GLEEP Decommissioning Project
Client: British Nuclear Fuels Ltd. (BNFL)
Location: Harwell, Oxfordshire
Date: November 2003
The decommissioning of this Nuclear Reactor was one of the first big projects we were involved in. It was hailed as a huge success and even featured on the cover of Hoist - the international factory crane magazine.
As a small company, (known at the time as RS Cranes) it was a big feather in our cap to gain this contract over some much bigger and more established national crane companies.
GLEEP (Graphite Low Energy Experimental Pile) was a triumph for British scientists pioneering nuclear technology in the UK. Built in the aftermath of the Second World War at Harwell, the reactor started operation on the 17th August 1947 and was the first reactor in Western Europe. 57 years later, the reactor core & outer structure had served it’s time and was scheduled to be demolished.
UKAEA oversaw the removal of over 13,500 graphite blocks each weighing up to 48 Kg. The size, quantity & weight of the graphite blocks made the task unsuitable for manual handling and the only access & egress from the reactor was through a 3 metre square roof opening, which prevented the blocks from being lifted from outside the reactor. Our team devised a way to move 13,500 blocks one by one.
We designed and installed a light crane system, which could be passed through the 3- metre roof opening and once assembled inside the reactor could provide an 8-metre square coverage. The crane was power driven on all (Hoisting, Cross & Long travel) motions and operated by a hand held remote control system. The blocks were lifted individually using a drill and tap machine suspended from the crane system, which was integrated and operated by the hand held remote control system.
The internal crane system was used to lift individual graphite blocks into fabricated steel baskets capable of holding up to 20 blocks at a time. The baskets were then lifted out from inside the reactor using an inverter controlled power slew jib crane, which had been installed onto the outside roof of the reactor also by RSIS. This could then pick up from inside the reactor, slew round and lower the baskets onto electric powered hydraulic scissor tables 13 metres below for processing.
RSIS also devised a solution for handling the blocks for processing as each block required checking on all sides for radiation. RSIS designed & installed a retractable free standing runway system above electric/hydraulic scissor tables that could be retracted to allow the jib crane on the roof of the reactor lowered the baskets of blocks onto the floor at the side of the scissor tables, and then repositioned over the basket to remove the blocks from inside the baskets onto the scissor tables for monitoring. Running along the runway system was a vacuum-lifting device with a special suction cup, with a head of under 100 mm designed for handling the blocks. As one basket was being lowered another was being filled inside the reactor. The process was carried out continually until all 13,500 blocks had been removed.