Skip to main content

The Next Big Thing in Nuclear Power: Think Smaller & Safer

Dr. Everett Redmond
The following is a guest post by Dr. Everett Redmond, NEI's Senior Director, Policy Development.

There’s a lot to like about the small modular reactor design that NuScale Power submitted yesterday to the Nuclear Regulatory Commission. Most often people talk about the ability to build such reactors in a factory and ship them by truck or rail, in nearly-finished form, to where they are needed, and to add generating capacity to a plant in modest increments, as demand grows. But it’s easy to overlook another strength of the NuScale design: one of its intrinsic features is a simple way to enhance the safety of the reactor fuel.

There’s a fancy name for this feature: a high surface-to-volume ratio. In plain English, as a container gets smaller, its surface area gets larger relative to its volume, a phenomenon obvious to anyone who cooks. Take a hardboiled egg out of the pot of boiling water and put it into a bowl of cold water, and the egg cools very quickly. It does that because the water draws away the heat much faster than air could, and the area of the egg shell is relatively large compared to volume of the egg. Contrast this with a boiled potato that would take longer to cool because its surface area is smaller in comparison to its volume.
Cooling the NuScale SMR is like chilling a hard boiled egg.*
The NuScale module’s core is about one-twentieth the size of a standard large unit. The NuScale cores each sit in their own containment, a vessel a little like a thermos bottle. The containments are submerged in a huge pool of water. Like a thermos, the NuScale design uses a vacuum between the inner wall and the outer wall of its containment vessel, so the reactor can produce steam without heating up the surrounding water.

If there’s a problem, valves will break the vacuum and the steam from the reactor will flow into that vacuum space, and condense into water. So that space, which used to be a vacuum, and insulating layer, will become filled with water which will conduct heat away from the core. The heat will naturally travel through that water and to the outer wall of the module, and from there into the pool. The heat will bleed away fast enough so that the core can’t heat up to the point of damaging the fuel.

That principle leads to other advantages. The design is intended to be “walk-away safe,” with no short-term actions required by the operators. And existing reactors keep safety-grade backup diesel generators on site, but NuScale does not need these, because it doesn’t need the electricity to pump water or run mechanical systems to draw away heat. In fact this simple design does not use pumps when running normally to move the useful heat out of the core so it can be turned into electricity; that happens through natural convection.

Of course, an inherently safe design is always a good idea. But there’s another advantage here. The NRC has yet to evaluate NuScale’s application, but NuScale’s engineering shows that the emergency planning zone for its plant should extend only as far as the plant fence. The reactor can be located close to where electricity is needed the most.

That will make the NuScale reactor a good candidate for replacement power at old fossil-fueled sites in the United States, and in fast-growing cities around the world that do not have adequate electric local generation or a strong power grid to carry in power from distant places.

*Photo by Andrea Nguyen, provided under a Creative Commons license.

Comments

Popular posts from this blog

A Design Team Pictures the Future of Nuclear Energy

For more than 100 years, the shape and location of human settlements has been defined in large part by energy and water. Cities grew up near natural resources like hydropower, and near water for agricultural, industrial and household use.

So what would the world look like with a new generation of small nuclear reactors that could provide abundant, clean energy for electricity, water pumping and desalination and industrial processes?

Hard to say with precision, but Third Way, the non-partisan think tank, asked the design team at the Washington, D.C. office of Gensler & Associates, an architecture and interior design firm that specializes in sustainable projects like a complex that houses the NFL’s Dallas Cowboys. The talented designers saw a blooming desert and a cozy arctic village, an old urban mill re-purposed as an energy producer, a data center that integrates solar panels on its sprawling flat roofs, a naval base and a humming transit hub.

In the converted mill, high temperat…

Hurricane Harvey Couldn't Stop the South Texas Project

As Hurricane Harvey battered southeast Texas over the past week, the devastation and loss of life in its wake have kept our attention and been a cause of grief.

Through the tragedy, many stories of heroics and sacrifice have emerged. Among those who have sacrificed are nearly 250 workers who have been hunkered down at the South Texas Project (STP) nuclear plant in Matagorda County, Texas.

STP’s priorities were always the safety of their employees and the communities they serve. We are proud that STP continued to operate at full power throughout the storm. It is a true testament to the reliability and resiliency of not only the operators but of our industry.

The world is starting to notice what a feat it is to have maintained operations through the catastrophic event. Forbes’ Rod Adams did an excellent job describing the contribution of these men and women:

“STP storm crew members deserve to be proud of the work that they are doing. Their families should take comfort in the fact that…

New Home for Our Blog: Join Us on NEI.org

On February 27, NEI launched the new NEI.org. We overhauled the public site, framing all of our content around the National Nuclear Energy Strategy.

So, what's changed?

Our top priority was to put you, the user, first. Now you can quickly get the information you need. You'll enjoy visiting the site with its intuitive navigation, social media integration and compelling and shareable visuals. We've added a feature called Nuclear Now, which showcases the latest industry news and resources like fact sheets and reports. It's one of the first sections you'll see on our home page and it can be accessed anywhere throughout the site by clicking on the atom symbol in the top right corner of the page.
Most importantly for you, our loyal NEI Nuclear Notes readers, is that we've migrated the blog to the new site. Moving forward, all blog posts will be published in the News section, along with our press releases, Nuclear Energy Overview stories and more. Just look for the &qu…