Patent Number: 052176800
Section: summary

BACKGROUND OF THE INVENTION The present invention relates to a method of filling liquid into a high-temperature and high-pressure vessel and to an apparatus therefor, said method and said apparatus being used, for example, to fill a liquid into a reactor or a steam generator which causes generation of a high-temperature and high-pressure steam. Conventionally, an emergency cooling apparatus for reactor core which is based on the use of a static means includes, as a first prior art, one which is disclosed in Japanese Patent Unexamined Publication No. 60-235092. In the emergency cooling apparatus disclosed in this document at the time when a loss-of-coolant accident has taken place due to, for example, breakage of reactor pipings, the pressure within a water storage tank disposed at a level higher than that corresponding to a pressure vessel of the reactor is equalized with the pressure within the latter. The coolant within the water storage tank is thereby supplied into the pressure vessel by the action of the gravitational force. More specifically, a first piping having a first valve at a midway thereof connects a top section of the reactor pressure vessel and a top section of the water storage tank. A second piping having a second valve at a midway thereof connects a bottom of the water storage tank and the reactor pressure vessel. A differential pressure gage is provided on a piping communicating an upper section of the reactor pressure vessel with an upper section of the water storage tank. Where a loss-of-coolant accident has occurred, the first valve is opened. As a result, the steam generated within the pressure vessel is led to a position above the water surface of the water storage tank by way of the first piping. Thus, the pressures within the pressure vessel and within the water storage tank are equalized with each other while both are being monitored by the differential pressure gage. Thereafter, the second valve is opened. In consequence, the water within the water storage tank is filled into the pressure vessel by utilizing the gravitational force. This type of liquid filling apparatus is disclosed in Japanese Patent Unexamined Publications Nos. 57-69289, 62-212594 and 60-259995. A second prior art is disclosed in Japanese Patent Unexamined Publication No. 62-170886. In this Publication, a reactor container is provided in a state wherein it stores a pressure vessel therein and another upper reactor container is added thereto at a position higher than that corresponding to said pressure vessel. At the time when a loss-of-coolant accident has taken place, the suppression pool water within the pressure vessel of the lower reactor container is pressure fed to the upper reactor container by utilizing the increased pressure within the pressure vessel. The suppression pool water is stored in the upper reactor container as a coolant. Thereafter, a spray system within the lower reactor container is caused to operate so as to condense the steam within the same. During this spraying operation, the pressure within the lower reactor container is decreased. Thereafter, the coolant as above stored is filled from the upper reactor container into the lower one by the gravitational force. By repetition of this operation, the reactor core within the pressure vessel of the lower reactor container is cooled. When the coolant within the upper reactor container is exhausted, a rise in pressure within the reactor container is waited while, for example, the operation of the spray system is kept stopped. Thereafter, the suppression pool water within the reactor container is pressure fed again to the upper reactor container. The reactor core within the pressure vessel of the lower reactor container is cooled through repetition of the above operation. According to the first prior art, upon completion of filling into the pressure vessel the amount of the coolant as stored in the water storage tank, any further filling of coolant becomes impossible. Accordingly, the first prior art is unsuitable for a long period filling of coolant. According to the second prior art, the pressure within the pressure vessel of the reactor is forcedly decreased by operation of the spray system and, only when that pressure has been decreased, the coolant as stored in the upper reactor container is filled into the pressure vessel of the reactor by the action of the gravitational force. For this reason, a large amount of time is required until the filling of the coolant into the pressure vessel is started. In addition, it is premised that the operation of the spray system is secured, so that the coolant filling must rely upon the normality of movable section such as a pump motor for the spray system. Accordingly, not a static means but a dynamic means is inevitably employed in substance. Furthermore, where the pressure equalizing means of the first prior art is adopted in the second prior art, the coolant can be expected to be more speedily filled into the pressure vessel. However, only the use of the pressure within the suppression pool within the lower reactor container fails, from the standpoint of pressure balance, to cause the pool water to be fed to the interior of the upper reactor container, whose pressure has been increased by the pressure equalizing means, and thus stored again in the same. Re-filling of coolant, therefore, is not smoothly effected. SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a liquid filling apparatus which is capable of repeatedly filling a liquid into a high-temperature and high-pressure vessel without employing any dynamic equipment or appliance. A second object of the present invention is to provide a liquid storage tank which is suitable for use in repeatedly filling liquid into a high-temperature and high-pressure vessel without using any dynamic equipment. A third object of the present invention is to secure safety, for a long period of time and without using any dynamic equipment, at the time of a loss-of-coolant accident on a steam generator in the case where the same is constituted by a high-temperature and high-pressure vessel. A fourth object of the present invention is to secure safely, for a long period of time and without using any dynamic equipment, at the time of a loss-of-collant accident on a pressure vessel of a reactor in the case where the same is constituted by a high-temperature and high-pressure vessel. A fifth object of the present invention is to provide a liquid filling method which is capable of repeatedly filling a liquid into a high-temperature and high-pressure vessel without employing and dynamic equipment. To attain the above object, according to one aspect of the present invention, there is provided a liquid filling apparatus for high-temperature and high-pressure vessel, which comprises a high-temperature and high-pressure vessel, a closed liquid storage tank disposed at a level higher than that at which liquid is filled into the high-temperature and high-pressure vessel, a liquid filling flow passage through which liquid is filled from the closed liquid storage tank into the high-temperature and high-pressure vessel, a pressure supplying flow passage through which pressure is supplied from the high-temperature and high-pressure vessel into the closed liquid storage tank, valves provided on the liquid filling flow passage and the pressure-supplying flow passage respectively, and a liquid source for the filling of the liquid, the liquid source being allowed to communicate with the interior of the closed liquid storage tank via a valve, whereby the environmental surroundings of the closed liquid storage tank are lower in temperature than the interior of the high-temperature and high-pressure vessel. To attain the above object, according to another aspect of the present invention, there is provided a liquid filling apparatus for high-temperature and high-pressure vessel, which comprises a looped flow passage composed of the interior of a high-temperature and high-pressure vessel, the interior of a closed liquid storage tank disposed at a level higher than that at which liquid is led to the high-temperature and high-pressure vessel, and a plurality of flow passages for allowing the communication between the interior of the high-temperature and high-pressure vessel and the interior of the closed liquid storage tank, a valve provided on each of said plurality of flow passages, and a liquid source for the filling of the liquid, the liquid source being allowed to communicate with the interior of the closed liquid storage tank via a valve, whereby the environmental surroundings of the closed liquid storage tank are lower in temperature than the interior of the high-temperature and high-pressure vessel. To attain the above object, according to still another aspect of the present invention, there is provided a closed liquid storage tank for filling of liquid which comprises a liquid inlet allowed to communicate with a liquid source via a check valve for checking the flow of the liquid from the liquid storage tank toward the liquid source, a pressure inlet through which the pressure from the high-temperature and high-pressure vessel is introduced into the liquid storage tank via a valve, and a liquid supply port for supplying liquid of the liquid souce into the high-temperature and high-pressure vessel via a valve. To attain the above object, according to a further aspect of the present invention, there is provided a liquid filling method comprising the steps of causing the pressure within the high-temperature and high-temperature pressure vessel and the pressure within the closed liquid storage tank to vary in level so as to make both the pressure equal to each other and then filling liquid from the closed liquid storage tank into the high-temperature and high-pressure vessel by the action of the gravitational force, the liquid filling method further comprising the step of rendering ineffective the communication between the interior of the high-temperature and high-pressure vessel and the interior of the closed liquid storage tank in advance of the filling of liquid and the step of performing the dissipation of the heat within the closed liquid storage tank to the outside thereof to cause a decrease in level of the pressure therewithin and causing a liquid of the liquid source to be sucked therein to thereby cause the liquid to be stored therein. According to the present invention, when the valve provided on the pressure-supplying flow passage is opened, the pressure within the high-temperature and high-pressure vessel becomes substantially equal in level to that within the closed liquid storage tank. In this state, when the valve provided on the liquid-feeding flow passage is opened, the liquid stored within the liquid storage tank is passed therethrough by the gravitational force to be introduced into the high-temperature and high-pressure vessel. Thereafter, when the valves on both the flow passages are closed, the liquid storage tank is cooled by the environmental surroundings, so that the interior thereof comes to have a pressure level relatively lower than that of the liquid source. Consequently, liquid enters the closed liquid storage tank by way of another valve. Thereafter, when the valves are opened in a state wherein reverse flow toward the liquid source is checked by said another valve, re-introduction of liquid from the closed liquid storage tank into the high-temperature and high-pressure vessel, based on the utilization of the gravitational force, is carried out. Through repetition of this operation, a long period liquid introduction action is realized without employing any dynamic equipment. According to the present invention, when the respective valves of the flow passages are opened, the looped flow passages comes into a condition wherein the liquid is allowed to circulate therethrough. Consequently, the pressure difference between the interior of the high-temperature and high-pressure vessel and that of the closed liquid storage tank comes to be substantially zero. For this reason, liquid is allowed to flow by the gravitational force from the closed liquid storage tank at a higher location to the high-temperature and high-pressure vessel at a lower location. When the liquid stored in the closed liquid storage tank has been exhausted, the respective valves of the flow passages are closed so as to permit the residual high temperature atmosphere within the closed liquid storage tank to be cooled by the atmosphere prevailing outside the tank, thus causing the pressure within the closed liquid storage tank to become relatively lower in level than the pressure within the liquid source, thus causing the liquid of the liquid source to be sucked into the closed liquid storage tank via said another valve, thus causing that liquid to be stored into the same. Thereafter, when the respective valves of the flow passages are opened and the flow of the liquid toward the liquid source is checked by said another valve, re-introduction into the high-temperature and high-pressure vessel is started. Through the repeated performance of this operation, a long-period introduction of liquid can be realized with no use of any dynamic equipment. According to the present invention, the closed liquid storage tank for filling of liquid receives the pressure from the high-temperature and high-pressure vessel, so that the internal pressure thereof balances with that of the high-temperature and high-pressure vessel. Consequently, the liquid stored in the closed liquid storage tank becomes easy to enter the high-temperature and high-pressure vessel. On the other hand, when the communication between the liquid storage tank and the high-temperature and high-pressure vessel has been rendered ineffective, the pressure within the liquid storage tank can be easily decreased in level merely by cooling the closed liquid storage tank and without receiving any effect produced by the pressure and temperature of the high-temperature and high-pressure vessel. This makes it easy for the liquid of the liquid source to enter the closed liquid storage tank, thus enabling the performance of the action of causing liquid to be stored again into the closed liquid storage tank. According to the present invention, the closed liquid storage tank is allowed to communicate with the high-temperature and high-pressure vessel so as to make a change in level of the pressures thereof and thereby make them equal to each other. Then, the liquid within the closed liquid storage tank can be fed therefrom into the high-temperature and high-pressure vessel by the action of the gravity. Upon completion of such feeding of liquid, the communication between the high-temperature and high-pressure vessel and the closed liquid storage tank is rendered ineffective. Thus, the heat prevailing within the closed liquid storage tank is dissipated to the outside thereof so as to make the pressure within the tank lower in level than that of the liquid source. Thus, the liquid from the liquid source is sucked into the tank and thus is stored therein. Thereafter, the communication between the high-temperature and high-pressure vessel and the closed liquid storage tank is rendered effective, thus re-opening the introduction of liquid into the vessel.