Scottish CND     Safety of Trident
The 3 main radioactive materials used in the Trident programme are uranium, plutonium and tritium. There are dangers associated with the production and handling of all three. Nuclear warheads are assembled using old facilities at Aldermaston and were tested at the Nevada test site. The submarine reactors are similar to a full scale prototype which operates in a Ministry of Defence (MoD) establishment at Dounreay. Figures 1 and 2 are flow charts which show the overall cycles for reactor cores and nuclear warheads including materials production.
Within the Trident programme uranium is used in 3 ways. Firstly, a Trident nuclear warhead may contain 10 - 20 kgs of Highly Enriched Uranium (HEU). Secondly, HEU is used as the fuel for submarine reactors. Thirdly, uranium is used in magnox fuel for reactors which produce weapons grade plutonium for warheads. The total amount of natural uranium (0.7% U235) required for the Trident programme is estimated at around 1,300 tonnes.
Natural uranium used in the British nuclear programme is imported from the US, Canada and Australia. A Nuclear Energy Agency report says "Uranium miners ... are routinely among the most highly exposed workers in the nuclear fuel cycle". Workers are exposed to gamma radiation and can breathe in uranium dust which emits alpha radiation. The general public can be exposed to radiation hazards from the "tailings" which are left from mining and there is a particular hazard from radon gas.
The British Nuclear Fuels (BNF) site at Springfields is used to convert natural uranium into uranium hexafluoride (Hex). The Hex is used for both civil and military purposes. The main hazard during the production of Hex is from the toxic chemicals involved. Springfields makes fuel rods for land based reactors and may play a part in fuel rod fabrication for submarine reactors. There is the potential for accidental criticality during fuel rod fabrication.
BNF Capenhurst is a uranium enrichment facility which is involved in the 3 aspects of uranium procurement related to Trident. Capenhurst has been used to produce HEU for use in nuclear warheads. It also enriches uranium for magnox reactors which produce weapons grade plutonium. Capenhurst is involved in the first stage of enrichment for submarine reactor fuel. The second stage is carried out at a plant in Portsmouth, Ohio, US, where the uranium is enriched to 95 - 97 %. Around 1980 a new plant was proposed for Capenhurst which would be dedicated to military production and separate from civil facilities. The main risk associated with enrichment is accidental criticality, "nuclear criticality is always a concern when working with enriched uranium".
Separation and processing of uranium is carried out at Sellafield. See Section 1.2.
Rolls Royce and Associates (RRA) design and manufacture submarine reactors. Final fabrication of the fuel core modules for the Trident PWR 2 reactors is likely to take place at the RRA site in Derby.
Plutonium is used in the Trident nuclear warhead. If each has 4 kg of plutonium then the total required is around 1.6 tonnes. Plutonium can be stockpiled for long periods of time. It can be removed from old nuclear weapons and after processing, reused in new nuclear weapons.
Production - Windscale reactors The original 2 reactors at Windscale were established solely for the production of plutonium for nuclear weapons. Although they were closed in 1957 some of the plutonium produced there may be used in the Trident programme. Some of the plutonium will have been used, exploded in nuclear tests, but the remainder will have been recycled for use in successive generations of nuclear weapons, including Trident. The MoD has a programme for recycling over 90 % of the plutonium from old nuclear weapons.
On 20th October 1957 there was a major accident at the Number 1 Pile at Windscale. During a routine release of energy the reactor overheated and uranium and graphite caught fire. Fans were switched on to cool the reactor pile, but they actually made the fire more intense. The second reaction was to add carbon dioxide which also made the situation worse. The third solution was to flood the reactor with water. This was successful, but risky.
While the government claimed that the wind was blowing out to sea there was a temperature inversion and low level winds may have been blowing inland. A total of 14 workers were exposed to serious radiation doses. The activity released from the chimney included 7.4 x 1014 Bq of Iodine 131. A ban was placed on cows milk over a 520 km2 area and it has been estimated that 95 people are expected to die from cancer throughout the UK between 1957 and 1997 as a result of the accident. The official history of the event admits that it was inevitable.
During the fire polonium which is a dangerous, if short lived, alpha emitting radioactive isotope was dispersed into the atmosphere, however local authorities were not informed of its presence. Polonium was used as a trigger device in early nuclear weapons but this method soon became obsolete and by 1957 was regarded as outdated. In order to conceal the dependence of British nuclear weapons on polonium, the fact that it had been released at Windscale was kept secret.
Production - magnox reactors
Chapelcross and Calder Hall nuclear powers station each have 4 magnox reactors. The operators, BNF, have admitted that Calder Hall was built "with the primary function of manufacturing military plutonium". Chapelcross was built for the same reason with electricity production being secondary. These facilities were used to build up a stockpile of plutonium for the MoD and may have been used more recently to meet the requirements of the Trident programme. Plutonium is produced as a result of the fissioning of uranium during normal power generation in magnox reactors. In order to produce weapons grade plutonium the operating cycle of the reactor is adjusted to produce a higher proportion of Pu239.
There have been problems with the embrittlement of steel pressure vessels in magnox reactors operated by Nuclear Electric. Tests carried out at Risley on 6th October 1966 showed that a magnox pressure vessel could explode if it was subjected to temperatures higher than normal operating temperatures and if there were weaknesses in the structure. As a result Dr Irvine, a former employee of the Safety Division of the United Kingdom Atomic Energy Authority (UKAEA), has said that magnox reactors should be shut down. While Chapelcross and Calder Hall use the same design, the Nuclear Installations Inspectorate (NII) has indicated that these reactors are less prone to the problem because of their particular operating regime. Nevertheless the likelihood of an accident may increase as the reactors become older. By 1994 Calder Hall will have been in operation for 38 years and Chapelcross for 36 years.
There was a serious incident at the Number 2 reactor at Chapelcross in 1967. The reactor had just been refuelled when it was discovered that the gas flow through one of the fuel channels was mechanically blocked. The fuel in the channel melted and must have been hotter than 1100o C. A major disaster was averted but the reactor was shut down for 2 years for repairs. At the time of the incident the reactor may have been about to produce plutonium for use in nuclear warheads. Some of the plutonium produced at this time will have been recycled for use in Trident nuclear warheads.
Unlike Chapelcross and Calder Hall, other magnox reactors were designed primarily for electricity generation, however they do have a secondary capability to produce weapons grade plutonium. Prior to 1967 it is likely that plutonium from some of these reactors was used to produce plutonium for military purposes. There has been speculation that reactors at Bradwell and Berkerley in particular may have been used in this way.
Spent fuel from magnox reactors is taken into the B205 reprocessing building at Sellafield. From the spent fuel B205 separates plutonium and uranium. Some spent fuel consignments from Calder Hall and Chapelcross contain weapons grade plutonium. Military production has accounted for a significant proportion of the work carried out by B205 since it was opened in 1964. B205 is expected to continue to operate until beyond 2010.
In February 1986 there were a series of incidents at Sellafield which led to a Health and Safety Executive Inquiry. The inquiry found that, in B205, 17 % of equipment was substandard and there were defects in the ventilation system. The report said that "the condition of the B205 plant .. appears to us to have been subordinated to the requirements of current production". Almost half of 36 other buildings which were examined were found to be substandard. The report criticised attitudes to safety "the thoroughgoing and positive dedication to every aspect of safety that is characteristic of the best parts of the chemical industry has yet to be achieved".
There are a wide range of hazards in reprocessing including the risk of criticality, dangers of fire, explosion and leaks. External factors such as weather and seismic events can lead to an accident. "The potential risk is increased by the fact that during all stages of the process the materials are in easily dispersible forms .. and are being subjected to sometimes vigorous chemical and physical reactions". There has been at least one occasion when there was a fire at Sellafield during decanning of fuel from magnox reactors in preparation for reprocessing. A criticality incident occurred in a facility for recovering plutonium from residues at Sellafield on 24th August 1970 when flow stopped in a solution containing 2.5 kgs of plutonium . On 26th September 1973 there was a substantial accidental release of radioactive ruthenium 106 from a facility for the initial treatment of oxide fuels at Sellafield.
There was also a facility within Sellafield which was designed to recycle plutonium from nuclear weapons. Weapons grade plutonium contains a proportion of plutonium241 which decays to americium241 an unwanted by-product. The building at Sellafield was designed to remove americium from plutonium from dismantled nuclear weapons. The plutonium would then be reused in other weapons. It has been reported that this facility closed in 1987 .
Concern has been expressed about some of the staff in the plant. Douglas Wilkinson, a clinical psychologist, was commissioned by the Senior Medical Officer at BNFL to look at staff at Sellafield. In his report he said that he found that some of the scientific staff were neurotic and incompetent. He said he was surprised "that such obviously unstable people were employed at the plant in the first place".
Tritium is an essential component of a boosted fission nuclear device, such as the Trident warhead. It is a gas with a radioactive half life of 12.5 years which decays at a rate of around 5.5% per year. It is believed that one nuclear test conducted by the UK in Nevada in 1974 was designed to test the effect of using aged tritium in a warhead. Initially tritium may have been procured from the US, subsequently a programme was initiated to produce tritium in the UK. Because it can only be stored for short periods there will be a programme to replace the tritium component in warheads every 7 - 8 years. If each warhead has 4 g of tritium then to keep 400 Trident warheads in service for 30 years would require around 4.8 kg of tritium.
In 1976 BNF was awarded a contract by the MoD to produce tritium at Chapelcross. There are 3 stages in production: the production of lithium 6 targets, the irradiation of lithium in the reactor to produce tritium and the subsequent processing. Since 1980 Chapelcross has had special facilities for this 3 stage operation.
Figure 3. These vehicles are used to transport radioactive materials across Britain. The two in the photograph drove from Coulport through Helensburgh on 11th August 1993 under UKAEA Police escort and were probably transporting Tritium. Chapelcross was due to be decommissioned but this has been delayed until 2004, probably so that the MoD can retain a tritium production capability. There are fears that BNF may have plans to build another reactor capable of producing tritium at Chapelcross although at the moment the proposals are for a PWR reactor which would not be suitable. The US has a facility to remove decay products so that the remaining tritium can be reused but there is no equivalent in the UK An alternative approach to the long term supply of tritium would be to build up a large stockpile of tritium and then use US facilities to process this to remove decay products. This would mean increased production of Tritium at Chapelcross prior to 2004.
Discharges of tritium to the atmosphere from Chapelcross are higher than from other UK power stations. In Canada there is a reactor at Pickering which also discharges a large amount of tritium. There is concern that this may be the cause of birth defects in the area. In 1990 discharges of tritium from Pickering were 9 x 1014 Bq, while discharges from Chapelcross were twice as much, 1.9 x 1015 Bq. It has also been suggested that tritium could be a factor in the high incidence of birth defects around the Hanford nuclear site in the US and may be a source of other health problems near nuclear installations. The radiation from tritium is regarded in the nuclear industry as a minor problem, however dangers of the beta emissions from tritium may have been underestimated by the International Commission on Radiological Protection (ICRP) . The Health and Safety Executive (HSE) report into Sellafield and leukaemia found a correlation between incidence of childhood leukaemia and the father's exposure to tritium during his work at Sellafield .
1.4 WARHEAD PRODUCTION
The Atomic Weapons Establishment (AWE) Aldermaston has been involved in the development of the Trident warhead since the mid 1970s with the main development period being from 1980 to 1987. This work has included the manufacture of warheads for tests in Nevada. Production of plutonium pits for Trident warheads began in January 1988 and has continued for 6 years using old facilities. The A1.1 building which is vital for this production was first operational in 1952. In 1996 production was continuing in A1.1 and A45...
Following staff concern about radioactive contamination on site, a major investigation was carried out into safety at Aldermaston in 1978. The Pochin inquiry discovered that the levels of radiation monitored in many parts of the site, including plutonium processing facilities, were considerably higher than ICRP limits. Incidents of health problems among workers were also discovered, which could be attributed to their work with radioactive materials. The inquiry recommended that new facilities were needed. There was also a need for new buildings because the old A1.1 and A45 buildings were not able to produce warheads fast enough to meet the demands of the Trident programme. Because of a series of delays the new building, A90, was not ready when production of plutonium pits began in 1988. Initial delays meant that the MoD decided to start Trident production in the old buildings and to continue producing the first batches of warheads. A1.1 and A45 continue to be used 15 years after they were criticised for inadequacy by the Pochin inquiry. Peter Jones, who was director of Aldermaston until 1987 has said that these old facilities should never have been used at all for Trident production, because of concerns about their safety.
Bays 1 and 2 of A90 completed red commissioning in 1995 and the first plutonium pit was produced from them in December 1995.
Aldermaston is involved in a wide range of work related to nuclear weapons research and production. It is involved in recycling old nuclear warheads and may take over the task of removing decay products from old warheads, which was done at Sellafield.
Other sites involved in warhead production include the UKAEA establishment at Harwell which may carry out some work on plutonium and AWE Cardiff34. The work at Cardiff involves handling beryllium which is a serious toxic hazard. The danger is that workers and members of the public could inhale particles of beryllium dust. Cardiff also carries out work on depleted uranium for the tampers of nuclear warheads. This also creates a radiation hazard. In 1983 AWE Cardiff was authorised to store 50 tonnes of natural or depleted uranium35.
1.5 WARHEAD TESTS
The development programme for the Trident warhead included a number of tests which were conducted in the Nevada desert. The local people of the Western Sheshone Nation have been exposed to radiation with consequent health problems as a result of decades of nuclear tests. While these tests were conducted underground, they have contributed to the radioactive contamination of the area.
The Chief Strategic Systems Executive at the MoD, Rear Admiral Irwin, said in March 1993 - "There have been, I think, three - I wait to be corrected - specific tests to Trident"36. Between January 1980 and December 1987 the MoD carried out 11 underground nuclear explosions in the Nevada test site. Some of these may have been final tests of Chevaline warheads and others related to the development of a warhead for the Tactical Air to Surface Missile. At least three will have been specific Trident tests. Information obtained from other tests will have been used in the development of the Trident warhead.
The MoD have a Naval Reactor Test Establishment at Dounreay. Known as HMS Vulcan the facility is operated by Rolls Royce and Associates who design and build Britain's submarine reactors. The prototype PWR 2 reactor at HMS Vulcan was handed over to the MoD in October 198738. This type of reactor is only used on Trident submarines. The prototype will be used to test how the reactor functions through a simulated core life with probably 3 cores over a period of 20 - 30 years. There are hazards associated with the operation of this reactor, similar to many of those which affect submarine reactors, which are detailed under Trident submarine and reactor accidents.
Scottish CND     Safety of Trident