Exploitable results Plate out of radon daughter aerosols in domestic and mine environments A 6-channel, parallel, multiscreen diffusion battery, utilising silicon diffused junction detectors to detect alpha particle emissions from filters downstream from the scrrens, has been used to determine the activity size distribution of the aerosol in the atmosphere of mines and homes to which radon-222 daughters are attached. The battery was modified to allow resolution of the unattached fraction of radon daughters, having diameters in the range 0.5-3 nm. Previously reported measurements of unattached fraction of potential alpha energy concentration (PAEC), fp, in homes have given values of 0.04 to 0.34. Measurements in a kitchen while cooking was in progress yielded a mode with activity median diameter of 11 nm. In living rooms close to kitchens, a mode between 6 and 14 nm occurs during and following cooking. The accumulation mode in the activity size distributions measured had a modal diameter between 110-130 nm. Aerosol conditions in above ground workplaces, (eg schools) were similar to those in homes. Limited data has been obtained on activity size distributions of radon daughters in mines. In homes, the average radon gas concentration is a better estimate of dose to the lungs than is measurement of average total PAEC, but this is not so in mines. In homes, factors affecting the equilibrium factor, F, and unattached fraction, fp, act in opposite senses, so that increasing fp, which would increase the dose to the lungs, is offset by a falling F, tending to reduce the dose. In mines, because of high aerosol concentrations, independent of varying ventilation conditions, fp is always low (less than 0.02). In homes, an annual average radon concentration of 20 Bqm{-3} results in an effective dose equivalent of 1 mSv. Application of CR-39 track etch detectors to low background counting and particle sizing of air samples The technique of alpha particle registration on CR-39 plastic was developed with a view to its use for the routine assay of long lived alpha activity collected on personal air samplers (PAS), which are used for routine individual monitoring of workers at risk of exceeding 30% of the annual limit on intake (ALI) of long lived alpha emitters. The activity on the filters is usually measured using alpha drawer counters, but, in monitoring chromic exposures to plutonium, the sensitivity is too low, the minimum detectable activity being equivalent to about0.1 ALI. The results of the study were as follows: autoradiography of PAS filters could provide a sensitivity at least a factor of 5 greater than present counting techniques; activity attached to aerosols of greater than 400 nm could be assessed separately; the dynamic range of the technique was limited by tracks overlapping in the centre of the autoradiograph on high activity samples; these could be remeasured by exposing them to CR-39 for a shorter period; even with automatic image analysis, the technique was more labour intensive than present techniques; clusters of tracks were difficult to identify among evenly spread tracks unless there was a large difference in track density; quality control of etched-track counting was difficult; the technique entailed a delay of several weeks before obtaining a result; although antoradiography of PAS filters provided useful extra information, it was deemed unsuitable for routine use. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
