High Quality Content by WIKIPEDIA articles! The VVER, or WWER, (from Russian: Водо-водяной энергетический реактор; transliterates as Vodo-Vodyanoi Energetichesky Reactor; Water-Water Energetic Reactor) is a series of pressurised water reactors (PWRs) originally developed by the Soviet Union, and now Russia, by OKB Gidropress. Power output ranges from 440 MWe to 1200 MWe with the latest Russian development of the design. VVER power stations are used by Armenia, Bulgaria, China, Czech Republic, Finland, Hungary, India, Iran, Slovakia, Ukraine, and the Russian Federation.