History of ROP margins erosion and power recovery at Gentilly-2

Regional Over-Power Protection (ROP) trip setpoints have a direct impact on power levels at which reactors can operate safely. An issue common to all types of nuclear power plants is the gradual decrease in operating margins as plant equipment is affected by ageing. Our experience shows that the dominant adverse ageing mechanisms in the heat transport system are associated with pressure tubes, steam generators and to a lesser degree, feeders. This paper presents the evolution of the Regional Overpower Protection Trip Setpoints since first commissioning of Gentilly-2 and the relative contribution of the various ageing mechanism which impact the safety margin and reactor power at Gentilly-2. Corrective actions to restore full power are also revisited and conclusions and lessons learned are highlighted. (author)