Dounray dilemma of sunken atomic junkyard

A deep hole on a remote Scottish cliff top is one of Britain's two most awkward and dangerous radioactive sites. Yesterday its owners, the UK Atomic Energy Authority (UKAEA), announced three more research contracts into how the Dounreay waste shaft can be made permanently safe.

It has promised to present firm proposals to ministers by the end of this year. One option is to freeze the 200ft depth of the water-filled, vertical shaft. But, whatever solution is embraced, the highest priorities will be to eliminate the risk of a chemical explosion or a ``criticality'' - a runaway nuclear chain-reaction.

For 20 years, starting in 1957, radioactive waste from Dounreay, on the northernmost coastline of mainline Britain, was dropped into the shaft; a volume equivalent to a medium-sized house took the plunge. It has left Dounreay under a pall of intense criticism and would never be contemplated today.

In 1977, a hydrogen explosion blew the concrete lid off the shaft, scattering small quantities of radioactive material. Dumping ceased and ever since the shaft has been monitored for any build-up of explosive gas. Were that to happen, nitrogen would be pumped in to prevent a blast.

But this is not a permanent solution; for the next few tens of thousands of years, any escape of waste from the shaft would be highly dangerous. Unless a breakwater is built, and that too is under consideration, the sea will breach the shaft in about 200 years. Only UKAEA's sealed-off Number One pile at Windscale, Cumbria, site of the 1957 reactor fire which was Britain's worst nuclear accident, presents greater clean-up difficulties.

The UKAEA Dounreay director, Roy Nelson, said: ``Clearly, the shaft is the most challenging task we face here.'' A solution will cost hundreds of millions of pounds. Dounreay, 20 miles from John O'Groats, was where Britain spent 40 years trying to perfect the fast-breeder reactor, which turns uranium into plutonium - ``breeding'' its own fuel.

Three reactors were built and all have shut. The programme was killed because of costs, but the site will employ hundreds of people and absorb billions of pounds into the next century. The 15ft-diameter shaft was used to haul away rock carved out when a tunnel was bored out to sea, taking Dounreay's liquid low-level radioactive waste 600 yards offshore.

In the 1950s, permission was obtained to use the shaft as a dump for low and intermediate-level radioactive waste. A concrete plug was placed at the bottom to seal the shaft from the tunnel and the sea. Some 10,000 items were taken there in flasks from plants and laboratories around Dounreay. These would open and the waste plunge into the fresh water which had seeped in. UKAEA has been combing old logbooks to find out what was dumped and has interviewed retired Dounreay workers.

Items as big as lathes went down the shaft. So did glove boxes, used to shield workers as they manipulated highly radioactive materials. The 1977 explosion was caused by a mixture of sodium and potassium, the volatile coolant in fast-breeder reactors, inadvertently dumped in the shaft. The mixture reacted with water to produce hydrogen. All that was needed was a spark to ignite it and because sodium burns in air, that was readily available.

It will take thousands of years for radioactivity in the waste to decay to negligible levels. Making it safe in the long term may require pulling it out of the shaft and placing it in a permanent repository. It is too dangerous a task for humans, so remote-controlled arms and grabs combined with closed-circuit television will be used. The worst nightmare is a nuclear chain-reaction beginning in a sludge of uranium and plutonium particles which may build up at the bottom of the shaft.

Doug Graham, a scientist at Dounreay, said such a "criticality" was inconceivable in the undisturbed shaft. But any technique devised for removing the waste would have to provide absolute assurance that no chain-reaction could happen.

While the ultra long-term solution will probably involve emptying the shaft, UKAEA is also considering interim solutions. One option is to pump in refrigerants through bore holes to freeze the water and waste.

Start your day with The Independent, sign up for daily news emails
Have you tried new the Independent Digital Edition apps?
ebooks
ebooksA celebration of British elections
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Ashdown Group: Part-time Payroll Officer - Yorkshire - Professional Services

£25000 per annum: Ashdown Group: A successful professional services firm is lo...

Ashdown Group: Helpdesk / Trainee Application Support Analyst - Hampshire

£25000 per annum + pension, 25 days holiday: Ashdown Group: A highly reputable...

Ashdown Group: Helpdesk Analyst / Trainee Application Support Analyst - Essex

£25000 per annum: Ashdown Group: A highly reputable business is looking to rec...

Ashdown Group: IT Support Engineer - Hertfordshire -Large Established Business

£22000 - £28000 per annum + study support, gym: Ashdown Group: A large busines...

Day In a Page

Fishing for votes with Nigel Farage: The Ukip leader shows how he can work an audience as he casts his line to the disaffected of Grimsby

Fishing is on Nigel Farage's mind

Ukip leader casts a line to the disaffected
Who is bombing whom in the Middle East? It's amazing they don't all hit each other

Who is bombing whom in the Middle East?

Robert Fisk untangles the countries and factions
China's influence on fashion: At the top of the game both creatively and commercially

China's influence on fashion

At the top of the game both creatively and commercially
Lord O’Donnell: Former cabinet secretary on the election and life away from the levers of power

The man known as GOD has a reputation for getting the job done

Lord O'Donnell's three principles of rule
Rainbow shades: It's all bright on the night

Rainbow shades

It's all bright on the night
'It was first time I had ever tasted chocolate. I kept a piece, and when Amsterdam was liberated, I gave it to the first Allied soldier I saw'

Bread from heaven

Dutch survivors thank RAF for World War II drop that saved millions
Britain will be 'run for the wealthy and powerful' if Tories retain power - Labour

How 'the Axe' helped Labour

UK will be 'run for the wealthy and powerful' if Tories retain power
Rare and exclusive video shows the horrific price paid by activists for challenging the rule of jihadist extremists in Syria

The price to be paid for challenging the rule of extremists

A revolution now 'consuming its own children'
Welcome to the world of Megagames

Welcome to the world of Megagames

300 players take part in Watch the Skies! board game in London
'Nymphomaniac' actress reveals what it was really like to star in one of the most explicit films ever

Charlotte Gainsbourg on 'Nymphomaniac'

Starring in one of the most explicit films ever
Robert Fisk in Abu Dhabi: The Emirates' out-of-sight migrant workers helping to build the dream projects of its rulers

Robert Fisk in Abu Dhabi

The Emirates' out-of-sight migrant workers helping to build the dream projects of its rulers
Vince Cable interview: Charging fees for employment tribunals was 'a very bad move'

Vince Cable exclusive interview

Charging fees for employment tribunals was 'a very bad move'
Iwan Rheon interview: Game of Thrones star returns to his Welsh roots to record debut album

Iwan Rheon is returning to his Welsh roots

Rheon is best known for his role as the Bastard of Bolton. It's gruelling playing a sadistic torturer, he tells Craig McLean, but it hasn't stopped him recording an album of Welsh psychedelia
Morne Hardenberg interview: Cameraman for BBC's upcoming show Shark on filming the ocean's most dangerous predator

It's time for my close-up

Meet the man who films great whites for a living
Increasing numbers of homeless people in America keep their mobile phones on the streets

Homeless people keep mobile phones

A homeless person with a smartphone is a common sight in the US. And that's creating a network where the 'hobo' community can share information - and fight stigma - like never before