Abstract: A response surface model is created without a drawback of creating a linear model that does not approximate to samples belonging to a partitioned region. Provided are: an input unit 1 that inputs samples composed of factor values and a response value; a sample placement unit 21 that places the samples in spaces, the samples being input by way of the input unit 1; a linear modeling unit 230 that creates the linear model for each region, based on coordinate values of the samples belonging to the region; a region partition unit 22 that partitions the linear model, based on the samples belonging to the region; a partition region determination unit 221 that determines whether it is possible to partition the region, based on the samples belonging to the region to be partitioned; and a modeling unit 23 that creates a response surface model by placing each linear model in the spaces when the partition region determination unit 221 has determined that partition is impossible in all the regions.

Abstract: A steam separator comprises an outer main swirler and an inner auxiliary swirler which is smaller than the main swirler. The swirlers are provided so as to be concentric on the inner wall at the lower side of the first stage inner cylinder. In the steam separator, when the gas-liquid two-phase flow which flows in the vicinity of the axial center of the first stage inner cylinder passes the auxiliary swirler, it is separated into steam and water by the centrifugal force. The separated water (droplets) is introduced into the main swirler. When the separated water (droplets) passes the main swirler, it is separated at the inner wall side of the first stage inner cylinder by the centrifugal force. Pressure loss in a steam separator is reduced and steam separation capability is increased without increasing the moisture from the steam separator.

Abstract: A steam separator comprises an outer main swirler and an inner auxiliary swirler which is smaller than the main swirler. The swirlers are provided so as to be concentric on the inner wall at the lower side of the first stage inner cylinder. In the steam separator, when the gas-liquid two-phase flow which flows in the vicinity of the axial center of the first stage inner cylinder passes the auxiliary swirler, it is separated into steam and water by the centrifugal force. The separated water (droplets) is introduced into the main swirler. When the separated water (droplets) passes the main swirler, it is separated at the inner wall side of the first stage inner cylinder by the centrifugal force. Pressure loss in a steam separator is reduced and steam separation capability is increased without increasing the moisture from the steam separator.

Abstract: Pipes are mounted horizontally on an outlet portion of a gas vent pipe in a condenser-type heat removal system, and have-openings which are formed only in a portion below a horizontal plane in which axes of these pipes lie, thereby enlarging a region where uncondensed steam is mixed with water in a suppression pool. With this arrangement, a surface portion of the water of the suppression pool is prevented from becoming hot, and the temperature of this pool water is uniformed. As a result, the temperature of the water surface of the suppression pool is lowered, thereby decreasing the pressure within a primary containment vessel. This enhances the reliability of the primary containment vessel, and reduces a design strength of the primary containment vessel.

Abstract: A reactor containment facility having a reactor pressure vessel containing a core; a dry well in which the reactor pressure vessel is arranged; a suppression chamber holding suppression-pool water and forming above the suppression-pool water a wet well; and a plurality of vent pipes allowing the dry well to communicate with the suppression-pool water; a steel wall which is in contact with the suppression-pool water of the suppression chamber and which surrounds at least the pool water so as to form a containment vessel which houses the dry well and the suppression chamber; and an outer peripheral pool containing cooling water in contact with the outer peripheral surface of the steel wall.

Abstract: In a boiling water nuclear reactor, a reactor primary cooling water line is filled with water at the start-up time, and the inside of a pressure vessel is pressurized by a pressurized tank and at the same time control rods are withdrawn to thereby heat cooling water in a state of single-phase flow to high temperature. Succeedingly, the pressurization is released and the pressure of the pressure vessel is gradually approximated to the saturation pressure corresponding to the cooling water temperature to thereby make the cooling water transit into a state of two-phase flow, and thereafter the cooling water is heated by nuclear reaction in the state of two-phase flow to thereby obtain predetermined reactor running temperature and pressure.

Abstract: A reactor containment vessel comprises typically a reactor pressure vessel housed in a dry well of the reactor containment vessel, a vent passage through which steam in the dry well is introduced into coolant accommodated in a pressure suppression chamber of the reactor containment vessel, a closed space formed at a position lower than the level of the normal liquid surface of the coolant, a first passage having an inlet opened into the pressure suppression chamber at a level higher than that of the normal liquid surface of the coolant and an outlet opened into the closed space, and a second passage communicating between the closed space and the dry well through a counter flow preventing arrangement for checking the flow directed toward the closed space, and therefore, noncondensable gas and liquid accumulated in the pressure suppression chamber are discharged into the dry well the pressure in which is higher than that in the pressure suppression chamber by making use of a difference in water head increased d

Abstract: A natural circulation reactor includes a reactor pressure vessel, a cylindrical shroud disposed within the reactor pressure vessel to surround a reactor core and to extend to a position above the reactor core, and a coolant descending passage defined between the reactor pressure vessel and the shroud for allowing the coolant discharged from the top of the reactor core to be again supplied to the bottom of the reactor core. In such a natural circulation reactor, a liquid level of coolant in the coolant descending passage is adjusted on the basis of a reactor power request signal at a position below a liquid level of coolant in the shroud, and thus reactor power is controlled so that it may reach a predetermined reactor power by adjusting the liquid level of coolant in the coolant descending passage.

Abstract: The emergency core cooling structure according to the present invention is provided with a water storage container which holds therein emergency cooling water to be supplied to a core region in a nuclear reactor in case of an emergency, for example, when the primary cooling water flows out from a reactor vessel, so as to maintain the temperature of the emergency cooling water in the upper portion of the water storage container in a level higher than the level of that of the emergency cooling water in the lower portion thereof, the lower portion of the water storage container, which is filled with the low-temperature cooling water, being communicated at all times with the core of the nuclear reactor by a means which has substantially no movable member.

Abstract: An emergency reactor core cooling structure comprises a flow passage provided on an upper core plate so as to extend downward therefrom into the core. The flow passage has an orifice member at a lower portion thereof. The orifice member has such a portion that the cross-sectional area of the flow passage is made minimal at the orifice member. The flow passage causes the cooling water held on the upper plate by vapor flowing up on an accident to flow down therethrough, whereby the core is cooled rapidly.

Abstract: In this invention, the liquid metal passage is branched into a high temperature passage and a low temperature passage cooled by cooling means, and in a coupling passage connecting these high temperature and low temperature passages, high temperature liquid metal and low temperature liquid metal are flown in the state facing each other and they are thus mixed in this coupling passage. In this manner, the flow variation owing to deposition of the oxide in the cooled passage is detected, and the saturation temperature of an oxide is determined from the temperature at which the flow variation occurs.