United States Nuclear Regulatory Commission - Protecting People and the Environment
Home > NRC Library > Document Collections > Fact Sheets > Backgrounder on New Nuclear Plant Designs

Backgrounder on New Nuclear Plant Designs

Printable Version

On this page:


The NRC has long encouraged standardized nuclear power plant designs to help enhance safety and improve the licensing process. The Commission expects advanced reactors' safety systems to be simpler and use natural effects such as gravity or other innovative approaches. The agency's new reactor regulations (Part 52 in Title 10 of the Code of Federal Regulations) provide a predictable certification review for new nuclear plant designs. The certification process, based on decades of experience and research involving reactor design and operation, includes public participation as it resolves safety issues.

Pre-Application Review Process

The NRC's July 1986 "Statement of Policy for Regulation of Advanced Nuclear Power Plants" encourages reactor designers to discuss licensing issues with agency staff before submitting a full license application. The NRC provided additional "pre-application" guidance for advanced reactor design reviews in the June 1988 NUREG-1226, "Development and Utilization of the NRC Policy Statement on the Regulation of Advanced Nuclear Power Plants." Pre-application reviews of advanced reactor designs are expected to identify:

  • any issues that could require Commission policy decisions,
  • major technical issues that could be covered by existing NRC regulations, and
  • any research needed to resolve identified issues.

To top of page

Design Certification Review

The NRC certifies a standard reactor by writing the approved design into the regulations through a rulemaking. This rulemaking certifies a design for 15 years. Applicants must provide enough information to show their design meets the NRC's safety standards. Applicants must also show their design resolves any existing generic safety issues, as well as issues that arose after the Three Mile Island accident. Applications must include a detailed analysis of the design's appropriate response to accidents or natural events, as well as all the inspections, tests, analyses and acceptance criteria to verify the construction of key design features. The NRC also requires design certification applicants to assess how the designs protect the reactor and spent fuel pool from the effects of a large commercial aircraft impact. The review does not look at site-specific issues.

Certified Designs

The NRC has certified four designs that utilities can reference when applying for a combined license (COL) to build and operate a nuclear power plant. They are:

  1. Advanced Boiling Water Reactor (ABWR) design by GE Nuclear Energy (May 1997, amended to assess aircraft impacts in 2011, renewal under review);

  2. System 80+ design by Westinghouse (formerly ABB-Combustion Engineering) (May 1997, expired June 2012);

  3. AP600 design by Westinghouse (December 1999); and

  4. AP1000 (Amended) by Westinghouse (January 2012).

  Artist's rendering of a nuclear plant

Active Reviews

  • ABWR Renewal - Toshiba applied in October 2010 to renew the version of the ABWR used in the South Texas Project new reactor license application. GE-Hitachi applied for renewal of its ABWR version in December 2010. The staff expects the renewal reviews to continue through 2015.
Artist's rendering of ESBWR plant design cutaway  
  • ESBWR - GE-Hitachi applied to certify the ESBWR on Aug. 24, 2005. The staff issued a final design approval in March 2011 and expects to complete the rulemaking to certify the ESBWR in late 2014.
  • EPR - Areva applied to certify the EPR on Dec. 11, 2007. The staff expects the certification process to continue through 2015.

  • US-APWR - Mitsubishi Heavy Industries (MHI), a Japanese firm, applied to certify the U.S.-specific version of its Advanced Pressurized Water Reactor Dec. 31, 2007. The staff expects certification to continue through 2015

Pre-Application Reviews

  • PBMR - A South African firm, Pebble Bed Modular Reactor (PBMR) Pty. Limited notified the NRC in a letter dated Feb. 18, 2004, that it intended to apply for design certification in the near future and requested discussions with the NRC to plan the scope and content of the preapplication review. NRC staff have held several public meetings with PBMR to discuss its activities and plans to submit pre-application information. PBMR has continued to submit pre-application information through 2007 and expects to submit a design certification application in late 2009.

Artist's rendering of a cutaway reactor model
  • mPower - On April 14, 2014, Babcock & Wilcox announced the restructuring of its small modular reactor program to focus on mPower technology development.  The company has yet to determine a date for submitting an application. The NRC continues to examine policy issues regarding all small modular reactor designs.

  • NuScale - NuScale notified the NRC in a March 2014 letter it intends to submit its small modular design for certification in the second half of 2016. The NRC continues to examine policy issues regarding all small modular reactor designs.

  • SMR-160 - Holtec notified the NRC in a January 2014 letter that the company has yet to determine a date for submitting its small modular SMR-160 design for certification. The NRC continues to examine policy issues regarding all small modular reactor designs.

  • Westinghouse SMR - Westinghouse notified the NRC in a January 2014 letter that it is re-evaluating the date for submitting its small modular design for certification. The NRC continues to examine policy issues regarding all small modular reactor designs.

Inactive Reviews

  • IRIS - In May 2006, Westinghouse and the NRC staff discussed the International Reactor Innovative and Secure. Westinghouse submitted topical reports related to the planned test programs and would need to submit additional reports to support more pre-application discussions.

  • Next-Generation Nuclear Plant (NGNP) - The Department of Energy and the NRC are following direction from the Energy Policy Act of 2005 in pursuing the NGNP advanced reactor project. DOE continues discussions with potential industry partners to select a reactor design for eventual NRC certification review.  On July 17, 2014, the NRC provided feedback to the Department of Energy on key licensing issues for the NGNP (ML14174A626).

  • PBMR - A South African firm, Pebble Bed Modular Reactor (PBMR) Pty. Limited notified the NRC in a letter dated Feb. 18, 2004, that it intended to apply for design certification. NRC staff held several public meetings with PBMR to discuss its activities and plans to submit pre-application information. PBMR has been mentioned as a possible NGNP design choice.

  • Toshiba 4S - On Feb. 2, 2005, the NRC staff met with the city manager and vice mayor of Galena, Ala., to discuss the city's plans to build a Toshiba 4S reactor to provide its electricity. Toshiba held pre-application discussions with NRC staff through 2008.

To top of page

Regulatory Structure for New Plant Licensing

In 2007, the NRC recognized that reactor vendors could submit designs that use advanced technologies. The NRC has prepared for this by developing technology-neutral guidelines for plant licensing to encourage future designs to incorporate additional safety and security where possible. The staff issued in December 2007 a "Feasibility Study for a Risk-Informed and Performance-Based Regulatory Structure for Future Plant Licensing" (NUREG-1860).

The NRC developed the "Report to Congress: Advanced Reactor Licensing," in August 2012 (ML12153A014) to address a provision in the Consolidated Appropriations Act, 2012. This report identifies the strategy to enhance regulatory predictability and stability for advanced reactors.

In 2013, the DOE Office of Nuclear Energy and the NRC began an initiative to address the "General Design Criteria for Nuclear Power Plants," Appendix A to 10 CFR Part 50, relative to licensing advanced non-light water reactor designs. DOE will complete the initial phase of this by the end of 2014. Eventually, the NRC expects to issue regulatory guidance.

Design Descriptions

Artist's rendering of a cutaway reactor model   ABWR:  The ABWR, with a rated power of 1,300 megawatts electric (MWe) improves on the electronics, computer, turbine and fuel technology of existing BWRs. The design's safety enhancements include protection against overpressurizing the containment, passive methods to cool accident debris, an independent water resupply system, three emergency diesels and a combustion turbine as an alternate emergency power source

AP600:  The Advanced Passive 600 is a 600 MWe advanced pressurized water reactor that incorporates passive safety systems and simplified system designs. The passive systems respond to emergencies by relying on gravity and other natural forces rather than electric-powered pumps and other support systems. The system uses redundant, non-safety-related equipment and systems where possible to avoid unnecessary safety-related system activation.

AP1000 (Amended):  The amended Advanced Passive 1000 is a larger version of the AP600. This 1,100 MWe advanced pressurized water reactor also relies on passive safety systems and simplified system designs. It is similar to the AP600 design but generates more power by accommodating more fuel in a longer reactor vessel and using larger steam generators and a larger pressurizer.

APR 1400: The APR 1400 is an approximately 1,300 MWe pressurized water reactor based on the Korean Standard Nuclear Power Plant. Its updated safety features include additional systems to add cooling water in an emergency, systems to prevent hydrogen buildup during an accident and a floodable space below the reactor to catch and cool any material that escapes the reactor.

EPR:  The Evolutionary Power Reactor is a 1,600 MWe pressurized water reactor with four sets of active safety systems, each capable of cooling the reactor on its own. Other EPR safety features include a double-walled containment, and a "core catcher" for holding and cooling any melted reactor core materials after a severe accident. The first EPR is under construction at the Olkiluoto site in Finland, with another being built at the Flammanville site in France.

  Artist's rendering of a cutaway reactor model

ESBWR:  The Economic and Simplified Boiling Water Reactor is a 1,500 MWe boiling water reactor with passive safety features. This design is based on the 670 MWe Simplified BWR (SBWR) and also utilizes some ABWR features. The ESBWR enhances natural heat transport by using a taller vessel, a shorter core, and by enhancing water flow. The design's isolation condenser system controls high-pressure water levels and removes decay heat when active systems are unavailable. After the automatic depressurization system operates, a gravity-driven cooling system controls low-pressure water levels. Another passive system cools the reactor containment.

IRIS:  The International Reactor Innovative and Secure is a pressurized, medium-power (335 MWe) reactor, under development for several years by an international consortium. The IRIS "integral" reactor vessel houses not only the nuclear fuel, control rods and neutron reflector, but also all the major reactor coolant system components including pumps, steam generators and pressurizer. The IRIS integral vessel is larger than a traditional PWR pressure vessel, but the IRIS containment is a fraction of the size of comparable current reactor containment designs.

Artist's rendering of a cutaway reactor model


PBMR:  The Pebble Bed Modular Reactor is a high-temperature reactor cooled by helium. A single PBMR consists of eight reactor modules, each generating 165 MWe. The design can store 10 years' worth of spent fuel, with additional storage capability in onsite concrete silos. The PBMR core is based on German high-temperature gas-cooled reactor technology and uses baseball-sized graphite spheres to hold ceramic-coated uranium fuel.

System 80+:  This 1,300 MWe pressurized water reactor is an improved Combustion Engineering System 80 nuclear steam supply system and a balance-of-plant design developed by Duke Power Co. The System 80+ design's safety systems provide emergency core cooling, feedwater and decay heat removal. The design also has a reactor depressurization system, a gas-turbine generator as an alternate AC power source beyond the required emergency diesel generators, and an in-containment refueling water storage tank to enhance the reactor's safety and reliability.

Toshiba 4S:  The Toshiba 4S reactor design would generate about 10 MWe. The reactor's steel-clad metal-alloy fuel would remain in place for the design's 30-year operating lifetime. Three piping loops would cool the reactor: the primary loop (using molten sodium), an intermediate sodium loop between the radioactive primary system and the steam generators, and a water loop to generate steam for the turbine. The 4S layout places the pumps and intermediate heat exchanger inside the primary vessel.

US-APWR:  The Mitsubishi Heavy Industry US-APWR design is a 1,700 MWe pressurized water reactor being licensed and built in Japan. It includes high-performance steam generators, a neutron reflector around the core to increase fuel economy, redundant core cooling systems and refueling water storage inside the containment building, and fully digital instrumentation and control systems.

August 2014

To top of page

Page Last Reviewed/Updated Friday, December 12, 2014