Abstract
Cascade centripeters and personal air samplers were used for a period of one year to measure the particle size of radioactive aerosols in various buildings at A.E.R.E. Harwell, and to examine the relationship between personal exposure and exposure measured by an environmental (static) sampler. The particle size distribution of the airborne activity in all buildings was approximately log-normal. In the incinerator building and filter house the activity median aerodynamic particle diameter was 5–6 µm for both α and β activity with a geometric standard deviation of 2·5–3·0. Similar size distributions were obtained for β activity in the high-activity handling building and in the wet decontamination area, but airborne a activity in the latter had a median diameter of 3·5 µm with a geometric standard deviation of 4·3. The air concentrations measured by samplers operating on a weekly basis were statistically analysed, and the convenience of the log-normal distribution is demonstrated. It is shown that in areas where the source of airborne contamination is widespread and not directly associated with particular operations, the long-term mean exposure indicated by personal samplers is similar (within a factor of 2 or 3) to that indicated by the static (centripeter) sampler. However, in an area such as the decontamination area, where each man generates a localised aerosol, the mean exposure indicated by personal samplers is often 10 or more times higher than that shown by a static sampler.

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