One of the most catastrophic failures observed in gas turbine powered electrical powerplants is the fracture of the turbine rotor. A simplified model consisting of 3 macro-elements is suggested to model the dynamical behavior of the shaft with a propagating torsional crack. A modal analysis is carried out in order to calculate the response spectrum of the rotor and the relevant natural frequencies of the dynamical system. The residual service life of the rotor shaft is estimated from existing dα / dΝ-ΔκIII graphs for the rotor material. When the calculated residual service life approaches the ordering-delivery time for the rotor components plus a safety margin, then the order is placed and thus the idling time for fracture to replacement (if fracture happens prematurely) or the waiting time until actual fracture occurs is minimized. In this way the financial benefit from the proposed just-in-time scenario is maximized. A case study corresponding to the 3, 50MW industrial gas-turbine rotor of the Public Power Station in Chania, Greece is also presented.