VVER

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The VVER, or WWER, (from Russian: Водо-водяной энергетический реактор; transliterates as Vodo-Vodyanoi Energetichesky Reactor; Water-Water Power Reactor) is a series of pressurised water reactor designs originally developed in the Soviet Union, and now Russia, by OKB Gidropress.^[1][2] 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.

The earliest VVERs were built before 1970. The VVER-440 Model V230 was the most common design, delivering 440 MW of electrical power. The V230 employs six primary coolant loops each with a horizontal steam generator. A modified version of VVER-440, Model V213, was a product of the first nuclear safety standards adopted by Soviet designers. This model includes added emergency core cooling and auxiliary feedwater systems as well as upgraded accident localization systems.^[3]

The larger VVER-1000 was developed after 1975 and is a four-loop system housed in a containment-type structure with a spray steam suppression system. VVER reactor designs have been elaborated to incorporate automatic control, passive safety and containment systems associated with Western third generation nuclear reactors.

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.^[4]

In 2012 Rosatom stated that in the future it intended to certify the VVER with the British and U.S. regulatory authorities.^[5]

The Russian abbreviation VVER stands for water-cooled, water-moderated energy reactor. This describes the pressurised water reactor (PWR) design. The main distinguishing features of the VVER^[2] compared to other PWRs are:

• Horizontal steam generators
• Hexahedral fuel assemblies
• No bottom penetrations in the pressure vessel
• High-capacity pressurisers providing a large reactor coolant inventory

Reactor fuel rods are fully immersed in water kept at 15 MPa of pressure so that it does not boil at normal (220 to over 300 °C) operating temperatures. Water in the reactor serves both as a coolant and a moderator which is an important safety feature. Should coolant circulation fail the neutron moderation effect of the water diminishes, reducing reaction intensity and compensating for loss of cooling, a condition known as negative void coefficient. Later versions of the reactors are encased in massive steel pressure shells. Fuel is low enriched (ca. 2.4–4.4% ²³⁵U) uranium dioxide (UO₂) or equivalent pressed into pellets and assembled into fuel rods.

Reactivity is controlled by control rods that can be inserted into the reactor from above. These rods are made from a neutron absorbing material and depending on depth of insertion hinder the chain reaction. If there is an emergency, a reactor shutdown can be performed by full insertion of the control rods into the core.

As stated above, water in the primary circuit is kept under constant pressure to avoid boiling. Since the water transfers all the heat from the core and is irradiated, integrity of this circuit is most crucial. In the circuit four subsystems can be distinguished:

1. Reactor: Water flows through fuel rod assemblies and is heated by the nuclear chain reaction.
2. Volume compensator: To keep the water under constant but controlled pressure, the volume compensator regulates pressure employing self-regulation of saturated steam-water interface and by means of electrical heating and relief valves.
3. Steam Generator: In the steam generator, heat from primary coolant water is used to boil water in the secondary circuit.
4. Pump: The pump ensures proper circulation of the water through the circuit.

To ensure safety primary components are redundant.

The secondary circuit also consists of different subsystems:

1. Steam Generator: Secondary water is boiled taking heat from the primary circuit. Before entering the turbine remaining water is separated from the steam so that the steam is dry.
2. Turbine: The expanding steam drives a turbine, which connects to an electrical generator. The turbine is split into high and low pressure sections. To prevent condensation (Water droplets at high speed damage the turbine blades) steam is reheated between these sections. Reactors of the VVER-1000 type deliver 1 GW of electrical power.
3. Condenser: The steam is cooled and allowed to condense, shedding waste heat into a cooling circuit.
4. Deaerator: Removes gases from the coolant.
5. Pump: The circulation pumps are each driven by their own small steam turbine.

To increase efficiency of the process, steam from the turbine is taken to reheat coolant before the deaerator and the steam generator. Water in this circuit is not supposed to be radioactive.

The cooling circuit is an open circuit diverting water from an outside reservoir such as a lake or river. Evaporative cooling towers, cooling basins or ponds exhaust waste heat from the generation circuit, releasing it into the environment. In addition to generating electricity most VVERs have a capability to supply heat for residential and industrial use. Operational examples of such systems are the plants at Bohunice and Dukovany. ^[6]

A typical design feature of nuclear reactors is layered safety barriers preventing escape of radioactive material. VVER reactors have four layers:

1. Fuel pellets: Radioactive elements are retained within the crystal structure of the fuel pellets.
2. Fuel rods: The zircaloy tubes provide a further barrier resistant to heat and high pressure.
3. Reactor Shell: A massive steel shell encases the whole fuel assembly hermetically.
4. Reactor Building: A concrete containment building that encases the whole first circuit is strong enough to resist the pressure surge a breach in the first circuit would cause.

Currently operating Russian VVERs are inherently safer designs than the RBMK reactors of Chernobyl disaster.^{[citation needed]} The Soviet Union opted to construct graphite-moderated RBMK series nuclear reactors without containment structures on grounds of cost as well as the relative ease of re-fueling RBMK reactors.^{[citation needed]} Fuel elements in a RBMK reactor can be replaced while still operational, allowing continued operation and plutonium extraction compared to the VVER which needs to be shut down. Many levels of protection and containment have both been proposed and constructed for RBMK and VVER type reactors.^{[citation needed]}

When first built the VVER design was intended to be operational for 35 years. A mid-life major overhaul including a complete replacement of critical parts such as fuel and control rod channels was thought necessary after that.^[7] Since RBMK reactors specified a major replacement programme at 35 years designers originally decided this needed to happen in the VVER type as well, although they are of more robust design than the RBMK type. Most of Russia's VVER plants are now reaching and passing the 35 year mark. More recent design studies have allowed for an extension of lifetime up to 50 years with replacement of equipment. New VVERs will be nameplated with the extended lifetime.

In 2010 the oldest VVER-1000, at Novovoronezh, was shut down for modernization to extend its operating life for an additional 30 years; the first to undergo such an operating life extension. The works include the modernization of management, protection and emergency systems, and improvement of security and radiation safety systems.^[8]

The VVER-1200 (or NPP-2006 or AES-2006)^[4] is an evolution of the VVER-1000 being offered for domestic and export use.^[9] Specifications include a $1,200 per kW electric capital cost, 54 month planned construction time, and expected 50 year lifetime at 90% capacity factor. The VVER 1200 will produce 1,200 MWe of power. Safety features include a containment building and missile shield. It will have full emergency systems that include an emergency core cooling system, emergency backup diesel power supply, advanced refueling machine, computerized reactor control systems, backup feedwater supply and reactor SCRAM system. The nuclear reactor and associated systems will be hosted in one single building and there will be another building for the turbogenerators. The main building will comprise the reactor, refueling machine and diesel backup power supply, steam generators and reactor control systems.

If a VVER-1200 experiences a loss of coolant accident or loss of power accident the turbogenerators 'coast down' for 30 seconds, during which time a shutdown can be initiated using residual power in the system. Further emergency power is available from a backup set of diesel generators kept on standby to maintain cooling flow to the reactor. The reactor design has been refined to optimize fuel efficiency.

The first two units are proposed for Leningrad Nuclear Power Plant II and Novovoronezh Nuclear Power Plant II. A standardized design has not been elected. Mainly are more reactors with a VVER-1200/491 like the Leningrad-II-design are firmly planned (Kaliningrad and Nizhny Novgorod NPP) and under construction. The VVER-1200/392M^[10] under construction at the Novovoronezh NPP-II is selected for the Seversk, Zentral and South-Urals NPP. A standard version was developed as VVER-1200/510 and referred to as VVER-TOI.

A passive heat removal system has been added to the existing active systems in the AES-92 version of the VVER-1000 used for the Koodankulam Nuclear Power Plant in India. This has been retained for the newer VVER-1200 and future designs. The system is based on a cooling system and water tanks built on top of the containment dome.^[11] The passive systems all safety functions for 24 hours, and core safety for 72 hours.^[4]

A number of designs for future versions of the VVER have been made:^[12]

• MIR-1200 (Modernised International Reactor) - designed in conjunction with Czech company ŠKODA JS^[13] to satisfy European requirements^[14]
• VVER-1500 - VVER-1000 with dimensions increased to produce 1500 MWe gross power output, but design shelved in favour of the evolutionary VVER-1200^[15]
• VVER-TOI is aimed at development of typical optimized informative-advanced project of a new generation III+ Power Unit based on VVER technology, which meets a number of target-oriented parameters using modern information and management technologies.^[16]

As of July 2011, 10 VVER-1000s and 6 VVER-440 were in operation, and 6 VVER-1200s and 3 VVER-1000s were under construction.^[4]

List of operational VVER installations

Power plant	Country	Reactors	Notes
Akkuyu	Turkey	(4 × VVER-1200/491) (AES-2006)	Plan in place.
Balakovo	Russia	4 × VVER-1000/320 (2 × VVER-1000/320)	Unit 5 and 6 construction suspended.
Belene	Bulgaria	(2 × VVER-1000/446)	Planned.[17]
Bohunice	Slovakia	2 × VVER-440/230 2 × VVER-440/213	Split in two plants, V-1 and V-2 with two reactors each. VVER-440/230 units decommissioned in 2007.
Bushehr	Iran	1 × VVER-1000/446 (3 × VVER-1000/446)	A version of the V-320 adapted to the Bushehr site.[18] Unit 2 and 3 planned, unit 4 cancelled.
Dukovany	Czech Republic	4 × VVER 440/213	Now upgraded to 502 MW in 2009-2012.
Greifswald	Germany	4 × VVER-440/230 1 × VVER-440/213 (3 × VVER-440/213)	Decommissioned. Unit 6 finished, but never operated. Unit 7 and 8 construction suspended.
Kalinin	Russia	2 × VVER-1000/338 1 × VVER-1000/320 (1 × VVER-1000/320)	Unit 4 under construction, operational 2011.
Khmelnitskiy	Ukraine	2 × VVER-1000/320 (2 × VVER-1000/392B)	Unit 3 and 4 under construction.
Kola	Russia	2 × VVER-440/230 2 × VVER-440/213
Koodankulam	India	(2 × VVER-1000/412) (AES-92)	Under construction, operational 2008/2009 with four additional units planned.
Kozloduy	Bulgaria	4 × VVER-440/230 2 × VVER-1000	VVER-440/230 units decommissioned 2003-2006.
Leningrad II	Russia	2 × VVER-1200/491 (2 × VVER-1200/491)	The units are the prototypes of the VVER-1200/491 (AES-2006) and under construction.
Loviisa	Finland	2 × VVER-440/213	Western control systems, Totally different containment structures. Later modified for a 496 MW output.
Metsamor	Armenia	2 × VVER-440/230	One reactor was shut down in 1989.
Mochovce	Slovakia	2 × VVER-440/213 (2 × VVER-440/213)	Units 3 and 4 construction suspended due to lack of funds, planned to be operational in 2012.
Novovoronezh	Russia	1 x VVER-210 (V-1) 1 x VVER-365 (V-3) 2 × VVER-440/179 1 × VVER-1000/187	All units are prototypes. Unit 1 and 2 shutdown. Unit 3 modernised in 2002.[19]
Novovoronezh II	Russia	(2 × VVER-1200/392M) (AES-2006)	The units are the prototypes of the VVER-1200/392M (AES-2006) and under construction.
Paks	Hungary	4 × VVER-440/213	Two VVER-1000/320 plan was cancelled.
Rheinsberg	Germany	1 × VVER-210	Unit decommissioned
Rivne	Ukraine	2 × VVER-440/213 2 × VVER-1000/320 (2 × VVER-1000/320)	Unit 5 and 6 planning suspended.
South Ukraine	Ukraine	1 × VVER-1000/302 1 × VVER-1000/338 1 × VVER-1000/320 (1 × VVER-1000/320)	unit 4 construction suspended.
Stendal	Germany	(4 × VVER-1000/320)	All 4 units construction cancelled after Germany reunification.
Temelin	Czech Republic	2 × VVER-1000/320 (2 × VVER-1000/320)	Unit 3 and 4 construction suspended. Now unit 3 and 4 in planning again (operated in 2025).
Tianwan	China	2 × VVER-1000/428 (AES-91) (6 × VVER-1000/428)	Unit 3 to 8 firmly planned.
Volgodonsk	Russia	2 × VVER-1000/320 (2 × VVER-1000/320)	Unit 3 and 4 is under construction and planned to be operational in 2013 and 2014.
Zaporizhzhia	Ukraine	6 × VVER-1000/320	Largest nuclear power plant in Europe.

See the Wikipedia pages for each facility for sources.

Russia recently installed two nuclear reactors in China at the Tianwan Nuclear Power Plant, and an extension consisting of a further two reactors was just approved. This is the first time the two countries have co-operated on a nuclear power project. The reactors are the VVER 1000 type, which Russia has improved incrementally while retaining the basic design. These VVER 1000 reactors are housed in a confinement shell capable of being hit by an aircraft weighing 20 tonnes and suffering no expected damage. Other important safety features include an emergency core cooling system and core confinement system. Russia delivered initial fuel loads for the Tianwan reactors. China planned to begin indigenous fuel fabrication for the Tianwan plant in 2010, using technology transferred from Russian nuclear fuel producer TVEL.^[20]

The Tianwan Nuclear Power Plant uses many third party parts. While the reactor and turbo-generators are of Russian design, the control room was designed and built by an international consortium. In this way the plant was brought to meet widely recognised safety standards; safety systems were already mostly in place but the previous monitoring of these systems did not meet international safety standards. The new VVER 1000 plant built in China has 94% of its systems automated, meaning the plant can control itself under most situations. Refueling procedures require little human intervention. Five operators are still needed in the control room. The IAEA has referred to the station as the "safest nuclear power plant in the world".^[21]

In May 2010 Russia secured an agreement with the Turkish government to build a power plant with four VVER-1200 reactors at Akkuyu, Turkey.^[22][23] However, due to the accident experienced in Fukushima, anti-nuclear environmentalist groups heavily protested the proposed reactor at Akkuyu.^{[citation needed]}

On 11 October 2011 an agreement was signed to build Belarus’ first nuclear power plant at Ostrovets, using two NPP-2006 reactors with active and passive safety systems. The first unit is planned to be completed by 2017.^[24]

• Russian floating nuclear power station
• VBER-300

• WWER-type reactor plants, OKB Gidropress
• AES-2006 (VVER-1200), Rosatom
• VVER Reactor, Virtual Nuclear Tourist