Power plant design
Russia’s next VVER27 October 2009
Two designs of the VVER reactor, V-392M and V-491, are fighting for dominance in the country’s aggressive domestic and international new-build programme. Although broadly similar, the reactor designs have different engineering approaches to reactor safety systems.
According to the Rosatom State Atomic Energy Corporation’s long-term operation programme for 2009-2015, a total nuclear power plant capacity will be increased from the current 23GW up to 33GW. Annual electricity production will be brought up to 234.4TWh – that is 145% of the 2008 level – by 2015. The programme is to be managed by Atomenergoprom that consolidates civil nuclear assets of Russia. At present, Russia is simultaneously building nine nuclear power units. These include four units to be fitted with VVER 1200 reactors.
The design of the plant with a VVER1200 reactor incorporates the best solutions and expertise gained in the development of previous nuclear power plant projects, including the first phase of the Russian-built Tianwan NPP in China, completed in 2007, and Kudankulam NPP (India), which is now under construction. The design takes IAEA recommendations into account, broadly uses additional passive safety systems in combination with traditional active systems. In particular, it includes engineering solutions such as the core melt trap and improved containment capable of withstanding a direct hit by an aircraft weighing up to 5.7 tons and flying at a speed of 100 meters per second, as well as a shock wave of up to 30kPa and earthquake of up to 0.12g (about 7 points on the Richter scale).
In 2008, Russian regulatory authority Rostechnadzor granted two construction licences for VVER 1200 plants – second phases of Novovoronezh (NVNPP-2) and Leningrad (LNPP-2) nuclear power plants. Their first nuclear power units are planned to come on line in 2012 at NVNPP-2 and 2013 at LNPP-2. The new nuclear power units are constructed by Atomenergoprom’s engineering companies – Moscow and St. Petersburg Atomenergoproekt institutes – to slightly different versions of VVER-1200 (V-392M for Novovoronezh and V-491 for Leningrad). Both reactors will be built in the context of the AES-92 nuclear power plant design. The reactors are designed by the Podolsk, Moscow-based Experimental Design Bureau Gidropress, which is an affiliate of Atomenergoprom.
While being basically similar, the designs have inherent competitive advantages. Passive safety systems prevail in the new modernised V-392M design, while the V-491 design focuses on active safety systems borrowed from Tianwan NPP design. Thus, the number of active safety channels is different (V-392M has two channels, while V-491 has four channels), and their turbine hall layouts are different too.
Also, engineering solutions to safety systems and beyond-design-basis accident (BDBA) management systems differ. In the V-392M there is a focus placed on avoidance of redundancy aiming at higher cost-effectiveness of the plant construction and operation. This goal is met through higher nominal power, primary and secondary parameters, better fuel consumption and operating characteristics (see Table 2).
Both designs feature a rather large number of common structural components, equipment and piping, as well as common main engineering solutions to design bases and common characteristics of the reactor systems and equipment. In terms of the combination of active and passive safety barriers, both designs meet the reliability level of Generation III+ technologies.
The V-392M and V-491 designs include a common emergency core cooling system (ECCS) passive section (GE-1). In the V-392M design the ECCS active section is represented by a combined two-channel high and low pressure system, while the V-491 design utilizes a segregated four-channel high and low pressure system. Anticipated transient without scram (ATWS) accident consequences are managed by a two-channel emergency boron injection system in the V-392M design and a four-channel system in the V-491 design.
Unlike the traditional four-channel emergency feedwater system that is used in the V-491 design, the V-392M design features a closed two-channel steam generator (SG) emergency cooldown system. To mitigate consequences of beyond design basis accidents involving total loss of alternating current sources, both designs use a passive heat removal system, which is air-cooled in the V-392M and water-cooled in the V-491. Additionally, the V-392M design is fitted with a four-channel emergency passive core flooding system (GE-2; see Table 3).
The final choice between the two versions is expected to be made based on results of the construction of the first VVER 1200 reactors at NVNPP-2 and LNPP-2. To this end, a relevant methodological basis of economical and safety factors is being developed at present. The selected reactor design will become the basis for a massive series build of standard nuclear power plants in Russia: by 2030 the nuclear share should exceed 25% in the country’s energy mix.
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