Environmental monitoring in the vicinity of Sellafield following deposition of radioactivity from the Chernobyl accident

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Abstract
British Nuclear Fuels plc carries out an extensive programme of routine environmental monitoring around its operating sites. Following the reactor accident at Chernobyl, USSR, in April 1986, special monitoring arrangements were implemented and expanded as the situation developed. Results from the Sellafield Site were of special significance as they showed that West Cumbria was an area of high deposition. Descriptions of the monitoring carried out around Sellafield, and the results obtained, are presented here. Analysis of these results is described in terms of assessment of radiological significance of the incident to the population of Cumbria. Additionally, the effects of the accident on Sellafield environmental monitoring results for 1986 are described and the implications for 1987 and future years considered as a supplement to the summary of annual environmental monitoring data. The major radionuclides detected were 131I, 134Cs and 137Cs. Early results for rainwater indicated concentrations of iodine and caesium more than 30 times those recorded in lakes. Up to 200 Bq kg-1 131I was recorded in leafy green vegetables growing in the fields at the time of the incident, although with much lower concentrations in other crops. Concentrations of 131I and 137Cs in milk peaked around 360 Bq l-1. The consequences of the deposition, although modest in radiological terms when compared with the relevant ERLs, were sufficient to dominate the results of monitoring during 1986 for caesium, iodine, ruthenium and other 'Chernobyl' radionuclides in the terrestrial environment around Sellafield.