Method of detecting the extent of raptures in a pressure vessel of a nuclear power plant

Purpose: To enable accurate ratpure detection by estimating the position and the area of raptures in a pressure vessel due to the change of state in a BWR type power plant. Method: By utilizing the fact that the states inside of a reactor pressure vessel or the states of a plant including a control equipment (generally, the system control equipment) are changed depending on the extent of the rapture accident in liquid phase and vapor phase, and by dynamically evaluating the change of specific states, the extent of the ratpure is conversely estimated. Specifically, the dynamic transfer characteristics from the flowrate issued from the rapture points of the liquid phase and the vapor phase to the status amount under observation are previously evaluated, and the flowrate issuing from the rapture points are estimated conversely due to the change between the converse characteristics of the transfer characteristics and the change in the status amount under observation. If the flowrate from the rapture points can be estimated, the rapture area can also be estimated due to the reactor pressure and the enthalpy. (Kawakami, Y.)