Study on character of core barrel beam mode vibration during PWR refueling cycle

The method of monitoring core barrel of PWR is studied based on neutron noise which is from ex-core neutron detector. Through calculating CPSD, coherent and phase of the relative channel ionization chamber, the frequency of core barrel beam mode vibration is obtained. With the method, we calculated the trends of core barrel beam vibration frequency and CPSD amplitude in PWR refueling cycle under normal operation state. The results illustrate that in the condition of normal operation of reactor, the core barrel beam vibration frequency turns out to drifts and decreases, and the magnitude of CPSD at this frequency along with corresponding the core burnup increasing. (authors)