Ontario Hydro's Load Following Requirements, Issues, Experience and Strategy

Abstract

It was forecast that from 1986 to the late 1990s the nuclear plus hydraulic baseload generation capability within Ontario Hydro will frequently exceed the total syslem electrical demand. As a result, nuclear units will increasingly be required to meet changes in demand in order to minimize the operating costs.This paper discusses Ontario Hydro's electrical system requirements regarding nuclear generating stations and the key issues affecting their operation. It summarizes the economic impact of nuclear maneuvering, reviews the operating experience to date, and presents the long-term strategy that is being pursued.The results of our analysis indicate significant savings on fuel replacement costs due to nuclear maneuvering capability. This is achieved by eliminating the need for shutting down baseload nuclear units and then having to replace the required demand load from maneuverable but expensive coal-fired stations. Between 1986 and 1987, Pickering NGS-B and Bruce NGS-B demonstrated the nuclear maneuvering capability of CANDU reactors and saved Ontario Hydro one million dollars in fuelcosts. A typical load cycle at Bruce NGS-B consisted of reducing power to 50% FP, holding at that power, then returning to full power when system requiredit. Deeper nuclear maneuvers, where power is reduced to 20%-25% FP, have also been successfully demonstrated.A joint work program within Ontario Hydro is being pursued by Operations, Research, Design, and Systems Planning departments to anticipate potential areas of concern during the coming periods of significant unutilized energy. In particular, the potential long-term effects on equipment include a scheme to anticipate, monitor and evaluate the impact on equipment reliability and performance.