Method of measuring bending of a
nuclear reactor fuel channel. According to the method a
fiber-
optic sensor is equipped with a gravity
pendulum that is suspended for angular motion at the lower end of the fibre-
optic sensor; a flexible hollow carrier rod with the fibre-
optic sensor is passed along the central tube of a fuel
assembly and using a photoreceiver and a computer the shift of an interference pattern of a reflected
light signal in a gas gap between the upper end face of the gravity
pendulum and the lower end face of fibre-optic lines connected to the photoreceiver and fastened to the sensor is registered, said gas gap varying during the passage of the fibre-optic sensor as a result of the angular motion of the gravity
pendulum away from the axis of the bowed central tube of the fuel
assembly. On the basis of the registered shifts of the interference pattern of the reflected
light signal, profilograms of the variations of the gas gap for each fibre-optic line of each fibre-optic sensor are recorded; and on the basis of the obtained gas gap profilograms, the magnitude and direction of bending of the central tube of the fuel
assembly from the
vertical axis are calculated, according to which the presence and magnitude of bending of the
nuclear reactor fuel channel are determined.