Patent ID: 8571163
Filing Date: 2013-10-29
Classification: G21C,G21D,Y02E

Abstract:
1. 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.