Trend analysis for light water reactor units performance: Availability predictions for Finnish nuclear power units

Operational performances of LWR units have been analysed. The load factor has been used as the basic measurement in quantifying operational performances of LWR units. The whole operating history, in the sense of the annual and cumulative load factors achieved by all Western commercial PAR and AIR units until the end of 1984 has been taken into consideration. Furthermore, a set of the annual load factors available from the WWER units of the CMEA countries is given but is not included in the ordinary data base of the study. Many publications and journals give only general averages of the load factors, or of some other availability relates quantities, with the aid of which they seek to represent nuclear power performances. The generic load factor averages, however, conceal wide variations from unit to unit and from year to year. Through the regression analyses some contributing factors (the unit size, vintage and age) have been found that interacting with each other correlate with nuclear power performance. Accordingly some trends in the operational performance of LWR plants have been identified. Furthermore, the annual load factors of duplicate units have been compared with those of their predecessors at the same nuclear power site. The LWR units supplied by different contractors and/or located in different countries font an inhomogeneous population with respect to the achieved load factors, i.e., the load factors of LWR units supplied by some contractors and/or located in certain countries deviate clearly and regularly from general load factor averages. The U.S. units and the units supplied by U.S. contractors to other countries are especially influential on load factor averages of LWR units. Some estimates for future load factors have been made based only on the load factor trends established by PWR and WAR units up to date. It was a delibrate aim to find regression equations, in which the current "Finnish factors", or the Soviet Atomenergoexport and the Swedish ASEA-Atom (as the reactor contractors) and Finland itself (as the site country), could be included; and through which the future load factor trends in Finnish PWR and BWR units could be predicted.