RUSSIAN STATE NUCLEAR CORPORATION ROSATOM ranks second in the world in nuclear capacity and the number of units in operation. It has 39 units in Russia at 11 sites, including the Akademik Lomonosov floating nuclear power plant now providing power in the Arctic northeast.

The total installed capacity is 28.9GWe — 10.9% of the country’s total.

In 2014 a state programme was approved to meet international standards for life extension.

Most reactors were originally licensed for 30 years. Since 2000, licences have been issued by the Federal Service for Ecological, Technological and Nuclear Supervision (Rostekhnadzor) for extension at 29 units totalling 21GWe: Beloyarsk 3, Novovoronezh 3-5, Kola 1-4, Kalinin 1&2, Balakovo 1-3 Rostov 1, Kursk 1-4, Leningrad 1-4, Smolensk 1-3, and Bilibino 1-4. Some had a second licence extension — Novovoronezh 4, Kola 1&2, Rostov 1 and Bilibino 2-4 — and three are being decommissioned (Bilibino 1, Leningrad 1 and Novovoronezh 3).

There are three reactor design types in Russia: VVER (pressurised water reactors), channel reactors and fast neutron reactors. Of the VVERs, all are based on original designs by OKB Gidropress. Twelve are VVER-1000s (mostly V-320 design). Three are new-generation VVER-1200s — two V-392s at Novovoronezh II and one V-491 at Leningrad II. There are five smaller VVER-440s: two V-213s and two V-230s at Kola, and a V-179 (the oldest) at Novovoronezh 4.

Channel reactors operate until replacements ready

The ten channel reactors comprise three sites with 1000MWe RBMK light-water-cooled graphite-moderated reactors, and three small graphite-moderated EGP-6 boiling water reactors (at Bilibino).

Following the Chernobyl accident, all RBMKs underwent significant design modifications and extensive refurbishment, including replacement of fuel channels. The project primarily aimed to improve the neutronics of the core and reactor safety.

Life extension began in the early 2000s, and in 2003 Leningrad 1 received permission to operate until 2018. All 11 RBMK units had 15-year operating licence extensions, but four at Leningrad are now being replaced by Generation 3+ VVER-1200s (Leningrad II).

Leningrad 1 is already undergoing decommissioning following the start-up of Leningrad II-1 in 2018.

The four RBMKs at Kursk are also closing and are to be replaced at Kursk II by VVER-TOI reactors — an evolution of the VVER-1200 with more power and lower costs. Kursk II will have an automated digital system to manage costs and schedule during construction. When Kursk II-1 and II-2 are commissioned — scheduled for 2023/24 and 2024/25 — Kursk 1&2 will be decommissioned.

The three RBMKs at Smolensk will be replaced by VVER- TOIs but not in the immediate future. Smolensk 1&2 have already undergone work to extend their lives for 15 years, to 2028 and 2030. Rostechnadzor recently issued a licence to extend Smolensk 3’s life to 2034. All three Smolensk RBMKs are used to produce cobalt-60 for use in medicine, industry and agriculture in Russia and abroad.

The four 12MWe EPG-6s at Bilibino were built in the 1970s for cogeneration and the Akademik Lomonosov will replace them. Bilibino 1 was shut down in 2018. Bilibino 2 began operation in 1974 and won a 15-year extension in 2004. In December, Rostekhnadzor allowed a further extension to 2025. Work is under way to extend the lives of Bilibino 3&4.

Extensions for VVER-1000s

In a VVER, neutron irradiation causes embrittlement in the reactor pressure vessel. Annealing largely restores its physical and mechanical properties and has been used at VVER-440s to increase their lifetime from 30 to 60 years. It has proved difficult to apply to larger VVER-1000 units, which have a larger diameter and thicker walls. In addition, elements of the vessel fastening system are in a reactor shaft very close to the heating area.

However, in 2018, Rosatom piloted a new technology from the Kurchatov National Research Centre that could extend VVER-1000 life by 15-30 years. It was first used in November at Balakovo 1.

According to Mikhail Kovalchuk, president of the Kurchatov Institute, the new annealing technology can be adapted for water-moderated reactors of any design and capacity. At Balakovo it has added 15 years to the plant’s service life.

Its development took a number of years. Between 2009 and 2013, specialists from the Kurchatov Institute and the KM Prometey Central Research Institute developed a specific temperature-time annealing mode. OKB Gidropress calculated the effect of applying the technology at a nuclear plant. NPF TermIKS with NPO Tsnitmash designed and manufactured the annealing equipment. Between 2015 and 2017, the equipment passed tests on a full-scale model of a reactor at Atommash in Volgodonsk. All the specialists who participated in the operation at Balakovo had previously undergone training at Atommash.

The Kurchatov Institute supervised annealing at Balakovo, including installation and testing of equipment, loading the heating device into the reactor vessel, and the heat treatment, which was carried out in several stages and lasted 220 hours.

After fuel and other in-vessel elements and equipment were removed, the heating device, consisting of 18 independent heating zones, was placed inside the reactor. The reactor vessel was slowly heated to 565°C and kept in this state for 100 hours. As a result, the welded joints and base metal in the reactor vessel core almost entirely regained their mechanical properties. Once the metal had cooled to 70°C, the heating device was dismounted. Standard visual and ultrasonic inspections were used to check the results.

The new technology makes possible cost-effective life- extension for the fleet of ageing reactors. “Today, there are about 37 VVER-1000s around the world. Annealing is the new and, currently, only technology in the world that allows the extension of the service life of such a reactor. This technology will be available for export,” said Rosatom director general Alexey Likhachev.

In May 2015, nuclear utility Rosenergoatom (part of Rosatom) said it had uprated all VVER-1000 reactors to 104%. It has been investigating further uprates to 107-110% of their original capacity and Kola 3&4 are now able to operate at 107%, following modernisation work.

Uprates for RBMKs are not being considered.

Distant prospects for newer designs

For the newer VVER-1200 and VVER-TOI reactors, life extension is a distant prospect, as their initial design life is 60 years.

The VVER-1200, an evolution of the VVER-1000, combines passive and active safety systems. It has protection against earthquakes, tsunamis, hurricanes and aircraft crash. Examples of the enhancements are the double containment; a core-melt trap under the reactor vessel; and a passive residual heat removal system.

The VVER-1200 (V-491) was developed by Atomenergoproekt (St Petersburg) and the VVER-1200 (V-392M) by Atomenergoproekt (Moscow) and OKB Gidropress, under the supervision of the Kurchatov Institute. It complies with Russian, International Atomic Energy Agency (IAEA) and European utilities requirements. The design was developed using the ISO 9001:2000 Quality Assurance International Standard.

The design of the VVER-1200 involved two historically independent design organisations. Atomenergoproekt designed the V-491 with active safety systems, while Atomenergoproekt designed the V-392M, with passive safety systems. Both meet Russian and international requirements and standards. Today both organisations are part of the ASE group of companies, which forms Rosatom’s engineering division.

The VVER-TOI is a further evolution of Atomenergoproekt’s version of the AES-2006 power plant with the V-392M reactor. Development involved OKB Gidropress (chief designer), the Kurchatov Institute (scientific supervisor), All-Russian Scientific and Research Institute for Nuclear Power Plant Operation or VNIIAES (architect-engineer) and NIAEP-ASE (as developer of turbine building and a block desalination unit). Turbine supply is a joint venture of Alstom-Atomenergomash.

Design began in 2009 and was completed in 2012. It was submitted to regulator Rostechnadzor in 2013 for licensing, with a view to subsequent international certification as the standard future export model.

The VVER-TOI pressure vessel has four welds (rather than six), and will use a new steel which significantly reduces radiation embrittlement.

Power has been increased to 3312MWt (1255MWe), and the core design (with 163 fuel assemblies) has better cooling reliability. The VVER-TOI will be the basis for future Russian plants and for serial construction, with reduced costs for design, construction, operation, servicing and decommissioning and enhanced safety.

Author information: Judith Perera, Contributing Editor, Nuclear Engineering International