FS-1 Will “Smaller and Smarter” replace “Bigger and Bulkier”? Presently, around the world there are 435 nuclear reactors operating generating roughly 374 GWe of electrical power (World Nuclear Association, 2013). Most of these reactors are large (>1000 MWe) and require a substantial infrastructure to support them (Earp, 2013). Small Modular Reactors (SMRs), which are about one-third (<300MWe) of the size of existing nuclear power plants, are currently being pursued. So, will “Smaller and Smarter” replace “Bigger and Bulkier”? The growing concern about global warming and climate change has instilled a sense of urgency to develop and deploy electricity-generating technologies that do not emit CO2 or other greenhouse gases (GHGs). SMRs can be manufactured in U.S. factories and then be transported to construction sites that include remote locations or military bases where large reactors are not practical. SMRs offer the advantage of lower initial capital investment, scalability and siting flexibility at locations unable to accommodate conventional larger reactors. SMRs could be used by smaller utilities, by smaller countries with financial or infrastructural constraints, in isolated regions or for distributed power needs, and for various non-electrical applications (process heat, desalination, oil recovery for tar sands and oil shale, and district heating). SMRs can be coupled with other energy sources, including renewable (such as, wind, biomass, geothermal, hydro and solar) and fossil energy. Retrofitting of aging conventional power plants with SMRs is an option that would leverage the existing siting and electrical grid transmission system (Halfinger and Haggerty, 2012). The modular approach enables a "plug and play" implementation that requires minimal on-site preparation (U.S. DOE, SMR Fact Sheet). "You can put them together like Legos on a job site," says Christopher Mowry of B&W (USA Today, 2012). Additional modules can be incorporated FS-1 incrementally as the demand for energy increases and financing becomes available. According to Peter Lyons, Assistant Secretary for Nuclear Energy at DOE, costs for an SMR plant are $4700 to $6000 per KWe or about $900 to $1200 million for a 200 MWe plant. For SMRs to be an economically viable alternative to standard GWe scale reactors, they must be deployed in large numbers (Glaser et al., 2013). Orders of several plants per year would be required before an automated factory for building these plants could be justified (ANS Nuclear Café, 2013). Although some of the technology has been used for naval propulsion applications, these systems have not yet been commercialized in the U.S. The components of the SMRs will be “Made in the U.S.A.,” which will create new jobs and increase exports. But, there is competition from other countries racing to design, build and market an offering of SMRs. The World Nuclear Organization reports that worldwide there are currently two SMRs operating, three SMRs under construction, 12 different small reactors with technology sufficiently advanced for near-term deployment, and another eight reactors in the same capacity range are listed as being in earlier stages of design. These reactors all have a generating capacity of at least 25 MWe. Countries with SMRs under design or already designed include Pakistan, India, Russia, Argentina, China, South Korea, South Africa, Japan and the U.S. (World Nuclear Organization, 2013). Examples of foreign advanced SMR designs include the 100 MWe integral pressurized water reactor (iPWR) South Korean System-Integrated Modular Advanced Reactor (SMART) and China’s twin 210 MWe HTR-PM gas-cooled reactors. Potential sales of SMRs to foreign nations could be lucrative for the U.S., especially if fuel sales contracts are established. If the spent fuel is returned to the U.S., it would help alleviate worldwide proliferation concerns. However, due to the higher fissile content in the spent fuel FS-1 they generate, SMRs could present increased proliferation risks unless offset by specific safeguards or design features (Glaser et al., 2013). Key benefits of SMR technology are reliance upon passive safety systems, use of natural circulation for emergency feedwater cooling, and elimination of the need for external emergency power. SMRs offer increased safety by eliminating major accident initiators (for example, large pipes in primary circuit), by improving decay heat removal and including more efficient passive heat removal from the reactor vessel, and use of seismic isolators for increased earthquake safety (Vujic et al., 2012). SMR vendors purport that the potential consequences of an accident relative to that of a large plant are reduced due to the small size of the reactor and the low power density limits. It can be argued that these reactors are safer than traditional nuclear power plants since they include a containment vessel surrounded by concrete and are located underground. While the development of new reactor concepts offers the potential for revolutionary improvements to reactor performance and safety, it is necessary to demonstrate that engineered safety features provide an acceptable level of protection to workers and the public. Critics of SMRs point to the possibility of a new set of problems associated with these reactors. Reducing the size of the unit results in a loss of economy of scale and operating more units increases the chances of a safety incident occurring at one of them. As with any new design, the full details will only be understood once an SMR is built and operated for some period of time. The successful licensing and widespread deployment of SMRs hinges to a large extent on siting considerations. The U.S. Department of Energy (DOE) Office of Nuclear Energy’s Small Modular Reactor Licensing Technical Support program is working to advance the licensing and commercialization of domestic SMR designs that are relatively mature and can be deployed in the next decade. The NRC is engaged in pre-application discussions with vendors advocating FS-1 SMR designs based upon three different technologies – light water reactors, high-temperature gas reactors and liquid metal-cooled reactors (Trikouros, 2012). SMRs that are designed to use light water reactor technology are considered by the nuclear community to be the most promising candidates for near-term SMR deployment since they have the most mature designs and are currently involved in pre-application interactions with the Nuclear Regulatory Commission (NRC) (NEI Position Paper, 2012). There are currently four iPWR designs currently being developed by U.S. industry (Holtec, mPower, NuScale and Westinghouse). Department of Energy Sponsored SMR Development To develop a new generation of domestically-produced nuclear power, the Obama administration announced on November 20, 2012 that it will fund up to half the cost of a five-year project to design and commercialize SMRs in the United States. The Department of Energy (DOE) is supporting the development and deployment of SMRs through two public-private partnerships: 1. Former Secretary of Energy Dr. Steven Chu stated when announcing the first award, “Low-carbon nuclear energy has an important role to play in America's energy future." President Obama's thrust is for an energy strategy that reduces GHG emissions and provides affordable energy. The first round of DOE funding was awarded to the mPower America project team consisting of B&W, Bechtel and the Tennessee Valley Authority (TVA). In April 2013, an agreement was signed providing B&W with $79 million in federal funding for commercialization of the mPower design. The team has set milestones of submitting the design certification application to the NRC in 2014. TVA may also submit a combined construction and operating license application to the NRC in 2015 for two SMRs to be built at the Clinch River site in Oak Ridge, Tennessee. FS-1 2. NuScale Power, LLC was selected on December 12, 2013 as the winner of the second round of the U.S. DOE’s competitively-bid, cost-sharing program to develop nuclear SMR technology. In announcing the second award, Energy Secretary Moniz said, “Small modular reactors represent a new generation of safe, reliable, low-carbon nuclear energy technology and provide a strong opportunity for America to lead this emerging global industry.” As part of the award, NuScale will receive up to $225M in federal funding over a five-year period to support the accelerated development of its 45 MWe NuScale Power Module™ SMR technology. The design features natural circulation, coolant flow residual heat removal and emergency core cooling systems powered by natural forces and a common pool that provides seismic dampening and radiation shielding. During extreme events, such as those that occurred at the Fukushima nuclear plant, 30 days of core and containment cooling are provided without the addition of water (Reyes, 2013). These public-private partnerships represent a significant investment in first-of-a-kind engineering, design certification and licensing for SMRs. DOE’s goal is to have these reactors operational in the early 2020’s. Description of mPower Design The focus of this essay is on the Generation mPower design. The origins of mPower reactor can be traced to the nuclear-powered merchant ship, the Otto Hahn, from the B&W maritime reactor program (Halfinger and Haggerty, 2012). The reactor aboard the Otto Hahn had an integral steam generator, located above the core, which provided superheated steam to drive turbines for power. The mPower reactor is an iPWR design in which the primary coolant system and all components (i.e., pressurizer, steam generators, and reactor coolant pumps) are enclosed within a single FS-1 pressure vessel (shown in Figure 1). As a result, the coolant remains within the vessel, except for an instrumentation tap, pressurizer spray line, and small penetrations located above the core for letdown, purification and makeup. Decay heat removal, reactor vessel depressurization, lowpressure coolant injection and reactor cavity flooding are provided by passive safety systems. Large seismically qualified tanks are available to supply cooling water for at least seven days. Each Generation mPower reactor is designed to provide 180 MWe, in contrast to about 1,000 MWe for a typical large reactor, and is envisioned to operate in pairs sharing a common turbinegenerator unit. To enhance safety and security, these light-water-cooled SMRs have separate, independent underground containments and safety systems for each reactor (Figure 2). The containment building and spent fuel pool facility are seismic category I flood-resistant structures located below grade level. In the event of an accident, radioactive material is confined by the containment building and passive hydrogen recombiners prevent the buildup of explosive hydrogen. The passive safety systems work without AC power or operator action for a period of 72 hours to protect the core, provide cooling and prevent the release of radioactive materials to the environment. The mPower reactor will operate on a 48-month cycle, after which the core will be completely changed out. The fuel consists of shortened versions of standard 17 x 17 commercial uranium oxide (<5.0wt% 235U) fuel assemblies. An extensive testing program to verify specific component design features and assess integrated system performance is being conducted. The Integrated System Test facility in Bedford County, Virginia is a scaled prototype of the mPower reactor used to confirm integral system design, demonstrate passive engineered safety systems and plant control systems, develop emergency procedures, train operators, confirm the design FS-1 verification methodology, and document reactor performance over a full spectrum of normal and transient operating conditions (Martin et al., 2013). Figure 1. The B&W mPower SMR integrates the Figure 2. Underground containment nuclear core and steam generators in a single vessel structure housing two B&W mPower SMR (source: greencarcongress.com). modules (source: generationmpower.com). INL’s Role in Advancing SMR Technology The Idaho National Laboratory (INL) is advancing the development of nuclear reactor technology in several key areas (Grossenbacher, 2013). INL has a strong capability in the computational modeling of fuels and reactor performance. This includes the development of the Multiphysics Object-Oriented Simulation Environment (MOOSE) “herd” of computer codes (e.g., BISON, MARMOT, FOX, ELK, etc.), as well as the new Reactor Excursion and Leak Analysis (RELAP)7 and the legacy RELAP5-3D systems code. Development and testing of new fuels and materials is performed through partnerships with industry and universities at the Advanced Test Reactor National Scientific User Facility (NSUF). Facilities and equipment for examining unirradiated and irradiated fuels and materials is available at the Center for Advanced FS-1 Energy Studies and the Materials and Fuels Complex. Design certification and licensing activities are supported by the SMR Licensing Technical Support Program. The INL sponsors student internships to train the future nuclear workforce. Conclusion This is an exciting time to be entering or working in the nuclear field. Several design certification applications for new reactors, including the Advanced Boiling Water Reactor (ABWR), Advanced Passive 1000 (AP1000), Economic Simplified Boiling Water Reactor (ESBWR), U.S. EPR and U.S.-Advanced Pressurized Water Reactor (APWR) have been submitted to the U.S. NRC. Worldwide, over 70 new nuclear reactors are under construction (World Nuclear Association, 2013). In the U.S., four new Westinghouse AP1000 reactors are being built at the Vogtle site in Georgia by Southern Co. So, will today’s “Smaller and Smarter” modular reactors replace the “Bigger and Bulkier” mindset of yesterday? There are applications for which SMRs are ideally suited, but it is not likely that they will completely replace large gigawatt-scale reactors. Rather, they will be another option to incorporate into the current energy mix that includes coal, natural gas and renewables. I am optimistic that construction of multiple SMRs in the U.S. is on the horizon. It would be exciting if an SMR was constructed at the INL site. Perhaps this would be a liquid-metal cooled, fast reactor to provide a domestic capability for testing advanced fuels and materials. This could be part of the NSUF Program, providing opportunities for students (like me!) to contribute to the next generation of nuclear technology. I am planning to go to college at Penn State. During a private tour, I was able to see the Breazeale Nuclear Reactor, a one MWt Training, Research, Isotopes, General Atomic reactor. The nuclear future looks bright and I am eager to be a part of it! FS-1 References ANS Nuclear Café, Small Modular Reactors at ANS 2013 Winter www.ansnuclearcafe.orf/category/small-modular-reactors, accessed 11/28/13. Meeting, Earp, J.E., Briefing: Small Modular Reactors, Proceedings of the ICE – Energy, Vol. 166, Issue 2, April 2013, p. 53-57. Glaser, A., et al., Resource Requirements and Proliferation Risks Associated with Small Modular Reactors, Nuclear Technology, Vol. 184, Number 1, October 2013, p. 121-129. Grossenbacher, J., A Perspective on the Challenge Facing SMRs, presented at From Concept to Reality: Small Modular Reactors, Realizing the Potential of SMRs in the U.S. for the Future of Nuclear Power, Idaho Falls, Idaho, October 20 – November 1, 2013. Halfinger, J.A., and Haggerty, M.D., The B&W mPower Scalable, Practical Nuclear Reactor Design, Nuclear Technology, Vol. 178, Number 2, May 2012, p. 164-169. Martin, R.P., et al., Thermal-Hydraulic Design for the B&W mPower SMR, Nuclear Technology, Vol. 109, Number 1, November 2013, p. 2269-2272. Nuclear Energy Institute, Position Paper, Small Modular Reactor Source Terms, December 27, 2012. Reyes, J.N., NuScale Plant Safety in Response to Extreme Events, Nuclear Technology, Volume 178 , Number 2, May 2012, p. 153-163. Trikouros, N.G., A Perspective on Small Reactor Licensing and Implementation, Nuclear Technology, Vol. 178, May 2012, p. 233-239. U.S. Department of Energy, Small Modular Reactor Fact http://www.ne.doe.gov/pdfFiles/factSheets/2012_SMR_Factsheet_final.pdf, 2012 Sheet USA Today, http://www.usatoday.com/story/news/nation/2012/11/26/nuclear-small-modularreactors/1727001/, November 27, 2012. Vujic, J., Bergmann, R.M. Skoda, R., and Miletic, M., Small Modular Reactors: Simpler, Safer, Cheaper?, Energy, 45 (2012), p. 288-295. World Nuclear Association, http://world-nuclear.org/Nuclear-Basics/Global-number-of-nuclearreactors/, accessed 12/16/13. World Nuclear Organization, Information Library, Small Nuclear Power Reactors, www.worldnuclear.org/info/Nuclear-Fuel-Cycle/Power-Reactors/Small-Nuclear-Power-Reactors, accessed 11/26/13.