RESUMEN
A fire in a nuclear reactor at Windscale Works (Sellafield, England) in October 1957 led to an uncontrolled aerial release of radionuclides. At the time of the accident air was sampled at various locations in Europe to monitor atmospheric pollution, and the opportunity was taken to measure the sampling filters for activity concentrations of iodine-131, caesium-137 and polonium-210 at the Harwell research establishment (United Kingdom); when it was not possible to perform measurements at Harwell, original measurement data were supplied. This programme of activity measurements was performed in the context of work by the Advisory Committee on Nuclear Radiation of the International Geophysical Year (IGY; July 1957-December 1958). The International Geophysical Year was an international programme of research into a comprehensive range of geophysical phenomena. The results of this measurement programme were originally reported in Harwell Memorandum AERE-M857 (1961) and this Harwell report is reproduced in this paper because of its historical interest and because it is no longer readily accessible to researchers.
