Monitoring method and monitoring program for boiling water reactor, and acoustic damping method for boiling water reactor

A monitoring method for a boiling water reactor which comprises:

• a reactor pressure vessel;
• a steam pipe for transporting steam generated in the reactor pressure vessel out from a steam dome position 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 supplied to the feedwater heater;
• at least one pressure sensor provided in a steam line including the steam dome and the steam pipe to detect a fluctuating pressure in the main steam line to produce a fluctuating pressure signal;
• and
• a monitor and control system connected to the at least one pressure sensor for controlling the bleeding valve by monitoring the fluctuating pressure signal,
• wherein the method comprises the steps of:
• monitoring the fluctuating pressure signal from the at least one pressure sensor;
• monitoring the boiling water reactor based on the fluctuating pressure signal monitored by the monitor and control system,
• wherein the monitor and control system executes the steps of:
• an analytical studying step for analytically studying an acoustic resonance phenomenon in the steam line and calculating resonance frequency and sound pressure distribution in the steam line;
• a detected signal analyzing step for processing the fluctuating pressure signal from the pressure sensor and calculating resonance frequency and fluctuating pressure distribution;
• a determination step for comparing results obtained by the analytical studying step and the detected signal analyzing step and determining whether or not a difference in the comparison is equal to or lower than an allowable difference value;
• an analytical studying condition changing step for changing an analytical studying condition in the analytical studying step if the difference in the comparison is more than the allowable difference value;
• a fluctuating pressure distribution calculating step for calculating fluctuating pressure distribution applied to a surface of a structure in the steam line by the analytical studying step if the difference in the comparison is equal to or lower than the allowable difference value;
• a stress distribution calculating step for calculating stress distribution caused in the structure by the fluctuating pressure distribution applied to the surface of the structure;
• a threshold pressure amplitude calculating step for calculating a threshold pressure amplitude of the pressure sensor that is required for the structure to reach a fatigue fracture free stress;
• and
• a monitoring step for monitoring whether or not fluctuating pressure amplitude obtained by the fluctuating pressure signal from the pressure sensor is equal to or lower than the threshold pressure amplitude.