Swiss Army knife-style tool aids Dounreay deactivation
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Engineers in Scotland are using a giant Swiss Army knife-style tool to help decommission a nuclear reactor.
The 40ft (12m) 16-piece tool, designed and built by French nuclear company Framatome, is being used to harvest the last of the plutonium and uranium from inside the Dounreay Fast Reactor, which was shut in 1977.
‘It’s too toxic in there for anyone to do the job manually,’ said Alex Potts, the engineer in charge of the project at Dounreay Site Restoration. ‘The radiation levels are still very high and the residual traces of liquid metal coolant add to the hazard — so we need a tool capable of doing the job by remote control.’
The detachable tool bits, each costing £100,000 and weighing between 37kg and 93kg, enable a custom-built retrieval arm to mill, cut, grab and manipulate the 977 vertical metal rods that were left in the reactor core after its shutdown.
Up to three bits can be used at a time and replaced by another three carried in a ‘tool box’ without removing the arm from the reactor. The rest of the bits are stored above the reactor, ready to be swapped during service breaks.
Each rod will be cut free from its mounting in a hexagonal rack in the ‘breeder zone’ around the near-empty core. Engineers will also have to remove the single remaining fuel pin stuck in the core itself.
The rods will then be transferred to a basket and lifted through the roof of the reactor. The whole operation is expected to take three years.
Radiation-proof cameras and spotlights will guide operators working around the clock in a control room 20ft above the reactor in the hall of the containment sphere.
The shutdown operation between 1959 and 1977 saw around half of the nearly 2,000 original rods surrounding the core removed.
But 977 were left in place because some had become jammed and there was a shortage of storage space at the site. Now, the rest of the rods need to be removed so the reactor can be dismantled and the site demolished.
Part of an animation showing how the breeder material will be removed from the reactor using remotely operated cutting and retrieval tools.
Readers' comments (3)
Mike Boardman | 20 Jul 2011 5:51 pm
I visited Dounreay some 30 years ago, and had a very informative visit, it seems crazy that all that effort and experience has just gone to waste. Particularly as uranium by its very nature is a rare element, and production of Plutonium for peaceful means could be one solution to our energy needs for the future, particularly as all the uranium fuel has to be imported, with all its cost implications. Maybe the time is not far off that breeder reactors are the option of the wise.
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Brian Reed | 22 Jul 2011 2:50 pm
Mike is correct than plutonium is a potentially important fuel as uranium becomes hard to find.
Unfortunately there is no difference between plutonium for reactors & that for weapons. What it comes down to is 'who can you trust with a stockpile of plutonium?'. A further question might be 'who is going to maintain & guard the hazardous waste depository for several thousand years?'
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DJW | 27 Jul 2011 9:28 am
As a 'switch' on 'back up' concept I only have the usual contamination concerns about Nuclear Energy. The bigger problem I have is what is left after the 'event'. i.e. 30 years clear up and still counting!
So who is paying for this? Is this on the price of electricity, no. So 'supposed' higher renewalble energy tariffs are cost effective, I say so because I know it.
If the Nuclear Industry paid for 'the whole package' suddenly Renewable Tariffs are the real prices to pay.
Has anybody really professed to the world just exactly how much 'free' power we have available in wind & sun.
Just remember, all those resisting renewables that the gas you don't see is what is killing you not the turbine on the hill. A wind turbine occupies a 5m diameter piece of land, which when technology has progressed to something better can be removed, the ground re-seeded and back to green earth again.
DJW.
An Engineer in the Industry.
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