Lepse dismantlement on schedule and 1000 times safer

The bow of the Lepse. (Photo: Nerpa Shipyard)
The bow of the Lepse. (Photo: Nerpa Shipyard)

Publish date: April 5, 2016

Written by: Anna Kireeva

Translated by: Charles Digges

MURMANSK – The Lepse nuclear fuel storage ship, for decades one of the most poignant radiation hazards in Northwest Russia, no longer exists, as such. What's left of it now is what is called a “storage package,”ready to be tucked away at a designated long-term storage site and containing what used to be the vessel's bow section with 639 fuel assemblies still inside, by all accounts a major step forward.

MURMANSK – The Lepse nuclear fuel storage ship, for decades one of the most poignant radiation hazards in Northwest Russia, no longer exists, as such. What’s left of it now is what is called a “storage package,”ready to be tucked away at a designated long-term storage site and containing what used to be the vessel’s bow section with 639 fuel assemblies still inside, by all accounts a major step forward.

This is what Alexander Malyshkin, the engineer heading up the so-called SR3 Lepse project, now underway at the Nerpa Shipyard, north of Murmansk, told the region’s Public Chamber on Safe Use of Nuclear Energy.

What’s more is that the radiation dangers surrounding the nightmare vessel have been reduced by 1000 times. This is an impressive accomplishment on a boat that for 27 years refueled the Soviet nuclear icebreaker fleet at sea, taking on 639 spent nuclear fuel assemblies, many of them damaged, before it was decommissioned in 1988 and left essentially to rot at dockside a stone’s throw from Murmansk’s 305,000 residents.

The good news has been a long time in the coming.

It’s been almost four years since the Lepse – considered the most dangerous waterborne radioactive hazard in Murmansk harbor – was towed to the Nerpa Shipyard’s Slip No 6 for final dismantlement. There it bobbed, neglected, in the water until 2014 when, during poor weather conditions and thick fog, it was finally docked.

Lepse-dock-201x300 The Lepse in dry dock. Credit: Nerpa Shipyard

“The vessel fit the dock like it was second skin. The complexity of the operation lay in the fact that the vessel wasn’t going onto a standard slipway, but into a prepared bow storage package,” said Malyshkin in a wide-ranging interview with Bellona. “A special section for the bottom of the boat was manufactured in the storage package, as were two side sections.”

In accordance with the radiation conditions on the boat and engineering plans, the vessel must be separated into five parts: the stern section, which is considered relatively clean; the section with liquid radioactive waste tanks; the engine and boiler room, and two packaged bow sections, one containing the notorious 639 spent nuclear fuel assemblies, and the other of which is also relatively clean.

A lion’s share of this work was done on the vessel while on its dry dock: putting together a heating system and biological and technological safety shields in areas of high radiation levels.

When the Lepse was hauled onto its slipway, the bow storage package, along with the side sections, was completely enclosed, and a heating circuit, as well as other heating equipment, was installed to ensure proper climate controls for the spent nuclear fuel assemblies inside. The vessel was also fitted with a communications system, and a ventilation system and trace gas detection equipment to ensure a safe work environment for the some 5000 technicians working on its dismantlement.

“Because there is a significant quantity of spent nuclear fuel on the vessel and the radiation conditions are rather difficult, it was necessary to do additional work to detail the radiation conditions in specific spots,” Malyshkin told Bellona. “So, some equipment was brought in from [the former nuclear submarine spent fuel storage facility] at Andreyeva Bay.”

Bio-protection-Lepse Steel bio-protection shields surrounding the Lepse's bow. Credit: Nerpa Shipyard

He said that the radiation conditions on the vessel prior to what’s been undertaken so far measured 4600 microsieverts, and surface contamination on the vessel’s spent fuel section measured up to 25,000 beta particles per square centimeter.

Another troublesome spot on the Lepse was the tank holding liquid radioactive waste siphoned from the nuclear vessels it refueled at sea. The tank put off some 4,500 microsieverts of ionizing radiation and had to be put into dry dock in that condition.

After Nerpa received all official permissions it needed, engineers began forming the storage packages – basically big blocks that will hold the remainders of the vessel and that will be shipped to long-term storage in Sayda Bay, a completely refurbished storage site on the coast of Kola Bay, now housing dozens of decommissioned submarines and surface ships’ reactor compartments.

The bow and aft section packages were completed in a workshop beforehand to minimize radiation hazards to personnel. Now, the entire stern section has been cut off the ship and the stern storage package assembled completely. The only thing left to do is to give it a coat of protective paint, which will be done during the warmer season of the year.

In September 2015, the boiler section was disassembled, which was the most challenging area in terms of fire safety, Malyshkin said.

A month later, the fittings for the rearward bulkhead sections were completed.

This coming September, the Lepse’s stern storage package, along with reactor compartments from a number of dismantled nuclear submarines, will be sent off to Sayda Bay.

Now, all the agreements have been inked to erect a shelter over the Lepse’s dry dock. This will house a workshop for the intensely challenging job of removing the 639 spent nuclear fuel assemblies to be then sent on for reprocessing at the Mayak Chemical Combine in the Urals Chelyabinsk Region.

Work on the shelter is expected to be complete in 2017, and by 2020 Nerpa’s engineers are expected to finish the delicate task of unloading the fuel rods.

This month, Nerpa will undertake building the storage package for the relatively clean portion of the bow section, and expects to finish it by July 2017.

backside-Lepse The Lepse's stern section, cut away. Credit: Nerpa Shipyard

But the radiation conditions in the bow section holding the spent fuel rods are dangerous. Malyshkin explained the personnel dealing with the radiation conditions in the bow section had to be divided into two groups.

“Certain spots were identified where personnel would get an annual dose within three minutes of their being there, and then they couldn’t work in the contamination control area for the entire year,” Malyshkin said.“In order to avoid these impacts and the harm to personnel’s health, a plan of organizational and engineering measures was developed to reduce the radiation burdens.”

After the overall plan for dismantling the vessel was agreed to, work began immediately. Extra safety shields were installed. These shields are made of steel 10 millimeters thick. Additional layers of shielding were welded to the sides of the bow section. A concrete wall about two meters high now surrounds the entire perimeter of the vessel. But even these measures didn’t entirely remove high human exposure risks.

As a result, certain areas on the ship – such as the vessel’s holds and the cofferdams, which are the empty spaces between tanks of various purposes built in to prevent accidental liquid mixing – were sealed with cement. The cumulative result of all these safety measures has reduced radiation dangers around the vessel by 1000 times.

On March 1, the European Bank of Reconstruction and Development – the main donor to the Lepse dismantlement – conducted an inspection of the project. Bank representatives are reported to have been satisfied that the Nerpa was keeping to the agreed project schedule, and satisfied with the progress overall.