TRIDENT warheads carried regularly by road to the Clyde naval base could explode if they are involved in a major crash, an internal Ministry of Defence report reveals.
The report – which seems to contradict previous MoD assurances on safety – states that the warheads’ key safety feature could be disabled by a plane crash or vehicle pile-up. In the worst-case scenario, this could trigger a nuclear explosion, unleashing a burst of lethal radiation.
Defence ministers and MoD officials have repeatedly insisted that such an accident is impossible. And last week an MoD spokesman claimed its own report was mistaken, saying that an explosion could be ruled out because the warheads were not armed.
The MoD stance was dismissed by Jane Tallents from Nukewatch Scotland, a group which monitors nuclear weapons convoys.
“We have been misled,” she said. “The prospect of a nuclear bomb accidentally exploding while it is being transported through Glasgow, Edinburgh, Stirling or anywhere else is too horrific to contemplate. The only safe option is to dismantle every warhead.”
Convoys of nuclear weapons travel about six times a year between the Atomic Weapons Establishment at Burghfield in Berkshire and the Royal Naval Armaments Depot at Coulport on Loch Long. According to the MoD, they pass through 21 local authorities in Scotland.
The safety of the convoys, which involve more than six vehicles, has been assessed by the MoD’s directorate of nuclear movements and nuclear accident response group. In a report dated December 16, 2004, it said there is a risk of an “inadvertent yield” from a nuclear explosion.
This could result in huge radiation doses to members of the public of between one and 10 sieverts, it says. According to the government’s Health Protection Agency, doses of more than four sieverts can cause acute radiation poisoning and death within days.
“Multiple failures” caused by vehicle accidents or aircraft crashes could mean that “the nuclear weapon may not retain its single point safety nature”, the report says.
“Single point safety” is the main barrier to an accidental nuclear explosion. To explode a nuclear bomb, a sphere of plutonium has to be rapidly compressed by a series of conventional high explosives. Bombs are designed so that if they suffer a hit at a single point, all the explosives will not detonate.
The MoD report argues the chances of an accidental explosion are so low – less than three in a billion per year – it is therefore acceptable. “Nuclear safety risks are tolerable,” it concludes, “when balanced against the strategic imperative to move nuclear weapons.”
But this is angrily rejected by Mark Ruskell, the Green MSP for Mid Scotland and Fife, who obtained the report under the Freedom of Information Act.
“The horror of a nuclear accident anywhere on a convoy route would be so great that even a minute risk is utterly unthinkable,” he said.
“I have always assumed that while leaks of nuclear material from a damaged convoy are feasible, an explosion would be impossible. This new information blows away our perceptions of what the hazards are.”
Ruskell is also concerned that nuclear weapons convoys could be a target for terrorists. “Given the nature of post-9/11 politics and terrorism, nuclear weapons are more of a liability than a deterrent,” he warned.
Nigel Chamberlain, a nuclear analyst with the British American Security Information Council in London, accused the MoD of transporting nuclear warheads across the country “with a distasteful mix of secrecy, arrogance and complacency”. Reassurances about the inherent safety features of warhead design had now been exposed as “overstated”, he said.
The MoD has always maintained a convoy accident could not trigger a nuclear explosion. “Even in the highly unlikely event of an accident involving the detonation of the conventional explosives within a warhead and a subsequent fire, there would not be a nuclear explosion,” says a statement from the MoD’s Atomic Weapons Establishment.
Yesterday, the Ministry of Defence did not deny that there were circumstances in which a nuclear bomb could lose its single point safety. But an MoD spokesman suggested that this may not be the only protection against accidental detonation. “A nuclear bomb-type explosion could not take place because the nuclear weapon is unarmed. It is in such a state that fission could not take place,” he said.
“There has never been an accident involving a nuclear weapons convoy which has led to, or has come anywhere near leading to, any release of radioactive contamination. We are confident that the continued application of stringent safety procedures will continue to prove effective in preventing such an accident.”
But Frank Barnaby, an expert on nuclear bombs who used to work for the Atomic Weapons Establishment, was more sceptical. “I wouldn’t be prepared to take the MoD’s word for it, given the seriousness of the consequences,” he said.
The MoD’s “obsessional secrecy” prevented any independent assessment of the risks, he argued. “The public have the right to be totally reassured, but because of the secrecy that is not possible. That is worrying.”
The MoD report is one of a series of documents released under the Freedom of Information Act about plans to speed up the nuclear bomb convoys. In order to reduce the risk of terrorist attack, the MoD has changed to a system of “continuous running” which cuts the time taken for the convoys to complete their journey from three days to 24 hours.
But the documents say that the change, “if inadequately conceived or implemented, would have the potential to create a significant hazard to the operation”. Dangers cited included poor visibility at night, tiredness and getting lost.
In the past four months, the convoy has been seen making two journeys through Scotland. On April 1, anti-nuclear campaigners claim the 44-tonne truck carrying the bomb went over a bridge with a 13-tonne weight limit near Stirling. On May 7, the convoy was halted in Balloch, north of Glasgow, when a protester lay down in the road in front of it.
THE DANGERS OF A BOMB EXPLODING BY ACCIDENT
A safety assessment prepared by the Ministry of Defence says that a nuclear weapon involved in a serious road or aircraft accident could explode and expose people to radiation doses of between one and 10 sieverts.
radiation dose / health effects
>half a sievert / nausea, diarrhoea, hair loss, drop in white blood cell count
1-2 sieverts / some people die within weeks from bone marrow damage and infections
4 sieverts / 50% of people will die from acute radiation poisoning
6 sieverts and above / everyone exposed will die
source: Health Protection Agency
THE SCOTTISH COUNCILS CROSSED BY NUCLEAR WEAPON CONVOYS
Argyll & Bute, City of Edinburgh, City of Glasgow, Clackmannanshire, Dumfries & Galloway, East Ayrshire, East Dunbartonshire, East Lothian, East Renfrewshire, Falkirk, Fife, Highland, Midlothian, North Lanarkshire, Perth & Kinross, Renfrewshire, Scottish Borders, South Lanarkshire, Stirling, West Dunbartonshire, West Lothian.
In addition to the 21 councils in Scotland, military nuclear materials may pass through or fly over 13 local authorities in Wales and 91 in England.
Source: Ministry of Defence