A study of the movement of radioactive material discharged during the windscale fire in October 1957

In October 1957, an accident involving a fire in a nuclear reactor at Windscale Works, Sellafield, on the Cumbrian coast of England released a quantity of radioactive material into the atmosphere. Past studies have examined the resultant ground-level concentrations of radioactivity in the UK and the rest of Europe using trajectory models or the analysis of milk samples taken at the time. Presented here is the latest study into the levels of radioactivity attributed to these releases which has been undertaken using the Met Officeʹs Nuclear Accident Model, NAME. The study examines the direction and timing of the transport, indicating the most likely spread within Europe of radioactive material from the accident. Best estimates are presented of likely time-integrated air concentrations and ground-level air concentrations of radioactivity throughout the initial few days after the accident. Although these estimates were not expected to be very accurate due to the source term being ill-defined, the results have been presented for completeness. The report concludes that NAME manages to successfully recreate the general movement of the radioactive plume and is in broad agreement with previous analyses. Discrepancies between modelled and measured plume arrival and activity for certain locations are primarily associated with errors in the calculation of the wind fields used by the model. Model predictions for this event could be improved by reducing the uncertainties in the release scenario and Met data used by NAME, and this possibility will be explored in future work.