The paper presents the results of the specific vibration condition monitoring approach for maintenance of unique critical equipment provided complete access impossibility to its components (due to radiation environment) throughout the entire operation period. The approach bases on the previously proposed S-discriminants of vibrations which are calculated with adaptation to the reference state of the equipment. The method showed its high efficiency in detecting the moment of machine operation process imbalance and in tracking the equipment components degradation, starting from the earliest stage. It is illustrated on the example of the movable neutron reflector PO-3 of the IBR-2 research reactor that it is possible not only to detect in time the moment when a fault occurs, but also to make a preliminary express diagnosis of its condition.
