VVER

VVER power stations have been installed in Russia, Ukraine, Belarus, Armenia, China, the Czech Republic, Finland, Hungary, Slovakia, Bulgaria, India, and Iran.

Countries that are planning to introduce VVER reactors include Bangladesh, Egypt, Jordan, and Turkey.

The VVER-1200 is the version currently offered for construction, being an evolution of the VVER-1000 with increased power output to about 1200 MWe (gross) and providing additional passive safety features.

The main distinguishing features of the VVER[3] compared to other PWRs are: Reactor fuel rods are fully immersed in water kept at (12,5 / 15,7 / 16,2 ) MPa (1812/2277/2349 psi) pressure respectively so that it does not boil at the normal (220 to over 320 °C [428 to >608°F]) operating temperatures.

Should coolant circulation fail, the neutron moderation effect of the water diminishes due to increased heat which creates steam bubbles which do not moderate neutrons, thus reducing reaction intensity and compensating for loss of cooling, a condition known as negative void coefficient.

These rods are made from a neutron absorbing material and, depending on depth of insertion, hinder the chain reaction.

[13] A typical design feature of nuclear reactors is layered safety barriers preventing escape of radioactive material.

It does not have the graphite-moderated RBMK's risk of increased reactivity and large power transients in the event of a loss of coolant accident.

The RBMK reactors were also constructed without containment structures on grounds of cost due to their size; the VVER core is considerably smaller.

[14] In 2024 Rosatom started testing fuel which contains neutron absorber erbium and uranium enriched to 5% (instead of typical 3%-4.95% range).

As the V-230 and older models were from the outset not built to resist a design-critical large pipe break, the manufacturer added with the newer model V-213 a so called Bubble condenser tower, that – with its additional volume and a number of water layers – aims to suppress the forces of the rapidly escaping steam without the onset of a containment-leak.

As a consequence, all member-countries with plants of design VVER-440 V-230 and older were forced by the politicians of the European Union to shut them down permanently.

Whereas in the case of the Greifswald Nuclear Power Plant, the German regulatory body had already taken the same decision in the wake of the fall of the Berlin Wall.

A mid-life major overhaul including a complete replacement of critical parts such as fuel and control rod channels was thought necessary after that.

[17] In 2018 Rosatom announced it had developed a thermal annealing technique for reactor pressure vessels which ameliorates radiation damage and extends service life by between 15 and 30 years.

In July 2012 a contract was agreed to build two AES-2006 in Belarus at Ostrovets and for Russia to provide a $10 billion loan to cover the project costs.

[26] The plant supply contract was signed in 2013, but terminated in 2022 mainly due to Russian invasion of Ukraine.

[32] In 2025 welding lasted for 20 days was completed for the upper half of the VVER-1200 reactor vessel for El Dabaa Nuclear Power Plant, new materials and technologies will help to increase the service life to 100 years.

[38] The main improvements from the VVER-1200 are:[4] The construction of the first two VVER-TOI units was started in 2018 and 2019 at the Kursk II Nuclear Power Plant.

[41][4] In June 2019 the VVER-TOI was certified as compliant with European Utility Requirements (with certain reservations) for nuclear power plants.

A WWER-1000 (or VVER-1000 as a direct transliteration of Russian ВВЭР-1000), a 1000 MWe Russian nuclear power reactor of PWR type.
1: control rod drives
2: reactor cover [ 10 ] or vessel head [ 11 ]
3: Reactor pressure vessel
4: inlet and outlet nozzles
5: reactor core barrel or core shroud
6: reactor core
7: fuel rods
The arrangement of hexagonal fuel assemblies compared to a Westinghouse PWR design. Note that there are 163 assemblies on this hexagonal arrangement and 193 on the Westinghouse arrangement.
VVER-440 reactor hall at Mochovce Nuclear Power Plant
Layout of the four primary cooling circuits and the pressurizer of a VVER-1000
Construction of a VVER-1000 reactor vessel at Atommash .
The two VVER-440 units in Loviisa , Finland have containment buildings that fulfil Western safety standards.
Control room of a VVER-1000 in 2009, Kozloduy Unit 5