ROSATOM’s VVER reactors are among the world’s most widely-used reactors. VVER plants have proved their reliability over more than 1300 reactor years of operation. Since the commissioning of the first VVER power unit in the 1960s, the technology has been providing safe and affordable electricity throughout the world, from Armenian mountains to the countryside of the Czech Republic, above the Arctic Circle and at the southern tip of India.
The VVER reactor is a pressurised-water nuclear power reactor with a pressure vessel, working with thermal neutrons. It is used for production of thermal energy released by fission of nuclear nuclei in fuel. The equipment of the reactor circuit is intended for dry saturated steam production for turbine generators, where the thermal energy of steam transforms into electrical energy.
The current VVER design is an evolution of the well-proven VVER technology being used in Russia and abroad since the 1960s.
New Russian NPPs with VVER reactors are designed to meet all the latest international safety requirements for Gen 3+ nuclear power plants. Gen 3+ NPP design safety systems are based on a combination of active and passive safety systems. Active systems are able to function if at least one alternative power supply is available. Passive systems are able to function independently without power supply and without human intervention.
The VVER reactor itself was developed by ROSATOM subsidiary OKB Gidropress, while the nuclear power stations employing the VVER have been developed by the power plant design organisations within ROSATOM: Moscow Atomenergoproekt, Saint-Petersburg Atomenergoproekt (a branch of VNIPIET), and Nizhniy Novgorod Atomenergoproekt.
The VVER is a pressurised-water reactor (PWR), the most common type of nuclear reactor worldwide, employing light water as coolant and moderator. However, there are some significant differences between the VVER and other PWR types, both in terms of design and materials used. Distinguishing features of the VVER include the following:
A Brief History of the VVER
First VVER Units
A total of 67 VVER reactors have been constructed since the 1960s. The first VVER unit was commissioned in 1964, at Novovoronezh nuclear power plant, in the Voronezh region, Russia. The first unit was called the V-210, the second the V-365 (the numbers were initially corresponding to electrical output).
From that time, the Novovoronezh nuclear power plant has been a testing ground for new VVER units. Today, ROSATOM continues the commitment to such an approach – only export the technology that has been thoroughly tested at home.
VVER-1200 – AES-2006
The AES-2006 design is the latest evolution in the long line of VVER plants. It meets all the international safety requirements for Gen III nuclear power plants. The first AES-2006 units are now under construction in Russia; two units in Sosnovyi Bor (Leningrad II), two units in Novovoronezh (Novovoronezh II) and two units in the Kaliningrad Region (Baltic project). In addition, construction contracts have been signed and site preparation is ongoing for four units in Turkey and two units in Belarus. It is also proposed for Temelin 3-4 (Czech Republic) and Hanhikivi 1 (Finland).
Safety Requirements and Principles
The VVER-1200 (AES-2006) plant was designed to meet the Russian general safety requirements issued in 1997, which were consistent with the IAEA’s International Nuclear Safety Group (INSAG) recommendations. The INSAG group recommendations led to the development of what were called ‘Generation (Gen) III’ nuclear power plants, and the current IAEA safety standard on nuclear power plant design safety, issued in 2012, builds on the same principles. The Russian general safety requirements are also consistent with the safety objectives specified by WENRA (Western European Nuclear Regulators Association) in 2010 for new nuclear power plants.
The VVER-1200 (AES-2006) design takes account of Design Extension Conditions (DEC), in accordance with the current IAEA safety standard. Thus all new VVER-1200 plants under construction already have design features that take fully into account the main ‘Fukushima lessons learned’, including:
• Long-term cooling of reactor core without electrical power
• Long-term decay heat removal that does not rely on primary ultimate heat sink (sea, river, cooling tower)
• Protection of reactor containment integrity with dedicated systems after a core meltdown accident.
The safety systems are designed to have the capability for stable operation under adverse conditions due to natural phenomena, such as; earthquakes, floods, storm winds, hurricanes, snowfalls, tornadoes, low and high extremes of temperature, as well as man-induced events, including; aircraft crash or impact from aircraft parts, air shock wave, fire and flooding caused by water pipe breaks.
The main principles include:
• The inherent safety principle, that is, the ability of the reactor to ensure safety based on natural feedback processes and characteristics.
• Defence in depth principle, that is, use of successive barriers that prevent the release of ionising radiation and radioactive substances to the environment, as well as a system of technical and organisational measures for protection of these barriers.
The main concept for providing fundamental safety functions are:
• Passivity: Passive means are used to deal with ‘design extension conditions’ and ‘beyond design basis accidents’ (passive SG cooling system, passive containment cooling system) and provide back-up for active safety systems.
• Multiple train redundancy: The plant utilises four trains for safety systems and for their control systems.
• Diversity: The back-up systems for the systems providing basic safety functions use different equipment from the backed-up safety system and, if possible, also a different operating principle.
• Physical separation: All four trains of safety systems and their control systems are physically separated, which addresses common mode failures due to fire, aircraft accident or terrorist act. Unit control rooms (main control room and emergency control room) are also physically located in separate rooms/buildings.