The 40th anniversary of the Windscale fire (1011 Oct 1957) has been marked by some news media interest in its effects and implications. The Windscale fire occurred in a graphite moderated, air cooled, military reactor used to produce plutonium for Britain's nuclear weapons programme. Overheating caused the failure of one or two nuclear fuel channels in Pile 1 at Windscale, which led to a fire in about 150 fuel channels on Thursday 10 October 1957, with subsequent releases of fission and activation products into the atmosphere. The fire was eventually put out on Friday 11 October 1957 by flooding the reactor with large volumes of water.
NRPB has published several reports and scientific papers on the radiological consequences of the Windscale fire. The work by Crick and Linsley1,2,3 gave the first NRPB assessments of doses to the general population of the UK and northern Europe from the accident, and used risk estimates for cancer and hereditary effects available at the time. The papers published by Professor Clarke4,5, Director of NRPB, and Robinson6 are updated assessments of the radiological consequences, allowing for increases in risk estimates for cancer and hereditary effects which became accepted internationally in the late 1980s.
The main radionuclide of concern in the releases from the fire was iodine-131 which concentrates in the thyroid gland. The average radiation dose to the thyroids of the local adult population was typically 5 to 20 millisieverts (mSv), and between 10 and 60 mSv for local children from iodine-131. The expected health effect would be an increase in the risk of thyroid cancer, and the lifetime risk of radiation-induced thyroid cancer in the most exposed individuals may be estimated at 1 in 300. These risks are for the few infants who were estimated to receive thyroid doses of up to 160 mSv; for adults with the highest doses, the risks are about a factor of five less.
The fire also released significant quantities of polonium-210 into the atmosphere. This radionuclide, which also occurs naturally, gave effective doses of about 2 mSv to the local adult population and about 3 mSv to local children. The average annual natural background effective dose in the UK from all sources of exposure (eg, terrestrial, cosmic and medical) is about 2 mSv per year.
The annual risk of lung cancer from the polonium-210 released is estimated to be about 5 in 1,000,000 compared with an average risk (which includes the risk from smoking) of about 1,100 in 1,000,000 for men and 400 in 1,000,000 for women in the UK.
The additional risks from the Windscale fire are small in comparison with normal cancer rates. Taking into account all nuclides and pathways, the total fatal cancer risk from the Windscale fire to the most exposed individual is about 6 in 1,000,000 per year. For comparison, the normal fatal cancer risk for a member of the UK population is about 1 in 300 per year.
The Windscale fire was a serious nuclear accident leading to a significant release of radionuclides into the atmosphere. However, the reactor was not large compared to modern power reactors, and a filter on the stack managed to restrict the atmospheric discharge, particularly of iodine-131. This, coupled with countermeasures applied at the time, especially the imposition of restrictions on the consumption of cows' milk, meant that the risks to the most exposed individuals and to the population as a whole were small. It is unlikely that any effects could be seen in the population that could be attributed to the Windscale fire. This is in contrast to the Chernobyl nuclear power plant accident where the releases of iodine-131, iodine-132 and tellurium-132 were 1,000 times higher and there were long delays in implementing appropriate countermeasures in some local areas. There are therefore observable health effects in the surrounding population in Belarus, the Ukraine and the Russian Federation, particularly non-fatal thyroid cancers in children7,8.
1 Crick, M J, and Linsley, G S. An assessment of the radiological impact of the Windscale reactor fire, October 1957, Chilton, NRPB-R135 (1982) (London, HMSO).
2 Crick, M J, and Linsley, G S. An assessment of the radiological impact of the Windscale reactor fire, October 1957. Addendum to report NRPB-R135. Chilton, NRPB-R135 Addendum (1983) (London, HMSO).
3 Crick, M J, and Linsley, G S. An assessment of the radiological impact of the Windscale reactor fire October 1957. Int. J. Radiat. Biol., 46, No 5, 479506 (1984).
4 Clarke, R H. Current radiation risk estimates and implications for the healthconsequences of Windscale, TMI and Chernobyl accidents. Medical Responses to Effects of Ionising Radiation. Editors: W A Crosbie and J J Gittus. Oxford, Elsevier Applied Science, pp 102118 (1989).
5 Clarke, R H. The 1957 Windscale Accident Revisited. The Medical Basis for Radiation Accident Preparedness. Editors: R C Ricks and S A Fry. New York, Elsevier Science Publishing Co. Inc., pp 2819 (1990).
6 Robinson, C A. Windscale and Chernobyl: a comparison of the effectiveness of countermeasures taken in the UK. IN Proceedings of a Seminar on the Comparative Assessment of Radionuclides Released During 3 Major Nuclear Accidents: Kysktym, Windscale, Chernobyl, Luxembourg, 15 October 1990. Luxembourg, CEC, EUR 13574 7 1041 (1990).
7 World Health Organisation. Health consequences of the Chernobyl accident. Scientific Report. Editors: G N Souchkevitch and A F Tsyb. Geneva, WHO (1996).
8 International Atomic Energy Agency. One Decade after Chernobyl; Summing up the Consequences of the Accident. Proceedings of an International Conference, Vienna, IAEA (1996).
First issued 10 October 1997
Last updated 10th October 1997