Chapelcross

Major problems and incidents:
Fuel blockage 1967
Pressure Vessel embrittlement
Crack in heat exchanger 1997
Inadequate earthquake protection
Contaminating the environment
Fuel rods dropped July 2001

The nuclear bomb factory
The risks from tritium
Ageing reactors
Replacement reactors
The risk from tritium
Nuclear Waste

Closure

In June 2004 BNFL announced that Chapelcross power station would close immediately.

The nuclear bomb factory

While Chapelcross has never been involved in the assembly of nuclear weapons it has, throughout its life, played a key role in the British nuclear weapons programme. In the 1950s the UK decided to build up a large arsenal of nuclear bombs and missile warheads. The first batches of weapons grade plutonium in the 1950s had been produced at Windscale (now renamed Sellafield). However this facility was destroyed in Britain's worst nuclear accident in 1958. Two nuclear plants were constructed to provide the bulk of the plutonium required for Britain's bombs. The first was at Calder Hall, within Windscale/Sellafield. The second was at Chapelcross and became operational in February 1959. For many years Chapelcross was one of the main sites where plutonium was produced for atomic and hydrogen bombs. The Trident nuclear weapons which are at Faslane today almost certainly contain plutonium from Chapelcross.

Because of its military role, the reprocessing of spent fuel from Chapelcross was kept outside of international regulation. However in 1998 the government announced that: "All re-processing from defence reactors at Chapelcross will in future be conducted under EURATOM safeguards and made liable to inspection by the IAEA". This signalled an end to military plutonium production.

However this has not ended Chapelcross's role in bomb making. Modern nuclear weapons contain small quantities of tritium. Tritium is a radioactive material which plays a key role in the thermonuclear process of a hydrogen bomb and is also used to boost the yield of atomic bombs. It is used on British Trident warheads. Tritium is a radioactive material with a short halflife of 12 years. Because it decays so quickly it has to be replaced. The tritium in British nuclear weapons is replaced after 7 or 8 years. So the military demand a constant supply of tritium - and in our case this comes from Chapelcross. Tritium is produced in the reactors of the power station and processed at facilities on the site.

5,000 tonnes of Depleted Uranium are also stored at Chapelcross. This was part of a massive military stockpile of this material which has been controversially used in weapons. In 1998 Britain announced that the material at Chapelcross would no longer be considered as military material and would be placed under EURATOM and IAEA safeguards.

The risks from tritium

The health hazards from tritium are not clearly understood and the dangers associated with this gas are disputed. Tritium is produced at the Pickering nuclear plant in Canada. Researches have found an 80 % increase in Downs syndrome around the Pickering plant and have associated this with tritium. Discharges of tritium from Chapelcross are between one and a half and two times greater than from Pickering. Discharges can be over 100 TBq per month. The following are total discharges of tritium to the air recorded in 1996/7 at Chapelcross:

Ian Fairlie, a researcher at Imperial College London has warned of the dangers of tritium. In 1997 he said: "I would not recommend a pregnant woman or young children to be living in farms downwind of Chapelcross". Levels of tritium in vegetables grown near the plant may be 100 times higher than those grown 8 miles away, according to 1995 statistics. A fraction of any tritium which is ingested stays in the body and is taken into the cell structure. Mr Fairlie is concerned about the effect which this Organically Bound Tritium (OBT) has on cell nucleuses. This is an area which scientists do not clearly understand.

Ageing reactors

The original design life of the reactors at Chapelcross was 20 years. On this basis they would have been closed in 1979. The life of the plant was extended by a series of reviews. In 1990 the Nuclear Installations inspectorate said that it could operate for 40 years and then in 1998 they said it could carry on for 50 years. These recomendations are highly suspect. It was suggested that the NII had avoided allocating its most rigorous inspectors to reviewing Chapelcross. The Ministry of Defence has been keen to stretch the life of these reactors as far as possible. In 1999 the Armed Forces Minister, John Spellar MP said: "The Ministry of Defence is currently in the very early stages of discussions with BNFL about the prospects for a further extension of the life of Chapelcross beyond the period quoted." (Hansard 28/1/99) Local campaigner Harry Johnston was quoted in the press saying: "Chapelcross's age makes it very dangerous. They had to carry out massive repairs to get it through its last check - yet they are proposing to keep it open until 2010. It's irresponsible." The station was closed in 2004.

Replacement reactor

Proposals to replace Chapelcross have been around for more than a decade. In 1991 planning permission was given for boreholes to be dug for a Pressurised Water Reactor to replace the existing plant. This plan would have involved flooding several valleys to build a reservoir to supply water for the plant. BNFL's current plans are that Chapelcross would close down between 2008 and 2010. BNFL is likely to be seriously considering its options for replacing Chapelcross in the immediate future.

Major Incidents and Problems

Fuel blockage 1967

In 1967 there was a serious accident in number 2 reactor at Chapelcross. The reactor had just been refuelled when it was discovered that the gas flow through one of the fuel channels was mechanically blocked. The fudl in the channel melted and must have been hotter than 1100 degrees Celcius. A major disaster was averted but the reactor was shut down for 2 years for repairs.

Pressure Vessel embrittlement

There has been serious concern about the effect of radiation on the materials in the Reactor Pressure Vessel of Magnox reactors. This has been a factor in the decision to decommision these stations in the past. The worry is that the steel pressure vessel could become more brittle as a result of radiation. The reactors at Calder Hall and Chapelcross were run on a different regime to other Magnox reactors, because they were primarily intended for weapons production. BNFL have argued that this means that they are less susceptible to problems than others of this design and can be operated for longer. However in1999 it was disclosed that there was concern that there could be increased embrittlement of the Reactor Pressure Vessel at Calder Hall, as a result of thermal neutron dose damage.

Crack in heat exchanger 1997

In June 1997 a crack was found in heat exchanger 6, part of the pressure system of the reactor. The crack extended for 230 mm and through 90 per cent of the thickness of the pressure retaining shell. The repair was carried out using novel welding methods. At the time the cause of the defect could not be identified and plans were made to inspect the other heat exchangers at both Chapelcross and Calder Hall. BNFL argued that the problem was not related to the age of the reactor.

Inadequate earthquake protection

In designing modern nuclear plant considerable attention is given to the effects of an earthquake. A new structure should be able to withstand the type of seismic event which could be expected to occur once in 10,000 years. However when Chapelcross was planned in the 1950s this issue was ignored. As a result the facility falls well below modern safety standards. A review by the NII identified one area where this was a particular problem. It was calculated that the cooling ducts which linked the reactor to the heat exchangers would fail in the event of predictable seismic activity. In 1997 the design was modified to provide greater protection for the ducts. However it is highly likely that there remain other aspects of the reactors' design which would fail in the event of an earthquake.

Contaminating the environment

Chapelcross is permitted to discharge large quantities of radioactive material into the sea and air. In addition to this there have been a serious of unauthorised discharges from the site.

Particles of irradiated uranium have been found on the shore of the Solway Firth. In the early 1990s five such particles were discovered only 10 metres from the Chapelcross discharge pipe. The level of radiation from one of these particles was such that if it was in direct contact with the skin for 25 hours then the recognised safety limit for public exposure would be reached. BNFL said that they thought that the particles had been discharged in the 1970s.

In December 1998 there was a leak of radioactive tritium. In January 1999 BNFL discharged two batches of effluent, each consisting of 13,000 gallons, without first checking the level of radioactivity of the effluent. A formal warning was given to BNFL by SEPA. In September 1999 700 gallons of waste were spilled. As a result of this BNFL were fined 5,000 pounds in September 2000.

Fuel rods dropped July 2001

On 5 July 2001 highly radioactive fuel rods were dropped several feet during the refuelling of a reactor at Chapelcross. 24 rods were involved in the accident, 12 of them dropped 80 feet and three of those were broken . Initially BNFL claimed that the rods only fell 2 feet. Because of the risk of fire carbon dioxide was pumped over the fallen fuel.

Radioactive waste from Chapelcross

The most hazardous waste produced is the used fuel which is High Level Waste. This is not included in the following figures which only cover Intermediate Level Waste (ILW) and Low Level Waste (LLW). The figures are from the UK Radioactive Waste Inventory 1994. This assumed that the station would close in 1999. Its continued operation to 2008 will alter the timescale and increase the volumes. The volumes are in cubic metres, as stored. Conditioning of waste will increase volumes.