Leningrad NPP

Leningrad NPP

Largest producer of electric energy in North-Western Russia

42 km

from the administrative boundary

of Saint Petersburg

The plant covers over 55% of energy consumption of Saint Petersburg and the Leningrad Region. The share of Leningrad NPP in the energy mix of the North-Western Region is 28%. Leningrad NPP is the most important backbone enterprise in the town of Sosnovy Bor located on the southern shore of the Gulf of Finland 42 km away from the administrative boundary of Saint Petersburg.

Leningrad NPP consists of six power units and is the only plant in Russia operating two different power unit types: pressure-tube uranium-graphite units (RBMK) and water-cooled water-moderated power units (VVER).

  • 27,893mln kWh

    of electric power were generated by the NPP in 2020

  • 4 400MW

    plant installed capacity

Start-up of power units

  • 01

    RBMK-1000

    1 000 MW

    1973

  • 02

    RBMK-1000

    1 000 MW

    1975

  • 03

    RBMK-1000

    1 000 MW

    1979

  • 04

    RBMK-1000

    1 000 MW

    1981

  • 05

    VVER-1200

    1200 MW

    2018

  • 06

    VVER-1200

    1 200 MW

    2021

reactor type

installed capacity

operational

decommissioned

Nuclear power plant configuration

RBMK type power units with the capacity of 1,000 MW are the “heart” of Leningrad NPP-1

RBMK-1000 reactor unit

Four power units with RBMK-1000 reactors were constructed at Leningrad NPP. Power units No. 1 and No. 2 were shut down (on December 23, 2018 and on November 10, 2020) after 45 years of operation and switched to “non-generation operation” mode as they reached the end of their service life.

Units No. 3 and No. 4 are running power units of Leningrad NPP.

Water-cooled graphite-moderated pressure-tube boiling reactors are employed at Leningrad nuclear power plant. This reactor is designed for generation of saturated steam under a pressure of 7.0 MPa. The heat output of the reactor is 3,200 MW; its power generating capacity is 1,000 MW.

Реакторная установка РБМК-1000

The reactor hall accommodates a unique refueling machine enabling fuel reloading at the running reactor.

Each power unit includes:

  • an RBMK-1000 high-capacity uranium-graphite pressure-tube thermal neutron reactor with a circulation circuit and auxiliary systems;
  • a steam pipeline and a condensate-feed pipeline;
  • two turbines with 500 MW generators.

Process flow chart of a power unit with an RBMK-1000 reactor

The process flow chart of a pressure-tube uranium-graphite power unit (RBMK) at Leningrad NPP comprises a single circuit: steam supplied to the turbines is formed directly in the reactor as the coolant boils while passing through it. Ordinary purified water circulating along the closed loop is used as the coolant.

Fuel contained in fuel assemblies is placed in process channels, where a chain fission reaction occurs generating a lot of heat. This heat is removed by water circulating through the fuel channels along the repeated forced circulation circuit. The steam-water mixture flows from the reactor to the drum separator, where it is separated into steam and water. Dry saturated steam is supplied to the blades of the turbine. Exhaust steam from the turbine enters the condensers to be cooled down there by sea water from the Gulf of Finland. After purification, heating and deaeration, condensate returns to the drum separator, where it is mixed with feed water and supplied to the reactor fuel channels. Generators producing electric energy are installed on the same shaft as the turbines. Electric energy is supplied to the power system through switchgears via 330 kV and 750 kV power transmission lines.

Replacement power units with generation III+ VVER reactors with the capacity of 1,200 MW

VVER reactor unit

New-generation units No. 5 and 6 with VVER-1200 reactors are running power units of Leningrad NPP. The expected service life of the new units is 50 years; the expected service life of the main equipment is 60 years.

The VVER-1200 reactor is a shell-type water-cooled water-moderated power reactor. The reactor is housed in a sealed protective containment structure. It prevents any external effects or radionuclide release into the environment in case of a hypothetical accident.

VVER-1200 reactor

Water with boric acid, whose concentration varies during operation, is the coolant and the neutron moderator of this reactor. Low enriched uranium dioxide is used as a fuel in the reactor core.

The heat balance diagram of the power unit contains two coolant circulation circuits.

The primary circuit consists of the reactor, the main circulation pumps, the steam generators, and the pressurizer. It is intended for heat removal from the reactor and transfer to water in the secondary circuit. The coolant in the primary circuit is high-purity water under a pressure of 162 atm with boric acid dissolved in it, which is a strong neutron absorber.

Water is pumped by the main circulation pumps through the reactor core, where it is heated up to 290-320 degrees due to heat generated as a result of the nuclear reaction. Water in the primary circuit transfers heat to water in the secondary circuit through metal walls of the heat-exchange tubes in the steam generator and returns to the reactor. Radioactive elements contained in water in the primary circuit cannot penetrate the secondary circuit.

Process flow chart of a power unit with a VVER-1200 reactor

The secondary circuit is non-radioactive. It consists of a steam-producing part of the steam generators, the main steam pipes, the turbine unit with a regeneration system, the feed water unit, and several auxiliary systems. The secondary circuit is designed for steam generation. Steam is supplied to the steam turbine. The turbine, in its turn, turns a magnet rotor. Electric current is produced as a result of electromagnetic induction. As the magnet rotor is turning, electric current occurs in the winding of the surrounding stator. All that is left to do is to deenergize the winding and transmit electric power to external consumers. Spent steam is cooled down in the condensers and turns into water, which is then delivered back by the pump into the steam generators. A recycled water supply system is used to remove heat generated during the condensation of steam from the condensers of the turbines.

Two natural draught evaporative cooling towers 150 m in height each are used for power unit No. 1 and one higher cooling tower (167 m) is employed for power unit No. 2.

  • 3 200MW

    rated heat output of the reactor

  • 162atm

    pressure on water in the primary circuit

Nuclear power plant safety systems

The safety of RBMK and VVER power units is based on the self-protection of the reactor unit and the defense-in-depth concept, which involves the operation of several safety barriers.

The design of the new power units includes 4 independent safety system trains, each of which can fulfill the functions of the entire system.

Defense-in-depth concept

The defense-in-depth concept is applied to compensate for potential human errors or mechanical failures. This concept is based on several levels of protection with a sequence of barriers opreventing the release of radioactive materials into the environment. This concept involves protection of the barriers through prevention of a damage to the plant or to the barriers. It includes further measures to protect the population and the environment against any impacts if the barriers are not sufficiently effective.

Safety barriers

  • 1

    The first barrier is a fuel matrix (i.e. a pellet).

  • 2

    The second barrier is fuel cladding.

  • 3

    The third barrier is the main circulation circuit: the reactor, circulation pumps, the main circulation pipeline, etc.

  • 4

    The forth barrier is reinforced concrete walls of the buildings housing the equipment of the repeated forced circulation circuit.

Self-protection principle

VVER and RBMK reactors have a configuration of the reactor core ensuring “self-protection” or “self-regulation” of the reactor. When the reactor power increases and, consequently, the temperature of the reactor core rises, the nuclear reaction dies out due to natural feedback.

In order to stop the chain reaction quickly and efficiently, neutrons involved in this process must be absorbed. An absorber (boron carbide) is used to accomplish this. Rods made of boron carbide are inserted into the reactor core to reduce the neutron flux level or to shut down the reactor completely.

Electromagnets are used as the drives for the rods to ensure their immersion into the reactor core. This principle guarantees that the rods will drop even if the power unit is de-energized: the powered down electromagnets will stop holding the absorber rods and these will drop down by gravity.

Another way to stop the chain fission reaction is to increase the concentration of boric acid in the coolant: where necessary, the boric acid solution is used by numerous emergency systems.

Multiple redundancy of safety channels

Generation 3+ VVER power units employ 4 independent safety system trains, each of which can fulfill the functions of the entire system. Each channel has its own reserves of the boric acid solution. Standby power supply is ensured by diesel generators and batteries.

The main feature of the VVER-1200 is a unique combination of active and passive safety systems.

More specifically, the following devices are used at a unit with a VVER-1200 reactor: a core catcher - a device used to catch molten fuel in the nuclear reactor core, a system for passive heat removal through steam generators intended to ensure prolonged heat removal from the reactor core in the absence of any power sources, etc.

Environmental safety

Environmental safety

The basic principle of safe operation of a nuclear power plant is to preventan uncontrolled escape of radioactive products beyond the safety barriers, whose integrity is ensured by the operation of various systems of the plant

The findings of environmental radiation monitoring carried out by specialists confirm that over many years of its operation, Leningrad NPP has made no impact on the regional environment. Regular analyses of source and waste water prove that the nuclear power plant has no adverse effect on water bodies.

Monitoring systems inside Leningrad NPP and the automated radiation monitoring system (ARMS) constantly monitor the radiation level in the buffer area and in the control area in real time.

The ARMS continuously monitors the radiation level and transmits the necessary information to Leningrad NPP and environmental radiation monitoring systems.

In this way, Leningrad NPP strives to provide a safety level at which the impact on the environment, the personnel and the population does not exceed the prescribed limits, while the risk of occurrence of emergency situations is minimized.

Social responsibility

State Atomic Energy Corporation Rosatom is a responsible corporate citizen whose operations a strong economic contribution to the situation in numerous Russian regions and a number of foreign countries where NPPs and other facilities are under construction

A broad range of social programs are being implemented at Leningrad NPP defining the level of obligations of the enterprise in the field of social protection of the employees and its contribution to the development of local and regional infrastructure.

The employees are provided with financial support to improve their housing, to ensure they have a good rest and receive high-quality healthcare services, higher and secondary vocational education, etc.

The plant has always supported the town of Sosnovy Bor. ROSATOM has a Charity Policy Framework within which the enterprises are acting. Specifically, JSC Rosenergoatom and Leningrad NPP annually allocate about 9-12 million rubles to the town of Sosnovy Bor.

The range of charity initiatives is very broad. In recent years, assistance has been provided primarily to Sosnovy Bor. The assistance covers kindergartens, a music school and an art school, sports clubs, and even orthodox parishes.

Contacts

  • Leningrad Nuclear Power Plant
    Branch of Rosenergoatom JSC

  • Leningrad NPP, Sosnovy Bor town,
    Leningrad Region 188540