Patent Number: 
Section: claims

1. A boiling water reactor comprising:a reactor pressure vessel;a control rod drive configured to drive and control control rods;a steam pipe configured to transport 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 configured to heat feedwater supplied to the reactor pressure vessel using bleed steam flowing from the high pressure turbine to the feedwater heater;a bleeding valve configured to adjust a flow rate of the bleed steam supplied to the feedwater heater;a detector provided in a main steam line including the steam dome and the steam pipe and configured to detect a fluctuating pressure in the steam dome,feedwater temperature determining means for determining a temperature of the feedwater that is supplied from the feedwater heater to the reactor pressure vessel;steam temperature determining means for determining a temperature of steam that is transported out from the reactor pressure vessel, andflow rate determining means for determining a flow rate of steam that is transported out from the reactor pressure valve,wherein the boiling water reactor further comprises a monitor and control means for checking whether or not the fluctuating pressure detected by the detector is larger than a predetermined level and whether or not a product given by Es×Q is constant, where Es is an enthalpy difference based on a difference between the temperature of the feedwater that is supplied from the feedwater heater to the reactor pressure vessel, determined by the feedwater temperature determining means, and a temperature of steam that is transported out from the reactor pressure vessel determined by the steam temperature determining means, and Q is a flow rate of steam that is transported out from the reactor pressure vessel determined by the flow rate determining means. 2. A boiling water reactor according to claim 1, wherein, if the fluctuating pressure of the main steam line detected by the detector is larger than the predetermined level, the monitor and control means lowers the temperature of the feedwater that is supplied from the feedwater heater to the reactor pressure vessel by decreasing an opening degree of the bleeding valve. 3. A boiling water reactor according to claim 1, wherein, if the fluctuating pressure of the main steam line detected by the detector is larger than the predetermined level, the monitor and control means lowers the temperature of the feedwater that is supplied from the feedwater heater to the reactor pressure vessel by decreasing an opening degree of the bleeding valve, as well as lowers an amount of generating steam by controlling nuclear fission product energy of the uranium fuel by controlling the control rod drive.