Radon Surface Exhalation Research Articles

Radon exhalation from sub-slab aggregate used in home construction in Canada

Exposure to elevated levels of radon in homes has been shown to result in an increased risk of developing lung cancer. The two largest contributors to indoor radon are radon in soil gas, formed from the rocks and soil surrounding the home, and building materials such as aggregate. This study measured the surface radon exhalation rates for 35 aggregate samples collected from producers across Canada. The radon exhalation rates ranged from 2.3 to 479.9 Bq m(-2) d(-1), with a mean of 80.7±112 Bq m(-2) d(-1). Using a simple, conservative analysis, the aggregate contribution to radon concentrations in an unfinished basement was determined. The maximum estimated radon concentration was 32.5±2.7 Bq m(-3), or ~16 % of the Canadian Radon Guideline. It can be concluded that under normal conditions radon exhalation from aggregate contributes very little to the total radon concentration in indoor air.

Measurement of natural radioactivity and radon exhalation rate in fly ash samples from a thermal power plant and estimation of radiation doses

Abstract Fly ash produced by coal-burning in thermal power station has become a subject of world wide interest in recent years because of its diverse uses in construction activities and considerable economic and environmental importance. Fly ash is used in the production of bricks, sheets, cement and also in land filling etc. Indian coals used in thermal power plants are found to have high ash contents, resulting in the production of large amount of fly ash. Coal contains radionuclides including uranium (the source of inert gas radon), Th and K. Thus coal combustion results in enhanced concentration of natural radionuclides 226 Ra, 232 Th and 40 K. Since these radionuclides concentration in fly ash plays an important role in health physics it is important to measure radionuclides concentration in fly ash. In the present work enhanced radioactivity and radon exhalation rate from fly ash samples collected from a thermal power plant of NTPC (National Thermal Power Corporation), Dadri (U.P.) India, have been measured. A high resolution gamma ray spectroscopic system has been used for the measurement of natural radioactivity ( 226 Ra, 232 Th and 40 K). Gamma spectrometric measurements were carried out at Inter-University Accelerator Centre, New Delhi using a coaxial n-type HPGe detector (EG&G, ORTEC, Oak Ridge, USA). Activity concentration of 226 Ra varies from 81.8 ± 2.2 to 177.3 ± 10.0 Bq kg −1 with an average value of 118.6 ± 7.4 Bq kg −1 and of 232 Th from 111.6 ± 3.2 to 178.5 ± 3.9 Bq kg −1 with an average value of 147.0 ± 3.4 Bq kg −1 . 40 K activity was found to be below detection limit in some samples while other samples have shown potassium activity to vary from 365.9 ± 4.8 to 495.9 ± 6.2 Bq kg −1 with an average value of 352.0 ± 4.5 Bq kg −1 . Surface radon exhalation rates ( E A ) and Mass exhalation rates ( E M ) in these samples were measured by “Sealed can technique” using LR-115 type II track detectors. E A is found to vary from 80.1 ± 9.3 to 242.7 ± 16.3 mBq m −2 h −1 with an average value 155.5 ± 12.8 mBq m −2 h −1 , while E M varies from 3.1 ± 0.4 to 9.3 ± 0.6 mBq kg −1 h −1 with an average value of 6.0 ± 0.5 mBq kg −1 h −1 . Radium equivalent activity ( Ra eq ), related to the external gamma dose and internal dose due to radon and its daughters range from 283.2 to 422.4 Bq kg −1 with an average value of 353.9 Bq kg −1 . The calculated values of external hazard index ( H ex ) vary from 0.77 to 1.87 with an average value of 1.03. Most of the samples show the value of Ra eq close to the allowed upper limit of 370 Bq kg −1 and H ex close to unity respectively except in two samples. Annual effective dose varies from 0.15 to 0.23 mSv y −1 with an average value 0.19 mSv y −1 .

A model to predict radon exhalation from walls to indoor air based on the exhalation from building material samples

In recognition of the fact that building materials are an important source of indoor radon, second only to soil, surface radon exhalation fluxes have been extensively measured from the samples of these materials. Based on this flux data, several researchers have attempted to predict the inhalation dose attributable to radon emitted from walls and ceilings made up of these materials. However, an important aspect not considered in this methodology is the enhancement of the radon flux from the wall or the ceiling constructed using the same building material. This enhancement occurs mainly because of the change in the radon diffusion process from the former to the latter configuration. To predict the true radon flux from the wall based on the flux data of building material samples, we now propose a semi-empirical model involving radon diffusion length and the physical dimensions of the samples as well as wall thickness as other input parameters. This model has been established by statistically fitting the ratio of the solution to radon diffusion equations for the cases of three-dimensional cuboidal shaped building materials (such as brick, concrete block) and one dimensional wall system to a simple mathematical function. The model predictions have been validated against the measurements made at a new construction site. This model provides an alternative tool (substitute to conventional 1-D model) to estimate radon flux from a wall without relying on 226Ra content, radon emanation factor and bulk density of the samples. Moreover, it may be very useful in the context of developing building codes for radon regulation in new buildings.

Surface Radon Exhalation Rates of Building Material and Soil Affect on Indoor Air Radon Concentration

By using RAD7 professional radon monitor which detecting data is reliable, selecting a one-story cottage in Shenzhen city area as the research object, the measurement results showed the radon concentration in the soil around the one-story cottage area was low background; the soil surface radon exhalation rate of soil was higher and was about two times that of cement floor of the room which indicated that the soil is the largest source of indoor radon; the surface radon exhalation rate of cement floor was higher than that of ceramic tile floor and was about 4 times that of the ceramic tile floor. The indoor radon concentration in the room covered with cement floor was higher than that of the room covered with ceramic tile floor due to the larger surface radon exhalation rate of cement floor. Therefore, in order to reduce indoor radon concentration, the laying floor material with low surface radon exhalation should be selected and windows should be kept open for ventilation.