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Benefits of Flexible Nuclear Energy Operations for Renewables

  • Nuclear PowerKeeping the balance: How flexible nuclear operation can help add more wind and solar to the grid.
  • A new model finds operating nuclear plants flexibly can reduce electricity costs, increase revenue for nuclear plants, and cut carbon emissions in electric power systems.
  • Power plants that balance nuclear and renewable energy could increase revenues from electricity markets and reduce variable operating and maintenance costs, according to a collaboration involving Argonne scientists and MIT.

Nuclear power plants typically run either at full capacity or not at all. Yet the plants have the technical ability to adjust to the changing demand for power and thus better accommodate sources of renewable energy such as wind or solar power.

Researchers from the U.S. Department of Energy’s (DOE) Argonne National Laboratory and the Massachusetts Institute of Technology (MIT) recently explored the benefits of doing just that.

If nuclear plants generated power in a more flexible manner, the researchers say, the plants could lower electricity costs for consumers, enable the use of more renewable energy, improve the economics of nuclear energy and help reduce greenhouse gas emissions.

The new study “gives us tools to further explore potential benefits of flexible nuclear operations to work in tandem with greater shares of variable sources of renewable power generation …” — Jesse Jenkins, graduate researcher at the MIT Energy Initiative.

mitlogo“What this study shows is that rather than shut down nuclear plants, you can operate them in a way that makes room for renewables,” says MIT Energy Initiative researcher Jesse Jenkins.

“It shows that flexible nuclear plants can play much better with variable renewables than many people think, which might lead to reevaluations of the role of these two resources together.”

The team explored technical constraints on flexible operations at nuclear power plants and introduced a new way to model how those challenges affect how power systems operate.

“Flexible nuclear power operations are a ‘win-win-win,’ lowering power system operating costs, increasing revenues for nuclear plant owners and significantly reducing curtailment of renewable energy,” wrote the team in an Applied Energy article published online on April 24. (Citation and link at end of this blog post)


Audun Botterud, a principal energy systems engineer in Argonne’s Energy Systems division, is encouraged by how, for the first time, “this research evaluates and demonstrates the potential value of flexible nuclear operations in a realistic power system in the United States challenged by high variability in renewable-energy generation.”

The study helps to dispel long-held views that nuclear power plants must operate in “baseload” mode, producing power at maximum rated capacity whenever they are online.

Nuclear plants can even respond dynamically to hourly electricity market prices and second-to-second frequency regulation needs, the team found. Power systems that include renewable energy must be more flexible to balance supply and demand at all times. Nuclear operators in France, Germany and other countries are familiar with this approach, but less so in the United States.

The researchers developed a mathematical representation of the physics-induced operational constraints arising from nuclear reactor dynamics and the fuel irradiation cycle in the Applied Energy article and a companion paper, published in Nuclear Technology.

The interdisciplinary team then combined the new approach with power system simulation models to evaluate the overall cost of electricity generation, market prices and resulting revenues for power plants, assuming different levels of nuclear flexibility.

“Nuclear power plants are governed by a different set of principles compared to other generators, and our approach enables the representation of these relationships in the analysis of power systems and electricity markets,” said Francesco Ganda, the principal investigator of the project and a principal nuclear engineer in Argonne’s Nuclear Science and Engineering division.

By being flexible, plant operators can lower overall operating costs in the power system. For example, operators could generate less nuclear power whenever renewable energy is widely available. Nuclear plants could then exploit their spare capacity to sell valuable “operating reserves,” or the ability to quickly change power output to help grid operators rebalance supply and demand when unexpected events occur, such as power plant failures or errors in demand forecasts.

This flexibility could increase the profitability of nuclear plants by increasing revenues from electricity markets and reducing variable operating and maintenance costs. Overall, nuclear plant flexibility can also help integrate more wind and solar resources and reduce production of fossil fuel-fired energy and related carbon dioxide emissions.

Jesse Jenkins, graduate researcher at the MIT Energy Initiative, notes how the researchers’ modeling approach and study “gives us tools to further explore potential benefits of flexible nuclear operations to work in tandem with greater shares of variable sources of renewable power generation on the pathway towards low-carbon electricity supply.”

Other Argonne study authors include Richard Vilim, Zhi Zhou and Roberto Ponciroli. The research was funded, in part, by Argonne’s Laboratory Directed Research and Development program.


  • Nuclear power plants are subject to different operational constraints than other power plants.
  • The authors provide a mathematical representation of these distinct constraints on nuclear flexibility.
  • Benefits of nuclear flexibility are significant in a power system with high shares of renewables.
  • Benefits include lower power system operating costs and increased revenue for nuclear plants.


Nuclear power plants are commonly operated in a “baseload” mode at maximum rated capacity whenever online. However, nuclear power plants are technically capable of flexible operation, including changing power output over time (ramping or load following) and providing frequency regulation and operating reserves.

At the same time, flexibility is becoming more valuable as many regions transition to low-carbon power systems with higher shares of variable renewable energy sources such as wind or solar power.

We present a novel mixed integer linear programming formulation to more accurately represent the distinct technical operating constraints of nuclear power stations, including impacts of xenon transients in the reactor core and changing core reactivity over the fuel irradiation cycle.

This novel representation of nuclear flexibility is integrated into a unit commitment and economic dispatch model for the power system. In a case study using representative utility data from the Southwest United States, we investigate the potential impacts of flexible nuclear operations in a power system with significant solar and wind energy penetration.

We find that flexible nuclear operation lowers power system operating costs, increases reactor owner revenues, and substantially reduces curtailment of renewables.

Keywords: Nuclear energy; Flexible operations; Renewable energy integration; Unit commitment; Economic dispatch; Mixed integer linear programming

Full text of the paper is available for purchase online:
Applied Energy, Volume 222, 15 July 2018, Pages 872–884

About Argonne National Laboratory and the U.S. Department of Energy

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.

The U.S. Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.

Original Post

Content Discussion

wind smith's picture
wind smith on May 1, 2018

If it can replace coal and especially gas as back up to maximizing wind and solar,
I’m on board.

Engineer- Poet's picture
Engineer- Poet on May 1, 2018

Increasingly, renewables are eating their own markets.  When they are abundant, they drive auction prices to their own marginal cost (zero) and thus could not survive without subsidies in some form.  This cannot go on forever, so it won’t.

Intermittent, unreliable generation requires flexible, variable load which can follow it.  I went over the issue here so I won’t repeat myself.

Willem Post's picture
Willem Post on May 2, 2018


France generates about 80% of all its generation by nuclear.
It has balanced all of its generation with its own generators for decades.
No imports or exports, no curtailments, etc., are required.

Next-door Germany exports when it is windy and sunny, i.e., overproduces, and imports when it is not windy and sunny, i.e., it underproduces.

Germany is using adjacent grids as a crutches/safety valves, because Germany’s REMAINING traditional generators can no longer deal with the variable wind and solar production.

RE aficionados and Reality: RE aficionados often repeat the wholesale prices of wind and solar have come down and are now competitive with fossil, about 5 c/kWh. However, that is only true:

– Because wind and solar are highly subsidized, and only in
– Areas with much wind, such as the Great Plains and Texas, and areas with much sun, such as the US Southwest.

However, in New England, with mediocre wind and solar, their highly subsidized wholesale prices utilities pay to producers are:

– Onshore/ridgeline wind about 9.5 c/kWh
– Offshore wind about 21 c/kWh
– Large-scale, field-mounted, competitively auctioned solar about 13.5 c/kWh
– Residential, roof-mounted solar about 19 c/kWh

NOTE: Those prices would be about 50% higher without the subsidies.

RE aficionados say, just over build “low-cost”, highly subsidized, wind and solar so there will be plenty of “low-cost” electricity, even when the wind is barely blowing and the sun is barely shining, and even with snow and ice on most of the panels.

That likely would be very expensive with one 4-day wind lull, followed a few days later by another 4-day wind lull, not an unusual occurrence in New England, during December through March, with solar near zero most of the time, and when with snow and ice on most of the panels.

They say, when the wind IS blowing and the sun IS shining, just curtail the excess electricity, or export any surplus electricity at near-zero or negative prices, as Germany and Denmark have been doing for decades; the excessive exports could upset the grids of neighbors.

Germany and Denmark, both RE leaders, with highest household electric rates in the EU (about 30 eurocent/kWh) have been practicing such expensive follies for at least 15 years. As there is no free lunch, except in RE LaLaLand, their subsidy costs:

– Show up as surcharges, taxes and fees, mostly on household electric bills. Industry and commerce are mostly spared for competitive reasons.
– Show up as higher prices for goods and services.
– Are added to the national debt and state debts.

Bas Gresnigt's picture
Bas Gresnigt on May 2, 2018

Nuclear share in French electricity production decreased from 88% in 2004/2005 via 80% in 2009/2010 towards 72% in 2016 (fossil 10%, renewable 18%).

It has balanced all of its generation with its own generators for decades.
No imports or exports, no curtailments, etc., are required.

In the autumn of 2016 Germany kept a coal plant near the French border longer open on request of the French in order to help France out (part of its NPP was closed because of the fraud with nuclear certification by Areva’s Cleusot forge).
When it gets cold in early spring Germany often also has to help France out as part of their nuclear reactors are then refueling or have major maintenance.

Recently offshore wind in the North Sea was contracted unsubsidized which implies ~€3cent/KWh whole sale prices. In NL 700MW (this spring) and in Germany 1280MW (last autumn). Prices are expected to decrease further with the increase of wind turbine sizes towards 16MW.
The continued price decreases of wind & solar will create more and more unsubsidized power (so ~3cnt/KWh) in the near future.

As new nuclear is far more expensive (~€15cent/KWh) and the French nuclear reactors get old, so have to be closed coming years (EDF plans ~5 in 2018/2019), France is busy with fast renewable expansion now.
No plans for new nuclear plants except the one under construction since 2007 which may start in 2019.

Helmut Frik's picture
Helmut Frik on May 2, 2018

France relies heavily on the power generation ressources of the neighbouring countries, it expoerts when the nuclear power stations produce too much for the internal demand, and imports on high demand days in winter, when its own fleet of generation is significant smaller than demand.
Germany exports due to wind and solar production, and inflexible nuclear power plants and combined generation only a few hours per year, and only imports due to lower prices e.g. for surplus french nuclear power, german generation capacity always significant exceeds demand.