Unit 1 of the Leningrad nuclear power plant has been withdrawn from service after 45 years of safe operation, Russian state nuclear corporation Rosatom has announced. It said the lead unit in the RBMK-1000 series was shut down at 11:30pm on 21 December.

Plant personnel in the control room of Leningrad unit 1 (Image: Rosatom)

The reactor was gradually shut down in accordance with the technological regulations before being disconnected from the national grid. The unit was commissioned on 21 December 1973 and had since generated 264.9 TWh of electricity. In all its years of operation it has not experienced a single serious incident, Rosatom said.

Vladimir Pereguda, director of the Leningrad plant, said the unit had "reliably and safely" served the national economy both in Soviet times and in modern Russia.

"The last stage of the life cycle of any nuclear facility begins with decommissioning," he said. "Now our task is to safely and securely maintain the shutdown unit, unload nuclear fuel from the reactor and prepare all its systems for decommissioning."

According to federal regulations, a shutdown nuclear power unit is considered to be in operation until its fuel has been removed, which is tentatively scheduled for completion in 2023, Rosatom said. Procedures performed for the closure of a unit are not unlike those for routine repair work and thus plant personnel are fully prepared for this task, it added.

Andrey Petrov, general Director of Rosenergoatom, Rosatom's operator subsidiary, said that this year a VVER-1200 - Leningrad II-1 - had been put into operation ahead of the retirement of unit 1.

"Therefore, for electricity consumers, the replacement of the retired capacity of the Soviet period will be gradual and imperceptible," he said. "Compared to RBMK units, the newly commissioned units have a number of advantages: they are equipped with the most modern security systems, they are 20% more powerful, the design life of the main equipment is twice as long at 60 years."

Even with the closure of unit 1, the Leningrad plant remains Russia's biggest nuclear power plant, with an installed capacity of 4200 MWe. It provides more than 50% of the energy consumption of Saint Petersburg and the Leningrad Region, Rosatom noted.

The Soviet-designed RBMK (reaktor bolshoy moshchnosty kanalny, high-power channel reactor) is a pressurised water-cooled reactor with individual fuel channels and using graphite as its moderator. It is also known as the light water graphite reactor. It is very different from most other power reactor designs as it derived from a design principally for plutonium production and was intended and used in Russia for both plutonium and power production. The combination of graphite moderator and water coolant is found in no other power reactors in the world.

The Leningrad nuclear power plant was the country's first plant with RBMK-1000 reactors. The decision on its construction was made in September 1966. In the 45 years since the unit was commissioned, another ten RBMK-1000 units were successfully brought into operation in Russia - at the Leningrad, Kursk and Smolensk nuclear power plants - and they account for almost 30% of nuclear generation in the country.

The design life of the RBMK-1000 was initially 30 years, but after a large-scale modernisation programme, the service life of each of the four units of the Leningrad plant was extended for another 15 years. The modernisation work concerned more than 90% of the systems and equipment of the units. They all fully comply with the same international safety standards for new units under construction, Rosatom said.

Nuclear power produces 19% of the total electricity generation in Russia.