By: Donald Jones, P.Eng., retired nuclear industry engineer, 2017 July 28.
This article, edited for space, appeared in the 2017 June edition of the Canadian Nuclear Society`s BULLETIN as a Letter to The Editor.
BULLETIN Publisher’s Note: The CNS Nuclear Canada Yearbook commenced using PRIS data this year. Data was no longer available from the CANDU Owners Group, and data from public sources such as Nuclear Engineering International or Nucleonics Week had become either incomplete or late in publication.
When the author was preparing an article on the performance of Ontario’s CANDU nuclear units (reference 1) he wanted to include some idea of the amount of energy being curtailed by a unit at the Bruce Nuclear Generating Station due to load cycling. To do this required a close look at the published performance indicators in the Power Reactor Information System (PRIS) database of the International Atomic Energy Agency (IAEA)(reference 2) and this revealed some discrepancies.
The performance of some of Ontario’s nuclear generating stations is affected by the surplus baseload generation (SBG) in the province (reference 1). Some nuclear units saw electricity output reductions during periods of surplus baseload generation (SBG). This means the CFs (Capacity Factors) are not a true performance indicator for those units (reference 3). A better metric of performance in these cases would be the Unit Capability Factor (UCF – used by Ontario Power Generation and by Bruce Power). The Energy Availability Factor (EAF) is another performance indicator and is shown in the Power Reactor Information System (PRIS) database of the International Atomic Energy Agency (IAEA), (reference 2). The EAF adjusts the available energy generation for energy losses attributed to plant management, planned and unplanned, and for external energy losses beyond the control of plant management while the UCF only includes energy losses attributed to plant management and excludes the external losses beyond control of plant management like load cycling/load following, grid failures, earthquakes, cooling water temperature higher than reference temperature, floods, lightning strikes, labour disputes outside the plant etc. The UCF seems a much better indicator of how well the unit is being managed than either CF or EAF. The UCF rather than the CF would also be the more appropriate number to use when calculating the Equivalent Full Power Hours (EFPHs) on the reactor pressure tubes of Bruce units that use steam bypass at constant reactor power since steam bypass operation does not affect the EFPHs on the pressure tubes. Only reactor power changes would do that.
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