Optimized Capacity: Global Trends and Issues 

2012 edition

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This WNA report draws upon data collected in the International Atomic Energy Agency’s (IAEA’s) Power Reactor Information Service (PRIS) database to present a snapshot of the performance of the world’s operating nuclear power reactors as well as a breakdown of the principal causes of capacity loss. This is the second edition of this report and covers the period to the end of 2010. 

In the 20-year period from 1980 there was a significant rise in the median global actual energy utilization of reactors’ maximum power capability – known as the capacity factor – from 68%, culminating in 2002 in a historical maximum of 86%. Since around the turn of the century this growth has levelled off and has remained constant at around the 85% mark for the last ten years. However, best performers manage to consistently achieve around 95% or higher which suggests that renewed focus should be placed on optimizing capacity factors amongst the existing nuclear fleet. 

In 2010 the global median capacity factor was 84.8%, but there was a very broad spread in this performance indicator between individual units. Generally, this variance is not explained by the reactor type used, or by age of the reactor. Indeed, the best performing units continue to represent a range of technologies, vendors and regions – suggesting that performance is not fundamentally limited by these factors. 

Examining the performance of all plants globally, in recent years 94% of unavailable capacity is due to reasons under management control; the dominant cause being shut downs for planned maintenance combined with refuelling. Best performing operators have significantly shorter and better-controlled outages while still maintaining essential safety standards. Speaking more broadly, best performers maximize their availability and minimize their unplanned unavailability; they plan for success and are able to mitigate any contingencies.

It is seen that the major direct cause of unplanned loss is failure or problems with plant equipment, with the turbine and auxiliary system having the greatest effect, followed by electrical power supply systems and main generator systems. Of these, the electrical power supply systems have become substantially more significant as a source of unplanned loss in the two years since the publication of the first edition of this report. 

Additionally we see that indicators of plant safety and capacity are linked: a well-managed plant is generally both productive and safe.

With potentially significant benefits available in economics, security, environmental performance and safety it is clear that further work on optimizing the current global nuclear fleet’s capacity has merit. The Capacity Optimization Working Group continues to provide the global forum for helping the worldwide industry realize these benefits.