VVER

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. 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 (Emergency Core Cooling System). VVER reactor designs have been elaborated to incorporate automatic control, passive safety and containment systems associated with Western generation III 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. The construction of the first VVER-1300 (VVER-TOI) 1300 MWE unit was started in 2018. == Design ==

4: inlet and outlet nozzles5: reactor core barrel or core shroud6: reactor core7: fuel rods The Russian abbreviation VVER stands for 'water-water energy reactor' (i.e. water-cooled water-moderated energy reactor). The design is a type of pressurised water reactor (PWR). The main distinguishing features of the VVER ( away), Leopoldov ( away), and Hlohovec ( away), and Temelín NPP (Czech Republic) supplying heat to Týn nad Vltavou away and České Budějovice away. Plans are made to supply heat from the Dukovany NPP to Brno (the second-largest city in the Czech Republic), covering two-thirds of its heat needs. Safety barriers , Finland have containment buildings that fulfil Western safety standards. A typical design feature of nuclear reactors is layered safety barriers preventing escape of radioactive material. VVER reactors have three layers: • Fuel rods: the hermetic zirconium alloy (Zircaloy) cladding around the uranium oxide sintered ceramic fuel pellets provides a barrier resistant to heat and high pressure. • Reactor pressure vessel wall: a massive steel shell encases the whole fuel assembly and primary coolant hermetically. • 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. Compared to the RBMK reactors – the type involved in the Chernobyl disaster – the VVER uses an inherently safer design because the coolant is also the moderator, and by nature of its design has a negative void coefficient like all PWRs. 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. Fuel cycle extension In 2024, Rosatom started testing fuel which contains a neutron absorber (erbium), and uranium enriched to 5% (instead of the typical 3%-4.95% range). The experiments have been carried out at the MIR.M1 research reactor at the Dimitrovgrad Research Institute of Nuclear Reactors. It will allow to extend the current fuel cycle from 12-18 months to 24 months. Remix Fuel The Balakovo Nuclear Power Plant is used for Remix Fuel experiments. In December 2024 the third final 18-month phase of the pilot program has started with the goal to achieve a closed nuclear cycle for VVER reactors. A mixture of enriched uranium with recycled uranium and plutonium received from the used nuclear fuel of other VVER reactors is used instead of a standard enriched uranium. After the first 2 stages of 3, fuel elements were inspected and were approved for the 3rd final stage. The 3rd stage concluded by the end of March 2026 when the fuel was unloaded, and after some time spent in the used fuel pool, it will be further studied in the Research Institute of Atomic Reactors (JSC SSC RIAR). Remix fuel has a lower plutonium content of up to 5% compared with MOX fuel. == Versions ==

VVER-440 One of the earliest versions of the VVER-type, the VVER-440, manifested certain problems with its containment building design. 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 V-213 model, a so called Bubble condenser tower that – with its additional volume and a number of water layers – aims to suppress the forces of rapidly escaping steam without the onset of a containment-leak. As a consequence, all member-countries with plants of the VVER-440 V-230 type, as well as older types, were forced by the politicians of the European Union to shut them down permanently. Because of this, the Bohunice Nuclear Power Plant had to close two reactors and the Kozloduy Nuclear Power Plant had to close four. Whereas in the case of the Greifswald Nuclear Power Plant, the German regulatory body had already made the same decision in the wake of the fall of the Berlin Wall. VVER-1000 Unit 5 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. 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 20 years; the first to undergo such an operating life extension. The work includes the modernization of management, protection and emergency systems, and improvement of security and radiation safety systems. 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. This had been demonstrated on unit 1 of the Balakovo Nuclear Power Plant. VVER-1200 in Bangladesh that consists of two 1200 MWe VVER-1200 reactors The VVER-1200 (or NPP-2006 or AES-2006) is an evolution of the VVER-1000 being offered for domestic and export use. The reactor design has been refined to optimize fuel efficiency. Specifications include a $1,200 per kW overnight construction cost, requiring about 35% fewer operational personnel than the VVER-1000. The VVER-1200 has a gross and net thermal efficiency of 37.5% and 34.8%. The VVER 1200 will produce 1,198 MWe of power. VVER-1200 has a 60 years design lifetime with the possibility of extension by 20 years. The first two units have been built at Leningrad Nuclear Power Plant II and Novovoronezh Nuclear Power Plant II. More reactors with a VVER-1200/491 like the Leningrad-II-design are planned (Kaliningrad and Nizhny Novgorod NPP) and under construction. The type VVER-1200/392M as installed at the Novovoronezh NPP-II has also been selected for the Seversk, Zentral and South-Urals NPP. A standard version was developed as VVER-1200/513 and based on the VVER-TOI (VVER-1300/510) design. In July 2012, the construction of two AES-2006 reactors at the Ostrovets NPP in Belarus was agreed upon. The total cost was said to be $10 billion. An AES-2006 was discussed for the Hanhikivi Nuclear Power Plant in Finland in 2014. The plant supply contract was signed in 2013, but terminated in 2022 mainly due to the Russian invasion of Ukraine. From 2015 to 2017, Egypt and Russia came to an agreement for the construction of four VVER-1200 units at the El Dabaa Nuclear Power Plant. On 30 November 2017, concrete was poured for the nuclear island basemat for the first of two VVER-1200/523 units at the Rooppur Nuclear Power Plant in Bangladesh. The power plant will be a 2.4 GWe plant. The two units were planned to be operational in 2023 and 2024. From 2020 an 18-month refuelling cycle will be piloted, resulting in an improved capacity utilisation factor compared to the previous 12-month cycle. The VVER-1200 is designed to be capable of varying power between 100% and 40% for daily load following, which was tested in 2024. Safety features The nuclear part of the plant is housed in a single building acting as containment and missile shield. Besides the reactor and steam generators this includes an improved refueling machine, and the computerized reactor control systems. Likewise protected in the same building are the emergency systems, including an emergency core cooling system, emergency backup diesel power supply, and backup feed water supply, A passive heat removal system had been added to the existing active systems in the AES-92 version of the VVER-1000 used for the Kudankulam 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. The passive systems handle all safety functions for 24 hours, and core safety for 72 hours. The core catcher will be deployed in the Rooppur Nuclear Power Plant and El Dabaa Nuclear Power Plant. The ones on Akkuyu Nuclear Plant are based on AES-2006 with updated seismic and regulatory conditions from VVER-TOI to satisfy both Turkey's geographical conditions and post-Fukushima measures. VVER-TOI The VVER-TOI is developed from the VVER-1200. It 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. The main improvements from the VVER-1200 are: In June 2019 the VVER-TOI was certified as compliant with European Utility Requirements (with certain reservations) for nuclear power plants. The construction of the first two VVER-TOI units was started in 2018 and 2019 at the Kursk II Nuclear Power Plant. VVER-S-600 The medium-powered VVER-S-600 is an under-development VVER technology that aims to facilitate the closure of the fuel cycle by utilizing a full load of MOX fuel. Rosatom claims that this could reduce the consumption of natural uranium by 50%. This is accomplished by taking out the water displacer rods found in designated fuel assembly channels within the core. These displacers are introduced into the core at the start of the fuel cycle to lower the moderator-to-fuel ratio, thereby hardening the neutron spectrum, which enhances neutron capture in U-238 and leads to the production of Pu-239. ==Power plants==

== Technical specifications ==