Method of determining and evaluating the emergency shutdown margin for a pressurized water nuclear reactor

摘要

The emergency shutdown margin is determined and evaluated by calculating a shutdown margin with the general formulaPP Mar=Pg+Pp-Pr,PPwhere Mar is the shutdown margin being sought, Pg is the negative reactivity attributed to the full set of the reactor's control rods when that set moves from withdrawn to fully inserted position, Pp is the reactivity brought about by the change from nominal power to zero power and Pr is the negative reactivity already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.