Rosatom reports that the last batch of uranium beryllium used nuclear fuel has been removed from the former 574th coastal technical base of the Northern Fleet in Gremikha in the Murmansk region. The fuel was used to power nuclear submarines equipped with liquid metal (lead-bismuth) cooled fast reactors.
In the 1970s, the Soviet Union developed Alfa-class small fast, attack submarines. Their titanium hull and fast neutron reactor enabled rapid speed and deep diving. The reactors used uranium-beryllium fuel with enrichment of more than 90%. The subs were refuelled at Gremikha and the used fuel assemblies (OVCh – Otrabotabshikh Viemnikh Chastei) were stored there. The lead-bismuth coolant stays liquid as long as the reactor is operating. However, when the subs were taken out of service in the 1980s and sent for storage pending dismantling, the coolant solidified, trapping the fuel elements.
In 1998, the government transferred responsibility for the disposal of nuclear submarines from the Navy to Minatom (later Rosatom). By 2000, four vessels were waiting to be defuelled, three of which were in disrepair. The main feature of uranium beryllium used fuel is its high enrichment which increases the risk of a spontaneous fission chain reaction. The situation in Gremikha was also complicated by ageing equipment and systems, unreliability of the physical protection system, as well as an increased level of gamma background radiation – 3.21 m3v/h compared with natural background in the Murmansk region of 0.08-0.16 mSv/h.
In 2000, Minatom established the North-Western Centre for Radioactive Waste Management, SevRAO, in Gremikha (which became a branch of Radon in 2023). In 2003, the concept of rehabilitation was put forward and the international community joined the project including allocation of funding. By the end of 2004, the centre’s staff had repaired the main equipment and infrastructure and prepared it for nuclear and radiation-hazardous work.
In 2005, unloading of OVCh began, initially in 2005 and 2006 from submarines with serial numbers 105 and 120 were removed. Seven specialists involved in this work received state awards for courage and high professionalism shown in the performance of official duty at the risk of their lives.
When it came to damaged vessels 900 and 910, international experts suggested that the work should be postponed indefinitely and that the reactor facilities should be sent to Sayda Bay, a site for long-term storage of reactor compartments and radioactive waste. However, the Russian nuclear community did not want to leave such a dangerous legacy to future generations. The Institute of Physics & Power Engineering (IPPE), the NA Dollezhal Research & Design Institute of Power Engineering (Nikiet), the Gidropress Experimental Design Bureau and the Afrikantov Experimental Design Bureau of Mechanical Engineering developed regulations and technologies for handling damaged reactors, the IPPE developed technology for disassembling uranium beryllium fuel, and the Mayak production association in Ozersk developed its processing.
The main problem with vessel 910 was europium, which leaked from the control rods after they were depressurised. The radiation level there reached 35 Sv/h. In Sosnovy Bor, the KM-1 stand, which in Soviet times was used to create reactor installations with liquid metal coolant, tested the cleaning technology – first on a mock-up. Painstaking work produced good results and the radiation situation was normalised. OVCh unloading was then carried out using the same technology as for vessels 105 and 120. For this work, 20 specialists from SevRAO and Rosatom institutes received state awards.
Handling the nuclear installation of submarine 900 was also difficult and technically dangerous. At the time of an accident in 1971, the 170 kg of uranium beryllium fuel contained in the reactor was only about 3% depleted and the reactor compartment was prepared for sinking – the cavities were filled with furfural, concreted from above and filled with tar.
The designers studied the capabilities of the equipment in Gremikha and decided it was possible to disassemble the reactor. SevRAO specialists manually removed the concrete and tar, cut out the reactor with solidified coolant and fuel assemblies, delivered it to the workshop and turned it upside down. The bottom was cut off, the alloy was heated and poured into a container. The core was disassembled, and the assemblies were packed in specially made shipping containers. In 2012, the core disassembly was completed, and the removal of uranium beryllium fuel began.
Disassembly of the core of the submarine 900 showed that the technique was working. Since 2014, Gremikha has been dismantling one vessel every year (with the exception of 2023) and sending it to Mayak for processing. In November, the last one – the 11th – was transferred on a specialised vessel Rossita. It was part of the OK-550KM prototype reactor plant that was delivered to Gremikha in 2017 from the Scientific Research Technological Institute (NITI) in Sosnovy Bor, where it was deployed as part of the KM-1 facility.
“A thorough study of the dismantling technology, the highest competence of specialists at all levels, the cooperation of the nuclear community, strict compliance with the principles of nuclear and radiation safety, and the courage and bravery of the performers of the project for the disposal of submarine parts made it possible to complete all the work in Gremikha without a single nuclear incident,” said Vasily Tinin, Rosatom’s Director for state policy in the field of nuclear fuel and decommissioning of nuclear and radiation-hazardous facilities.
Rusia’s experience of handling active zones in a liquid metal coolant is unique — such operations have not been performed anywhere in the world. These developments can now be used when handling the active zones of reactors with liquid metal coolant. The closest example is Brest-OD-300 with lead coolant, which is being built in Seversk as part of the Proryv project.
The successful completion of the project to remove used nuclear fuel from Gremikha means that today there is only one used nuclear fuel storage facility in the Russian part of the Barents Sea – in Andreyev Bay, where more than half of the used nuclear fuel has already been removed, and work is planned to be completed by the end of this decade,” said Tinin.
