A method is provided for recovering operating margin in a nuclear reactor. The reactor includes a steam generator, a Reactor Coolant System (RCS) having a hot leg with a temperature, T.sub.hot, and a cold leg with a temperature, T.sub.cold, a Reactor Trip System (RTS) having an Over Temperature Delta Temperature (OTDT) trip function and an Over Power Delta Temperature (OPDT) trip function, and a control system. The method improves the RTS by filtering only the hot leg temperature signal of the RCS. Thus, the needs for separate T.sub.avg and Delta-T filters, and for filtering of temperature signals in both the hot leg and cold leg are eliminated. A reactor system is also disclosed.