Under the name of VVER ( water-water power reactor, Russian Водо - водяной энергетический реактор, ВВЭР ) summarizes certain types of pressurized water reactors of Soviet design. The term water-water stands for wassermoderiert and water-cooled. We distinguish four generations of reactors. The first number indicates the reactor model, usually corresponds to the approximate performance of the reactors. The second number is the version of the reactor or the project name. The first two prototypes of this type of reactor were used and researched in the nuclear power plant Novovoronesh. Were developed, the reactors of Gidropress.
For series VVER -440 which is the old type WWER-440/230 and the newer, improved in key areas WWER-440/213 type. There is also a special type, which was developed only for the Finnish Loviisa nuclear power plant to meet the existing security requirements there. Like all pressurized water reactors VVER -440 also uses the water for both cooling of the reactor core and for generating steam and for moderating the neutrons. The fuel is low-enriched uranium dioxide. Special features of this WWER-440/230 counts the construction of double blocks with a common nacelle.
According to the manufacturer, the radioactive dose rate increases in the vicinity of a nuclear power plant of the type VVER -440 by less than 0.5 mSv per year.
For the transport and interim storage of the fuel, for example, Castor containers GNS can be used that have been developed specifically for the VVER -440 series. The container of the type CASTOR 440/84 can accommodate 84 fuel assemblies. It is 4.08 m long and has a diameter of 2.66 m. Its weight is 116 tons.
The VVER -440 has a particularly slender reactor pressure vessel. Therefore, the reactor core is located close to the steel walls of the water-filled gap between them is only sixteen inches wide, so much narrower than most built in the western nuclear power plants. The neutrons are slowed down more in a wider gap, so that the radiation exposure of the steel is low and this is why a lot slower aging and brittle.
A researched by the EU-funded research project called "Long Life" Versprödungsprozesse various steel alloys under the influence of neutrons. It is co-ordinated under the direction of Eberhard Altstadt by scientists at the Forschungszentrum Dresden -Rossendorf. The research also examined to steel samples of three blocks of 1973-1990 powered Greifswald nuclear power plant from the VVER type. Due to the different operating duration of the blocks of steel used in them was different extents irradiated with neutrons. Thus, the embrittlement of the steel can be determined as a function of neutron bombardment and compared with the previous benchmarks for aging steel in nuclear power plants.
The reactors of the first generation VVER - 230 have a number of security flaws:
- Low redundancy of the safety devices
- Not everything surrounding containment
- Sufficient emergency cooling at break of a main coolant pipe
- Poor spatial separation of the (redundant) safety devices
- Confusing and outdated control system and control valves
Reactors WWER-440/230 series have included in Kozloduy and Bohunice in operation. The European Union had stated that reactors of the type WWER-440/230 " can not be brought to the required level of safety " and therefore must be decommissioned by the EU on accession of the countries - the corresponding WWER-440/230 were shut down by 2007. In the GDR, this type of reactor was in Greifswald in use and was - like all other nuclear power plants in the GDR - shut down in the wake of reunification.
In type WWER440/213 numerous deficiencies have been corrected. Thus, the emergency cooling system is now able to intervene effectively in all defects of the coolant feeding. Further, the security systems have been designed with triple-redundancy and improved fire protection significantly. In addition, this series has an attached Bubble Condenser. Also great - - Leak released radioactive steam propagation space and more can also condense into water templates before the design pressure is reached so that the one receives.
Besides WWER-440/230 also type reactors WWER-440/213 in Greifswald were in operation - these were shut down after 1989. Reactors WWER-440/213 series are in the EU in Dukovany, Bohunice, Mochovce and Paks.
An export version of the WWER-440/213 is the WWER-440/318. This should come in the nuclear power plant Juraguá used. In contrast to the standard range of 213 WWER-440/318 has a containment.
The VVER -1000 is an evolution of the VVER -440 with improved safety equipment - including a containment vessel - and more power (1,000 MW ), but proven components were taken from the VVER -440. The VVER - 1000 reactors can be brought with enough time and effort to a higher level of security. It must be replaced, the entire control system, and the computer is slow. Furthermore, part of the ever more user- unfriendly monitoring systems and indicators will be modernized. In the VVER -1000 coolant pumps are of the type GCNA -1391 with a net requirement of 5 MW per pump is used. The pump speed is 1000 rpm. The steam generator of VVER -1000 type ПГВ - 1000М.
Reactors WWER-1000/320 series are including in Balakowo, and Kalinin NPP. The reactors of the type WWER-1000/392 found in nuclear power plants called AES -91 and AES -92 use (see Atomstroiexport ). The first nuclear power plant of the type AES -91 has been built in Tianwan in China with an adapted for this project WWER-1000/428 reactor. The adapted for India version is called WWER-1000/412 and is used in the Kudankulam nuclear power plant of the type AES -92. Both were equipped with Western control systems, but more passive safety devices were provided for the variation AES -92. The nuclear power plant of the type AES -91 has, in contrast to type AES -92 additional protection against earthquakes.
According to the manufacturer In VVER from the series WWER-1000/320 is the outbreak of corium ( mixture of fuel and material of the fuel rod cladding ) impossible for a meltdown. To the reactor pressure vessel is cooled from the outside by means of passive measures to ensure that the steel of the reactor pressure vessel has a more sufficient strength to keep the melt in the interior of. However, since the understanding of the behavior and flow of a meltdown still in the basic scientific stage, no guarantee regarding the controllability of core melt scenarios can be given.
For some time experimenting with new fuel element types for all VVER reactors. The plan is to recycle the spent fuel from the RBMK reactors and to use these as fuel for VVER reactors. These have up to 2.5% more efficiency than the conventional WWER fuel. The fuel is currently experimentally in the reactors of the Kalinin nuclear power plant in operation. The spent fuel can in turn be further processed into MOX fuel, it will be used since the beginning of 2008 the nuclear power plant Beloyarskaya.
According to the manufacturer, the radioactive dose rate increases in the vicinity of a nuclear power plant of the type VVER -1000 to less than 0.5 mSv per year.
The reactor VVER -1200 is a further development of the reactor VVER -1000 and AES -91 and AES -92. The basis for the development of the reactor, the construction of the nuclear power plant and Tianwan nuclear power plant Kudankulam. From their technology and security systems, then the WWER-1200/491 have been developed and achieved improved performance. This type of reactor is to be used in a newly designed nuclear power plant AES 2006. Developed the reactor, as well as all others, by the company Atomstroyexport and OKB Gidropress. Also works have already been received. The reactor VVER -1200 is designed for a useful life of 60 years. What will be in these VVER novel, is the high-speed steam turbine, which is only used for new nuclear reactors. As with the VVER -1000 are also in the VVER -1200 type pumps GCNA -1391 for use and steam generators of the type PGW 1000MKP.
Differences of the VVER -1200 compared to the VVER -1000 include:
- Larger diameter of the reactor vessel
- Efficient use of the fuel rods
- Possible increase in reactor thermal power of 3200 MW to 3300 MW
In the course of the project, 2007-2015, a plan was developed to meet the growing energy needs of Russia and to take the old reactors from the mains. Here we sat among other things, on the VVER -1200 (AES- 2006). A total of 28 reactors are planned. The first reactors to be built at the nuclear power plant Novovoronesh II. A VVER -1160, which is built in Leningrad II, is to be built on the basis of the VVER -1200.