AP1000

AP1000
source
Name	AP1000
Generation	Generation III+
Designer	Westinghouse Electric Company
Coolant	Light water
Moderator	Light water
Fuel	Uranium dioxide
Power	1117 MWe (gross)

AP1000. The AP1000 is a Generation III+ pressurized water reactor designed by the Westinghouse Electric Company. It incorporates advanced passive safety systems that rely on natural forces like gravity and convection to enhance safety and simplify plant design. The design received final design certification from theUnited States Nuclear Regulatory Commission in 2011, paving the way for its construction in several countries.

Design and safety features

The core design philosophy centers on passive safety, utilizing systems like the Passive Core Cooling System and Passive Containment Cooling System which function without active components such as pumps or operator action. Key features include a large water tank located above the steam generator compartment for gravity-fed emergency cooling and a steel containment vessel that promotes natural air circulation for heat removal. This approach significantly reduces the number of valves, pumps, and piping compared to earlier designs like the System 80 or Advanced Boiling Water Reactor, aiming to improve reliability. The design also incorporates lessons from historical events, including those at Three Mile Island and Fukushima Daiichi, to enhance severe accident mitigation.

Development and deployment

The AP1000 design evolved from the earlier AP600 project, with development significantly supported by the United States Department of Energy as part of its advanced reactor programs. The first units to begin construction were Sanmen Nuclear Power Station Unit 1 in Zhejiang province, China, and Haiyang Nuclear Power Plant in Shandong, under agreements with the State Nuclear Power Technology Corporation. In the United States, the Vogtle Electric Generating Plant in Georgia and the now-canceled V.C. Summer Nuclear Generating Station project in South Carolina were the primary deployment sites. International interest has also been shown by countries like the United Kingdom, where the design is under consideration for sites including Moorside.

Technical specifications

The reactor produces approximately 1117 megawatts of electrical power gross from a thermal output of 3400 MWth, utilizing a two-loop pressurized water reactor configuration. The nuclear steam supply system includes two steam generators and four reactor coolant pumps driven by advanced sealless canned motor pumps. The fuel assemblies use uranium dioxide pellets with an enrichment of up to 5% Uranium-235, housed in an alloy of zirconium. The reactor pressure vessel is constructed from low-alloy steel with an internal stainless steel cladding, and the entire plant is designed for a 60-year operational lifespan. The control room integrates advanced digital instrumentation and control systems from companies like Emerson Electric.

Operational history and performance

The world's first AP1000 reactors achieved criticality and grid connection at Sanmen Nuclear Power Station in 2018, followed by units at Haiyang Nuclear Power Plant. These plants, operated by China National Nuclear Corporation and State Power Investment Corporation, respectively, have since entered commercial operation and provide baseload power to regional grids like the East China Power Grid. Performance data from these initial units is used to validate the design's efficiency and safety parameters. The construction and commissioning of units at the Vogtle Electric Generating Plant in the United States, led by Southern Company and Bechtel, have experienced significant delays and cost overruns, impacting the overall deployment timeline in North America.

Economic and regulatory aspects

The economic case for the AP1000 emphasizes standardized design and modular construction techniques to control costs, though projects in the United States have faced substantial financial challenges. Regulatory approval has been a lengthy process, with the design certified by the United States Nuclear Regulatory Commission and undergoing assessment by the Office for Nuclear Regulation in the United Kingdom as part of its Generic Design Assessment. Financing for projects has involved complex arrangements with entities like the United States Department of Energy for loan guarantees and state-level public service commissions, such as the Georgia Public Service Commission. The global market competition includes other Generation III+ designs like the European Pressurized Reactor from Framatome and the VVER-1200 from Rosatom.