Decommissioning nuclear storage ponds

Decommissioning one of the oldest nuclear storage ponds has reached new depths in risk reduction thanks to the use of mini submarines as Remotely Operated Vehicles (ROV).

Sellafield Ltd has already successfully used ROVs to survey the contents of one of the historic fuel storage ponds and they have now been used to pick up an individual fuel rod and place it in a designated container.

The 12kg fuel rod was recovered from the bottom of the 7 metre deep radioactive pond using a robotic arm attached to the ROV.

Sellafield Ltd Technical Manager, Phil Toomey said: “The delicate operation required great operator dexterity in order to manoeuvre the ROV into position to safely pick up the fuel rod and place it in a fuel skip.

“The bespoke hydraulically driven manipulator arm was designed by Hydrolek Ltd and extensively tested at the James Fisher Nuclear’s facility in Egremont and Rovtech Systems Ltd at Barrow docks. Formal accredited training for the operators was provided by MTCS Ltd, which was followed by several weeks practice in order to master the operation and reach this decommissioning milestone.”

The fuel rod recovery took place in the First Generation Magnox Storage Pond (FGMSP) which was constructed in the 1950s to store, cool and prepare Magnox fuel for reprocessing. During its 26 year operating lifetime it processed almost 2.5 million fuel rods, from the UK’s nine Magnox stations, along with Magnox fuel from both Italy and Japan.

The pond holds some 14,000m3 of contaminated water, in which is stored the Magnox spent nuclear fuel, radioactive sludges, miscellaneous nuclear wastes and skips. The plan is to progressively retrieve and treat these radiological materials.

Martin Leafe, Head of FGMSP Programme Delivery said: “This achievement is a real breakthrough and paves the way to recover fuel rods that have become dislodged from their containers and to repackage them. We’re working hard to decommission the First Generation Magnox Storage Pond and recovering fuel from the pond floor will help reduce one of the high hazards at Sellafield.

“The use of ROVs has allowed us to work remotely underwater in a radioactive environment, whilst keeping our workforce safe. One of the biggest challenges for the team was the lack of detailed knowledge of the inventory in the ageing facility and the underwater survey provided valuable data about the fuel, its position and condition.”

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