What will happen to 140-tonne stockpile of combustible sodium at Dounreay?
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Dounreay's operators have still to decide what to do with the remaining 140 tonne stockpile of sodium on site.
Plans are afoot to build a new plant to neutralise what is one of the most hazardous legacies from its days as the UK's testbed for fast reactors.
But Magnox Ltd has not ruled out hauling the material to a disposal plant, if it can find one able and willing to do the job.
An update was given at Wednesday evening's meeting of Dounreay Stakeholder Group (DSG) when the site management came under fire for not dealing with the issue years ago.
Around 137 tonnes of the payload comprises sodium, nearly all of which is stored in drums in the the turbine hall adjoining the former prototype fast reactor, where it was used as a coolant.
The rest is remnants of a sodium/potassium alloy, known as NaK, which was used to cool the earlier DFR, dome-shaped reactor.
The bulk of the highly combustible chemical, which reacts with air and moisture, was destroyed in two disposal plants, which have since been demolished.
Operations director Mick Moore said it has been unable to identify a UK site which would take the material.
While continuing with its search, its current preferred option is to deal with it on site.
Its provisional schedule is to build a new disposal plant in 2027 with a view to processing the sodium in the early '30s.
DSG honorary member Roger Saxon believes the issue should have been dealt with long before now.
"The problems with sodium pre-dated privatisation at Dounreay – it's been there for quite some time," he said.
"It's a bit surprising that it's been stored for so long in what looks like an inadequate store, given it had a leaking roof. To my mind, this hazard should have been dealt with quite some time ago.
"I'm disappointed that we're going to have to design and build another plant and that it will take years before we finally get round to dealing with the sodium."
Mr Saxon, a former DSG chairman who worked at Dounreay for many years, believes there is a site near Southampton that could potentially take and treat the sodium.
The PFR sodium hit the headlines recently after enforcement action was taken over the condition the drums were being kept.
The Office for Nuclear Regulation found storm damage to the roof of the building had caused water ingress.
There was evidence of corrosion and bowing or swelling to some of the lids of drums. The regulators also found problems with record-keeping.
In June, the Scottish Environment Protection Agency (Sepa) issued a warning letter about a minute leak of radioactive tritium from one of the drums in November last year.
A leak at the sodium tank farm sparked an overnight emergency in April 2022 with Sepa finding that Dounreay's authorisation had been breached and earlier this year issued a final warning letter.
Mr Moore said: "We're making improvements to make the building weather-tight.
"This week we completed work on the roof – that has now been addressed.
"We have also improved our techniques for inspection and raised our action levels.
"Now if we find any issues, we can repack the drum."
