Measurements of the equilibrium factor for 222Rn daughters in dwellings in India

Pollution Monitoring Section, Bhabha Atomic Research Centre, Bombay, India.
Science of The Total Environment (Impact Factor: 4.1). 01/1991; 99(1-2):49-52. DOI: 10.1016/0048-9697(90)90209-D
Source: PubMed


As part of an ongoing project to assess the population dose from indoor radon and its daughters in India, a set of parallel measurements was made in more than 150 houses of different types to estimate indoor radon and progeny levels. Time-integrated solid state nuclear track detectors were employed for the measurement of radon concentration and potential alpha energy exposure level. From these values the equilibrium factor (F) between radon and its progeny was estimated for each house. An average F value of 0.39 was obtained.

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    ABSTRACT: This paper presents the results of the measurements of indoor Rn-222 and daughter levels in houses of different types located in different parts of Bangladesh. The passive time-integrated method of using a solid state nuclear track detector (CR-39) was employed for measuring both the Rn-222 gas concentration as well as the potential al pha energy exposure (PAEE) level from the short lived daughters of Rn-222. The Rn-222 concentration from cup exposure and the PAEE from the bare exposure were obtained directly from the track density using calibration curves. A total of 275 exposures were made in the bare mode in 15 locations and 71 exposures in the cup mode in 6 locations. The geometric mean PAEE level obtained is 9.5 mWL with a geometric standard deviation of 1.9. The corresponding value for Rn-222 concentration are 61.3 Bq.m-3 and 2.4. The total data was collected over a period of one and a half years. The monthly variation of the geometric mean of PAEE is also shown. The annual effective dose equivalent has been estimated for each location by using the conversion factor of 9 mSv per WLM as obtained from ICRP-50. The average PAEE level obtained from the total data is below the intervention level as suggested by US EPA. However, the individual averages for each location show that in 8 out of 15 locations intervention may be considered and in others no intervention is called for. The Rn-222 concentrations at the seven locations are equal or less than the equilibrium equivalent Rn-222 concentration value as suggested by EPA. Attempts have also been made to see the variation in the PAEE levels according to different type of construction material used for the houses.
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    ABSTRACT: Time-integrated solid-state nuclear track detectors were employed for the measurement of radon concentration and potential alpha-energy exposure level. From these values, the equilibrium factor F between radon and its progeny was estimated for each house. An average value of 0.40 was obtained. The experimentally and theoretically determined F values were compared.
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    ABSTRACT: Time-integrated measurements of environmental radiation levels are commonly carried out using solid state nuclear track detectors (SSNTDs). These detectors are particularly suitable for monitoring indoor radiation. Levels of radon were measured, during winter and summer seasons, inside 130 traditional and modern houses and multi-family apartment buildings. The traditional houses, modern houses and apartment buildings had average radon levels of 62 Bq.m-3, 125 Bq.m-3 and 133 Bq.m-3, respectively. Between the ground and second floor of the apartment buildings, radon levels diminished by a factor of more than three which indicates that entry of radon-bearing soil gas was largely responsible for the higher concentration of radon in the ground floor. The radon levels in winter exceeded by approximately 30% the radon levels during summer. From the experimental data the equilibrium factor (F) and the effective dose equivalent (HE) were also obtained.
    Science of The Total Environment 08/1994; 151(3):181-5. DOI:10.1016/0048-9697(94)90466-9 · 4.10 Impact Factor
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