pressurised water reactors pwrs also offer the possibility of increasing operation beyond the natural cycle length by taking advantage of the power and coolant temperature reactivity coefficients a decrease of reactor power and coolant temperature allows for a equivalent full power days efpd extension beyond natural fuel cycle length only nonstorable hydroelectrical capacity should be considered here in the mid s economic forecasts were calling for a moderate increase in energy demand for the coming years and for a substantial overcapacity of the french nuclear park the nuclear energy was supposed to be the marginal for about hours ie for more than of the year