The Generation Professionals Group is for utility professionals who work in biomass, coal, gas/oil, hydro, natural gas, or nuclear power generation fields. 


Delivering reliable electricity – nuclear plants just keep on running

Milton Caplan's picture
President, MZConsulting Inc.

Milt has more than 40years experience in the nuclear industry advising utilities, governments and companies on new build nuclear projects and investments in uranium.

  • Member since 2018
  • 102 items added with 136,919 views
  • Oct 29, 2020

On October 22, 2020 Darlington Unit 1 achieved a milestone never achieved before by a nuclear power plant running for 1,000 days continuously without an outage, either unplanned or planned1.  And it is still running.  This unit, operated by Ontario Power Generation (OPG) secured the world record for continuous operations last month, when it hit 963 days to take over from the Kaiga 2 unit in India, the previous record holder at 962 days achieved in 2018.  Kaiga took the record from Heysham 2 in the UK which reached 940 days in 2016 breaking the record set by the Canadian Pickering Unit 7 reactor 22 years earlier2.

Why does this matter? 


The world runs on energy.  We need it to keep warm (or cool, depending upon the climate), cook our food, light our homes, communicate with one another and travel from place to place; and to enable pretty much everything that drives our economies.  We need this energy to be affordable and most of all, we need it be reliable.  For most people in the developed world, we fully expect that when we flip the switch, the lights will come on.  Not sometimes, but each and every time.  We also want this energy to not harm the environment (although unfortunately we will concede on the environment rather than do without).  

And there is no more reliable low carbon source of energy than from nuclear plants.  Once in operation, they just run and run and run, like the energizer bunny.  These plants run in bad weather and good, during the day and during the night, providing 24 / 7 electricity to their customers. 

System reliability is not something we often think about until we experience an issue.  It came as a shock to many this year when California suffered ongoing blackouts and energy shortages.  There are many contributing factors to poor reliability as electricity grids are complex systems that require a never-ending balance between supply and demand, meaning a need for reliable generation and a robust transmission and distribution system.   In this case, the California Independent System Operator described the conditions that caused demand to exceed available supply: scorching temperatures and diminished output from renewable sources and fossil-fuelled power plants when electricity was needed most.

The president of the system operator blamed the California Public Utilities Commission for not ordering companies to make available sufficient supply.  A critical issue is the changing mix of generation with solar growing quickly without sufficient back up when the sun goes down and the air conditioning load remains high.  This demonstrates that solar power alone cannot meet the future energy needs of large energy intense systems like that of California, and that reliability must always be considered as we make structural changes to these systems. 

On the other hand, the US nuclear fleet continues to hum along providing 20% of the country’s electricity supply. 


Once again in 2019, the US nuclear fleet operated at a very high capacity factor (the percentage of time the plant is producing compared to if it ran 100% of the time) achieving 93.4%.  The US fleet continues this stellar performance, even as it is aging.  For the past 20 years the fleet has produced in the range of 90% capacity factor or more, demonstrating how robust a technology nuclear power really is.

This is not just true of the US.  It is true for the entire global nuclear fleet.  As shown in the WNA Nuclear Performance report 2020, more than a third of the world’s plants operate at 90% capacity factor or above and a full two thirds operate at capacity factors greater than 80%.

Nuclear technology is so robust that this excellent performance is not restricted to one specific type of plant.  Light water reactors, gas cooled reactors, heavy water reactors – they all operate great.  The distinguishing factor is more related to the expertise and excellence of the individual operator and to specific local market conditions, not to any specific technology.  International cooperation through organizations like INPO (Institute of Nuclear Power Operators) and WANO (World Association of Nuclear Operators) ensure best practices are shared and that all have access to the tools they need to achieve a high level of performance.  This is an industry that collaborates to ensure continuous improvement across the global fleet.

What really demonstrates the strength of nuclear technology is the continued strong performance, even as the plants age.  Heysham achieved it record run at 28 years of age and Darlington Unit 1 is 30 years old with only a year or so left before going down for refurbishment and a life extension outage.  Many would expect that the life cycle of a nuclear plant would look like an inverted bathtub, with less than average performance when it is new as the kinks are worked out and then declining performance with age as it nears its end of life.  But this is not the case.  Nuclear plants run well when they are new, when they are middle aged and actually tend to run their very best as they get old.

Need reliable electricity supply even when the sun is not shining, and the wind is not blowing? When it comes to reliable low carbon electricity, nuclear plants set the bar very high.  They just run and run and run some more…….

Every station in Canada had at least one unit set a station performance record this year.

It should be noted that the AGR units in the UK and the PHWR units in Canada and India use on-power fuelling, so they are not limited by the need for refuelling outages.

Bob Meinetz's picture
Bob Meinetz on Oct 30, 2020

"What really demonstrates the strength of nuclear technology is the continued strong performance, even as the plants age."

One reason for the longevity of nuclear plants, I've been told by a materials engineer, is that unlike a boiler in a coal or gas plant nuclear reactor vessels maintain a relatively stable temperature for up to 20 months at a time. The constantly-chainging thermal stresses between cold water inside and furnace outside take a much faster toll on coal-fired boilers, which require replacement every 30 years.

The US Energy Information Administration, AFAIK, calculates levelized cost for nuclear energy based on a 40-year license period. Plants in service, however, have shown the potential of operating for two periods or longer. When its LCOE is divided by two then compared to that of any other variety of dispatchable generation. nuclear's value is untouchable.

Matt Chester's picture
Matt Chester on Oct 30, 2020

On the other hand, the US nuclear fleet continues to hum along providing 20% of the country’s electricity supply. 

This has been quite reliable, and as you and Bob both point out the benefit is the long and stable life of the plants. But do you see reason for optimism this number will grow? It seems the build of new plants has been stalled and proposals to build more get hit with budget/schedule concerns and arguments that the construction of new plants is not as economical and the upfront capital is hard to come by. Will SMRs and other technological developments start to shift that equation? 

Bob Meinetz's picture
Bob Meinetz on Oct 30, 2020

Matt, private investment has never been interested in the big picture, in delivering returns 80 years from now. With a typical investment horizon of ~5 years, why would anyone want to invest in a nuclear plant? But it's always been that way. It's the reason why every nuclear plant in operation has been financed by either a government or a private/public partnership.

So we're at a point of reckoning in the U.S. Will we focus on delivering handsome returns to investors by 2025, or preventing changes to climate that will last 100,000 years? Seems obvious - big problems demand big commitments, not the promise of easy money. If we're forced to rely on venture capital to fight climate change, we might as well admit defeat.

Milton Caplan's picture
Thank Milton for the Post!
Energy Central contributors share their experience and insights for the benefit of other Members (like you). Please show them your appreciation by leaving a comment, 'liking' this post, or following this Member.
More posts from this member

Get Published - Build a Following

The Energy Central Power Industry Network® is based on one core idea - power industry professionals helping each other and advancing the industry by sharing and learning from each other.

If you have an experience or insight to share or have learned something from a conference or seminar, your peers and colleagues on Energy Central want to hear about it. It's also easy to share a link to an article you've liked or an industry resource that you think would be helpful.

                 Learn more about posting on Energy Central »