Russia’s Lepse floating technical base (PTB) in the Murmansk Region will be sealed and transferred for long-term storage to the village of Sayda Guba, where a long-term ground storage facility for reactor compartments is located, Russian state nuclear corporation Rosatom has announced.

The Lepse floating technical base, which served as a used fuel storage facility for the nuclear icebreaker fleet, was decommissioned in 1988. There were 639 used fuel assemblies in storage, some of which were damaged, making their extraction very difficult. For more than 20 years, the floating technical base was awaiting disposal afloat near Murmansk, posing an environmental and radiation threat to the entire North-West region. In July the last of six batches of used fuel assemblies were loaded into TUK-18 transport packaging containers and delivered to the special storage site at Atomflot by the motor ship Serebryanka. This left just 19 assemblies, which pose particular difficulties to be removed in 2021. The work started in May 2019, since when 620 used fuel assemblies have been cut out and unloaded from the FTB bow package using specially developed technologies and unique equipment.

The dry cargo ship Lepse was built in 1934, and converted into a floating technical base in 1961. Until 1981, it supported the refuelling of Russia's nuclear icebreakers and after 1981 served as a storage facility. In 1996, the project to deal with Lepse was included in the European Union’s TACIS programme (the CIS technical assistance programme) with funding allocated for the inspection of the used fuel.

In 2008, the initial executive grant agreement (GIS) was concluded for the disposal of the Lepse, the recipient of which was LC NFC, with the European Bank for Reconstruction and Development (EBRD) as the administrator. After 2011 with funding from Russia’s federal target programme “Ensuring Nuclear and Radiation Safety for 2008 and for the Period Until 2015”), a comprehensive radiation survey of the vessel was undertaken and preparatory work began. This included docking with partial conversion of the ship’s hull removing some radioactive material, decontamination, and installation of additional equipment. Lepse was then towed to the Nerpa Shipyard in 2012.

In September 2018, EBRD announced it had built a shelter for refuelling the vessel intended to create safe conditions to cut out the used fuel from the onboard storage tanks, transfer the nuclear material into new canisters and transport these for further storage at Mayak.

The EBRD said the cost of €23m shelter was financed through the Nuclear Window of the Northern Dimension Environmental Partnership (NDEP) Support Fund, an international fund with contributions from Belgium, Canada, Denmark, the European Union, Finland, France, Germany, the Netherlands, Norway and the UK, and managed by the EBRD.

"The next stage will be the preparation of the storage facility for long-term storage. The roof, from where the canisters with fuel are cut, will be sealed and brought into compliance with Russian standards to natural radiation levels. The facility will be moved to Sayda-Guba and placed there," Rosatom said. Before the start of conservation of the FTB in 2021, the last 19 fuel assemblies will be removed. “These 19 fuel assemblies are stored in caissons, where they were once placed for temporary storage. They will be unloaded using a separate technology developed jointly with the EBRD. It will be necessary to practice the actions of the personnel using the test bench," Rosatom noted.

Rosatom has also recently confirmed plans to raise sunken nuclear objects from the Arctic within the coming eight years. Rosatom said on 3 August that it expects to raise six of the most radiation-hazardous objects from the bottom of the Arctic zone of the Russian Federation in eight years – sunken parts of an icebreaker, nuclear submarines, reactors with used fuel. Although these are a small fraction of those located in the Russian Arctic, they are responsible for 90% of the radiation background in these places, Rosatom told Tass.

This is a long-standing problem. After the arms race, nuclear weapons and the nuclear fleet had to be disposed of. To solve this problem, several bases were deployed in the Murmansk region, in particular, in Andreeva Bay, Saiga Bay and near the village of Gremikha. During the transportation of nuclear submarines and icebreakers intended for decommissioning, accidents occurred, and a number were sunk.

"According to research estimates, about 95% of the 18,000 flooded objects are now in a safe state naturally, they are silted and the levels of gamma radiation around them correspond to natural background indicators,” Rosatom said. “The remaining 5% (1000 objects) are characterised by higher levels of gamma radiation. The greatest danger could be posed by six of these objects, namely reactors with used fuel from submarines K-11, K-19 and K-140, two intact submarines K-27 and K-159 and used fuel from the reactor of the icebreaker Lenin. These contain more than 90% of the total activity of sunken objects."

Rosatom said its experts believe even the extremely low probability of leakage of radioactive materials from these facilities is an unacceptable risk for the Arctic ecosystems. "We consider it necessary to raise all six objects, including K-159 and K-27. The lifting of all six objects, their safe transportation to the disposal site and their preparation for long-term storage will take at least eight years."

The research data, which Rosatom relies on, was obtained at the end of 2019, following the work of an international consortium that included Italian company Sogin, the Norwegian radiation protection agency NRPA (now DSA), UK company Nuvia and  Germany’s EWN. The technical and economic assessment of the action plan for the management of sunken radiation hazardous objects was carried out in the Kara and Barents Seas.

Based on the results of hazard modelling of all the listed objects, the consortium concluded that "at the moment these objects are only potentially dangerous and do not pose a real threat", and recommended raising two submarines (K-159 and K-27). For the rest, it is currently enough to conduct constant monitoring of the situation.

Photo: Fuel removal from Lepse in July (Photo credit: EBRD)