Abstract: A method for monitoring and acoustic damping a boiling water reactor which includes: a reactor pressure vessel; a steam pipe for transporting steam out from a steam dome of the reactor pressure vessel; a high pressure turbine driven by the steam; a feedwater heater which heats feedwater supplied to the reactor pressure vessel using bleed steam from the high pressure turbine; a bleeding valve which adjusts a flow rate of the bleed steam; and a pressure sensor provided in a main steam line including the steam dome and the steam pipe. The method includes monitoring a fluctuating pressure in the main steam line and controlling an opening degree of the bleeding valve based on a magnitude of the fluctuating pressure.

Abstract: A method for monitoring and acoustic damping a boiling water reactor which includes: a reactor pressure vessel; a steam pipe for transporting steam out from a steam dome of the reactor pressure vessel; a high pressure turbine driven by the steam; a feedwater heater which heats feedwater supplied to the reactor pressure vessel using bleed steam from the high pressure turbine; a bleeding valve which adjusts a flow rate of the bleed steam; and a pressure sensor provided in a main steam line including the steam dome and the steam pipe. The method includes monitoring a fluctuating pressure in the main steam line and controlling an opening degree of the bleeding valve based on a magnitude of the fluctuating pressure.

Abstract: A boiling water reactor includes a reactor pressure vessel; a steam pipe for transporting steam generated in the reactor pressure vessel out from a steam dome positioned at an upper part of the reactor pressure vessel; a high pressure turbine connected to the steam pipe and driven by the steam; a feedwater heater which heats feedwater supplied to the reactor pressure vessel using bleed steam flowing from the high pressure turbine to the feedwater heater; a bleeding valve which adjusts a flow rate of the bleed steam; and a pressure sensor provided in a main steam line including the steam dome and the steam pipe. The boiling water reactor further includes a monitor and control system which controls an opening degree of the bleeding valve based on a magnitude of fluctuating pressure in the main steam line that is detected by the pressure sensor.

Abstract: A natural circulation boiling water reactor provides to a chimney with a plurality of tubes. That is to say, each of the plurality of tubes partitions the coolant flow path above a core. Thus, unlike the conventional natural circulation boiling water reactor providing the flow path partition wall grid in which the plate members are made integral by welding and coolant flow paths are partitioned, the chimney of the natural circulation boiling water reactor can reduce the number of welded portions because the edges of the four corners of each flow path do not need to be welded. The natural circulation boiling water reactor can avoid removal as a single unit, as in the case of the flow path partition wall grid in the conventional natural circulation boiling water reactor, by detaching each tube. The chimney can be easily detached from the reactor pressure vessel.

Abstract: The object of the invention is to accurately evaluate integrity of vibration of a dryer of an actual system. The evaluating method for integrity of vibration of a steam dryer using a reduced model in a nuclear plant including the steam dryer for reducing moisture of steam generated inside a steam dome of a nuclear reactor pressure vessel, and a plurality of main steam pipes for transporting the steam to outside includes the steps of performing a steam test with the reduced model, calculating fluctuating stress applied to the steam dryer, and confirming integrity of vibration. According to the invention, it is possible to evaluate the pressure fluctuation of a dryer of an actual system more accurately.

Abstract: A handling method for a natural circulation boiling water reactor having a chimney having cylindrical chimney shell disposed above a core in a reactor pressure vessel, a plurality of square tubes disposed in the chimney shell, and a grid support plate with grid holes supporting and in communication with a lower end portion of the square tubes so that adjacent square tubes are disposed at an interval which exceeds the width of one square tube between them. The method includes steps shifting predetermined ones of the square tubes to the interval between the square tubes, and performing maintenance and inspection of members around a core via the grid holes which appear at positions from which the predetermined square tubes are taken out due to the shift of the predetermined square tubes.

Abstract: A handling method for a natural circulation boiling water reactor having a chimney having cylindrical chimney shell disposed above a core in a reactor pressure vessel, a plurality of square tubes disposed in the chimney shell, and a grid support plate with grid holes supporting and in communication with a lower end portion of the square tubes so that adjacent square tubes are disposed at an interval which exceeds the width of one square tube between them. The method includes steps shifting predetermined ones of the square tubes to the interval between the square tubes, and performing maintenance and inspection of members around a core via the grid holes which appear at positions from which the predetermined square tubes are taken out due to the shift of the predetermined square tubes.

Abstract: A boiling water reactor includes a reactor pressure vessel; a steam pipe for transporting steam generated in the reactor pressure vessel out from a steam dome positioned at an upper part of the reactor pressure vessel; a high pressure turbine connected to the steam pipe and driven by the steam; a feedwater heater which heats feedwater supplied to the reactor pressure vessel using bleed steam flowing from the high pressure turbine to the feedwater heater; a bleeding valve which adjusts a flow rate of the bleed steam; and a pressure sensor provided in a main steam line including the steam dome and the steam pipe. The boiling water reactor further includes a monitor and control system which controls an opening degree of the bleeding valve based on a magnitude of fluctuating pressure in the main steam line that is detected by the pressure sensor.

Abstract: A natural circulation boiling water reactor provides to a chimney with a plurality of tubes. That is to say, each of the plurality of tubes partitions the coolant flow path above a core. Thus, unlike the conventional natural circulation boiling water reactor providing the flow path partition wall grid in which the plate members are made integral by welding and coolant flow paths are partitioned, the chimney of the natural circulation boiling water reactor can reduce the number of welded portions because the edges of the four corners of each flow path do not need to be welded. The natural circulation boiling water reactor can avoid removal as a single unit, as in the case of the flow path partition wall grid in the conventional natural circulation boiling water reactor, by detaching each tube. The chimney can be easily detached from the reactor pressure vessel.

Abstract: A main steam system around a nuclear reactor which comprises two main steam nozzles in a reactor pressure vessel, each of the main nozzles being disposed at a symmetrical position with respect to a plane parallel to steam outlet faces of steam dryers provided inside the reactor pressure vessel and passing through a center of the reactor pressure vessel; and main steam pipes each connected to the main steam nozzles.

Abstract: A main steam system around a nuclear reactor which comprises two main steam nozzles in a reactor pressure vessel, each of the main nozzles being disposed at a symmetrical position with respect to a plane parallel to steam outlet faces of steam dryers provided inside the reactor pressure vessel and passing through a center of the reactor pressure vessel; and main steam pipes each connected to the main steam nozzles.

Abstract: A main steam system around a nuclear reactor which comprises two main steam nozzles in a reactor pressure vessel, each of the main nozzles being disposed at a symmetrical position with respect to a plane parallel to steam outlet faces of steam dryers provided inside the reactor pressure vessel and passing through a center of the reactor pressure vessel; and main steam pipes each connected to the main steam nozzles.