Developing Small Modular Reactor Designs in the U.S

Issue 2 and Volume 5.

By Brian Wheeler, Editor

The development of small modular reactors in the U.S. continues to gain support as the country searches for clean energy options. Although concepts are still being designed, the U.S. Department of Energy gave the sector a boost in March when it released a Funding Opportunity Announcement to establish cost-shared agreements to support the design and licensing of SMRs. A total of $450 million will be made available to support two SMRs over five years.

“America’s choice is clear,” said Energy Secretary Steven Chu. “We can either develop the next generation of clean energy technologies, which will help create thousands of jobs and export opportunities here in America, or we can wait for other countries to take the lead.”

The Energy Department said SMRs are about one-third the size of current nuclear power plants and are designed to offer a host of safety, siting, construction and economic benefits. The size, according to DOE, makes SMRs ideal for small electric grids and locations that cannot support large reactors. Also, the reduced cost due to factory production may make the SMR more attractive to utilities seeking to add a smaller amount of power.

“We really see a market right now that includes utilities that don’t have a large financial base and that are interested in clean, sustainable power. They are looking at the SMR as an investment of a billion dollars versus several billion dollars for large nuclear,” said John Goossen, vice president of Innovation and SMR Development at Westinghouse. “These utilities, in most cases, do not need large chunks of power and are looking to add power incrementally as part of their plans for growth.”

An artist rendering of the GE PRISM power block in a cutaway illustration. Photo courtesy of GE.

In February, the Electric Power Research Institute and the Oak Ridge National Laboratory released a study that stated the U.S. has the potential to generate 201 GW from SMRs. For their study, a small modular reactor was labeled as 350 MWe or less. The DOE defines an SMR as 300 MWe or less. The study stated that “350 MWe was considered a reasonable bounding estimate of an initial SMR installation.”

The U.S. is leading the world in the amount of SMR designs, but China could be the first country to have a SMR design operational. Launched in 2011, a 200 MWe HTR-PM reactor is under construction with the support of China Huaneng Group, China Nuclear Engineering and Construction, and Tsinghua University’s INET, according to the World Nuclear Association.

“The U.S. needs to move faster if we are going to compete with the South Koreans, the Chinese and the Russians,” said Bob Prince, vice chairman and CEO, Gen4 Energy.

The Funding Opportunity Announcement from DOE will fund up to two designs with the goal of deploying the SMRs by 2022.


Developed by Generation mPower, a joint venture between the Babcock & Wilcox Co. and Bechtel Corp., the mPower model is a reactor helping lead the development of SMRs in the U.S. The scalable, integral reactor design is capable of adding power generation in increments of 180 MWe with a four-year operating cycle, without refueling.

Conceptual drawing of B&W mPower nuclear reactor design. Photo courtesy of Babcock & Wilcox.

B&W is testing the reactor at its $100 million Integrated System Test facility in Virginia. Chris Mowry, president of Babcock & Wilcox Nuclear Energy, said the company is testing the reactor and its thermal hydraulics on a five-year baseline testing schedule.

B&W began the testing phase of its newly-constructed Integrated System Test facility before the end of 2011. The IST facility includes a scaled prototype of the B&W mPower reactor that will undergo testing. The prototype reactor is installed in a 117-foot tall tower where operators will run a variety of real-world scenarios to gather data to support licensing activities with the Nuclear Regulatory Commission.

As one of the first small modular reactors to be developed in the West, there are still many unanswered questions from regulators. For instance, how computer codes and methods that were developed for large reactors model the performance when used in a SMR. Although the underlying technology is similar, the architecture of the system is different.

“We do believe the codes and processes are properly modeled, but we do have to prove it,” said Mowry.

All of the technical features of the B&W mPower integral reactor are included in the IST, although the source of energy is electricity rather than nuclear.

Mowry said the program is not just a model of the reactor, either. The test system models 100 percent of the entire mPower nuclear island including every valve, component and heat exchanger.

“Everything that is in the real nuclear island is in this,” he said. “We can really evaluate the performance of not just the reactor, but the entire nuclear system of mPower. That is why the testing is more extensive.”

In June 2011, Generation mPower signed a Letter of Intent with the Tennessee Valley Authority for the designing, licensing and construction of up to six mPower SMRs at TVA’s Clinch River site in Tennessee. At the time, TVA planned to submit a construction permit application to the NRC in 2012 with Generation mPower planning to submit a Design Certification Application to the NRC in 2013, with plans to deploy the first mPower reactor by 2020.

“We are continuing to develop this reactor at a pace that supports (Clinch River), not only in the engineering but also the testing,” said Mowry. “This is really part of our long-term growth initiative. mPower is the way forward for our commercial nuclear business.”

Westinghouse SMR

In February 2011, Westinghouse Electric Co., the manufacturer of the 1,100 MWe AP1000 plant, announced its plans to develop a greater-than 225 MWe, integral pressurized water reactor. While the Westinghouse SMR is not a “mini-AP1000” reactor, Westinghouse is leveraging many of the same advanced passive safety program principles, systems and proven components that have been developed and tested over a 20-year timeframe.

The NRC-licensed safety features of the AP1000 will be extended to its SMR. Photo courtesy of Westinghouse.

“What we are trying to do with this design is use as much proven technology as we can,” said Goossen.

As the only vendor with licensed and tested passive safety systems and with hundreds of millions of dollars already invested into research and development for the AP1000, Goossen said Westinghouse will take a lot of the lessons learned from the development of the AP1000 and place that knowledge into the SMR. The Westinghouse SMR, though, is a stand-alone unit. The reactor is modular in the sense that it will be manufactured in a factory setting, shipped to the plant site and installed on-site over an 18-24 month timeframe.

Goossen pointed out that Westinghouse, as part of its development process, is drawing from as much experience, proven technology and testing as possible to achieve safety and economics.

“We’re balancing innovation and wisdom,” said Goossen. “We are trying to keep the untested or unproven innovations down so we can get through licensing as fast as possible, keep costs down and get to market first.”

The SMR will also use the same fuel as the AP1000, with changes implemented on the active fuel height. The AP1000 possesses a 14-foot-tall active fuel height, while the Westinghouse SMR has only an 8-foot active core. Westinghouse will test the fuel at its Columbia, S.C. nuclear fuel test facility.

The SMR will “require very little testing to qualify this fuel,” Goossen said.

The digital instrumentation and controls system used in the AP1000, the Ovation-based control system, will be used. One variation is the SMR will use internal control drive rod mechanisms (CRDMs) but based on proven AP1000 technology.

Using these similar systems, Goossen said, will help Westinghouse meet one of its goals: Making the SMR an economically-viable reactor.

“We are trying to make this most economic design that we can, so it competes with large reactors on a dollar per kilowatt basis,” he said.

Westinghouse will apply for DOE’s SMR FOA investment funds with a group of utilities.

“Access to this investment fund helps lower the barrier to market entry for American companies,” said Kate Jackson, chief technology officer and senior vice president of Research and Technology for Westinghouse.


Using technology that was conceived in 1981 and reviewed by the NRC from 1987-1994, GE has developed what they refer to as the nation’s first SMR concept. The PRISM, or Power Reactor Innovative Small Modular, is GE Hitachi Nuclear Energy’s 300 MWe next generation fast spectrum, sodium-cooled reactor.

“This reactor puts this nation on a different path as far as completely different technology,” said Eric Loewen, GE Hitachi Nuclear Energy’s chief consulting engineer for Advanced Plants Technology.

The next generation reactor uses passive design features, such as passive reactor core cooling. Passive safety systems eliminate the need for active systems and increase safety.

GE has said that the use of sodium as a coolant instead of water allows neutrons to have a higher energy that drives fission of the transuranics. The reaction produces energy that is converted into electricity by a steam turbine. The PRISM reactor has the ability to consume transuranics in used fuel from water-cooled reactors and turning waste into energy.

“We need to use used nuclear fuel,” said Loewen.

The concept GE has presented to DOE is referred to as an energy park. The GE PRISM energy park consists of three PRISM power blocks. Each power block consists of two reactors generating about 622 MW. The facility would also possess a fuel recycling center. By having continuous construction activities on-site and by levelizing resources, Loewen said project managers would not have to work around a big influx of construction workers. By staging the construction activities, project costs can be reduced.

Loewen said GE is comfortable where the PRISM stands in the licensing process. In 1994, PRISM received its initial first pass.

“We would pick up from that wisdom and update it,” said Loewen.

NuScale Power

Corvallis, Ore.,-based NuScale Power is developing a light water SMR design. Founded in 2007 from research conducted at Oregon State University, the company has designed a nuclear steam supply system and nuclear power plant that offers the benefits of nuclear power but takes away the issues presented by installing large capacity.

The NuScale SMR design is a 45 MW reactor with a combined containment vessel and reactor system, although a plant using NuScale’s design would be comprised of individual NSSS modules. A plant using this design can utilize as many as 12 NuScale reactors to produce up to 540 MW of capacity, adding modules as power is needed.

Thanks to an investment from Fluor Corp., NuScale is again moving towards the NRC licensing process after suspending operations in January 2011 due to investor problems. Fluor, in October 2011, committed to making an investment of over $30 million in the company. Both Fluor and NuScale said moving forward, NuScale will continue to operate as an independent company, although Fluor is now the majority shareholder. Fluor and NuScale also entered into a separate agreement giving Fluor the rights to provide certain services to NuScale as well as have exclusive rights to provide engineering and construction for future NuScale SMR facilities.

“We at Fluor had been looking for some time at the various technologies that were emerging on the SMR side of the business. And we were very intrigued with what we saw at NuScale,” said Chris Tye, senior vice president of Nuclear Operations for Fluor.

The reactor developer believes it has two advantages to meet NRC requirements, one being the light water reactor technology that the NRC is familiar with. The second is the test facility at Oregon State that NuScale uses to replicate the entire system at about one-third of the size.

“They have done a lot of work, even to the point of having a test facility that is up and running in Corvallis, Ore. And they have been working there for some time now,” said Tye.

NuScale did notify the NRC in 2008 of its intention to begin the pre-application process. NuScale did meet with NRC in 2008 and 2009 to discuss both the combined construction and operating license and design certification process. NuScale expects the first plant will enter service in the early-2020 timeframe.

General Atomics

Founded in 1955, General Atomics was created to research and deliver the benefits of nuclear technologies. Over 50 years later, the company is creating a reactor that may be able to address some of the concerns the nation has about spent nuclear fuel. General Atomics for the past three years has been developing the 240 MWe Energy Multiplier Module, or EM2, a gas-cooled fast reactor that runs on spent fuel, plutonium or depleted uranium.

The 240 MWe EM2 power module in a below-grade sealed containment. Photo courtesy of General Atomics.

“The reactor has a core design that allows it to operate for 30 years without refueling or reshuffling of the fuel,” said John Parmentola, senior vice president for Energy and Electromagnetic Systems for General Atomics.

“Not only is this reactor burning fuel, but it is creating fuel as the reactor goes along this 30-year cycle.”

After the 30-year operating period, the design allows the “waste” from the reactor to be used in the next EM2, with the addition of spent nuclear fuel, depleted uranium or plutonium. General Atomics has studied this process during a span of seven, 30-year cycles. Parmentola said they have yet to find anything that stops the cycle.

In the U.S., there are piles of used uranium in Ohio and Kentucky and spent nuclear fuel stored at sites around the country.

“If you look at energy stored in that material, it is equivalent to nine trillion barrels of oil. This type of reactor can take all of that, burn it and turn it into energy,” said Parmentola.

In terms of size, General Atomics refer to the EM2 as a compact reactor. Buried in a concrete vault below grade, the reactor is 12 meters in length and 5 meters in diameter.

“The amount of material that goes into this reactor is far less than a small light water reactor,” he said.

In addition to the reactor, General Atomics is inventing a high-speed, direct drive jet turbine generator. The generator uses the helium that is heated up in the reactor to drive the turbine before re-circulating it. The generator, which Parmentola said is 47 percent efficient, is about the same size of the reactor itself, so both can be transported via truck. Decreasing the diameter enhances the need to increase the speed of the rotation of the turbine, up to 12,000 RPM.

“The combination of the reactor and generator is the key to EM2 ,” Parmentola said.

General Atomics has launched a 12-year program to research and develop the EM2. The company is still in the early stages because they must prove the fuel elements and demonstrate the high-speed turbine. Design and testing are underway.

“The people working on this have a tremendous amount of confidence in being able to do this,” said Parmentola.

If successful, the EM2 could help address one of the biggest concerns in nuclear energy, which is disposing of waste from large reactors.

Gen4 Module

Based in Denver, Colo., and working with the Los Alamos National Laboratory to develop an advanced reactor design, Gen4 Energy, formally known as Hyperion Power Generation, is developing the Gen4 Module (G4M). The G4M is a liquid metal-cooled small modular reactor with potential to produce 25 MW.

“We are different from others because we are a Generation 4 reactor,” said CEO Bob Prince. “We went back to basic physics.”

NuScale Power has tested their design at its one-third scale test facility at Oregon State University. Photo courtesy of NuScale Power.

Without the use of water, Prince said the accidents at Fukushima, Chernobyl and Three Mile Island are not credible with their design. Another safety feature is in atmospheric pressure.

“There is no pressure, so there is no force to throw radioactive material around the environment, which has great safety significance,” said Prince.

Prince did acknowledge other possibilities that would need to be analyzed to ensure safety.

The G4M reactor is about the size of a Mini Cooper automobile and can be transported in something the size of a spent fuel cask. The reactor lasts about 10 years. With no fuel on site, after 10 years the reactor is either cooled and left at the plant until decommissioning or returned to the factory to analyze the fuel for re-use. With this design, Price said they do not plan on adding additional reactors to sites.

“We try to supply power to remote areas. Secure, safe power in a different concept,” he said.

Gen4 Energy is now engaging with a NSSS supplier and architect engineer to move into the licensing process in the U.S. and Canada, simultaneously. While Gen4 is encouraged by the government’s action to support first-of-a-kind engineering, design certification and licensing of next generation reactors, Prince said due to the history, they still may be a long shot for funding.

“Anything other than light water is a long shot,” said Prince. “But they opened it up so people like us can try and convince them to support alternatives which are smaller and safer because of the physics. I think they should support LWRs, but they should also support Generation 4.”


Holtec International subsidiary, SMR, LLC, in February 2011 completed proof-of-principle studies on its 140 MWe Holtec Inherently Safe Modular Underground Reactor, or HI-SMUR.

The core of this design is underground, operated by gravity-induced flow, does not rely on off-site power for shutdown, and can be installed as a single unit or as a cluster.

SMR, LLC said eliminating the reactor coolant pump and the need for emergency or off-site power to cool the reactor core in the event of a forced shutdown are among the distinguishing design features of HI-SMUR that define its mission of safety and security.

In June 2011, Holtec and SMR, LLC awarded a conceptual design contract to The Shaw Group. Holtec, at the time, said the initial tasks for the joint venture were to develop the design criteria and safety systems, develop the architectural layout of the plant and develop the plant’s cost estimate.

Construction is expected to take 24 months.


While the U.S. is still leading the world in nuclear power production, the timeframe for deployment of SMRs in North America is still a few years out. But the industry is optimistic.

“We see the market for the SMR here in North America, and globally, very promising,” said Goossen.

The DOE has entered into memorandums of agreement with three manufacturers of SMRs to help leverage the Savannah River Site’s land, facilities and experts to support the development, testing and licensing of prototype SMR designs. The DOE, Savannah River Site and the Savannah River National Laboratory entered three separate public-private partnerships with Gen4 Energy, SMR, LLC and NuScale Power. While the agreements will help these companies obtain information on potential SMR reactor siting at Savannah River and provide a framework for developing land use and site services agreements, the agreements do not constitute a federal funding commitment.

“We have a unique combination of nuclear knowledge and laboratory expertise, infrastructure, location and much more to make the Site a natural fit for advancing the small modular reactor technology,” said Dr. Dave Moody, DOE senior manager. “We are about reinvigorating SRS assets to impact national needs and influence new missions for the future of the Savannah River Site.”

The MOAs are expected to help break down engineering and testing barriers to advanced nuclear reactor research and development. The biggest challenge to get SMRs to the market is licensing.

“We have a lot of innovation in the U.S. America can regain a leadership in a new product line called the SMR,” said Loewen.

Loewen said to receive a license from the NRC for light water reactors takes about five to seven years.

Developing SMRs in the U.S. could lead to further job creation, especially on the manufacturing side of the business; jobs that the Obama administration continues to speak about.

“There is always job creation with new reactor build,” said Goossen. “In addition to jobs with building and operating nuclear plants, we are going to have to build modular assembly buildings.”

Test centers, such as Westinghouse’s nuclear fuel facility, will also need workers to certify these designs. And to keep the economics on the low end, factories will use an assembly line style of work, an obvious advantage for the SMR. With shipyards that need work, the U.S. could capitalize on this opportunity and venture into the SMR export market.

“The U.S. needs to move faster,” Prince said. “Get one licensed and get one or more companies out there.”

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