Bruce Center for Energy Research & Information

+Dounreay, Scotland

Contents

Introduction

Waste Shaft Explosion

Radioactive Discharge

Fishing Rights

Other problems

Cleaning Up and Costs

Dounreay advice to Fukushima

Introduction

In 1955, the United Kingdom Atomic Energy Authority (UKAEA) inaugurated the Dounreay Nuclear Power Development Establishment, in the town of Dounreay, on the north coast of Caithness, the northernmost county of Scotland. Over its lifetime, the DNPDE has been the site of three nuclear reactors and one facility for testing prototype nuclear submarine engines.

Although the 1977 explosion in Dounreay’s waste disposal shaft is considered the second worst nuclear disaster in Britain,[1] the major source of nuclear contamination at Dounreay has turned out to be its long-term discharge of liquid containing fragments of the radioactive fuel rods.

Waste Shaft Explosion

In the mid-fifties, the Dounreay engineering team drilled a vertical shaft 65.4 meters [211 feet] deep, with an average diameter of 4.6 meters [15 feet] to aid in the construction of the effluent discharge tunnel. A short horizontal tunnel was dug from the vertical shaft and met up with the in-process effluent discharge tunnel.

The Dounreay waste shaft in operation

The Dounreay waste shaft in operation

The shaft was used to remove broken-up rock and as the main pumping route to keep the tunnel dry during excavation. After the discharge tunnel was completed, the tunnel connecting it to the vertical shaft was plugged with concrete and Dounreay began using the vertical shaft for nuclear waste disposal. In 1959, the shaft was licensed for intermediate-level nuclear waste disposal, so this marks the beginning of its official use.[2] In the picture to the right, you can see waste being lowered through the hole in the middle of the plug at the top of the shaft.

On May 10, 1977 there was an explosion in the shaft. It was fairly impressive:

papers released under the Freedom of Information Act …. show the shaft’s concrete plug, weighing seven tonnes, was blown three to four metres [10 to 13 feet] into the air and thrown against a security fence, while a steel plate, nearly 1.5 metres [5 feet] in diameter, was blasted 12 metres [39 feet].

Debris was projected over the boundary fence on to the sea shore, lead sheeting was thrown over the security fence and two six-metre scaffolding poles were found outside the fence, one 40 metres [130 feet] away on the beach. The windows of the control room were also shattered and asbestos weather shields surrounding the shaft and a 20ft length of the nearby security fence were extensively damaged. About 50 spots of ground contamination were found to the north of the shaft and pieces of asbestos were discovered up to 75 metres [245 feet] away.[3]

The aftermath of the Dounreay shaft explosion

After the explosion. In the rear, you can see the square concrete plug (which the man was kneeling on in the above picture) and in the foreground the shattered concrete around the hole where the plug was.

What caused the explosion? A build-up of hydrogen gas under the cap of the shaft. The coolant for the Dounreay reactors was a mixture of sodium and potassium that is liquid at room temperature. This mixture was disposed of by dumping it down the waste shaft, which is a questionable idea since the waste shaft was mostly filled with sea water. Those who remember their high school chemistry will recall that both sodium and potassium react with water, producing lye, hydrogen gas, and a great deal of heat – potassium in fact usually explodes when submerged in water.

The dumping of wastes from the nuclear facility into this waste shaft was unsupervised and undocumented. And handled according to the whims of those disposing it:

There was unsupervised fly-tipping into the shaft and workers firing rifles into it to sink polythene bags floating on water, with no regard to the shaft’s hazardous contents.[4]

The shooting is interesting: in other words, some waste was dumped in plastic bags to minimize its contact with the water; it reacted in small amounts anyway, generating gas that caused the bags to float. The Dounreay workers shot the bags, causing them to sink again, and giving the sea water free access to their contents.

We don’t know what has transpired beneath the surface of the water, but in 1977 the hydrogen gas from these reactions had built up enough under the cap of the shaft that igniting it (a spark from pumping equipment is officially blamed) touched off the explosion.

Removing the waste that remains in the shaft is considered the most difficult decommissioning job at the Dounreay site, because at 65 meters deep it is the deepest nuclear decommissioning attempt in the world,[5] and because the shaft’s precise contents are unknown.[4]

Radioactive Discharge

Spectacular though Dounreay’s exploding waste shaft might have been, the centerpiece of its contamination of the surrounding ocean has been its 19-year discharge of radioactive metal fragments from its fuel rods.

Dounreay, conceived when uranium was scarce, was designed to recycle and reuse uranium reactor fuel. Between 1958 and 1996, as a first step in this process, the aluminum cladding was shaved away from the uranium core in large ponds, with the liquid protecting workers from the radiation. The shavings accumulated at the bottom of these ponds and was periodically collected and dumped into the shaft (see above) or the silo (see below). The liquid from these ponds was drained to large settling tanks to allow smaller shavings to settle out, and then the liquid was discharged into the sea.[6]

The result:

In theory, only the liquids drained off the top of Dounreay’s settling tanks would flow down this tunnel. But the waste did not settle properly. As well as the liquid, … pieces of fuel rod were also washed out. There is now a plume of radioactive particles on the seabed to the north of Dounreay covering hundreds of square kilometres.[7]

Two kilometres of beach outside the Dounreay nuclear plant have been closed since 1983, and fishing banned, when it was found old fuel rod fragments were being accidentally pumped into the sea. The cause was traced and corrected but particles – including plutonium specks, each capable of killing a person if swallowed – are still being washed on to this bleakly beautiful stretch of sand and cliff on mainland Britain’s northern edge.[8]

Dounreay staff documented evidence of shavings evading their control system in the mid-60s, including a discovery in 1965 that a cracked pipe had allowed milling-pond water to enter a storm drain. The practice of dumping shavings into the shaft and silo was halted in 1969, when shavings were discovered contaminating the land routes from the milling pond to those two destinations.

Filters were not installed on liquid pumped to the settling tanks until 1984-5. This followed several instances in the 70s and early 80s where high-pressure water had to be used to force effluent through the clogged discharge lines to the sea. The first reactor fuel shavings (generally called “radioactive particles” in the news) were discovered on neighboring beaches during this time. In 1992, new discharge lines and a new diffuser were installed. In 1995, more roadside contamination was discovered.[9]

Fishing Rights

Geoffrey Minter, the laird of the neighboring Sandside estate, is facing bankruptcy after the radioactive contamination from Dounreay closed his beach and rendered his salmon-fishing rights worthless. Minter ran out of funds after the government took years to set up a panel to evaluate his claims, and the panel then only awarded him a fraction of the damages he was seeking (the exact amounts don’t seem to be public knowledge).

The Scottish Environmental Protection Agency (SEPA) has ruled that the radioactive shavings will be a hazard for 300 years; however the panel only estimated that time as 30 years. They also attached no monetary value to the loss of the fishing rights.

“Since I have been handling… [the administration of the estate] there have been two expressions of interest in the salmon fishing rights,”
said James Stephen, the bankruptcy administrator for Minter[10]

In the months following the panel’s decision, the Sandside estate has been put up for sale. The beach is not included.[11]

Other problems

The vertical shaft was not the only dumping site at the Dounreay facility. As early as 1971, the staff realized that there were problems with the shaft and built an alternative facility.

Historical records show there was a significant risk of contamination spread at the top of the shaft as a result of the procedures used to dispose of waste. The area was contaminated frequently.[2]

In fact, the routine procedural contamination problems at the shaft dwarfed those from the explosion:

In 1995, research on the health physics implications of the … [1977 explosion] concluded that the significant ground contamination, which then remained in the vicinity of the shaft, resulted from the methods of waste disposal used in the 1960s.[12]

The wet silo – an engineered, concrete-lined bunker – was brought into use as an ILW store in 1971 to allow the shaft to be taken out of routine service. After 1971, the shaft was only used for items that were too large for the silo.[2]

Nor are these dumping sites the only reservoirs of dangerous waste on the Dounreay campus.

[The UKAEA] stationed [the facility] … in remote Caithness – because they feared their first test reactor might explode. They even encased it in a giant sphere of steel, known as Fred the Golf Ball – Fred standing for Fast Reactor Experiment in Dounreay – to contain any blast.

This 60-metre metal ball still dominates the site and might even be retained as a key landmark or possibly a visitor centre, according to Scottish Heritage. ‘Unfortunately, the sphere still contains about 50 tonnes of highly radioactive liquid metal coolant,’ said Simon Middlemas, Dounreay’s site director. ‘That will take an awful lot of cleaning before people can walk inside.’[8]

For reference, the official Dounreay documents analyzing the 1977 shaft explosion estimated that it resulted from the amount of hydrogen released by 2.5 kg (five and a half pounds) of liquid metal coolant reacting with water.[3]

 

Cleaning Up and Costs

Although the UKAEA kept no precise accounts for building and running Dounreay, it is known to have cost several billion pounds. Now a further £2.5 billion will be spent returning the site to its pre-nuclear condition, leaving only a vault, covered with grass, to hold low-level nuclear waste while high-level waste will probably be shipped to a central UK nuclear store yet to be approved. ‘An immense amount of money was spent here,’ admitted Steve Beckitt, a senior Dounreay project manager.[8]

Note that although the cost of the cleanup was given as £2.5 billion ($3.9 billion, € 2.9 billion) in the late oughts, the current (2013) contract for decommissioning Dounreay is reported at £1.6 billion ($2.5 billion, € 1.86 billion). The cost and difficulty of the decommissioning effort are increased by the ad hoc nature of Dounreay’s waste disposal in the past, and the lack of documentation. For example, once the plutonium building in the criticality test lab was declared unsafe and uncleanable in 1967, it was locked and left untended for 20 years. But it was also used to store “other radioactive junk” during the 70s and 80s, of which no record seems to have been kept.[12]

Similarly, unaccounted-for reactive material including Uranium 235 has been found during the current decommissioning process by opening and examining containers that had been sealed under Dounreay’s original management:

More than 200 drums filled with waste produced during past operations at the plant have been opened up and their contents inspected before being repacked for long-term storage.

Decommissioning engineer Bob McKiddie said equipment being used to detect what was inside the drums was far more accurate than anything available when the containers were originally filled.

Mr McKiddie said: “We had suspected that the historical results had under-estimated the uranium content in a number of waste items.

“The repackaging work has resulted in an overall gain in the amount of uranium declared.

“The figures from the repackaging work show that material previously considered ‘lost’ was in fact safely packaged as waste.”[14]

The champion, of course, for undocumented and randomly accumulated waste is the shaft:

Steve Efemey, who is in charge of the retrieval and treatment phase, said [of the waste shaft] … “We don’t know exactly what’s down there or what condition it is in as there are different degrees of degradation. That’s the challenge.

“The worst-case scenario is that the sodium drums are still intact. But that is unlikely after 50 years and 1500 tonnes of waste on top of them.”[4]

In the “Other Problems” section, we noted the presence of 50 tons of liquid metal coolant inside the giant sphere. In a major triumph, 1500 tons of liquid metal coolant from the second Dounreay reactor has been decontaminated,[15] but much remains from the original reactor:

The reactor has been de-fuelled apart from one stuck experimental fuel assembly and 977 breeder elements, at least 10 per cent of which are jammed or heavily damaged by earlier de-fuelling attempts. The secondary NaK [the liquid metal coolant] has been removed but the primary NaK is intact, with high levels of radioactive contamination.

The radioactive NaK and associated nine kilometres of reactor pipe work represent one of the most significant hazards at Dounreay.[16]

The cleanup of the radioactive reactor rod shavings that were flushed into the ocean, although the major environmental contamination at this point, is projected to be a relatively minor component of the cleanup costs, at £18-25 million ($28-39 million)[17] of which £800,000 has gone to the design and construction of a remotely-operated underwater robotic vehicle that travels along the sea floor, searching for and collecting the radioactive particles.[18]

However, the Scottish Environmental Protection Agency (SEPA) has accused the UKAEA of vastly misrepresenting the number of particles,[19] and essentially merely putting on a show with its underwater cleanup operation.

Dounreay advice to Fukushima

Don’t laugh. This is the current “senior manager in charge of contaminated land clean up at Dounreay” offering the advice, not people from the previous management team. That said, his comparison of the two sites does not bode well for Fukushima:

Mr Cartwright added: “Japan is at the start of a much bigger clean-up project with significant challenges both on and off site but the issues they face are similar to those we had to work through, even though ours were on a much smaller and more localised scale.”[20]

Citations

[1] The worst was when the uranium fuel in the Windscale reactor caught fire and burned for three days.

[2] “Disposals to shaft” , Dounreay Site Restoration Ltd. http://www.dounreay.com/decommissioning/shaft-and-silo/disposals-to-shaft

[3] “Dounreay chiefs played down major blast at plant”, The Scotsman, July 13, 2005. http://www.scotsman.com/news/scotland/top-stories/dounreay-chiefs-played-down-major-blast-at-plant-1-719857

[4] “No-one knows what is left in the Dounreay waste shaft”, The Herald, January 25 2007. http://web.archive.org/web/20081007172440/http://www.theherald.co.uk/news/news/display.var.1145249.0.0.php

[5] “Dounreay prepares for world’s deepest nuclear clean-up”, John O’Groat Journal and Caithness Courier, July 9, 2012. http://www.johnogroat-journal.co.uk/News/Dounreay-prepares-for-worlds-deepest-nuclear-clean-up-06092012.htm

[6] http://www.dounreay.com/UserFiles/Image/DMTR/DMTR%281%29.jpg

[7] “Dounreay’s catalogue of idiocy is a cautionary tale of nuclear danger”, The Guardian, September 11, 2006. http://www.theguardian.com/commentisfree/2006/sep/12/comment.politics

[8] “Robots scour sea for atomic waste,” The Observer, May 24, 2008. http://www.theguardian.com/environment/2008/may/25/pollution.conservation

[9] “Timeline”, Dounreay Site Restoration Ltd. http://www.dounreay.com/particle-cleanup/timeline

[10] “Scots laird facing ruin after Dounreay nuclear blast”, David Maddox, The Scotsman,  April 8, 2012. http://www.scotsman.com/news/scotland/top-stories/scots-laird-facing-ruin-after-dounreay-nuclear-blast-1-2222849

[11] “Estate in Dounreay legal wrangle goes on the market”, Alan Shields, John O’Groat Journal and Caithness Courier, June 29 2012. http://www.johnogroat-journal.co.uk/News/Estate-in-Dounreay-legal-wrangle-goes-on-the-market-29062012.htm

[12] “1977 shaft explosion”, Dounreay Site Restoration Ltd. http://www.dounreay.com/decommissioning/shaft-and-silo/1977-shaft-explosion

[13] “Experimental criticality laboratory”, Dounreay Site Restoration Ltd. http://www.dounreay.com/decommissioning/experimental-criticality-laboratory

[14] “’Lost’ radioactive material found”, BBC News, December 4, 2009. http://news.bbc.co.uk/2/hi/uk_news/scotland/highlands_and_islands/8393783.stm

[15] “Milestone in hazard reduction as liquid metal is destroyed”, Dounreay Site Restoration Ltd.  http://www.dounreay.com/news/2008-08-18/milestone-in-hazard-reduction-as-liquid-metal-is-destroyed

[16] “DFR Overview”, Dounreay Site Restoration Ltd. http://www.dounreay.com/decommissioning/dounreay-fast-reactor/dfr-overview

[17] “Particle Clean-up”, Dounreay Site Restoration Ltd.  http://www.dounreay.com/particle-cleanup

[18] “Robot collects 300 radioactive particles from Dounreay seabed (only 400 to go)”, The Scotsman, October 1, 2010. http://www.scotsman.com/news/robot-collects-300-radioactive-particles-from-dounreay-seabed-only-400-to-go-1-823186

[19] “Watchdog hits at Dounreay’s false reporting”, Mark Macaskill, The Sunday Times, April 16, 2006. http://www.thesundaytimes.co.uk/sto/news/uk_news/article199634.ece

[209] “Dounreay staff offer advice on Japan’s Fukushima”, BBC News, June 3, 2012. http://www.bbc.co.uk/news/uk-scotland-highlands-islands-18299011

[21] “Prototype Fast Reactor”, Dounreay Site Restoration Ltd.  http://www.dounreay.com/decommissioning/prototype-fast-reactor