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Pressurized water reactors (PWRs) are a type of nuclear reactor widely used for electricity generation. They belong to the family of light water reactors, which also includes boiling water reactors (BWRs). This article presents the history and characteristics of PWR technology, aimed at an informed audience unfamiliar with this particular subject.
History
The development of pressurized water reactors began in the USA in the 1950s, under the aegis of the Westinghouse Electric Corporation (1). The first commercial reactor of this type, the Shippingport reactor, was commissioned in 1958 (2). Since then, PWRs have become the world’s most widespread nuclear reactor technology, accounting for around two-thirds of reactors in operation in 2021 (3).
Features
Pressurized water reactors use light water (H2O) as coolant and neutron moderator (4). The nuclear fuel, generally enriched uranium or MOX (a mixture of plutonium and uranium oxides), is contained in fuel rod assemblies (5). The reactor core is surrounded by a pressure vessel to keep the water in a liquid state at high temperatures, generally around 300 to 325°C (6).
The operation of a pressurized water reactor relies on two separate cooling circuits (7). The primary circuit transports the water heated by the nuclear reaction through a steam generator, where it transfers its heat to the water in the secondary circuit. The water in the secondary circuit is then transformed into steam, which is used to drive a turbine and generate electricity. The steam is then condensed and returned to the steam generator to be reheated. This separation of circuits limits the spread of radioactivity in the event of a leak or accident.
Pressurized water reactors are designed with several safety systems, such as containment barriers, emergency cooling systems and automatic shutdown systems in the event of abnormal conditions (8). New-generation reactors, such as the EPR (European Pressurized Reactor) and AP1000, incorporate significant improvements in safety and efficiency over previous designs (9).
Statistics and facts
In 2021, there were around 440 nuclear reactors in operation worldwide, of which around 295 were pressurized water reactors (10). Countries with the highest number of PWR reactors in operation include the USA, France, China and Japan (11).
Pressurized water reactors typically have a power generation capacity of between 600 and 1,600 megawatts (MWe) (12). New-generation reactors, such as the EPR and AP1000, have even higher production capacities, up to 1,700 MWe (13).
In terms of energy production, pressurized water reactors account for a significant share of global nuclear power generation. In 2020, nuclear reactors generated around 10% of the world’s electricity, with pressurized water reactors contributing around 7% (14).
Pressurized water reactors are also used in marine applications, notably to power submarines and aircraft carriers. Naval reactors are generally smaller and more compact than their land-based counterparts, with power ratings ranging from a few dozen to a few hundred megawatts thermal (MWth) (15).
Outlook
Pressurized water reactor technology continues to develop, with the introduction of new designs and improvements to safety and efficiency systems. New-generation reactors, such as the EPR and AP1000, offer significant performance and safety advantages over older designs (16).
However, the deployment of new pressurized water reactors faces challenges such as high construction costs, competition with other energy sources, environmental concerns and nuclear waste management (17). In the long term, the future of PWR technology will depend on the nuclear industry’s ability to overcome these challenges and meet safety, economic and sustainability requirements.
Conclusion
Pressurized water reactors are a proven and widely deployed nuclear technology, with a long history and many achievements in power generation. Although faced with challenges, PWR technology continues to evolve and adapt to meet future energy, safety and sustainability needs.