Development of a Method for Malfunction Detection of the Primary Cooling Loop in a Research Reactor

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The primary cooling water of research reactor ia usually circulated by a single pump rotating at a fixed speed of revolution. Therefore, characteristic frequency components caused by the rotational motion of pump are contained in the vibration of the cooling system, the fluctuation of water-pressure and the variation of coolant flow rate, respectively. When an abnormal matter happens in the cooling circulation-loop, the vibration component of the cooling system breaks away from the characteristic frequency due to the load fluctuation of the pump.We have planned to develop a new method for malfunction detection of aresearch reactor using a spectrum analysis of vibration data in the cooling system. For this purpose, a mock-up cooling system was prepared with a circulation pump, a water thank and some valves. The data of vibration, water-pressure and coolant flow rate are sampled by a digital data logger, and the power spectra of frequency are analyzed by a FFT technique.Once abnormal matters such as the inhalation of air and the blockade of water loop have happened in the cooling system, the spectral shift of the frequency and amplitude appeared in analyzed date. We obtained two conclusions throughout this experiment : the present method is effective for malfunction detection of the primary cooling loop in a research reactor, and will enable a real-time diagnosis by means of some small-scale equipment connected to a personal computer.