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Backgrounder on New Nuclear Plant Designs

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The NRC encourages standardized nuclear power plant designs to help enhance safety and improve the licensing process. The Commission expects new reactors' safety systems to be simpler and use natural effects (such as gravity) or other innovative approaches. The NRC also regularly discusses new design issues with vendors proposing small modular and advanced (non-light water) reactors. The agency's new reactor regulations (Part 52 in Title 10 of the Code of Federal Regulations) provide a predictable review to approve, or certify, new nuclear plant designs. The NRC based the certification process on decades of experience and research into reactor design and operation. The public can participate as the process resolves safety issues.

Pre-Application Review

The NRC's July 1986 "Statement of Policy for Regulation of Advanced Nuclear Power Plants" encourages reactor designers to discuss licensing issues with the agency 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 new reactor designs are expected to identify and address:

  • unique design features or systems, structures, or components;
  • new methods supporting the acceptability of safety features and/or design basis accidents results especially methods never used by previously approved designs;
  • potential Commission-level policy decisions;
  • major technical issues potentially covered by existing NRC regulations; and
  • potential research to resolve identified issues.

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Design Certification Review

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 closely analyze the design's appropriate response to accidents or natural events, including lessons learned from the Fukushima accident. Applications must also lay out the inspections, tests, analyses and acceptance criteria that will 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. Certification reviews identify key information to consider in site-specific reviews for operating licenses. The NRC certifies acceptable reactor designs by adding them to agency regulations through a rulemaking. This rulemaking certifies a design for 15 years, and a reactor vendor can seek renewal of a certified design.

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Certified Designs

The NRC has certified five designs; two of those approvals have expired. Utilities can reference the other three designs when applying for a combined license (COL) to build and operate a nuclear power plant. The certified designs are:

  Artist's rendering of a nuclear plant

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Active Reviews

ABWR Renewal – GE-Hitachi applied for renewal of its ABWR version in December 2010. The staff expects the renewal review to continue through 2017.

APR 1400 – Korea Electric Power Corporation and Hydro & Nuclear Power applied to certify the design on Dec. 23, 2014. The staff expects the certification review to continue through 2018.

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. NRC review activities have been reduced at the applicant's request. The staff expects the applicant to update its certification review request in 2017.

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Pre-Application Reviews

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 was 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.

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Inactive Reviews

EPR - Areva applied to certify the EPR on Dec. 11, 2007. Areva asked the NRC suspend the EPR review in February 2015.

Next-Generation Nuclear Plant(NGNP) - The Department of Energy and the NRC complied with the Energy Policy Act of 2005 in examining the NGNP advanced reactor project. DOE discussed reactor design options with potential industry partners. On July 17, 2014, the NRC provided feedback to the Department of Energy on key licensing issues for the project (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.

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Regulatory Structure for New Plant Licensing

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

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 discusses enhanced regulatory predictability and stability for advanced reactors.

In 2013, the DOE Office of Nuclear Energy and the NRC began working on how to apply "General Design Criteria for Nuclear Power Plants," Appendix A to 10 CFR Part 50, to advanced non-light water reactor designs. The NRC and DOE have held Advanced Non-Light Water Reactors Workshops on issues related to developing and deploying advanced designs. The NRC has issued a "Vision and Strategy" on preparing for non-light water reactor designs.

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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 over pressurizing 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 reduce use of safety-related systems.

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.

ESBWR: The Economic and Simplified Boiling Water Reactor is a 1,500 MWe boiling water reactor with passive safety features. This design builds on the Simplified BWR (SBWR) and includes 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.

  Artist's rendering of ESBWR plant design cutaway

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.

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.

Artist's rendering of a cutaway reactor model


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 2016

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Page Last Reviewed/Updated Monday, December 19, 2016