Modern Reactors of Russian Design

VVER-1200 is a flagship nuclear reactor and a core product of ROSATOM's integrated solution. Being an evolution of VVER-1000 reactors that were built in Iran (Bushehr), India (Kudankulam) and China (Tianwan) in the 1990s and 2000s, the new design features improved performance across all parameters and a range of additional safety systems preventing radioactive substances from getting out of hermetically sealed containment in cases of emergency. VVER-1200 has a 20% higher power capacity while having a size comparable to VVER-1000. It also has an extended 60-year service life, load following capability, high capacity utilization (90%), and an 18-month refueling cycle. The unit is expected to produce 9.1 trillion kWh per year compared to the VVER-1000’s 7.5 trillion kWh per year. The number of personnel has been decreased by 30% to 40% (on a per MW basis) due to automation, and the centralization of functions and processes. Other innovative design aspects have been employed to cut costs. For example, the project employs only one cooling tower instead of two.

The new reactor was designed at Kurchatov Institute (Moscow) and OKB Gidropress (Podolsk) and is manufactured by Atommash (Volgodonsk). Capable of withstanding an SL-2 earthquake (?0.3 g), the design provides for a fuel burnup of up to 70 MWd/kgU. VVER-1200 can be optionally matched with a half-speed turbine and operate in a load following mode. Many modifications have been made to reactor internals (core barrel, core baffle, protective tube unit and sensors) to prevent accidents and extend the service life to 60 years. The reactor is also designed to accommodate MOX fuel.

VVER is a thermal neutron reactor with pressurized water used both as coolant and moderator. Its design provides for a two-circuit steam generating system with four cooling loops, main circulation pump, pressurizer, relief and emergency valves on steam pipes, and accumulator tanks of the emergency core cooling system (ECCS). Thus, VVER-1200 combines reliability of time-proven engineering solutions with a set of active and passive safety systems compliant with post-Fukushima requirements.

A spent fuel pool inside the containment, inter-containment space ventilation filters, a core catcher with a sacrificial concrete layer, an unparalleled passive heat removal system, and other cutting-edge technologies incorporated into VVER-1200 design undoubtedly make it a Generation III+ reactor. The emergency core cooling system also features advanced technologies, and one of them is cold boric acid stored under pressure in special tanks. In case of containment or pipeline rupture, valves open and boric acid is injected into the reactor core to stop the chain reaction and cool down the reactor. ECCS combined with other systems guarantees an extreme degree of the reactor safety.

The first VVER-1200 reactor was installed at Novovoronezh II Unit 6 brought online in August 2016. Generation III+ reactors are currently under construction in the USA, France and other countries, but Novovoronezh II was the first nuclear station to start up the latest generation reactor. At present, another VVER-1200 unit is connected to the grid on the same site. The plans are to build the same design units at Leningrad II and in Belarus (near the town of Ostrovets, Grodno Region). ASE Group acts as a general contractor in all the VVER-1200 construction projects.

VVER-1200 reactor units

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The VVER concept was first proposed by S.M. Feinberg from Kurchatov Institute. Design work started in 1955 at OKB Gidropress, coordinated by I. V. Kurchatov and A. P. Aleksandrov. The new design, known abroad as PWR (pressurized water reactor), is a backbone of the world's nuclear power industry. The first PWR-based nuclear power station was launched in Shippingport (USA) in 1957. In the Soviet Union, the first VVER reactor (VVER-210) was put in operation in 1964 in Novovoronezh. The first VVER-based nuclear station abroad was brought online in 1966 in Rheinsberg (German Democratic Republic, now German Federal Republic).

BN-800 is a Russian-designed sodium-cooled fast reactor operating at Beloyarsk Unit 4 near the town of Zarechny, Sverdlovsk Region. Its purpose is to refine the fast breeder technology, which will eventually be used to close the nuclear fuel cycle.

The reactor design was developed in 1983–1993 in a joint effort of Leipunsky Institute of Physics and Power Engineering (Obninsk, Kaluga Region), Atomenergoproekt Saint Petersburg Research and Development Institute (ASE Group) and OKBM Afrikantov (Nizhny Novgorod). The reactor capacity is 880 MW of electricity and 2,100 MW of heat.

BN-800 is unparalleled for its inherent safety features and is safe against external and internal factors. Its design provides for passive protection against reactivity, emergency cooling systems and a core catcher. Another important feature is a zero sodium void reactivity effect. All this minimizes a probability of core meltdown accidents and plutonium contamination during irradiated fuel reprocessing.

The task of BN-800 is to demonstrate the feasibility of a closed fuel cycle, and test new machinery and reactor design solutions intended to improve its cost efficiency, reliability and safety. BN-800 can accommodate either conventional (uranium oxide) or MOX (mixed uranium plutonium oxide) fuel. The use of MOX fuel helps dispose of weapons-grade plutonium and burn long-lived radioactive isotopes (actinides) in irradiated fuel from thermal reactors, thus making an eco-friendly, closed nuclear fuel cycle a reality of the future.

Putting BN-800 in operation has proved that ROSATOM still has practical know-how in the construction and commissioning of fast reactors. The BN-800 reactor is intended to secure fuel supplies for the Russian nuclear industry in the long term by reprocessing spent fuel from thermal reactors and radioactive waste through the inclusion of waste uranium and plutonium into its fuel cycle. In October 2016, POWER Magazine, the oldest American and one of the most reputable industry magazines worldwide, placed a high premium on these prospects and named Beloyarsk Unit 4 a winner of the Top Plant 2016 award in the nuclear generation category. It was specifically mentioned that the unit was the world's most powerful sodium-cooled breeder. The Top Plant award is given to the most advanced, innovative projects that map out the future of the industry. According to experts, the BN-800 project has made Russia a global leader in the fast reactor technology.

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Sodium-cooled fast reactors boast a high degree of inherent safety thanks to their physical and mechanical properties (low, almost atmospheric pressure of sodium coolant, large boiling point margins, low burn-up reactivity swing, high sodium heat capacity, etc.). If there is any deviation from the normal operating mode, the chain reaction in the fast reactor stops for natural reasons, without an operator’s command or a signal from the automatic safety system. The reactor has two (main and safety) vessels, one placed inside the other like a Matryoshka doll, and an integral layout, when all the primary loop systems exposed to radiation are consolidated inside the main vessel.

The Soviet Union was a leader in the construction and operation of commercial fast breeder reactors. The world's first fast reactor unit with BN-350 (350 MWe of installed capacity) was put in operation in 1973 on the eastern shore of the Caspian Sea near the city of Shevchenko (now Aktau, Kazakhstan). It was used to generate electricity and desalinate sea water, and was decommissioned in 1998, five years later than designed. Experience gained from its operation highlighted many challenges and issues related to fast reactors.

All of them were taken into account in the construction of Beloyarsk Unit 3 where another, more powerful 600 MWe fast reactor, BN-600, was brought online in 1980. Until BN-800 was commissioned in 2016, it had been the only commercial fast breeder reactor in the world. BN-600 generates electricity and is used to test new structural materials and nuclear fuel. It is the world's only commercially operated fast reactor that has been in use for more than 35 years and is still online.

In 1983, the Soviet Government made a decision to built four BN-800 reactors, but the Chernobyl disaster brought these plans to a halt. The Government got back to the project only in 1997 when it issued a construction license for a new fast reactor. Construction of the BN-800 reactor went very slowly. Criticality was achieved as late as in June 2014. The first electricity was generated on 10 December 2015, while commercial operation began almost a year later, on 1 November 2016.

Beloyarsk Unit 4 with the BN-800 reactor is a prototype for more powerful commercial reactors with a 1,200 MWe capacity. Any decision on the feasibility of their construction will depend on the experience gained from the operation of BN-800. BN-1200 is expected to become a flagship fast reactor and a model for commercial fast reactors of the future. The new design will consume 50% less steel, the number of primary loop valves will be reduced from 500 to 90, and the piping will be 30% shorter.