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Mini submarines recover medical isotopes

22nd April 2015


Mini submarines are being used to recover medical isotopes dating back to the 1950s, from storage ponds at Europe’s most complex nuclear site.

There are literally hundreds of different nuclear fuels and waste types in the historic storage ponds and these includes cobalt isotope cartridges produced for medical purposes, such as lifesaving radiotherapy treatment and the sterilisation of medical supplies.

The project will see hundreds of the cartridges retrieved from Sellafield’s Pile Fuel Storage Pond (PFSP) and First Generation Magnox Storage Ponds (FGMSP), which are high priority legacy nuclear plants on the site in West Cumbria, UK.

“We reckon there are about 800 of these cobalt cartridges, which were produced for a wide variety of medical and industrial uses. These included external beam radiotherapy, sterilisation of medical supplies and medical waste, sterilisation of food and industrial radiotherapy including weld integrity radiographs.” Head of PFSP, Paul Nichol said.

“These particular cartridges were irradiated in the early Magnox reactors at Calder Hall and Chapelcross have been safely stored in the pond since the 1950s and 60s. There are also a small number of cobalt isotopes that were discharged from the Windscale Pile reactors when they were shutdown and de-fuelled after the Windscale Fire in 1957.

“The Windscale Piles are probably best known for producing materials for the defence industry, however they were also the principal supplier of nuclear isotopes for research, medical and industrial uses created in the heart of the pioneering graphite reactors.”

Radiation is widely used in the medical industry with the most well-known uses being x-rays, scans and radiotherapy for the treatment of serious diseases, and the radioactive isotope sources need to be safely disposed of in the same manner as any other nuclear material.

The cobalt cartridges are stored underwater in open top skips and the team of experts at Sellafield Ltd is using Remotely Operated Vehicles (ROVs) in the form of mini submarines to retrieve the individual cartridges, which are one metre long and around 6kg in weight.

Dorothy Gradden, Head of FGMSP said: “It is often forgotten that radiation has many uses outside of the nuclear industry and it has brought many benefits to medicine over the decades, however  like any nuclear waste, the material still needs to be disposed of in a safety conscious manner, so the same rigorous principles apply.

“A few years ago remotely operated vehicles were thought of as expensive toys, but they are now becoming an integral part of our plan to clean up for our legacy fuel storage ponds.  We are now seeing the removal of decades-old material from Sellafield’s legacy ponds on a daily basis, significantly reducing the hazard at these historic facilities.”

The success of the ROV project has been unprecedented, and the focus on continuous research and deployment of new ROVs has directly impacted on the Sellafield site clean-up to date.

Dorothy added: “We have developed the ROV capability to deal with underwater, hazardous problems that need to be dealt with remotely and I’m proud to say that even the US Navy has implemented some of our innovations developed here at Sellafield.

“New potential uses for ROVs include floating fuel skips and large pieces of kit off the pond floor, after all if they can lift a sunken cruise ship from the sea bed, why can’t we lift skips that our in-pond crane can’t reach?”

Cobalt has a fairly short half-life, which means the radiation naturally decays quickly, however this material still requires careful handling.  ROVs are therefore used to safely repackage the cartridges to minimise the radiation dose to the workforce.

ROVs were initially only used to inspect pond contents and the pond structure, however they’re now doing much more.  Sellafield Ltd recently announced a major step in the clean-up of Europe’s most complex nuclear site with the removal of the first radioactive sludge from the FGMSP with a little help from ROVs.







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