Planning and Scheduling of Nuclear Power Plant Outages

The planning and scheduling of the operations involved in the outages of nuclear power plants has a great impact in terms of the outage costs (replacement power, labor cost, etc.), use of scarce resources and implementation of safety procedures. Prior to 1979, before the accident at Three Mile Island (TMI), refueling was the driving factor of outages of nuclear power plants: maintenance plans were governed by the projected duration of refueling activities. After the TMI accident, the focus turned to improving nuclear power plant eeectiveness. The duration of an outage was determined not only by refueling activities, but by the work and plant modiications required to make the plant safer and more eeective PSDI 94, Wallace 90]. Throughout the 1980s, backkts and the aging of nuclear power plants has reversed outage scope priorities and methodologies. Often the refueling activities no longer dictate the critical path in an outage. The problem of planning and scheduling nuclear power plant outages can be stated as follows: Given a set of outage activities (refueling operations, repairs, modiications, and maintenance activities), a set of resources, and a set of technological constraints 1 assign times and resources to the activities in such way that the completion of the outage is minimized while safely performing all the activities required by the outage. Depending on the planning and scheduling procedures of each particular plant, as well as the scope of the activities performed during the outage, the planning and scheduling of outages for nuclear power plants might involve from 15,000 up to 45,000 activities. During an outage several activities are performed, such as: Comments and opinions expressed by the authors are the authors' opinions and do not reeect the position of Rome Laboratory. y Carla O. Pedro Gomes works for Rome Laboratory as an independent consultant 1 Precedence and temporal relationships between activities as well as resource constraints.