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

An Ohio School Board Is Working to Save Nuclear Plants

Ohio faces a decision soon about its two nuclear reactors, Davis-Besse and Perry, and on Wednesday, neighbors of one of those plants issued a cry for help. The reactors’ problem is that the price of electricity they sell on the high-voltage grid is depressed, mostly because of a surplus of natural gas. And the reactors do not get any revenue for the other benefits they provide. Some of those benefits are regional – emissions-free electricity, reliability with months of fuel on-site, and diversity in case of problems or price spikes with gas or coal, state and federal payroll taxes, and national economic stimulus as the plants buy fuel, supplies and services. Some of the benefits are highly localized, including employment and property taxes. One locality is already feeling the pinch: Oak Harbor on Lake Erie, home to Davis-Besse. The town has a middle school in a building that is 106 years old, and an elementary school from the 1950s, and on May 2 was scheduled to have a referendu

Why Ex-Im Bank Board Nominations Will Turn the Page on a Dysfunctional Chapter in Washington

In our present era of political discord, could Washington agree to support an agency that creates thousands of American jobs by enabling U.S. companies of all sizes to compete in foreign markets? What if that agency generated nearly billions of dollars more in revenue than the cost of its operations and returned that money – $7 billion over the past two decades – to U.S. taxpayers? In fact, that agency, the Export-Import Bank of the United States (Ex-Im Bank), was reauthorized by a large majority of Congress in 2015. To be sure, the matter was not without controversy. A bipartisan House coalition resorted to a rarely-used parliamentary maneuver in order to force a vote. But when Congress voted, Ex-Im Bank won a supermajority in the House and a large majority in the Senate. For almost two years, however, Ex-Im Bank has been unable to function fully because a single Senate committee chairman prevented the confirmation of nominees to its Board of Directors. Without a quorum

NEI Praises Connecticut Action in Support of Nuclear Energy

Earlier this week, Connecticut Gov. Dannel P. Malloy signed SB-1501 into law, legislation that puts nuclear energy on an equal footing with other non-emitting sources of energy in the state’s electricity marketplace. “Gov. Malloy and the state legislature deserve praise for their decision to support Dominion’s Millstone Power Station and the 1,500 Connecticut residents who work there," said NEI President and CEO Maria Korsnick. "By opening the door to Millstone having equal access to auctions open to other non-emitting sources of electricity, the state will help preserve $1.5 billion in economic activity, grid resiliency and reliability, and clean air that all residents of the state can enjoy," Korsnick said. Millstone Power Station Korsnick continued, "Connecticut is the third state to re-balance its electricity marketplace, joining New York and Illinois, which took their own legislative paths to preserving nuclear power plants in 2016. Now attention should