Radon daughters concentration

Working level month (WLM) An exposure ot I WLM can be taken to be received by a person working in a Radon daughter concentration of 1 WL for 170 hours. 

Working Level Month (WLM)—A unit of exposure to radon daughters corresponding to the product of the radon daughter concentration in Working Level (WL) and the exposure time in nominal months (1 nominal month =170 hours). Inhalation of air with a concentration of 1 WL of radon daughters for 170 working hours results in an exposure of 1 WLM. 

Swedjemark G.A. and Mj0nes L., 1984, Radon and Radon Daughter Concentrations in Swedish Hones, Radiation Protection Dosimetry,... 

In Sweden, requirements on future building (Swedjemark, 1986) and the limits for existing dwellings will result in lower radon daughter concentrations in homes and to some part it already has. 

For the collective dose, however, the decrease will be very slow because of the low building rate compared with the housing stock. It has been estimated tha the average for the Swedish radon daughter concentration, 50 Bq/m EER, may be decreased to half that value after about 100 years, if the requirements mentioned above are fulfilled. 

In most other countries regulations or recommendations for a decrease of the radon daughter concentrations in homes have not been established. In USA and Canada limits have been given only for special cases, for example building on waste from uranium and phosphate industries (Atomic Energy Control Board, 1977 EPA, 1979 EPA, 1980). In Finland, there are general recommendations for homes (Finnish Radon Commission, 1982). 

Wolfs, F., Hofstede, H., deMeijer, R.J. and Put, L.W., Measurements of radon-daughter concentrations in and around dwellings in the northern part of the Netherlands a search for the influences of building materials costruction and ventilation. Health Phys, 47 ... 

Cliff, K.D., Assessment of Airborne Radon Daughter Concentrations in Dwellings in Great Britain, Phys. Med. Biol. 23 696-711 (1978a). 

Put, L.W. and de Meijer, R.J., Measurements of Time-averaged Radon Daughter Concentrations with Passive Dosemeters. Sci. Total. Environ. 45 389-395 (1985). 

For the determination of the radon daughter concentrations down to 1 Bq m 3 a counting and sampling time of 60 minutes and a counting time of 20-40 minutes after the end of sampling were used. From the counts of Po-218 and Po-214 of the two samples measured in different intervals the concentrations of the free and attached radon daughters were calculated (Wicke and Porstendorfer, 1983). 

Simultaneous measurements of the radon daughter concentrations, the ventilation rate and the size distribution of the inactive aerosol have been performed in two bedrooms, a living room and a cellar. The measured radon daughter concentrations were fitted by the room model to optimize the deposition rate of the unattached daughters. The mean value was 18/h in the rooms and 8/h in the cellar. 

The lower part of Figure 3 show the measured radon daughter concentrations. 

Bergman, H., and O. Axelson, Passive smoking and indoor radon daughter concentrations, Lancet 1308-1309 (1983). 

Moore, H.E., Poet, S.E. Martell, E.A. (1972) Tropospheric residence times indicated by radon and radon daughter concentrations. In Natural Radiation Environment II, CONF-720805, ed. J.A.S. Adams, W.M. Lowder T.F. Gesell, Springfield, Va, pp. 775-85. 

The activity concentration of radon daughters is much higher than the Derived Air Concentration value of artificial radionuclides. For example, the Pu public DAC (2.4 10" Bq m ) is lower than four orders of magnitude of a mean radon daughters concentration (30 Bq m ). 

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