Is smaller better for nuclear power plants?

Nuclear power plants 1/10 the size of current utility-scale plants may become reality some years from now. Faster construction, modular design, and easier financing are behind their development

Frank J. Bartos, P.E., Control Engineering

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Small nuclear power plants are not new. After all, the pioneer commercial reactors were small units, along with generations of nuclear reactors successfully applied in naval vessels. Conditions may now be favorable to build advanced nuclear power plants with one-tenth the output power of current utility-scale plants—and even physically smaller in overall size.

During my direct involvement in nuclear power plant design and development more than 30 years ago, those of us advocating smaller-scale plants were not popular with management or fully in-synch with prevailing market conditions. At that time, only large plant construction was on the radar screen of economics. Financing of capital projects also lived in a different world. Now, nuclear plant design with “smaller is better” in mind may have a chance to become reality. Benefits of small nuclear reactors are seen as:

• Faster plant construction with smaller, less complex reactor systems;
• Modular plant design, enabling simpler replication of multiple units;
• Real scalability of plant output to current power needs, and easier add-on of  units as demand increases;
• Simpler design, such as integrated reactor core and steam generator, less complex shutdown procedures; and
• Easier financing with less total cost involved.

Nuclear power has its share of opponents, extending to any new developments. In their view, downside of smaller plant design includes:

• Nuclear material and spent fuel dispersed to more sites;
• Safety: more potential terrorist targets (and possible plant sitings near urban areas); and
• Concern about overall cost of electricity generation.

These issues require proper resolution and assurance of being preventable to the most practicable degree. An emotional decision should not be the basis to turn away from a promising technology.

Numerous designs, developers

A significant number of companies worldwide are developing small nuclear plants of new, advanced design with intent to commercialize them.

One U.S. developer—Babcock & Wilcox Nuclear Energy Inc.—refers to its technology as the “world’s first advanced generation III” small modular reactor (SMR) nuclear plant and carries the catchy trademark name of “mPower.” To streamline production and lower project costs, the pressurized water reactor (PWR) rated for 125 megawatt electric (MWe) output would be factory built and transported to the plant site via barge or rail.

mPower’s design calls for burying the reactor and its containment dome below ground. Its spent fuel is to be stored onsite under water for the full 60-year design life of the reactor. Babcock & Wilcox (B&W) envisions initial SMR sitings at existing nuclear plant sites with space for future expansion and where obtaining a permit would be simpler. B&W intends to request certification of mPower from the Nuclear Regulatory Commission (NRC) in 2011 and projects first units going online after 2018.

Among other current small reactor designs are NuScale Power Inc.’s 45 MWe modules, 12 of which would be integrated to form a standard plant, and IRIS, a 100-335 MWe system from a group of companies led by Westinghouse (a unit of Toshiba Corp.). Both offerings are PWR designs.

NRC’s current licensing agenda focuses on new large-scale nuclear reactors—thus pending applications for “mini” nuclear plants will be considered later. However, with their shorter construction period, downsized nuclear power plants could be operating in about the same time frame as their new giant cousins.

For more on small nuclear plant designs, visit

www.world-nuclear.org/info/inf33.html;

www.babcock.com/products/modular_nuclear/;

www.nuscalepower.com; and

www.westinghousenuclear.com.

Frank J. Bartos, P.E., is a Control Engineering consulting editor. Reach him at braunbart@sbcglobal.net.

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