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Nuclear

Nuclear Energy Resources

Currently, 65 commercial nuclear power plants with 104 nuclear reactors are licensed by the U.S. Nuclear Regulatory Commission (NRC) to operate in the United States. These plants represent a highly reliable base-load electric power source across several large regions of the country. They constitute nearly 20% of the electricity generated and more than 70% of the country’s "zero-carbon" electricity capacity. For 2011, nuclear power plants generated approximately 790 billion kilowatt-hours (kWh). Thirty-one states have one or more operating commercial nuclear power plants. For 2011, nuclear power provided the largest percentage of electric power generated for seven of these 31 states (Nuclear Energy Institute 2012):

For this study, three different types of reactors were considered: (1) large light water reactors (LWRs) like those currently undergoing design certification and combined operating license reviews by the NRC; (2) small modular reactors (SMRs) based on pressurized-water reactor (PWR) technology, whose compact design features are expected to offer a host of safety, siting, construction, and economic benefits as well as ideal for small electric grids; and (3) high-temperature gas-cooled reactors (HTGRs), currently being considered for both electricity and process heat applications.

Conversion Technologies

Next-Generation LWRs

The large LWRs currently undergoing design certification and combined operating license reviews by NRC are commonly referred to as Generation III+ (Gen III+) designs; in the 1,100 to 1,600 MW(e) range. Those that are characterized as passive with regard to safety do not require active controls or operator intervention, but instead rely on gravity or natural convection to mitigate the impact of abnormal events and to provide emergency cooling. These reactors (both PWRs and boiling water reactors or BWRs) represent the next evolution of designs beyond those of the 104 currently operating commercial nuclear power plants. An example is Westinghouse’s approved AP-1000 PWR design (Figure 1).

Figure 1. Plant Design and Layout of Westinghouse AP-1000 PWR
Figure 1. Plant Design and Layout of Westinghouse AP-1000 PWR (Source: Westinghouse Electric Company LLC 2013)

Small Modular Reactors

SMRs have design features that will provide safety, siting, construction, and economic benefits. Furthermore, these smaller plants are ideally suited for small electric grids and for locations that cannot support large reactors, thus providing utilites with the flexibility to scale production as demand changes by by adding more modules or reactors in phases. The near-term SMR designs are based on existing PWR technology. They are characterized as "integral" PWRs (iPWRs), since these plants will have major equipment such as pumps, steam generators, ans pressurizers all located within the pressure vessel in an integrated, compact design. These designs are typically in the 25 to 250 MW(e) power range.

The four SMR vendors whose integral designs are based on PWR technology include the following:

  1. Babcock and Wilcox’s m-Power SMR: 180 MW(e) per reactor module, with the plan to deploy two 180-MW(e180-MW(e) modules/units at a time
  2. NuScale SMR: 45 MW(e) per reactor module, with the plan to deploy these 6 or 12 modules/units at a time
  3. Westinghouse SMR: 225 MW(e) per reactor module, with the plan to deploy one or more units individually
  4. Holtec's SMR-160: 160 MW(e) per reactor with the plan to deploy one unit or multiple units individually.

All of these designs feature underground siting for safety and security reasons. All four vendors presently indicate submitting applications for design certification in the 2013 to 2015 timeframe.

HTGRs

HTGRs are currently being considered for both electricity and process heat applications. The U.S. Department Energy (DOE) has been directed under the Energy Policy Act of 2005 to develop a high-temperature reactor in a cost-shared approach with industry. DOE's HTGR program is known as the Next Generation Nuclear Plant (NGNP). NGNPs do not have cooling water requirements like LWRs and SMRs and could be located near other industrial plants that potentially could use the process heat produced by such a reactor. Some designs use a gas turbine power conversion technology. HTGRs in the small- to medium-sized range are capable of high-temperature operation in excess of 700°C. These plants have the right combination of size, heat output, and passive safety features to make them favorable candidates for use in industrial settings.

The referenced NGNP concept includes a helium-cooled, graphite-moderated, thermal neutron spectrum reactor. The reactor core technology will be either a prismatic block or pebble bed concept using multi-layered graphite-coated particle fuel. The NGNP will produce both electricity and hydrogen by using an indirect cycle with an intermediate heat exchanger to transfer the heat to either a hydrogen-production demonstration facility or a gas turbine. DOE is providing support through NGNP research and development ranging from fundamental nuclear phenomena to the advanced fuels development that could improve the economic and safety performance of these advanced reactors. Figure 2 illustrates an NGNP conceptual design deployed with industrial facilities.

Figure 2. Conceptual Deployment of NGNP with Industrial Facilities
Figure 2. Conceptual Deployment of NGNP with Industrial Facilities (Source: NGNP Alliance 2013)

Reference

NGNP Alliance 2013, HTGR Home Page, http://www.ngnpalliance.org/index.php/htgr, Accessed June 2013.

NEI (Nuclear Energy Institute), 2012, homepage, http://www.nei.org. Accessed March 2013.

Westinghouse Electric Company LLC, 2013, AP1000 Homepage, http://ap1000.westinghousenuclear.com/index.html, Accessed June 2013. Reprinted with permission.