coolant 102 occurs. This geysering flow rate vibration phenomenon is caused by repeated generation and disappearance of the void 103 in the core. It should be noted that the Geiseling flow rate vibration has never been experienced at the start of 22 times in the Doddward furnace. However, if such Gaiseling flow vibration occurs, it is assumed that the generation and disappearance of the void 103 are repeated in the core, which may lead to a large flow vibration through nuclear heat feedback.

また、第２の不安定流動現象は、非特許文献４および非特許文献５に示されているフラッシング流量振動である。このフラッシング流量振動は、図７（ａ）〜（ｄ）に順次に示すように、チムニー部１０１の上部領域でのボイド１０３の発生がチムニー部１０１の水力ヘッドを低下させ、炉心１０２における自然循環流１０５としての炉心流量が増加し、その後チムニー部１０１のボイド１０３が消滅し、炉心流量が再び減少することにより発生する。このフラッシング流量振動は、凝縮を伴わないだけ緩慢である。ドッドワード炉でも、起動時にこのようなフラッシング流量振動現象が発生した可能性がある。しかしながら、このフラッシング流量振動が発生する期間において、炉心１０４の流れは単相である。そのため、炉心１０４ではボイドの発生および消滅が生じることがなく、核熱フィードバックが生じないので、深刻な問題とならないが、流量振動そのものは可能な限り抑制して、安定な起動方法を確立すべきものである。   The second unstable flow phenomenon is the flushing flow rate vibration shown in Non-Patent Document 4 and Non-Patent Document 5. As shown in FIGS. 7A to 7D in sequence, the flushing flow rate vibration is caused by the generation of the void 103 in the upper region of the chimney unit 101, which lowers the hydraulic head of the chimney unit 101, and natural circulation in the core 102. This occurs when the core flow rate as the flow 105 increases and then the void 103 of the chimney portion 101 disappears and the core flow rate decreases again. This flushing flow rate oscillation is slow only without condensation. Even in the Doddward furnace, such a flushing flow rate oscillation phenomenon may have occurred during startup. However, the flow of the core 104 is a single phase during the period in which the flushing flow rate oscillation occurs. Therefore, no generation and disappearance of voids occur in the core 104, and no nuclear heat feedback occurs, so this is not a serious problem, but the flow oscillation itself should be suppressed as much as possible to establish a stable startup method. It is.

従来、このような自然循環型ＢＷＲの起動方法として、冷温停止状態にある自然循環型ＢＷＲを起動する際に、原子炉内を脱気することにより、炉心入口サブクーリングを原子炉出力と炉心入口サブクーリングで決まる不安定発生条件以下に設定した後に出力上昇を開始する方法が提案されている（例えば特許文献１参照）。
特開平５−２５６９９１号公報 Startup of the Dodewaard Natural Circulation Boiling Water Reactor (GKN-Report 92-017/FY/R, 1992) Analysis of ESBWR Startup in Natural Circulation, ICAPP’05, (2005) Transient Behavior of Natural Circulation for Boiling Two-Phase Flow (2nd Report, Mechanism of Geysering), ICONE-1 (1991) Nuclear Coupled Flow Instability Study for Natural Circulation BWR Startup Transient, NUTHOS-6 (2004) Experimental Investigation of Natural-Circulation Flow Behavior under Low-Power/Low-Pressure Conditions in the Large-Scale PANDA Facility, Nuclear Technology, (2004) Conventionally, as a method for starting such a natural circulation type BWR, when starting the natural circulation type BWR that is in a cold shutdown state, the reactor core inlet subcooling is performed by degassing the inside of the reactor so that the reactor core inlet subcooling is performed. There has been proposed a method of starting output increase after being set below an unstable generation condition determined by sub-cooling (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 5-256991 Startup of the Dodewaard Natural Circulation Boiling Water Reactor (GKN-Report 92-017 / FY / R, 1992) Analysis of ESBWR Startup in Natural Circulation, ICAPP'05, (2005) Transient Behavior of Natural Circulation for Boiling Two-Phase Flow (2nd Report, Mechanism of Geysering), ICONE-1 (1991) Nuclear Coupled Flow Instability Study for Natural Circulation BWR Startup Transient, NUTHOS-6 (2004) Experimental Investigation of Natural-Circulation Flow Behavior under Low-Power / Low-Pressure Conditions in the Large-Scale PANDA Facility, Nuclear Technology, (2004)

原子炉内を脱気する上述した従来の起動方法は、現行の強制循環型ＢＷＲでも採用している起動時の脱気運転を自然循環型ＢＷＲに適用したものであり、自然循環型ＢＷＲの水頭ヘッドを考慮すると、起動時に炉心入口サブクール度は小さくならず、自然循環型ＢＷＲの起動時不安定流動現象を必ずしも十分に抑制する方法ではない。   The above-described conventional startup method for degassing the inside of the nuclear reactor applies the degassing operation at startup, which is also adopted in the current forced circulation type BWR, to the natural circulation type BWR. Considering the head, the core inlet subcooling degree is not reduced at the time of start-up, and it is not necessarily a method for sufficiently suppressing the unstable flow phenomenon at the time of start-up of the natural circulation type BWR.

自然循環型ＢＷＲの２つの不安定流動現象の発生条件を図８により説明する。図８は自然循環型ＢＷＲの起動時の原子炉圧力容器軸方向のエンタルピ分布を示したものである。自然循環型ＢＷＲでは水頭ヘッドが大きいため、飽和エンタルピは原子炉圧力容器１０６の上部ほど小さくなる。低温低圧からの起動時において、通常の昇温率の場合、原子炉圧力容器１０６内のエンタルピ分布は図８にＡまたはＢで示したように、チムニー部１０１の上部で、まず飽和状態になることから、フラッシング流量振動が発生する可能性がある。また、もし起動時に原子炉出力が大きい場合、図８にＣとして示したように、炉心１０４の出口で飽和状態になり、ガイセリング流量振動が発生する可能性がある。   The conditions for generating the two unstable flow phenomena of the natural circulation type BWR will be described with reference to FIG. FIG. 8 shows the enthalpy distribution in the axial direction of the reactor pressure vessel when the natural circulation type BWR is started. In the natural circulation type BWR, since the head is large, the saturation enthalpy becomes smaller toward the upper part of the reactor pressure vessel 106. At the time of startup from low temperature and low pressure, in the case of a normal temperature increase rate, the enthalpy distribution in the reactor pressure vessel 106 is first saturated at the upper part of the chimney portion 101 as shown by A or B in FIG. Therefore, there is a possibility that a flushing flow rate vibration occurs. Further, if the reactor power is large at the time of start-up, as shown as C in FIG. 8, there is a possibility that the reactor becomes saturated at the outlet of the core 104, and a geysering flow oscillation occurs.

本発明はこのような事情に鑑みてなされたものであり、予め冷却材が低圧となる条件を回避して、安定な起動を実現できる自然循環炉の起動方法を提供することを目的とする。   This invention is made | formed in view of such a situation, and it aims at providing the starting method of the natural circulation furnace which can implement | achieve the stable starting avoiding the conditions from which a coolant becomes low pressure previously.

発明者の検討によれば、上述した自然循環型ＢＷＲにおいては、大気圧から通常の運転圧力に昇圧させる過程において、とくに２〜３気圧の通過時点で流量が大きく振動する可能性があり、炉出力での不安定な反応度制御上に問題となることが判った。   According to the inventor's study, in the above-described natural circulation type BWR, in the process of increasing the pressure from the atmospheric pressure to the normal operating pressure, there is a possibility that the flow rate greatly oscillates particularly at the passage of 2 to 3 atmospheres. It turned out to be a problem for unstable reactivity control at the output.

すなわち、ガイセリング流量振動現象は、水と蒸気の密度比が大きい低圧の起動時に発生する可能性がある。そこで、冷却材の圧力を高くしたり、自然循環流量を多くすることにより水と蒸気の密度比を小さくすることで、ガイセリング流量振動現象の発生を抑制することが可能となると考えられる。例えば圧力を３気圧以上、冷却材の流速を２ｃｍ／ｓ以上とすれば、ガイセリング振動現象は発生しないと考えられる。   That is, the Geisel flow rate oscillation phenomenon may occur at the time of low pressure start-up where the density ratio of water and steam is large. Therefore, it is considered that the occurrence of the Geisel flow rate oscillation phenomenon can be suppressed by increasing the coolant pressure or decreasing the density ratio of water and steam by increasing the natural circulation flow rate. For example, if the pressure is 3 atm or more and the flow rate of the coolant is 2 cm / s or more, it is considered that the Geiseling vibration phenomenon does not occur.

本発明は以上の知見に基づいてなされたものであり、自然循環型沸騰水型原子炉を起動する方法であって、脱気運転を完了した後、原子炉圧力容器内に冷却材を燃料集合体が完全に浸漬される状態まで満たし、前記冷却材の液面より上方の原子炉圧力容器内空間に不凝縮ガスを供給して充満させ、この不凝縮ガスのガス圧力を３気圧以上、好ましくは１０気圧以上の高圧に加圧した後、核加熱による加圧を開始する自然循環炉の起動方法を提供する。   The present invention has been made based on the above knowledge, and is a method of starting a natural circulation boiling water reactor, and after completing a deaeration operation, the coolant is assembled into the reactor pressure vessel. Fill up to a state where the body is completely immersed, fill the reactor pressure vessel space above the coolant level with a non-condensable gas, and fill the non-condensed gas with a gas pressure of 3 atm, preferably Provides a method for starting a natural circulation furnace in which pressurization by nuclear heating is started after pressurization to a high pressure of 10 atmospheres or more.

本発明によれば、自然循環型ＢＷＲでは、ガイセリング流量振動は発生させないように、またフラッシング流量振動はなるべく短く穏やかになるように起動することができる。   According to the present invention, the natural circulation type BWR can be activated so as not to generate the Geisling flow rate vibration and to make the flushing flow rate vibration as short and gentle as possible.

以下、本発明に係る自然循環炉の起動方法の実施形態について、図１〜図４を参照して説明する。   Hereinafter, an embodiment of a method for starting a natural circulation furnace according to the present invention will be described with reference to FIGS.

［第１実施形態（図１）］
図１は、本発明の第１実施形態を説明するための自然循環型ＢＷＲ構成図である。この図１に示すように、本実施形態では、原子炉圧力容器１の下部プレナム２の上方に炉心３が設けられ、炉心３の上方にはチムニー４が設けられている。上部プレナム５の上方にはセパレータ６およびドライヤ７が設けられている。また、原子炉圧力容器１の上部には主蒸気出口８が設けられ、その下方には給水口９が設けられている。 [First Embodiment (FIG. 1)]
FIG. 1 is a natural circulation type BWR configuration diagram for explaining a first embodiment of the present invention. As shown in FIG. 1, in this embodiment, a core 3 is provided above the lower plenum 2 of the reactor pressure vessel 1, and a chimney 4 is provided above the core 3. A separator 6 and a dryer 7 are provided above the upper plenum 5. A main steam outlet 8 is provided at the upper part of the reactor pressure vessel 1, and a water supply port 9 is provided below the main steam outlet 8.

このような構成において、自然循環炉の起動は制御棒１１を引抜き、核加熱することにより行われる。核加熱開始により炉心３の出力が増加し、炉心３内の冷却材への伝熱が増加し、高温の非沸騰温水を経て気泡流に至るまで、流体の密度を下げることによって自然循環流が生じるようになる。すなわち、炉心３から上昇流が生じ、ダウンカマ１０内で下降流が生じる。   In such a configuration, the natural circulation furnace is activated by pulling out the control rod 11 and heating the core. As the nuclear heating starts, the power of the core 3 increases, the heat transfer to the coolant in the core 3 increases, and the natural circulation flow is reduced by reducing the density of the fluid through the hot non-boiling hot water to the bubbly flow. It comes to occur. That is, an upward flow is generated from the core 3 and a downward flow is generated in the downcomer 10.

ここで、自然循環炉の起動を開始する前の原子炉圧力容器１内では通常の脱気運転が行われ、冷却材は十分に脱気されていることを前提とする。また、炉心３を構成する燃料集合体３ａの上端まで冷却材である軽水によって完全に充満されている状態を前提とする。このような条件においては、燃料集合体３ａよりも上方にある冷却材の水面２７ａよりさらに上方の気相空間２８は一般的に水蒸気によって充満されていると考えられる。   Here, it is assumed that a normal degassing operation is performed in the reactor pressure vessel 1 before starting the natural circulation reactor and the coolant is sufficiently degassed. In addition, it is assumed that the upper end of the fuel assembly 3a constituting the core 3 is completely filled with light water as a coolant. Under such conditions, it is considered that the gas phase space 28 above the coolant water surface 27a above the fuel assembly 3a is generally filled with water vapor.

本実施形態ではこの状態で、まず不凝縮性ガスである窒素ガス１２を炉外から供給し、冷却材の水面２７ａ上方のガスを窒素ガス１２で置き換える。なお、窒素ガス１２は原子炉格納容器内に封入される不凝縮ガスであり、新たに他の非凝縮ガスを供給する必要はなく、高圧維持には最適のガスである。   In this embodiment, in this state, first, nitrogen gas 12 that is a non-condensable gas is supplied from outside the furnace, and the gas above the water surface 27 a of the coolant is replaced with nitrogen gas 12. The nitrogen gas 12 is a non-condensable gas sealed in the reactor containment vessel, and it is not necessary to supply another non-condensable gas, and is an optimum gas for maintaining a high pressure.

なお、ガス供給にあたっては、原子炉圧力容器１に接続される各配管を介して、供給した当該窒素ガス１２が原子炉圧力容器１から外部に漏洩しないように、原子炉圧力容器１に接続される全配管のうち、ガス供給配管を除く配管に接続される弁を閉じることによって隔離させておく。   The gas supply is connected to the reactor pressure vessel 1 through each pipe connected to the reactor pressure vessel 1 so that the supplied nitrogen gas 12 does not leak from the reactor pressure vessel 1 to the outside. All the pipes to be isolated are closed by closing the valves connected to the pipes other than the gas supply pipe.

このようにして密閉した状態で窒素ガス１２の供給を継続すると、窒素ガス空間圧力は供給量に応じて大気圧を超えて単調に上昇を開始する。ガス供給を中止する圧力の上限は場合にもよるが、一般的には窒素ガスの占める圧力が３気圧以上、およそ１０気圧程度まで高めるように運転計画する。目安となる１０気圧程度の高圧に達したことが確認されれば、その時点で窒素ガス１２の供給を終了させる。十分に時間が経過して定常状態に至ったことが確認されれば、ガス空間の最終圧力は供給ガスのみならず、下方に充満する水の飽和蒸気圧も加わったものとなる。   When the supply of the nitrogen gas 12 is continued in the sealed state in this way, the nitrogen gas space pressure starts to rise monotonously beyond the atmospheric pressure according to the supply amount. Although the upper limit of the pressure at which the gas supply is stopped depends on the case, the operation plan is generally made so that the pressure occupied by the nitrogen gas is increased to 3 atmospheres or more and about 10 atmospheres. If it is confirmed that a high pressure of about 10 atmospheres as a guide has been reached, the supply of nitrogen gas 12 is terminated at that point. If it is confirmed that a steady state has been reached after a sufficient amount of time, the final pressure in the gas space is not only the supply gas but also the saturated vapor pressure of water filling downward.

このように、本実施形態では、脱気運転を完了した後、原子炉圧力容器１内に冷却材を燃料集合体３ａが完全に浸漬される状態まで満たし、冷却材の液面より上方の原子炉圧力容器内空間に不凝縮ガスである窒素ガス１２を供給して充満させ、この窒素ガス１２のガス圧力を３気圧以上、好ましくは１０高圧以上に加圧する。   Thus, in this embodiment, after the deaeration operation is completed, the coolant is filled in the reactor pressure vessel 1 until the fuel assembly 3a is completely immersed, and atoms above the liquid level of the coolant are filled. Nitrogen gas 12 that is a non-condensable gas is supplied to the interior of the furnace pressure vessel to fill it, and the pressure of the nitrogen gas 12 is increased to 3 atmospheres or higher, preferably 10 pressures or higher.

この状態で核加熱による加圧を開始すれば、燃料集合体３ａの表面から冷却材の沸騰によって発泡する気泡と周囲の冷却材とが熱混合して、一般的には気体と液体とから構成される気液の二相流状態が形成される。その二相流の圧力は上方のガス圧（１０気圧程度の高圧）に水頭が加わった高圧状態で気泡が発生して上部に送られる。   If pressurization by nuclear heating is started in this state, bubbles that foam from the surface of the fuel assembly 3a due to boiling of the coolant and the surrounding coolant are mixed by heat, and generally composed of gas and liquid. A gas-liquid two-phase flow state is formed. As for the pressure of the two-phase flow, bubbles are generated in a high pressure state in which a water head is added to an upper gas pressure (a high pressure of about 10 atm) and sent to the upper part.

このような１０気圧を超える高圧においては、水と蒸気の密度比も大気圧下とは変化する。大気圧下の気液密度比はおよそ１／１６００と極めて大きな差があるが、１０気圧という高圧下では物性に変化が見られ、気液密度比も１／１５７と１０倍程度増加し、１に近づくようにすることができる。   At such a high pressure exceeding 10 atmospheres, the density ratio of water and steam also changes from that under atmospheric pressure. Although the gas-liquid density ratio under atmospheric pressure is extremely different, approximately 1/1600, changes in physical properties are observed at a high pressure of 10 atmospheres, and the gas-liquid density ratio is increased by about 10 times to 1/157. Can be approached.

本発明の目的は起動時の二相流が炉心上部のサブクール領域で気泡凝縮することによって発生する液位の増減（ガイセリング）を防止することにあるが、本実施形態の方法を採用すれば、ガイセリング発生の主原因である気液密度比を低減させることができ、懸念されたガイセリングを防止できる可能性を高めることができる。特に供給ガス量を１０気圧以上とした場合には完全にガイセリングを防止することが可能であり、３気圧以上であれば完全にガイセリングを防止できないまでも、振動を従来に比して大幅に軽減させることが可能である。また、本実施形態によれば、フラッシング流量振動は短く、穏やかにすることができる。   The purpose of the present invention is to prevent increase / decrease in liquid level (geysering) generated by bubble condensation in the subcool region in the upper part of the core of the two-phase flow at startup, but if the method of this embodiment is adopted, It is possible to reduce the gas-liquid density ratio, which is the main cause of the occurrence of geysering, and to increase the possibility of preventing the geysering concerned. Especially when the amount of gas supplied is 10 atmospheres or more, it is possible to completely prevent geysing, and when it is 3 atmospheres or more, vibrations can be greatly reduced compared to conventional cases, even if gaisering cannot be completely prevented. It is possible to make it. Further, according to the present embodiment, the flushing flow rate vibration is short and can be made gentle.

なお、本発明では不凝縮ガスとして窒素ガス以外のガスも適用可能であることは勿論であるが、窒素ガスを適用することが望ましい。窒素ガスは上述したように、原子炉格納容器に封入される不凝縮ガスであり、改めて窒素ガス以外の非凝縮ガスを供給する必要はなく、高圧維持には最適のガスであるからである。   In the present invention, it is of course possible to apply a gas other than nitrogen gas as the non-condensable gas, but it is desirable to apply nitrogen gas. As described above, the nitrogen gas is a non-condensable gas sealed in the reactor containment vessel, and it is not necessary to supply a non-condensable gas other than the nitrogen gas again, and is an optimal gas for maintaining a high pressure.

また、１０気圧以上まで昇圧が達成され、大規模なガイセリングの発生の懸念が無くなるような十分な高圧に達した後は、窒素ガスは不要なものとなり、原子炉圧力容器１の外部にガスは排出させる必要がある。核加熱の継続で次第に軽水の蒸発が盛んになった時点で、それまで隔離していた主蒸気ドレン配管との仕切り弁（主蒸気ドレン弁）を次第に開放して、窒素ガスを順次に原子炉圧力容器１の外に排出すればよい。最終的なガスの排出先は、タービン建屋を介して、放射線量が十分低いことを確認した後、外気に放出させればよい。   Further, after the pressure is increased to 10 atmospheres or more and a sufficiently high pressure is reached so that there is no concern about the occurrence of large-scale guying, the nitrogen gas becomes unnecessary, and the gas is outside the reactor pressure vessel 1. It is necessary to discharge. When the evaporation of light water gradually increases with the continuation of nuclear heating, the gate valve (main steam drain valve) with the main steam drain pipe that had been isolated until then was gradually opened, and the nitrogen gas was sequentially released into the reactor. What is necessary is just to discharge | emit outside the pressure vessel 1. FIG. The final gas discharge destination may be released to the outside air after confirming that the radiation dose is sufficiently low via the turbine building.

［第２実施形態（図２）］
図２は、本発明の第２実施形態を説明するための構成図である。なお第１実施形態と同一の構成については図２に図１と同一の符号を付し、重複する説明は省略する。 [Second Embodiment (FIG. 2)]
FIG. 2 is a configuration diagram for explaining a second embodiment of the present invention. In addition, about the structure same as 1st Embodiment, the code | symbol same as FIG. 1 is attached | subjected to FIG. 2, and the overlapping description is abbreviate | omitted.

本実施形態では、第１実施形態における不凝縮ガスとしての窒素ガスに代えて、水蒸気を用いる。すなわち、脱気運転を完了した後、原子炉圧力容器１内に冷却材を燃料集合体３ａが完全に浸漬される状態まで満たし、原子炉圧力容器１内における頂部近傍に位置する配管３１から発電所内の利用可能な所内蒸気３３を供給することにより、冷却材の水面２７ａで蒸気を凝縮させながら、冷却材を昇温させてその液面温度に対応する飽和圧力を保ちつつ、気相圧力を約３気圧以上、好ましくは１０気圧以上の高圧に加圧した後、核加熱による加圧を開始する。   In the present embodiment, water vapor is used instead of the nitrogen gas as the non-condensable gas in the first embodiment. That is, after the deaeration operation is completed, the coolant is filled in the reactor pressure vessel 1 until the fuel assembly 3a is completely immersed, and power is generated from the pipe 31 located near the top in the reactor pressure vessel 1. By supplying the in-house steam 33 that can be used in the station, while condensing the steam at the water surface 27a of the coolant, the temperature of the coolant is raised and the vapor pressure is maintained while maintaining the saturation pressure corresponding to the liquid surface temperature. After pressurizing to a high pressure of about 3 atmospheres or more, preferably 10 atmospheres or more, pressurization by nuclear heating is started.

蒸気の供給源としては、原子力発電所で使用する所内蒸気源３０および蒸気配管３１を利用する。所内蒸気源３０としては、原子炉圧力容器１内の水面２７ａより上方の気相空間４１に接続され原子炉圧力容器１の頂部近傍に位置する配管、例えば原子炉ベント配管を用いる。   As a steam supply source, an in-house steam source 30 and a steam pipe 31 used in a nuclear power plant are used. As the in-house steam source 30, a pipe connected to the gas phase space 41 above the water surface 27a in the reactor pressure vessel 1 and located near the top of the reactor pressure vessel 1, for example, a reactor vent pipe is used.

本実施形態によれば、第１実施形態と比較して、原子炉圧力容器１の上部空間の加圧時間が長くなるが、供給蒸気は大気圧以上の圧力で供給され、脱気は完了しても水面の飽和温度は８０〜９０℃であるので、蒸気配管３１からの供給蒸気は水面２７ａに接触して速やかに凝縮する。このような供給蒸気による凝縮が続く結果、冷却材は表面側から次第に水温を上昇させていく。そして、蒸気供給が継続されれば、水面２７ａの温度が高まるばかりでなく、水の熱伝導によって水面２７ａ付近の高温水領域４０のボリュームも増加する。あわせて、気相空間４１の圧力も窒素ガス供給ほど急ではないが、水面凝縮の効果が緩慢になると、空間の圧力を昇圧させることも可能となる。   According to this embodiment, compared with the first embodiment, the pressurization time of the upper space of the reactor pressure vessel 1 becomes longer, but the supply steam is supplied at a pressure higher than atmospheric pressure, and the deaeration is completed. However, since the saturation temperature of the water surface is 80 to 90 ° C., the supply steam from the steam pipe 31 comes into contact with the water surface 27a and condenses quickly. As a result of the continued condensation by the supplied steam, the coolant gradually increases the water temperature from the surface side. If the steam supply is continued, not only the temperature of the water surface 27a increases, but also the volume of the high-temperature water region 40 near the water surface 27a increases due to heat conduction of water. At the same time, the pressure in the gas phase space 41 is not as steep as the nitrogen gas supply, but the pressure in the space can be increased when the effect of water surface condensation becomes slow.

なお、本実施形態では、発電所内の利用可能な所内蒸気を供給することに代え、脱気器３２にて発生する蒸気を使用することも可能である。すなわち、原子炉圧力容器１内における頂部近傍にヒータを有する脱気器３２を配置して、冷却材の水面２７ａで蒸気を発生させ、冷却材を昇温させてその液面温度に対応する飽和圧力を保ちつつ、気相圧力を３気圧以上、好ましくは１０気圧以上の高圧に加圧した後、核加熱による加圧を開始する方法を採用することができる。   In this embodiment, it is also possible to use steam generated in the deaerator 32 instead of supplying in-house steam that can be used in the power plant. That is, a deaerator 32 having a heater is disposed in the vicinity of the top in the reactor pressure vessel 1, steam is generated at the water surface 27a of the coolant, and the temperature of the coolant is increased to achieve saturation corresponding to the liquid surface temperature. While maintaining the pressure, a method of starting pressurization by nuclear heating after pressurizing the gas phase pressure to a high pressure of 3 atmospheres or more, preferably 10 atmospheres or more can be employed.

このような方法でも、供給蒸気が水面２７ａに接触して速やかに凝縮するので、冷却材を表面側から次第に水温を上昇させ、蒸気供給の継続により、水面２７ａの温度を高め、水の熱伝導によって水面２７ａ付近の高温水領域４０のボリュームを増加させ、気相空間４１の圧力を昇圧させることができる。   Even in such a method, the supply steam comes into contact with the water surface 27a and quickly condenses, so that the water temperature is gradually increased from the surface side, the temperature of the water surface 27a is increased by continuing the supply of steam, and the heat conduction of water. Thus, the volume of the high-temperature water region 40 near the water surface 27a can be increased, and the pressure in the gas phase space 41 can be increased.

［第３実施形態（図３）］
図３は、本発明の第３実施形態を説明するための構成図である。なお第１実施形態と同一の構成については図３に図１と同一の符号を付し、重複する説明は省略する。 [Third Embodiment (FIG. 3)]
FIG. 3 is a block diagram for explaining a third embodiment of the present invention. In addition, about the structure same as 1st Embodiment, the code | symbol same as FIG. 1 is attached | subjected to FIG. 3, and the overlapping description is abbreviate | omitted.

本実施形態では、脱気運転を完了した後、原子炉圧力容器１内に冷却材を燃料集合体３ａが完全に浸漬される状態まで満たし、原子炉圧力容器１の炉心シュラウド３ｂ内面に開口端５１ａを有する供給配管５１を用いて、原子炉圧力容器１の外部に設置したタンク５２から脱気した高温水５３を炉心シュラウド３ｂ内の上部に供給した後、核加熱による加圧を開始する。   In this embodiment, after the deaeration operation is completed, the coolant is filled in the reactor pressure vessel 1 until the fuel assembly 3a is completely immersed, and an open end is formed on the inner surface of the core shroud 3b of the reactor pressure vessel 1. After supplying the hot water 53 deaerated from the tank 52 installed outside the reactor pressure vessel 1 to the upper part in the core shroud 3b using the supply pipe 51 having 51a, pressurization by nuclear heating is started.

すなわち、炉心３を囲む炉心シュラウド３ｂ上部の流体温度を、核加熱開始前に予め高めておくため、外部から高温水５３を供給するものである。供給配管５１としては、炉心シュラウド３ｂ内面に開口端５１ａを有する配管、例えばほう酸水注入ラインを利用し、炉心シュラウド３ｂの上部に高温水５３を供給してから核加熱による加圧を開始する。   That is, high temperature water 53 is supplied from the outside in order to increase the fluid temperature in the upper part of the core shroud 3b surrounding the core 3 before starting the nuclear heating. As the supply pipe 51, a pipe having an open end 51 a on the inner surface of the core shroud 3 b, for example, a boric acid water injection line is used. After the hot water 53 is supplied to the upper part of the core shroud 3 b, pressurization by nuclear heating is started.

あわせて、原子炉圧力容器１の底部に位置する配管５４を介して、高温水５３の供給量に対応する量の冷水５５を原子炉圧力容器１の底部から排出する。具体的には、例えばドレン配管や原子炉水浄化系配管などを利用して、高温水５３にほぼ釣り合う量の冷水５５を底部から抜く。こうすることによって、原子炉圧力容器１内の炉心シュラウド３ｂ上部内の高温ボリュームを速やかに高温水で満たすことが可能となる。   In addition, an amount of cold water 55 corresponding to the supply amount of the high-temperature water 53 is discharged from the bottom of the reactor pressure vessel 1 through the pipe 54 located at the bottom of the reactor pressure vessel 1. Specifically, for example, using a drain pipe or a reactor water purification system pipe, an amount of cold water 55 that is substantially balanced with the high-temperature water 53 is drawn from the bottom. By doing so, it becomes possible to quickly fill the high temperature volume in the upper part of the core shroud 3b in the reactor pressure vessel 1 with high temperature water.

このように、炉心上部の冷却材を予め加熱した状況の下で次第に核加熱を開始すれば、ガイセリングが生ずる条件の一つである燃料上部（上部プレナム）のサブクール水が振動で急落する際に、燃料集合体３ａへ接触する可能性を回避または軽減することができる。本実施形態によれば、完全なガイセリングの抑制とはならないまでも、凝縮の程度は大幅に軽減され、ガイセリングによる振動の程度（流体振動の振幅や周期）が軽減される。   In this way, if the nuclear heating is gradually started under the condition that the coolant in the upper part of the core is preheated, the subcooled water in the upper part of the fuel (upper plenum), which is one of the conditions that cause geelsing, suddenly drops due to vibration. The possibility of contact with the fuel assembly 3a can be avoided or reduced. According to the present embodiment, the degree of condensation is greatly reduced, and the degree of vibration (amplitude and period of fluid vibration) due to Geiselling is reduced, even if it is not completely suppressed.

［第４実施形態（図４）］
本発明の第４実施形態では、核加熱による加圧を開始した後、セパレータ温度および原子炉蒸気ドーム圧力を検出し、セパレータ温度と、原子炉蒸気ドーム圧力に対応する温度との比較により、セパレータでのボイド発生を判断し、このボイド発生期間に炉心出力を上昇させる方法について説明する。図４は、本発明の第４実施形態を説明するための構成図である。 [Fourth Embodiment (FIG. 4)]
In the fourth embodiment of the present invention, after the pressurization by the nuclear heating is started, the separator temperature and the reactor steam dome pressure are detected, and the separator temperature is compared with the temperature corresponding to the reactor steam dome pressure. A description will be given of a method of determining the generation of voids in the reactor and increasing the core power during the void generation period. FIG. 4 is a configuration diagram for explaining a fourth embodiment of the present invention.

本実施形態では、原子炉圧力容器１の下部プレナム２の上方に炉心３が設けられ、炉心３の上方にはチムニー４が設けられている。上部プレナム５の上方にはセパレータ６およびドライヤ７が設けられている。また、原子炉圧力容器１の上部には主蒸気出口８が設けられ、その下方には給水口９が設けられている。   In the present embodiment, a core 3 is provided above the lower plenum 2 of the reactor pressure vessel 1, and a chimney 4 is provided above the core 3. A separator 6 and a dryer 7 are provided above the upper plenum 5. A main steam outlet 8 is provided at the upper part of the reactor pressure vessel 1, and a water supply port 9 is provided below the main steam outlet 8.

さらに、自然循環炉の炉心出力計２４、原子炉蒸気ドーム圧力計２１、炉心入口温度計２５、チムニー温度計２３、セパレータ温度計２２、炉心流量計２６、原子炉水位計２７が設けられている。そして、これらの計器により、それぞれオンライン測定が行われ、これらの測定諸量、すなわち炉心出力計Ｑ、原子炉蒸気ドーム圧力Ｐ、炉心入口温度ＴＩｎ、チムニー温度Ｔｃｍｎ、セパレータ温度Ｔｓｅｐ、炉心流量Ｗおよび原子炉水位Ｌが出力制御装置６０に入力されるようになっている。   Further, a natural circulation reactor core power meter 24, a reactor steam dome pressure gauge 21, a core inlet thermometer 25, a chimney thermometer 23, a separator thermometer 22, a core flow meter 26, and a reactor water level meter 27 are provided. . Each of these instruments performs on-line measurements. These measurement quantities, namely, the core power meter Q, the reactor steam dome pressure P, the core inlet temperature TIn, the chimney temperature Tcmn, the separator temperature Tsep, the core flow rate W and The reactor water level L is input to the output control device 60.

このような構成のもとで、自然循環炉の起動は制御棒１１を引抜き、核加熱することにより行われる。すなわち、核加熱開始により炉心３の出力が増加し、炉心３内の冷却材への伝熱が増加し、高温の非沸騰温水を経て気泡流に至るまで、流体の密度を下げることによって自然循環流が生じ、炉心１１から上昇流が生じ、ダウンカマ１０内で下降流が生じる。   Under such a configuration, the natural circulation furnace is started by pulling out the control rod 11 and heating the core. That is, the output of the core 3 is increased by the start of the nuclear heating, the heat transfer to the coolant in the core 3 is increased, and the natural circulation is achieved by reducing the density of the fluid through the hot non-boiling hot water to the bubbly flow. A flow is generated, an upward flow is generated from the core 11, and a downward flow is generated in the downcomer 10.

そして、出力制御装置６０においては、セパレータ温度Ｔｓｅｐと原子炉蒸気ドーム圧力Ｐに対応する飽和温度との比較が行われ、これらの両者が等温と判断できるレベルにある場合には、セパレータ７部分の冷却材は飽和状態になり、ボイドが発生したと判断される。この時点で、出力制御装置６０において、セパレータ６でのボイドが発生する期間に限って、一時的に炉心出力を上昇させる。   Then, in the output control device 60, the separator temperature Tsep is compared with the saturation temperature corresponding to the reactor steam dome pressure P, and when both of them are at a level at which it can be determined that they are isothermal, It is determined that the coolant is saturated and voids are generated. At this time, in the output control device 60, the core output is temporarily increased only during the period in which voids occur in the separator 6.

このような第４実施形態によれば、セパレータ６でボイドが発生する期間を短縮させることが可能となるので、フラッシングによる流量振動（Flashing-induced oscillation）の期間を短縮することが可能となる。また、セパレータ６でボイドが発生する期間において、一時的に炉心出力を上昇させるため、低圧低温から高温高圧の起動時間を短縮することも可能となる。   According to the fourth embodiment as described above, it is possible to shorten the period in which the voids are generated in the separator 6, and thus it is possible to shorten the period of flow rate oscillation (Flashing-induced oscillation) due to flushing. Further, since the core output is temporarily increased during the period in which the voids are generated in the separator 6, it is possible to shorten the startup time from the low pressure to the low temperature to the high temperature and pressure.

なお、出力制御装置６０により、セパレータ６でボイドが発生する期間に限って一時的に炉心出力を上昇させる本実施形態では、過度に炉心出力を上昇させると、凝縮による流量振動（Condensation-induced oscillation）が発生する可能性も残される。したがって、炉心出力の上限はガイセリングが発生防止の出力までとする。すなわち、ズーバー数がサブクーリング数とフラッシング数の合計に等しくなる時の出力を満足するように出力制御装置６０で炉心出力を制御する。これにより、凝縮による流量振動（Condensation-induced oscillation）の発生する可能性を防止することができる。   In the present embodiment in which the output controller 60 temporarily increases the core output only during the period in which the voids are generated in the separator 6, if the core output is excessively increased, the flow-rate vibration due to condensation (Condensation-induced oscillation). ) May also occur. Therefore, the upper limit of the core power is limited to the power for preventing the occurrence of geysering. That is, the core output is controlled by the output control device 60 so as to satisfy the output when the number of zoomers is equal to the sum of the subcooling number and the flushing number. Thereby, it is possible to prevent the possibility of occurrence of flow-rate vibration (condensation-induced oscillation) due to condensation.

本発明の第１実施形態を示す説明図。Explanatory drawing which shows 1st Embodiment of this invention. 本発明の第２実施形態を示す説明図。Explanatory drawing which shows 2nd Embodiment of this invention. 本発明の第３実施形態を示す説明図。Explanatory drawing which shows 3rd Embodiment of this invention. 本発明の第４実施形態を示す説明図。Explanatory drawing which shows 4th Embodiment of this invention. 従来例を示すＥＳＢＷＲの起動過程説明図。Explanatory drawing of the starting process of ESBWR which shows a prior art example. 従来例を示す自然循環炉の第１の不安定流動現象説明図。Explanatory drawing of the 1st unstable flow phenomenon of the natural circulation furnace which shows a prior art example. 従来例を示す自然循環炉の第２の不安定流動現象説明図。Explanatory drawing of the 2nd unstable flow phenomenon of the natural circulation furnace which shows a prior art example. 従来例を示す自然循環炉の起動時昇温パターン説明図。Explanatory drawing of the temperature rising pattern at the time of starting of the natural circulation furnace which shows a prior art example.

符号の説明Explanation of symbols

１‥原子炉圧力容器、２‥下部プレナム、３‥炉心、３ａ‥燃料集合体、３ｂ‥炉心シュラウド、４‥チムニー、５‥上部プレナム、６‥セパレータ、７‥ドライヤ、８‥主蒸気出口、９‥給水口、１０‥ダウンカマ、１１‥制御棒、１２‥窒素ガス、２１‥原子炉蒸気ドーム圧力計、２２‥セパレータ温度計、２３‥チムニー温度計、２４‥炉心出力計、２５‥炉心入口温度計、２６‥炉心流量計、２７ａ‥水面、２７‥原子炉水位計、２８‥気相空間、３０‥所内蒸気源、３１‥蒸気配管、３３‥所内蒸気、４０‥高温水領域、４１‥気相空間、５１‥供給配管、５１ａ‥開口端、５２‥タンク、５３‥高温水、５４‥配管、５５‥冷水、６０‥出力制御装置。   1 reactor pressure vessel, 2 lower plenum, 3 core, 3a fuel assembly, 3b core shroud, 4 chimney, 5 upper plenum, 6 separator, 7 dryer, 8 main steam outlet, DESCRIPTION OF SYMBOLS 9 ... Water inlet, 10 ... Downcomb, 11 ... Control rod, 12 ... Nitrogen gas, 21 ... Reactor steam dome pressure gauge, 22 ... Separator thermometer, 23 ... Chimney thermometer, 24 ... Core power meter, 25 ... Core inlet Thermometer, 26 ... Core flow meter, 27a ... Water surface, 27 ... Reactor water level meter, 28 ... Gas phase space, 30 ... In-house steam source, 31 ... Steam piping, 33 ... In-house steam, 40 ... High-temperature water region, 41 ... Gas phase space 51. Supply pipe 51 a Open end 52 Tank 53 Hot water 54 Pipe 55 Cold water 60 Output control device.

Claims (6)

自然循環型沸騰水型原子炉を起動する方法であって、脱気運転を完了した後、原子炉圧力容器内に冷却材を燃料集合体が完全に浸漬される状態まで満たし、前記冷却材の液面より上方の原子炉圧力容器内空間に不凝縮ガスを供給して充満させ、この不凝縮ガスのガス圧力を３気圧以上の高圧に加圧した後、核加熱による加圧を開始することを特徴とする自然循環炉の起動方法。 A method for starting a natural circulation boiling water reactor, wherein after the deaeration operation is completed, the coolant is filled in the reactor pressure vessel until the fuel assembly is completely immersed, and the coolant Supplying and filling non-condensable gas into the reactor pressure vessel space above the liquid level, pressurizing the gas pressure of this non-condensed gas to a high pressure of 3 atmospheres or more, and then start pressurization by nuclear heating A natural circulation furnace start-up method characterized by the above. 自然循環型沸騰水型原子炉を起動する方法であって、脱気運転を完了した後、原子炉圧力容器内に冷却材を燃料集合体が完全に浸漬される状態まで満たし、前記原子炉圧力容器内における頂部近傍に位置する配管から発電所内の利用可能な所内蒸気を供給することにより前記冷却材の液面で前記蒸気を凝縮させながら前記冷却材を昇温させてその液面温度に対応する飽和圧力を保ちつつ、気相圧力を３気圧以上の高圧に加圧した後、核加熱による加圧を開始することを特徴とする自然循環炉の起動方法。 A method of starting a natural circulation boiling water reactor, wherein after the deaeration operation is completed, a coolant is filled in the reactor pressure vessel until the fuel assembly is completely immersed, and the reactor pressure Corresponding to the liquid surface temperature by raising the temperature of the coolant while condensing the steam at the liquid surface of the coolant by supplying the in-house steam available in the power plant from the pipe located near the top in the container A method for starting up a natural circulation furnace, characterized by starting pressurization by nuclear heating after pressurizing a gas phase pressure to a high pressure of 3 atm or higher while maintaining a saturation pressure. 自然循環型沸騰水型原子炉を起動する方法であって、脱気運転を完了した後、原子炉圧力容器内に冷却材を燃料集合体が完全に浸漬される状態まで満たし、前記原子炉圧力容器内における頂部近傍にヒータを有する脱気器を配置して前記冷却材の液面で蒸気を発生させ、前記冷却材を昇温させてその液面温度に対応する飽和圧力を保ちつつ、気相圧力を３気圧以上の高圧に加圧した後、核加熱による加圧を開始することを特徴とする自然循環炉の起動方法。 A method of starting a natural circulation boiling water reactor, wherein after the deaeration operation is completed, a coolant is filled in the reactor pressure vessel until the fuel assembly is completely immersed, and the reactor pressure A deaerator having a heater is disposed in the vicinity of the top in the container to generate steam at the liquid level of the coolant, and the temperature of the coolant is raised to maintain a saturation pressure corresponding to the liquid level temperature. A method for starting a natural circulation furnace, characterized in that pressurization by nuclear heating is started after pressurizing the phase pressure to a high pressure of 3 atm or higher. 自然循環型沸騰水型原子炉を起動する方法であって、脱気運転を完了した後、原子炉圧力容器内に冷却材を燃料集合体が完全に浸漬される状態まで満たし、前記原子炉圧力容器の炉心シュラウド内面に開口端を有する配管を用いて、前記原子炉圧力容器の外部に設置したタンクから脱気した高温水を前記炉心シュラウド内の上部に供給した後、核加熱による加圧を開始することを特徴とする自然循環炉の起動方法。 A method of starting a natural circulation boiling water reactor, wherein after the deaeration operation is completed, a coolant is filled in the reactor pressure vessel until the fuel assembly is completely immersed, and the reactor pressure Using piping having an open end on the inner surface of the reactor core shroud, high-temperature water degassed from a tank installed outside the reactor pressure vessel is supplied to the upper portion of the reactor core shroud, and then pressurized by nuclear heating. A start-up method of a natural circulation furnace characterized by starting. 前記原子炉圧力容器の底部に位置する配管を介して、前記高温水の供給量に対応する量の冷水を原子炉圧力容器底部から排出する請求項４記載の自然循環炉の起動方法。 The start-up method of the natural circulation reactor of Claim 4 which discharges the quantity of cold water corresponding to the supply amount of the said high temperature water from the bottom part of a reactor pressure vessel through piping located in the bottom part of the said reactor pressure vessel. 核加熱による加圧を開始した後、セパレータ温度および原子炉蒸気ドーム圧力を測定し、これらセパレータ温度と前記原子炉蒸気ドーム圧力に対応する温度とを比較し、両者が等温レベルにある場合にセパレータ部分の冷却材にボイドが発生したと判断して、このボイド発生期間中に一時的に炉心出力を上昇させる請求項１ないし請求項５のいずれか１項に記載の自然循環炉の起動方法。 After starting pressurization by nuclear heating, the separator temperature and the reactor steam dome pressure are measured, and the separator temperature and the temperature corresponding to the reactor steam dome pressure are compared. The method for starting a natural circulation reactor according to any one of claims 1 to 5, wherein it is determined that a void has occurred in a portion of the coolant, and the core output is temporarily increased during the void generation period.
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