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Backgrounder on New Nuclear Plant DesignsBackgroundThe NRC has long sought standardization of nuclear power plant designs, and the enhanced safety and licensing reform that standardization could make possible. The Commission expects advanced reactors to be safer and use simplified, passive or other innovative means to accomplish their safety functions. The NRC's regulation (Part 52 to Title 10 of the Code of Federal Regulations) provides a predictable licensing process including certification of new nuclear plant designs. This process reflects decades of experience and research involving reactor design and operation. The design certification process provides for early public participation and resolution of safety issues prior to an application to construct a nuclear power plant. Pre-Application Review ProcessThe NRC's "Statement of Policy for Regulation of Advanced Nuclear Power Plants," dated July 8, 1986, encourages early discussions, before a license application is submitted, between NRC and reactor designers to provide licensing guidance. In June 1988, the NRC issued NUREG-1226, "Development and Utilization of the NRC Policy Statement on the Regulation of Advanced Nuclear Power Plants." This document provides guidance on the implementation of the policy and describes the approach used by NRC in its review of advanced reactor design concepts. In general, the NRC conducts pre-application reviews of advanced reactor designs to indentify:
Design Certification Review ProcessThe review process for new reactor designs involves certifying standard reactor designs, independent of a specific site, through a rulemaking (Subpart B of Part 52). This rulemaking can certify a reactor design for 15 years. Design certification applicants must provide the technical information necessary to demonstrate compliance with the safety standards set forth in applicable NRC regulations (10 CFR Parts 20, 50, 73, and 100). Applicants must also provide information to close out unresolved and generic safety issues, as well as issues that arose after the Three Mile Island accident. The application must include a detailed analysis of the design's vulnerability to certain accidents or events, and inspections, tests, analyses, and acceptance criteria to verify the key design features. The NRC is considering a new rule that would require design certification applicants to assess their plant’s level of built-in protection for avoiding or mitigating the effects of a large commercial aircraft impact, reducing the need for human intervention to protect public health and safety. Currently there are four certified reactor designs that can be referenced in an application for a combined license (COL) to build and operate a nuclear power plant. They are:
Reactor Design Review StatusThe status of advanced reactor applications for both active and inactive design reviews is provided below in alphabetical order. A description of each design follows. Active Reviews
Pre-Application Reviews
Inactive Reviews
Regulatory Structure for New Plant LicensingIn the longer term, the NRC may be called on to review reactor designs that use a broader range of technology than those currently under review. Therefore, the NRC staff may develop technology-neutral guidelines for plant licensing in the future. These guidelines are intended to encourage future designs to incorporate additional safety and security where possible. The staff issued in Dec. 2007 a “Feasibility Study for a Risk-Informed and Performance-Based Regulatory Structure for Future Plant Licensing” (NUREG-1860). Design Descriptions
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 use natural driving forces without active pumps, diesels, and other support systems after actuation. Use of redundant, non-safety-related, active equipment and systems minimizes unnecessary use of safety-related systems. AP1000:The Advanced Passive 1000 is a larger version of the previously approved AP600 design. This 1,100 MWe advanced pressurized water reactor incorporates passive safety systems and simplified system designs. It is similar to the AP600 design but uses a longer reactor vessel to accommodate longer fuel, and also includes larger steam generators and a larger pressurizer.
ESBWR: The Economic and Simplified Boiling Water Reactor is a 1,500 MWe, natural circulation boiling water reactor that incorporates passive safety features. This design is based on its predecessor, the 670 MWe Simplified BWR (SBWR) and also utilizes features of the certified ABWR. The ESBWR enhances natural circulation by using a taller vessel, a shorter core, and by reducing the flow restrictions. The design utilizes an isolation condenser system for high-pressure water level control and decay heat removal during isolated conditions. After the automatic depressurization system operates, a gravity-driven cooling system provides low-pressure water level control. Containment cooling is provided by a passive system. IRIS: The International Reactor Innovative and Secure is a pressurized light water cooled, medium-power (335 MWe) reactor that has been under development for several years by an international consortium. The IRIS design utilizes an integral reactor coolant system layout. The IRIS 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 size of the IRIS containment is a fraction of the size of corresponding loop reactors.
System 80+: This standard plant design uses a 1,300 MWe pressurized water reactor. It is based upon evolutionary improvements to the standard CE System 80 nuclear steam supply system and a balance-of-plant design developed by Duke Power Co. The System 80+ design has safety systems that provide emergency core cooling, feedwater and decay heat removal. The new design also has a safety depressurization system for the reactor, a combustion turbine as an alternate AC power source, and an in-containment refueling water storage tank to enhance the safety and reliability of the reactor system. Toshiba 4S: The Toshiba 4S reactor design has an output of about 10 MWe. The reactor has a compact core design, with steel-clad metal-alloy fuel. The core design does not require refueling over the 30-year lifetime of the plant. A three-loop configuration is used: primary system (sodium-cooled), an intermediate sodium loop between the radioactive primary system and the steam generators, and the water loop used to generate steam for the turbine. The basic layout is a “pool” configuration, with the pumps and intermediate heat exchanger inside the primary vessel. US-APWR: The Mitsubishi Heavy Industry US-APWR design is an evolutionary 1,700 MWe pressurized water reactor currently being licensed and built in Japan. The design 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. June 2008 |
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