VVER440

VVER-440 is a family of Soviet-designed pressurized water reactors (PWR) produced by OKB Gidropress and operated in the Soviet Union and allied states. The designation VVER stands for Vodo-Vodyanoi Energetichesky Reaktor, and the 440 refers to the approximate electrical output in megawatts. The class was developed in the 1960s and entered commercial service in the 1970s, becoming one of the most widely installed PWR designs in Eastern Europe and the former Soviet Union.

Design and operation: The VVER-440 uses light water as both coolant and neutron moderator. It employs enriched uranium fuel assemblies arranged in a hexagonal lattice and four primary coolant loops that transfer heat to steam generators, which produce steam for a turbine-generator. Reactor protection relies on control rods and boron-containing coolant for reactivity control, with multiple safety systems and containment designed to limit releases in an accident.

Variants and deployment: The class includes early VVER-440/230 units and subsequent VVER-440/213 upgrades. It was widely deployed in the Soviet Union and Eastern Europe, with notable plants such as Paks in Hungary and Bohunice in Slovakia, among others, illustrating the regional role of this reactor design during the late 20th century.

Safety and modernization: Beginning in the 1990s and continuing into the 2000s, many VVER-440 units underwent modernization to enhance safety, reliability, and longevity. Upgrades typically included improved instrumentation and control, containment and safety system enhancements, and replacements of aging components such as steam generators and pumps.