INFLUENCE OF THE VENTILATION SYSTEM ON INDOOR RADON VARIABILITY

Transcription

1 VII Radon Forum and Radon in Environment Satellite Workshop, Veszprém, Hungary, May 2013 Low-Background Laboratory for Nuclear Physics Institute of Physics, University of Belgrade, Belgrade, Serbia INFLUENCE OF THE VENTILATION SYSTEM ON INDOOR RADON VARIABILITY Vladimir Udovičić, Aleksandar Dragić, Radomir Banjanac, Dejan Joković, Dimitrije Maletić, Nikola Veselinović, Jelena Filipović Institute of Physics, University of Belgrade, Belgrade, Serbia,

2 Motivation: - Indoor radon concentration varies daily and seasonally, mainly due to the changes of the atmospheric parameters (temperature, atmospheric pressure and relative humidity) and the exchange rate between indoor and outdoor air. For this reason, it is important to investigate short-term variations of the indoor radon because the short-term variation during the one day may be extreme. The physical origin of the variation in the indoor radon activity is not straightforward. In this paper, we pointed out the influence of the ventilation system on changes of the indoor radon concentration in the different environments.

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4 aver CRn [Bq*m -3 ] Short-Term Radon Measurements Continuous Radon Monitor Device Sun Nuclear - model 1029: A 4B 4C 4D 5 7 8A MEDIUM EXPOSURE 8B 9A 9B FIRST EAST EUROPEN RADON SYMPOSIUM INTERCOMPARISON EXERCISE 11 The short-term radon measurements are performed with SN1029 radon monitor (manufactured by the Sun Nuclear Corporation, NRSB approvalcode 31822). The device consists of two diffused junction photodiodes as a radon detector, and is furnished with sensors for temperature, barometric pressure and relative humidity. Measuring cycle of 0.5, 1, 2, 4, 8, 12, 16, 20 or 24-hour intervals is selectable by user. The duration of data sampling is limited to forty days by the device memory capacity or 720 measurements.

5 Low-Background Laboratory for Nuclear Physics, Belgrade, Serbia - The Low-Background Laboratory for Nuclear Physics at the Institute of Physics in Belgrade is a shallow underground laboratory. The laboratory was built in the loamy loess cliff on the bank of the river Danube with the overburden of 12 m of soil. It has an active area of about 45 m 2 (135 m 3 ). - The experiments and routine measurements in the underground Low-Background Laboratory for Nuclear Physics require low levels of radon concentration with minimum temporal variations.

6 System for radon reduction used in the Low-Background Laboratory for Nuclear Physics - The active area of the laboratory is completely lined up with aluminium foil of 1 mm thickness, which is hermetically sealed with a silicon sealant to minimize the diffusion of radon from surrounding soil and concrete used for construction. - The laboratory is continuously ventilated with fresh air, filtered through one rough filter for dust elimination followed by the battery of coarse and fine charcoal active filters. - The parameters of the ventilation system are adjusted to give an overpressure of about 2 mbar over the atmospheric pressure.

7 VENTILATION SYSTEM AND RADON VARIABILITY IN THE UNDERGROUND LABORATORY - Comparison the results of the radon concentrations when the ventilation system is switched on and off, demonstrates that the ventilation system is a crucial stage in the radon reduction system in our underground laboratory. This highlights the need for the ventilation systems to reduce the radon problem in the underground environments. - Published in: V. Udovičić, B. Grabež, A. Dragić, R. Banjanac, D. Joković, B. Panić, D. Joksimović, J. Puzović, I. Aničin; Radon problem in an underground low-level laboratory. Radiation Measurements 44, (2009).

8 AIR CONDITIONING SYSTEM AND RADON VARIABILITY IN THE GROUND LEVEL LABORATORY AIR-CON ON: AIR-CON OFF: <Rn> (sd) = 54(44) Bqm -3 <Rn> (sd) = 41(34) Bqm -3

9 AIR CONDITIONING SYSTEM AND RADON VARIABILITY IN THE COMPUTING LABORATORY AIR-CON ON: <Rn> (sd) = 30(15) Bqm -3 Radon time series inside the smaller well-insulated and thoroughly airconditioned room with almost constant temperature. This small room is situated on the second floor inside the building of the Institute of Physics, has area of 10 m 2 and 12 kbtu air-conditioning unit installed inside was adjusted to 23 o C.

10 AIR CONDITIONING SYSTEM (HEATING MODE) AND RADON VARIABILITY IN ONE FAMILY HOUSE The selected house is a typical one-family dwelling house building with standard construction materials such as blocks of brick, concrete, mortar. The house is thermally insulated with Styrofoam (depth of 5 cm). Air conditioning device is used during the hottest part of summer, and also for the heating in the autumn. The graphs presents transition between outdoor and indoor radon and temperature.

11 NATURAL VENTILATION AND RADON VARIABILITY IN ONE FAMILY HOUSE The selected house is, also a typical one-family dwelling house with three floors. The house is thermally insulated with Styrofoam (depth of 10 cm). In the selected time of the year (winter time), the ground floor is naturally ventilated, every day about 15 min during the indoor radon measurements.

12 CONCLUSIONS: - Ventilation system is a crucial stage in the radon reduction system in the underground environments. - In the real conditions and spaces (dwellings and workplaces) the used of the airconditioning systems are increased regarding climate changes. - Unfortunately, usage of the airconditioning system increases the levels of indoor radon in relation to the use of natural ventilation. - The natural ventilation is the first and simplest radon mitigation technique.

13 THANK YOU FOR YOUR ATTENTION