pwr

A pressurized water reactor (PWR) is a type of light-water nuclear reactor. It uses ordinary water as both coolant and neutron moderator and keeps the water in the reactor core under high pressure to prevent boiling. Heat produced by fission is transferred to a secondary loop, where steam is generated to drive a turbine and produce electricity.

In a PWR, the primary coolant loop circulates water through the reactor vessel, absorbing heat while remaining liquid at about 150–160 bar. The heat is transferred via steam generators to a secondary loop, whose water is allowed to boil and form steam that drives the turbine. The core is fed with enriched uranium fuel assemblies, and the same water also serves as a neutron moderator.

Reactor control is achieved with neutron-absorbing control rods and chemical volume control systems. The plant design includes multiple containment barriers and redundant cooling systems to remove residual heat after shutdown. A characteristic feature is the avoidance of boiling in the reactor core, contributing to a stable response to power changes due to the high-pressure primary circuit.

PWRs were developed in the 1950s and 1960s and became the most widely deployed class of commercial nuclear reactors. The Shippingport Atomic Power Station in the United States was the first large-scale PWR to generate electricity in 1957. Today, standardized designs such as AP1000 and regional variants like the EPR are operated or planned worldwide, including in the United States, France, Japan, South Korea, and China.

Typical electrical output per unit ranges roughly from 600 to 1,700 megawatts, with thermal efficiency around one-third. PWRs have shaped global nuclear safety standards, fuel cycles, and plant design practices, remaining a dominant technology in civilian nuclear power.

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