AP1000_brochure

YYoouu ccaann bbee ssuurree ...... iiff iitt’’ss WWeessttiinngghhoouussee Nuclear Power - The Environmentally Clean Option As the world's population rises, so does its reliance on electricity. Likewise, energy demands are soaring as new technologies and expanded development create additional energy needs. This trend will only continue as nations grow and developing countries emerge. For the most part, fossil fuels have powered whole nations and economies. But as fossil fuels dwindle and as the effects of pollution and global warming increase, it's time to look for better solutions to the world's energy needs. Continued reliance on fossil fuels for the vast majority of our energy needs is simply not realistic. Viewing the situation in a worldwide context magnifies the problem. With an additional two billion people expected to need energy by 2020, fossil fuels cannot adequately satisfy the demand without further harming the environment. Likewise, renewable energy sources are still in their infancy, as well as being an unrealistic means to provide baseload generation. It's time to realize a generation of power that is safe, plentiful, economical and clean. It's time for a new generation of nuclear power. Nuclear Power - The Environmentally Clean Option 1 The Nuclear Renaissance Starts Here. TM Featuring proven technology and innovative passive safety systems, the Westinghouse AP1000 TM pressurized water reactor can achieve competitive generation costs in the current electricity market without emitting greenhouse gases and further harming the environment. Westinghouse Electric Company, the pioneer in nuclear energy, once again sets a new industry standard with the AP1000. The AP1000 is the safest and most economical nuclear power plant available in the worldwide commercial marketplace, and is the only Generation III+ reactor to receive Design Certification from the U.S. Nuclear Regulatory Commission (NRC). The established design of the AP1000 offers three distinct advantages over other designs: Unequaled safety Economic competitiveness Improved and more efficient operations Based on nearly 20 years of research and development, the AP1000 builds and improves upon the established technology of major components used in current Westinghouse-designed plants. Components such as steam generators, digital instrumentation and controls, fuel, pressurizers, and reactor vessels are currently in use around the world and have years of proven, reliable operating experience. Historically, Westinghouse plant designs and technology have forged the cutting edge of nuclear plant technology around the world. Today, nearly 50 percent of the world's 440 nuclear plants are based on Westinghouse technology. Westinghouse continues to be the nuclear industry's global leader. (Generation III+ is the Department of Energy's nomenclature for Generation III Advanced Light Water Reactors with improved economics and safety.) AP1000 is a trademark of Westinghouse Electric Company LLC 2 at a Glance The AP1000TM is a two-loop pressurized water reactor (PWR) that uses a simplified, innovative and effective approach to safety. With a gross power rating of 3,415 megawatt thermal (MWt) and a nom- inal net electrical output of 1,117 megawatt electric (MWe), the AP1000, with a 157-fuel-assembly core, is ideal for new baseload generation. The standardized reactor design complies with the Advanced Light Water Reactor Utility Requirements Document (URD). The AP1000 received Final Design Approval from the U.S. NRC in September 2004, and Design Certification in December 2005. The AP1000 is the first and only Generation III+ reactor to receive such certification from the NRC. Additionally the European Utility Requirements (EUR) organization certified that the AP1000 pressurized water reactor has successfully passed all the steps of analysis for compliance with European Utility Requirements, confirming that the AP1000 can be successfully deployed in Europe. Simplified Plant Design Simplification was a major design objective of the AP1000. Simplifications in overall safety systems, nor- mal operating systems, the control room, construction techniques, and instrumentation and control systems provide a plant that is easier and less expensive to build, operate, and maintain. Plant sim- plifications yield fewer components, cable, and seismic building volume, all of which contribute to consid- erable savings in capital investment, and lower operation and maintenance costs. At the same time, the safety margins for AP1000 have been increased dramatically over currently operating plants. The Technology The AP1000 is comprised of components that incorporate many design improvements distilled from 50 years of successful operating nuclear power plant experience. The reactor vessel and internals, steam generator, fuel, and pressurizer designs are improved versions of those found in cur- rently operating Westinghouse-designed PWRs. The reactor coolant pumps are canned- motor pumps, the type used in many other industrial applications where reliability and long life are paramount requirements. Licensed Passive Safety Systems The unique feature of the AP1000 is its use of natural forces - natural circulation, gravity, convection and compressed gas - to operate in the highly unlikely event of an accident, rather than relying on operator actions and ac power. Even with no operator action and a complete loss of all on-site and off-site ac power, the AP1000 will safely shut down and remain cool. Because natural forces are well understood and have worked as intended in large-scale testing, no demonstration plant is required. The Westinghouse advanced passive reactor design underwent the most thorough pre-construction licensing review ever conducted by the U.S. NRC. Large Safety Margins The AP1000 meets the U.S. NRC deterministic-safety and probabilistic-risk criteria with large margins. The safety analysis is documented in the AP1000 Design Control Document (DCD) and Probabilistic Risk Assessment (PRA). Results of the PRA show a very low core damage frequency (CDF) that is 1/100 of the CDF of currently operating plants and 1/20 of the CDF deemed acceptable in the Utility Requirements Document for new, advanced reactor designs. It follows that the AP1000 also improves upon the probability of large release goals for advanced reactor designs in the event of a severe accident scenario to retain the molten core within the reactor vessel. Ready for Implementation Having received Design Certification, the AP1000 has the highest degree of design completion of any Generation III+ plant design. Demonstrating confidence in the AP1000 plant design and its readiness for implementation, several U.S. utilities have selected the AP1000 design in their app- lications to the U.S. NRC for combined construction and operating licenses (COL). Additionally, China is building four AP1000s with the first unit scheduled to be online by 2013. 4 Unequaled Safety The AP1000TM pressurized water reactor is based on a simple concept: in the event of a design-basis acci- dent, such as a main coolant-pipe break, the plant is designed to achieve and maintain safe shutdown condition without operator action, and without the need for ac power or pumps. Rather than relying on active components, such as diesel generators and pumps, the AP1000 relies on natural forces - gravity, natural circulation, and compressed gases - to keep the core and the containment from overheating. The AP1000 provides multiple levels of defense for accident mitigation (defense-in-depth), resulting in extremely low core-damage probabilities while minimizing the occurrences of containment flood- ing, pressurization, and heat-up. Defense-in-depth is integral to the AP1000 design, with a multitude of individual plant features including the selection of appropriate materials; quality assurance during design and construction; well-trained operators; and an advanced control system and plant design that provide substantial margins for plant operation before approaching safety limits. In addition to these protections, the following features contribute to defense-in-depth of the AP1000: Non-safety Systems. The non safety-related systems respond to the day-to-day plant transients, or fluctuations in plant conditions. For events that could lead to overheating of the core, these highly reliable non-safety systems actuate automatically to provide a first level of defense to reduce the likelihood of unnecessary actuation and operation of the safety-related systems. Passive Safety-Related Systems. The AP1000 safety-related passive systems and equipment are sufficient to automatically establish and maintain core cooling and containment integrity indefinitely following design-basis events, assuming the most limiting single failure, with no operator action, and no on-site or off-site ac power sources. An additional level of defense is provided through diverse mitigation functions that are included within the passive safety- related systems. In-vessel Retention of Core Damage. The AP1000 is designed to drain the high capacity in-containment refueling water storage tank (IRWST) water into the reactor cavity in the event that the core has overheated. This provides cooling on the outside of the reactor vessel preventing reactor vessel failure and subsequent spilling of molten core debris into the con- tainment. Retention of debris in the vessel significantly reduces uncertainty in the assessment of containment failure and radioactive release to the environment due to ex-vessel severe accident phenomena such as the interaction of molten core material with concrete. Fission Product Release. Fuel cladding provides the first barrier to the release of radiation in the highly unlikely event of an accident. The reactor coolant pressure boundary, in particular the reactor pressure vessel and the reactor coolant piping, provide independent barriers to prevent the release of radiation. Furthermore, in conjunction with the surrounding shield building, the steel containment vessel provides additional protection by establishing a third barrier and by providing natural convection air currents to cool the steel containment. The natural convection cooling can be enhanced with evaporative cooling by allowing water to drain from a large tank located at the top of the shield building on to the steel containment. AP1000 exceeds safety goals 5 Non Safety-related Active Systems for Defense-in-Depth Many of the active safety-related systems in existing and evolutionary PWR designs are retained in the AP1000 but are designated as non safety-related. The AP1000 active non safety-related systems support normal operation and are also the first line of defense in the event of transients or plant upsets. Although these systems are not credited in the safety analysis evaluation, they provide additional defense-in-depth by adding a layer of redundancy and diversity. In addition to contributing to the very low core damage frequency (CDF), the non safety-related, active systems require fewer in-service inspections, less testing and maintenance, and are not included in the simplified technical specifications. For defense-in-depth, most planned maintenance for these non- safety systems can be performed while the plant is operating. Examples of non safety-related systems that provide defense-in-depth capabilities for the AP1000 design include the chemical and volume control system, normal residual heat removal system, and the startup (auxillary) feedwater system. These systems utilize non-safety support systems such as the standby diesel generators, the component-cooling water system, and the service water system. The AP1000 also includes other active non safety-related systems, such as the heating, ventilation and air-conditioning (HVAC) systems, which remove heat from the instrumentation and control (I&C) cabinet rooms and the main control room. These are, in simpler form in the AP1000, familiar systems that are used in current PWRs as safety systems. In the AP1000, these HVAC systems are a simplified non-safety first line of defense, which are backed up by the ultimate defense, the passive safety-grade systems. This defense-in-depth class of systems includes the containment hydrogen control system, which consists of the hydrogen monitoring system, passive autocatalytic hydrogen recombiners, and hydrogen igniters (powered by batteries). Probabilistic Risk Assessment (PRA) From a letter dated July 20, 2004, from the Chairman of the Advisory Committee on Reactor Safeguards to the Chairman of the U.S. NRC on its Reactor Safeguards Report about the safety aspects of the Westinghouse Electric Company Application for Certification of the AP1000 Passive Plant Design: "The AP1000 Design Certification application included a PRA in accordance with regulatory requirements. This PRA was done well and rigorous methods were used. We found that this PRA was acceptable for certification purposes. The mean estimates of the risk metrics are: “These risk metrics are well within the agency's expectations for advanced plants. The fact that the PRA was an integral part of the design process was significant to achieving this estimated low risk." 6 Passive Safety Systems A major safety advantage of passive plants versus current or evolutionary light water reactors (LWRs) is that long-term accident mitigation is maintained without operator action or reliance on off-site or on-site ac power. The AP1000 uses extensively analyzed and tested passive safety systems to improve the safety of the plant. The Advisory Council on Reactor Safeguards (ACRS) and the U.S. NRC have scrutinized these systems and ruled that they meet the U.S. NRC single-failure criteria, and other safety criteria such as Three Mile Island lessons learned, and generic safety issues. The AP1000 passive safety systems require no operator actions to mitigate design-basis accidents. These systems use only natural forces such as gravity, natural circulation and compressed gas to achieve their safety function. No pumps, fans, diesels, chillers or other active machinery are used, except for a few simple valves that automatically align and actuate the passive safety systems. To provide high reliability, these valves are designed to move to their safeguard positions upon loss of power or upon receipt of a safeguards actuation signal- a single move powered by multiple, reliable Class 1E dc power batteries. The passive safety systems do not require the large network of active safe- ty support systems (ac power, diesels, HVAC, pumped cooling water) that are needed in typical nuclear plants. As a result, in the case of the AP1000, those active support systems no longer must be safety class, and they are either simplified or eliminated. With less safety-grade equipment, the seismic Category 1 building volumes needed to house safety-grade equipment are greatly reduced. In fact, most of the safety equipment can now be located within containment, resulting in fewer containment penetrations. The AP1000 passive safety systems include: Passive core cooling system (PXS) Containment isolation Passive containment cooling system (PCS) Main control room emergency habitability system Passive Core Cooling System The AP1000 passive core cooling system (PXS) performs two major functions: Safety injection and reactor coolant makeup from the following sources: • Core makeup tanks (CMTs) • Accumulators • In-containment refueling water storage tank (IRWST) • In-containment passive long-term recirculation Passive residual heat removal (PRHR) utilizing: • Passive residual heat removal heat exchanger (PRHR HX) • IRWST Safety injection sources are connected directly to two nozzles dedicated for this purpose on the reactor vessel. These connections, which have been used before on two-loop plants, reduce the possibility of spilling part of the injection flow in a large break loss-of-coolant accident. High Pressure Safety Injection with CMTs Core makeup tanks (CMTs) are called upon following transients where the normal makeup system is inadequate or is unavailable. Two core makeup tanks (CMTs) filled with borated water in two parallel 7 trains are designed to function at any reactor coolant system (RCS) pressure using only gravity, and the temperature and height differences from the reactor coolant system cold leg as the motivating forces. These tanks are designed for full RCS pressure and are located above the RCS loop piping. If the water level or pressure in the pressurizer reaches a set low level, the reactor, as well as the reactor coolant pumps, are tripped and the CMT discharge isolation valves open automatically. The water from the CMTs recirculates then flows by gravity through the reactor vessel. Medium Pressure Safety Injection with Accumulators As with current pressurized water reactors, accumulators are required for large loss-of-coolant acci- dents (LOCAs) to meet the immediate need for higher initial makeup flows to refill the reactor vessel lower plenum and downcomer following RCS blowdown. The accumulators are pressurized to 700 psig with nitrogen gas. The pressure differential between the pressurized accumulators and the drop- ping RCS pressure ultimately forces open check valves that normally isolate the accumulators from the RCS. Two accumulators in two parallel trains are sized to respond to the complete severance of the largest RCS pipe by rapidly refilling the vessel downcomer and lower plenum. The accumulators con- tinue delivery to supplement the CMTs in maintaining water coverage of the core. Low Pressure Reactor Coolant Makeup from the IRWST Long-term injection water is supplied by gravity from the large IRWST, which is located inside the containment at a height above the RCS loops. This tank is at atmospheric pressure and, as a result, the RCS must be depressurized before injection can occur. The AP1000 automatically controls depressurization of the RCS to reduce its pressure to near atmospheric pressure, at which point the gravity head in the IRWST is sufficient to overcome the small RCS pressure and the pressure loss in the injection lines to provide IRWST water to the reactor. Passive Residual Heat Removal The AP1000 has a passive residual heat removal (PRHR) subsystem that protects the plant against transients that upset the normal heat removal from the primary system by the steam generator feed- water and steam systems. The passive RHR subsystem satisfies the U.S. NRC safety criteria for loss of feedwater, feedwater-line breaks, and steam-line breaks with a single failure. The system includes the passive RHR heat exchanger consisting of a 100-percent capacity bank of tubes located within the IRWST. This heat exchanger is connected to the reactor coolant system in a natural circulation loop. The loop is isolated from the RCS by valves that are normally closed, but will open if power is lost or upon other signals from the instrumentation and control protection system. The difference in temperature and the elevation difference between the hot inlet water and the cold outlet water of the heat exchanger drives the natural circulation loop. If the reactor coolant pumps are running, the passive RHR heat exchange flow will be increased. The IRWST is the heat sink for the passive RHR heat exchanger. The IRWST water volume is suffi- cient to absorb decay heat for about two hours before the water starts to boil. After that, the steam from the boiling IRWST condenses on the steel containment vessel walls and then drains back into the IRWST by specially designed gutters. 8 Automatic Depressurization System The automatic depressurization system (ADS) depressurizes the reactor coolant system (RCS) and enables lower pressure safety injec