cnd logo    Scottish CND     Safety of Trident


The Deputy Controller (Nuclear) at the MoD, Mr Beaver, told the House of Commons Defence Committee "The circumstances seen by a weapon which could make it unsafe are varied and complex". When on the submarine the hazards are related to the overall safety of the vessel. This is discussed under Trident submarine. This section looks at the risks associated with the assembly, transport by road, and storage of warheads.

The effects of a warhead accident are discussed in the section on warhead accidents.


British nuclear weapons are assembled at the Atomic Weapons Establishment Burghfield where work goes on around the clock. The procedures probably mirror those carried out at the US nuclear weapons assembly site, Pantex. At Pantex there are many sub-assembly bays where explosives are worked and shaped and a smaller number of main assembly bays where the explosives are placed around the fissile material. It is at this second stage that an accidental detonation of the explosives would lead to a release of plutonium. The main assembly bays at Pantex have 2-ton blast doors and the roofs are covered in 6 m of gravel . This gravel is there to absorb some of the plutonium which would be dispersed in an accident. The conspicuous large half-domes at Burghfield may be of a similar design.

Every Trident warhead will be assembled at Burghfield. They are also expected to be dismantled here when they are retired. If there are problems with the weapons while in service the whole stockpile would have to be taken back to Burghfield, modified and reassembled - this happened in the 1980s with Chevaline warheads.

Assuming that the stockpile target is 300 Trident warheads, then the assembly bays at Burghfield will be used on at least 600 occasions for assembly and dismantling. If the warheads had to be returned for modifications then this would rise to 1200 operations. This suggests that there is a significant chance of an explosion which would disperse plutonium. Despite the protection provided by the assembly bay design there would be a major health risk to personnel within the establishment and to the local population downwind of an accident.

During assembly the tritium element is added. In a handling accident there could be a release of tritium which would be a serious problem for those in the immediate vicinity and a health hazard for the local population.


Once assembled, Trident warheads are stored temporarily on site. Later they are placed into containers and loaded onto lorries which travel in convoy to the Royal Naval Armaments Depot (RNAD) Coulport. From November 1992 onwards these convoys of 3 to 5 lorries, plus escort, were making this journey every one or two months. This is still going on On most occasions they take 3 days to travel from Burghfield to Coulport. The convoys normally passed London on the M25, on the M1/A1 to Newcastle then either West to the A74 or North around Edinburgh. The majority of Trident convoys have travelled through the centre of Glasgow on the M8.


Trident warheads are moved in containers which may measure around 3 m in length and 1.5 m in height and width. Monitoring of the procedures for loading and unloading Chevaline warheads at Coulport gives grounds for concern. Chevaline containers are tied down inside the vehicles within 1 or 2 minutes after which the back door is closed and not opened again until the vehicle arrives at its final destination. Fixing of the container appears to be done without any lighting inside the vehicle. This suggests that procedures for checking and double checking tie down arrangements on Chevaline containers may not be sufficiently rigorous. The same may apply to Trident warhead containers.

If containers are not correctly tied down then the consequences of a minor road accident could be very serious. In a collision one container could be propelled into the second container in the trailer or into the trailer walls.


Nuclear warheads are transported within special articulated vehicles built by Foden, the Truck Cargo Heavy Duty Mark 2 (TCHD Mk2). It has been established by Nukewatch that each vehicle can carry 2 Chevaline containers. Similar vehicles are being built for Russia and the dimensions of the containers for Russia suggests that they will also have a maximum of 2 containers in each vehicle. Nukewatch has observed procedures within Coulport which suggest that 2 Trident containers can be carried in each vehicle.

The vehicles are built to a special design. Foden normally supply 3 axle tractor units for articulated lorries. The TCHD Mk 2 tractor units have 4 axles, 2 of which are steering axles. The additional axle is needed because of the exceptional weight of the vehicles, 48 tonnes. This is the Gross Train Weight of tractor plus trailer and is visible on the vehicle plates.

The first convoy of Fodens to Coulport in July 1992 broke down on the return journey. Since then there have been a series of mechanical problems. On 8th November 1992 smoke was seen coming from the rear axle of a carrier when it made an unscheduled stop on the A68 near Consett - local people were warned to stay out of the way because of dangerous fumes. An MoD spokesman has said that on a number of occasions brakes have overheated and that there was "a problem of brake adjustment between the tractor and trailer elements of the vehicle". The heat generated by the brakes could result in a fire which could engulf the nuclear warheads. Poor synchronisation of tractor and trailer brakes might also result in a vehicle crashing out of control.

In the early hours of 18th May 1993 a convoy delivering Trident nuclear warheads left Burghfield. Instead of the usual 3 day journey, the convoy was attempting to travel all the way to Coulport in 1 day. The tractor units of one Foden broke down completely at the A82 exit from the Erskine Bridge, West of Glasgow. It was eventually towed away and replaced. During the change over the trailer, probably carrying two Trident warheads, was supported by the trailer props. Observation of practice at Coulport suggests that at no time is a tractor unit changed over while the trailer is loaded. At the time of the incident the trailer unit was in a dangerous position on the side of the road above a steep embankment. The convoy finally arrived at Coulport at 1 am on 19th May. The spare tractor unit may also have broken down earlier in the day as it was 2 hours late arriving on the scene.

During this incident a second carrier was in a dangerous position on the main road. Rather than split up the convoy, the remaining vehicles pulled into an adjacent lay-by. As this was too small to take the whole convoy, one vehicle, carrying Trident warheads, was parked in one lane of the A82, the main road North West from Glasgow.

There have been two further occasions when tractor units have been changed by the side of a road, once on the A1 and once on the M25. In all three of these incidents the problem was with the tractor unit. If there was a problem with the trailer this would have created even more difficulties. If the trailer was immobilised, then the Trident nuclear weapons would have to be moved into another vehicle. Such a transfer of nuclear weapons between carriers did take place when a convoy of old Mammoth Major carriers broke down on 1st December 1991. The M25 was closed and a crane was brought in to lift the nuclear weapons from one vehicle to another.


The fact that nuclear weapons carriers travel in large convoys increases the risk of them being involved in an accident. They are bunched together with a large escort for reasons of security, not safety. The abnormal flow of traffic which this creates can lead to accidents. On one occasion there was a crash on the A814 near Faslane when a driver was distracted by a convoy travelling in the opposite direction. He collided with the car in front. In February 1993 a police car escorting a convoy caused a road accident on the M8 in the centre of Glasgow.

Nuclear weapons convoys are escorted by between 4 and 6 motorcycles driven by RAF police, MoD police and civilian police which are frequently redeployed from one end of the convoy to the other. Motorcycles are more likely to be involved in accidents than other vehicles. Observers from Nukewatch once saw a motorcycle escorting a convoy swerving wildly on the M8 in Glasgow when it had a burst tyre. On 11th August 1993 an outrider was seriously injured in a collision on the A1 near Alnwick. The initial police description of the incident was that the motorcycle had veered across the road, although later accounts suggested that the collision was caused by a skip lorry travelling in the other direction.

One of the more serious accidents in which a weapons carrier could be involved would be a collision with a fast moving heavy lorry. Convoys transporting Trident warheads consist of between 3 and 5 carriers each with gross vehicle weight of 48 tonnes travelling at 50 mph. The other weapons carriers in the convoy present a serious hazard. One collision between two Mammoth Major warhead carriers took place on 25th June 1985 in the middle of Helensburgh. One vehicle braked suddenly and the carrier behind collided with it - the rear vehicle was damaged and had to be towed back to Coulport.

Normally if a lorry driver suspects he has a problem he will pull off the road onto the hard shoulder, or into a lay by. In the same circumstances the driver of a nuclear weapons carrier has to contact the convoy commander by radio who then arranges for the whole convoy to stop. This must make it less likely that a vehicle will stop if there is a minor problem.

Off-road accidents

A carrier could be badly damaged if it went off the road and collided with the abutment of a motorway bridge or if it fell from a high embankment. All Trident nuclear weapons delivered to Coulport in 1992 and 1993 were transported over the Erskine and Kingston Bridges in Glasgow. There is serious concern about the structural stability of the Kingston Bridge and officials are considering diverting Heavy Goods Vehicles (HGVs) off the bridge when the flow of traffic is very heavy. The Fodens in a Trident convoy have a combined weight of 240 tonnes and often cross this bridge, which is in the centre of the city, during the early evening rush hour. There have also been a number of serious accidents when HGVs have fallen off this bridge which is the busiest river crossing in Europe. Elsewhere in Britain there has been an accident in which a nuclear weapons carrier went off the road. On 10th January 1987 a Mammoth Major nuclear weapons transporter slid off an icy road and landed on its side in a ditch near Dean Hill in Wiltshire. Trident warheads have been transported in dangerous weather conditions in the middle of Winter.

Collisions involving other road users

However well trained the Foden drivers are they can still find themselves caught up in an accident because of the behaviour of other road users. On 17th September 1988 on the A303 Illminster bypass an MG sports car crossed the road and collided head on with a Mammoth Major nuclear weapon transporter. The driver of the MG was killed and petrol from the car spilled around the Mammoth Major but did not ignite. The carrier ended up inches from a steep embankment.

A convoy transporting Trident warheads has been observed on one occasion travelling on the same stretch of the A74 as a vehicle carrying a large quantity of commercial explosives. Convoys are frequently on the same roads as tankers carrying petroleum products and highly inflammable chemicals. There has been one recorded incident where a fire engine was called to deal with a diesel tanker when smoke was coming from its overheated brakes on the approach road to Coulport - a convoy had been expected to leave at around this time, but did not leave until 24 hours later.

Gas mains

In June 1983 a gas main exploded in Cardross shortly after a nuclear weapons convoy had passed. The gas main may have been weakened by the weight of the Mammoth Major carriers. At 48 tonnes, the Fodens used to transport Trident warheads are over the maximum weight limit for HGVs. There is a risk that 4 or 5 of these vehicles travelling in convoy could weaken a gas main in the future and cause a very dangerous explosion.

Probability of transport accidents

The examples above illustrate that between 1982 and 1992 there were occasions where nuclear weapon transporters were involved in fatal accidents, when there were collisions between transporters and when vehicles crashed off the road. Similar accidents are likely to occur in the large number of journeys required to transport Trident warheads to and from Coulport.

National and international regulations

The Director of HSE has said that nuclear weapons must be transported in a way which complies with International Atomic Energy Agency (IAEA) guidelines. He has also said that arrangements do comply with the guidelines, in that the packaging of nuclear weapons takes account of the explosive properties of the consignment. However the IAEA is concerned with the peaceful uses of nuclear energy and has said that these guidelines should not be used to prove the safety of nuclear weapons transport . The guidelines were not drafted with nuclear weapons in mind and cannot be used as a basis for any safety case.

The provisions in the guidelines are intended to take account of the explosive properties inherent in some civil consignments of radioactive material. They do not permit a package of explosives to be in contact with a package of radioactive material - "packages ...shall be segregated during transport ... from other dangerous goods". The explosive properties of a nuclear weapon are not inherent in the radioactive material but come from the deliberate combination of radioactive and explosive components. To comply with the guidelines these components would have to be segregated - but they are not.

The guidelines also say that "Fissile material shall be packaged and shipped in such a manner that subcriticality is maintained under conditions likely to be encountered during normal conditions and in accidents". A ball of plutonium surrounded by high explosive in a format designed to create a supercritical mass would not be permitted if it was a civil consignment.

The transport of explosives alongside radioactive material is contrary to British regulations, however there is an exemption for "instruments of war". A nuclear weapon is no safer than an identical package which was being transported in the civil industry. Neither these regulations nor the IAEA guidelines can be used to argue that nuclear weapons are being transported safely. On the contrary, they show how safety considerations are secondary to political concerns. The MoD is allowed to do what, on safety grounds, is illegal in the civil nuclear industry.


When the transporters carrying Trident nuclear warheads arrive at Coulport they are parked in an open car park which is dominated by two lightning conductors. The vehicles are then taken one at a time to a transfer facility where each container is loaded into a large black box. This black box is probably designed to provide a controlled environment for the warheads. It is assumed that the warheads are normally stored in Re-entry Body Magazines (RBMs) although some have been seen in the Ready Issue Magazines (RIMs) which are designed to hold loaded missiles. At their peak the RBMs could contain 128 Trident warheads. It is assumed that this magazine area is designed to limit warheads exploding one after the other with a domino effect, nevertheless a major fire could engulf a large number of nuclear warheads. An investigation into safety at the Polaris compound in Coulport has shown that fire engines are called in almost once a week. Assuming that 75 % of these are false alarms there may still be a real fire alert around once a month.

Warheads will be transported around Coulport from the RBMs to the Explosives Handling Jetty (EHJ) where they will be fitted onto missiles. The dangers in this operation are considered in section 3.4.

There is a Re-entry Body Process Building (RBPB) at Coulport which will carry out inspection of warheads and basic maintenance. An MoD spokesman has said "there are some lifed items within the warhead and they will need to be refurbished". One of the components which needs to be replaced every 7 or 8 years is the tritium element and the work will probably be done in the RBPB. With a stockpile of 300 warheads in service for 30 years, tritium replacement may be carried out 900 times. This involves removing warheads from their containers and taking off at least the nose cones. In the event of a handling accident it is possible that the explosive in the warheads could detonate. A fire within this building might also have very serious consequences.

On 2nd May 1986 a container was being opened in the Polaris area at Coulport when radiation alarms went off - the container may have contained tritium. While there were no casualties from this incident, a more significant release could endanger workers and could result in radioactive material being dispersed into the atmosphere.

The RIMs at Coulport are designed to hold 16 Trident D5 missiles with warheads attached. The MoD state that this capability is not required on a regular basis, but might be needed if a Trident submarine had to be taken to Devonport for an emergency docking. The MoD have also said that there could be other occasions when a smaller number of missiles will be removed for operational reasons. The dangers of a missile accident are discussed in Section 3.1 and 3.4.

The RIMs are designed to prevent the detonation of one missile setting off all the adjacent missiles in a domino effect. However the MoD has had great difficulty in meeting this criteria with the reinforcement configurations for the bunkers being changed on several occasions and the contractors finding great difficulty meeting them.

In addition to handling Trident warheads and missiles, there are other explosives at Coulport. The depot will continue to maintain and store Polaris missiles and nuclear warheads until they are withdrawn, around 1998. Coulport also has a contract to service Tigerfish torpedoes. An accident at the Soviet Naval Ammunitions Depot at Severomorsk showed how dangerous it can be to have large quantities of explosives and missiles in the same place. In May 1984 there was an explosion in a conventional ammunitions magazine which set off sympathetic detonations in a weapons store and in an area where missile fuels were stored. Approximately 200 people were killed and one third of the surface to air and cruise missiles of the Soviet Northern Fleet were destroyed.

An accident could occur at any point during the handling of nuclear warheads within Coulport. While the greatest risks are probably at the EHJ and in the RBPB, an accident could occur during unloading, storage or transport within the depot.

cnd logo    Scottish CND     Safety of Trident