Patent Number: 
Section: claims

1. A method of controlling a pressurized water nuclear reactor, said reactor comprising a core generating thermal power cooled by a primary coolant and instrumentation lines for measurement of representative data of a thermal power and for measurement of a temperature of the primary coolant;said method comprising:acquiring data corresponding to at least a thermal power and a temperature of the primary coolant of the core operating conditions via the instrumentation lines, andadjusting the temperature of the primary coolant responsive to the temperature of the primary coolant, for a given thermal power, being outside a predefined set temperature interval (ΔTREF) which is based on the thermal power, wherein said set temperature interval (ΔTREF) comprises:a variable temperature amplitude (ΔT) within a thermal power range between N % and 100% of a nominal power, where N is between 0 and 100, inclusive of 0 and exclusive of 100;a zero amplitude at 100% nominal power;a zero amplitude at N % of the nominal power. 2. The method of controlling a pressurized water nuclear reactor according to claim 1, wherein the set temperature interval (ΔTREF) has a maximum temperature amplitude (ΔT) for a thermal power or range of thermal powers on which frequency regulation is done for a nuclear reactor. 3. The method of controlling a pressurized water nuclear reactor according to claim 1, wherein the temperature amplitude (ΔT) of said interval (ΔTREF) is maximum between 40% and 80% of the nominal power. 4. The method of controlling a pressurized water nuclear reactor according to claim 2, wherein the temperature amplitude (ΔT) of said interval (ΔTREF) is maximum between 80% and 100% exclusive of the nominal power. 5. The method of controlling a pressurized water nuclear reactor according to claim 1, wherein said set temperature interval (ΔTREF) lies within a zone (ZH) in which the lower limit corresponds to the set temperature at 0% nominal power (TREFMIN) and the upper limit corresponds to the set temperature at 100% nominal power (TREFMAX). 6. The method of controlling a pressurized water nuclear reactor according to claim 1 further comprising adjusting at least one other core operating condition selected from the group consisting of an axial power distribution (AO) and a capacity for instantaneous return to power (Pmax), when the primary coolant temperature is within the set temperature interval (ΔTREF). 7. The method of controlling a pressurized water nuclear reactor according to claim 1, wherein said temperature interval (ΔTREF) has a variable amplitude (ΔT) at least over a thermal power range of between 50% and 100% nominal power. 8. The method of controlling a pressurized water nuclear reactor according to claim 1, wherein said set temperature interval (ΔTREF) is surrounded by a dead band (ΔBM).