What’s next for Leningrad?2 May 2019
Russia’s first RBMK reactor, Leningrad 1, retired at the end of 2018. Judith Perera examines the reactor decommissioning plans and strategies for managing the irradiated graphite in the core.
UNIT 1 OF RUSSIA’S LENINGRAD nuclear plant was withdrawn from service on 21 December 2018 after 45 years of operation. Since the unit was commissioned, on 21 December 1973, it had generated 264.9TWh of electricity without experiencing any serious incident.
“The last stage of the life cycle of any nuclear facility begins with decommissioning. 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,” said Vladimir Pereguda, director of the Leningrad plant.
Leningrad 1 is a Soviet-designed RBMK: a pressurised water-cooled reactor with individual fuel channels, which uses graphite as its moderator. It was developed from a design intended principally for plutonium production. Leningrad was the first plant with RBMK-1000 reactors. In the 45 years since unit 1 was commissioned, ten more RBMK-1000 units have been put into operation, at Leningrad (three more units), Kursk (four units) and Smolensk (three units). Together, they account for almost 30% of Russia’s nuclear generation.
Commissioning of unit 1 of the new Leningrad-II plant, a VVER-1200, began ahead of the retirement of Leningrad 1.
“Compared with 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,” said Andrey Petrov, general director of nuclear utility Rosenergoatom. The design life of the RBMK-1000 was 30 years, but after a large modernisation programme, the service life of the four Leningrad units was extended for 15 years. The second unit at Leningrad-II will be commissioned in early 2021, replacing Leningrad 2. Leningrad 3 is scheduled to close in 2024 and unit 4 in 2026.
Decommissioning an RBMK reactor poses a number of problems, including how to deal with the irradiated graphite core. Preparations for the closure of Leningrad 1 have been under way for a number of years. Just prior to the closure, a delegation from state nuclear corporation Rosatom’s Public Council visited the plant. The delegation included members of the Public Chamber of the Russian Federation, ecologists, and leaders at the plant and the Administration of the city of Sosnovy Bor, where the plant is sited.
Vladimir Pereguda presented them with a detailed report on the planned decommissioning and new nuclear industry competencies that may be developed at the site. Discussions included the possibility of using some areas of the site for new production, and for scientific research into the process of handling irradiated graphite.
“The topic of handling irradiated graphite is very important for all nuclear power plants in the world. This provides a huge opportunity for research work, and in Russia there is already some experience on this issue – at the Siberian Chemical Combine, for example,” said Pereguda. “But large RBMK-1000 channel reactors require their own developments. This is a challenge for applied science. We are ready to cooperate with interested parties”.
The management at Leningrad and Rosenergoatom are now considering how best to deal with the old power units, which occupy a large area and have a developed infrastructure. “Common sense dictates that if some infrastructure can continue to be useful, then there is not the slightest reason to dismantle them and send them to scrap,” Pereguda said during a 2017 interview with Tass. “This equipment can bring profit and provide jobs, and dismantling for the sake of dismantling is absurd.” However, he recognised that the process of adapting premises for new goals would be very difficult, especially given the lack of experience.
“The world practice of decommissioning uranium- graphite reactors, unfortunately, often shows how not to do it, because deferred disassembly is often the most popular strategy,” said Pereguda. “After the shutdown, the unit is simply conserved, no dismantling work is undertaken and there is no question of any conversion of the space. At decommissioned PWRs, the situation is somewhat simpler, as there is no need to handle reactor graphite.”
He added: “Worldwide, the process of decommissioning is costly, ... But the task is to reduce costs.”
Adapting the site for new purposes takes time. Unloading the reactor and fuel will take about five years, and it will be at least eight years before the site can be used. As to Leningrad 1, Pereguda believes one of the most effective options would be to use the buildings and structures to provide support services for the new reactors, for example repair services.
There could also be a centre to undertake an inventory of equipment and materials — to decide what should go to the smelter and what can be reused.
New enterprises could also be involved with radioactive waste management and developing a technology for using radioactive graphite. “We have every opportunity to find a final solution here on the site”, he said.
If the model of Leningrad is successful, the experience can be transferred to other stations, or a comprehensive service can be created that can be sold to colleagues in other countries.
Personnel development is another area of interest. “The education system is directly connected with new technologies, and we will have to work on the creation of, perhaps, new professions. We already have proposals from St Petersburg Polytechnic University to create a physics department here,” Pereguda noted. Creating a pilot demonstration engineering centre for decommissioning uranium-graphite reactors is also being considered.
The space that will be freed up after decommissioning may later become a technology park. Suggestions include a pharmaceutical cluster, medical institutions specialising in oncology and industrial facilities.
First a detailed business plan and a comprehensive analysis of opportunities will be made.
Rosenergoatom first deputy general director for operation, Alexander Shutykov, said that buildings should not be left empty. Already the plant can make available two buildings totalling 20,000 cubic metres. They have power and water supplies and compressed air systems, special sewerage, ventilation and heating. The site is very well located geographically — 80km from St. Petersburg and near the port of Ust-Luga — which simplifies logistics.
Graphite disposal challenge
Leningrad 1 is just one of 18 uranium-graphite reactors in Russia that will need to be decommissioned in the coming years. Three units at Beloyarsk are already closed awaiting decommissioning.
In all these cases, the treatment of irradiated reactor graphite, including conditioning it for disposal, is a critical task. It is complicated by the presence of long-lived radionuclides (primarily carbon-14 and chlorine-36) and its large volume. The total amount of irradiated reactor graphite in Russia may be 50-60kt.
The choice is between deferred or immediate dismantling. The main argument in favour of deferred dismantling — allowing the radiation levels to fall before work begins — is the high level of gamma radiation in the first 30 years and beta-decay of cobalt-60 and the need to reduce personnel dose rates during dismantling. However, this method also incurs continued operating cost, including maintaining the units in a safe condition.
In the case of RBMKs, even preparation for immediate dismantling can take decades, during which time radiation levels will have fallen. Preparations include decontamination and managing spent fuel and accumulated radioactive waste.
For Leningrad 1 the preparatory stage is expected to take at least eight years. Nikiet points out that after ten years, dose rates from the graphite will have fallen to levels permitted for transportation, “which will make it possible to handle graphite more safely and less expensively”.
Rosatom has therefore decided on immediate dismantling for Leningrad 1. “This means that we do not leave the problem to future generations, but solve it here and now,” said Pereguda.
However disposal of the graphite remains a problem. One small plutonium production reactor at the Siberian Chemical Company site in Seversk has been technically dismantled. But in fact, because the reactor was built underground, after peripheral structures had been removed the reactor core was filled with concrete and buried in situ. This is not feasible for RBMKs and the graphite will eventually have to be removed for disposal elsewhere. Nikiet continues to work on this issue and recommends:
- The introduction of a comprehensive R&D programme for handling graphite;
- Studies of the properties of irradiated reactor graphite;
- Creation of technologies for the extraction, conditioning, decontamination and disposal of reactor graphite;
- Development of methods and software codes to justify the safety of graphite disposal sites; and
- Search and justification of locations, research and the creation of graphite burial sites, etc.
Preparations for decommissioning are already under way at Leningrad 1. Under federal regulations, any Russian nuclear plant is considered to be in operation until all its fuel has been removed, and for Leningrad 1 this is tentatively scheduled for completion in 2023.
Rosatom says the procedures for closing a unit are similar to those for routine repair work so it believes plant personnel are fully prepared for this task.
In October 2017, an Engineering Centre was established in Sosnovy Bor to decommission RBMKs. It is a branch of the Energoatominvent research and production association. “Decommissioning of NPPs is a natural and necessary stage of their life cycle, which requires ensuring the quality of design solutions taking into account modern requirements of domestic regulatory documents, international standards, recommendations of the IAEA and other international organisations,” said Centre Director Denis Saveliev.
Eventually the centre’s work will be extended to decommissioning all types of reactors but it will begin with Leningrad 1. Its aim is to ensure the radiation safety of personnel, the public and the environment, environmental, technical and fire safety. The company will also be engaged in scientific research.
Author information: Judith Perera, Contributing Editor, Nuclear Engineering International