Sensor noise caused by vibrations of flaw detection probe generated in helical heating tubes in a fast breeder reactor and its countermeasures (2nd report, numerical simulations of probe vibration)

A diagnosis of a helical heating tube installed in a fast breeder reactor is operated by an insertion of an eddy current testing (ECT) probe with magnetic sensor into the tube. An undesirable vibration of the ECT probe always happens under a certain condition and makes the diagnosis difficult. The cause of the vibration has not been clear. Numerical simulation of the vibration is implemented on the assumption that the vibration is caused by the Coulomb's friction. An analytical model is derived as a large scale nonlinear vibration system and a lot of computational costs are ordinarily required to carry out the simulations. The Transfer Influence Coefficient Method is applied so that the simulation is efficiently carried out. The results of simulation qualitatively agree well with the experimental results. It confirms the validity of the assumption that the vibration is caused by the Coulomb's friction.