Supporting device for forming operation plan

The device of the present invention supports a re-start by forecasting the criticality of a reactor core at high speed and accurately after occurrence of unexpected reactor scram. That is, studies have been made previously for a relation of error between a simple calculated value and an actually measured value of a neutron multiplication factor in the reactor core relative to reactor core operation parameters (reactor power, flowrate, control rod insertion amount, amount of xenon and samarium and burnup degree) during normal reactor start up. After occurrence of unexpected reactor scram, the neutron multiplication factor of the reactor core is calculated by a simple calculation equation. In addition, the calculation error of the neutron multiplication factor at a planning point obtained by using the simple calculation equation is forecast and corrected by using the relation of simple calculation of the neutron multiplication factor of the reactor core to the operation parameters. With such procedures, the neutron multiplication factor of the reactor core can be forecast accurately along with the actual results, thereby enabling to aid an operator for planning the re-starting. (I.S.)