Abstract: Method for determining a evaluating the capacity of a pressurized water nuclear reactor to return to power rapidly, consisting in calculating a pick-up power by applying the general formula:Prip=Prel+.DELTA.Pin which Prip is the maximum pick-up power obtainable by acting on the control bars, Prel is the relative power delivered by the core, determined by the in-line measurement of the neutron flow emitted by the core and .DELTA.P is the additional power resulting from the potential reactivity of the assembly of control bars of the reactor when this assembly passes from the observed insertion to the minimum insertion, P being calculated from the measured position of the power regulation clusters, involving the axial power distribution measured (C1 to C6) and the previously defined exhaustion of the core.

Abstract: The emergency shutdown margin is determined and evaluated by calculating a shutdown margin with the general formulaMar=.DELTA.Pg+.DELTA.Pp-.DELTA.Pr,where Mar is the shutdown margin being sought, .DELTA.Pg is the negative reactivity attributed to the full set of the reactor's control rods when that set moves from withdrawn to fully inserted position, .DELTA.Pp is the reactivity brought about by the change from nominal power to zero power and .DELTA.Pr is the negative reactivity already consumed to bring the reactor into the situation it is in at the instant under consideration and is calculated from the negative reactivity derived from the measured position of the power control clusters (20), taking into account the axial power distribution as measured (C1 to C6) and the depletion of the core as defined in advance, from a term evaluating the reactivity contributed by the drop in power from nominal power to the current situation of the reactor and from a scale constant.