Russia’s Mayak Production Association (part of Rosatom) in Ozersk (Chelyabinsk region) announced that it is to build a new vitrification complex for high-level waste (HLW) generated at its radiochemical plant during the reprocessing of used fuel assemblies.
The existing vitrification complex was put into commercial operation in 1987. The vitrification method used at Mayak involves melting aluminophosphate glass in electric furnaces where it is mixed with solutions of radioactive waste and fluxing additives. The glass melt containing HLW is then poured into special containers where it solidifies to form of a mechanically strong and chemically stable monolith. The filled containers are placed in metal cases. After three containers are filled, the canister is closed with a lid, sealed and transported to the special storage site for vitrified HLW.
The newest electric furnace, EP-500/5, was put into operation at the end of 2016 in workshop 4 of the radiochemical plant. The previous four electric furnaces have been mothballed at the installation site after their service life expired.
“The new complex for vitrification of HLW should be put into operation in 2027, said Pavel Kozlov, head of the laboratory for the treatment and conditioning of radioactive waste at the central plant. “Design work will be carried out by the RAOPROEKT design organisation from St Petersburg. Specialists from our laboratory will provide scientific support for the design of the new complex.”
He added that the new complex will include a unified transport and technological system associated with the main technological redistribution of radiochemical production. “The main thing is that all the ceramic melters in it will be replaceable: when they are worked out, they will be dismantled, fragmented, packed in containers and transferred to storage at the Federal State Unitary Enterprise National Operator RAO.”
The new complex will be based on technological units that are designed to solve environmental problems related to the immobilisation of liquid radioactive waste (RW) that was accumulated in the early years of the enterprise.
“The new vitrification complex will use two types of ceramic melters: high-performance ones, such as EP-500 electric furnaces for producing aluminophosphate glass, and small ones for producing borosilicate glass,” said Evgeny Zubrilovsky, Deputy Director of the Radiochemical Plant for RW Management. “The high performance ones are intended for processing liquid HLW accumulated from the previous activities of the enterprise, as well as from processing special types of used nuclear fuel. The small ones will be used for vitrification of waste from reprocessing used fuel from power reactors.”
The design of high-performance electric furnaces will be based on time-tested technical solutions, adjusted based on accumulated operating experience. A fundamental innovation will be the ability to remove the furnace from the canyon and its fragmentation. The small-sized melter for borosilicate glass is much more compact than the previous electric furnaces. It has a bottom drain and air-cooled structural elements. The design of the small-sized melter has been developed by Mayak specialists over several years. The second prototype was tested last year. In 2021, a third will be assembled, taking into account the experience gained from the tests, as close as possible to an industrial design.
Mayak also announced on 2 February that Russia's largest centre for irradiation technologies is being built in Ozersk. The Regional Centre for Irradiation Technologies became the fifth enterprise to be cited at the Advanced Social and Economic Development Area in Ozersk. Mayak has invested over RUB200 million ($2.6m) in the project, which will be launched later this year. According to the Mayak website, unique work will be carried out at the new centre to provide comprehensive services for radiation modification of materials, sterilisation of medical devices, processing of food products and crops by cold sterilisation.
Construction work is underway at three large pavilions. The very heart of the construction site is a special pool, in which an industrial gamma plant will be based equipped with cobalt-60 radionuclide sources. Around the 5-metre-deep pool is a special reinforcing frame, made of a 150 massive concrete slabs.
Mayak was originally established in the late 1940s to produce plutonium for the Soviet nuclear industry. The main directions of the current activities include: fulfilment of the state defence order for the production of components of nuclear weapons; transportation and processing of used fuel; production and sale of isotope products; mechanical engineering and instrument making; research and production activities; and the solution of nuclear legacy problems. Like weapons production sites worldwide, there was little attention to safety in the early years and unregulated disposal of HLW left large areas highly contaminated. This was exacerbated in 1957 by the explosion of a waste tank. Mayak has since faced a huge remediation task, with which it is making positive headway. In 2015, after years of work and huge expense it completed the mothballing and remediation of Lake Karachai on the site where HLW had been dumped and which had been described by the Washington, DC-based Worldwatch Institute as the most polluted spot on Earth.
In late December 2020, Mayak received a contract from Rosatom for the decommissioning of radiochemical plant buildings contaminated with caesium-137, plutonium-239, strontium-90, and americium-241. Mayak will have to liquidate buildings 131-134 and carry out the rehabilitation and improvement of the adjacent territory of 2800 sq.m. The work, planned to be completed in 2022, is expected to generate about 360 cubic metres of solid HLW, which will undergo certification, before being sent to Mayak’s storage facilities as a temporary measure.
Since 2011, all enterprises are required to dispose of solid radioactive waste at final isolation points, and such a facility is now being established in Ozersk, designed to receive 225,000 cubic metres. Construction work is planned to begin this year for completion in 2023. The facility is primarily intended to accommodate radioactive waste generated at Mayak, but will also take waste from other generators. It will be operated by the Federal State Unitary Enterprise National Operator for Radioactive Waste Management (NO RAO).
Mayak is continuing to decommission other hazardous legacy facilities. According to the federal target programme (FTP) to 2030, financing of all work on legacy decommissioning at Mayak will cost RUB30 billion. At the radiochemical plant, according to the FTP, it is necessary to decommission 24 facilities from the late 40s to the early 80s. As part of a contract with Rosatom, two underground storage tanks for liquid radioactive waste were completely liquidated ahead of schedule in August 2020. The contract also included liquidation of five more facilities including buried old pumping and transfer stations for liquid radioactive waste. Preparation of the sites and territories is underway. Complex and extensive complex engineering and radiation surveys of all five facilities were carried out in 2018–2019.
Work to dismantle two large facilities is expected to begin this year including a pumping station for liquid waste, which was commissioned in 1948. In the period 1963-1964, the above-ground part of the building was destroyed. The rest of the building is almost 6 metres underground and comprises three rooms: a pumping station reservoir, a turbine hall and an additional turbine hall. These are to be dismantled and the area remediated.
Photo credit: Mayak PA