Measurement of Radon and Uranium Concentrations and Background Gamma Rays at the University of Baghdad -Jadiriyah Site

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1 Measurement of Radon and Uranium Concentrations and Background Gamma Rays at the University of Baghdad -Jadiriyah Site Shafik S. Shafik 1, Aamir A. Mohammed 2 1, 2 Department of Physics, College of Science, University of Baghdad -Baghdad-Iraq ABSTRACT Radon is a radioactive gas produced by uranium decay chain. The concentration of this gas in indoor is higher than that of outdoor. An indoor radon survey of a total of 112 locations with one dosimeter per site was carried out at the university of Baghdad- Jadiriyah site. In this study, the concentrations of radon and uranium, radon exhalation rate and background of gamma rays were estimated, and the dose due to indoor radon concentrations was calculated. The minimum, maximum and average of indoor radon concentrations were ±2.182, ±1.98 and ±1.157 respectively. Radon mass exhalation rate ranged from 2.851± to 4.240± with an average value of 3.31±0.13. The average concentrations of radon and uranium in soil samples were 66.73±2.62 and ±0.457 respectively. The average indoor inhalation exposure (radon) effective dose in the buildings was and the background dose rate of gamma rays was Keywords: Radon, Exhalation Rate, Uranium, Gamma ray, CR-39 detector. 1. INTRODUCTION The exposure to natural radiation may be due to external or internal according to the body radiation source geometry. External exposure comes mainly from the γ- emitter in man's surrounding environment which impacts the body and can be harmful to different organs due to the high penetration property of γ- rays. There has been interest in the determination of the average gamma radiation dose to which the population is exposed. The environmental radiation is composed of natural radiation, found in the ground, plus the cosmic radiation together with the contribution to background radiation from nuclear weapons tests and accidents which, eventually, will come down to the ground level. On the other hand, internal exposure comes from swallowing or inhaling radioactive materials as in the case of inhaling radon and its daughters (Saleh, 2007). [1] Radon is radioactive noble inert gas and very mobile gaseous daughter of uranium 238 U which is found in all rocks and soil. Radon is very soluble in water (Misdaq et al., 2000). [2] There are three natural isotopes of the radioactive element radon: 222 Rn originate in the 238 U decay series and has a half-life of 3.82 days, 220 Rn (thoron) is in the 232 Th chain with a half-life of 55.6 sec and 219 Rn (actinon) is in the 235 U series with its half-life of 4 sec. The chemical element radon with atomic weight 86 is the heaviest among of the inert gases, which include neon, argon, krypton and xenon as well (Wilkening, 1990). [3] The exposure to radon gas is the most signification element of human exposure to natural sources. It is distinguished from the other three elements of basic background because exposure varies markedly in ordinary circumstances, and because high exposure may be avoided with comparative ease. The most important mechanism of exposure is the inhalation of the short-lived decay products of the principal isotope, 222 Rn, with indoor air. Concentrations of 222 Rn and its progeny are usually higher in indoor air than in outdoor air, exceptions are in tropical regions, where 222 Rn concentrations in well- ventilated dwellings are essentially the same as in outdoor air (UNSCEAR 1993). [4] Sources of radon include soil, water, outdoor air, and building materials, but transport of radon bearing gas from soil is generally the most predominant source of indoor. The concentration of radon is expressed as Becquerel per cubic meter ( ) or picocuries per liter ( ) (Nagda, 1994). [5] The exposure to high level of radon gas through breathing of air increases the risk of lung cancer (Ramadhan, 2012). [6] When radon gas is inhaled, densely ionizing alpha particles emitted by deposited short- lived decay products of radon ( 218 Po and 214 Po) can interact with biological tissue in the lungs leading to DNA damage (WHO, 2009). [7] 2. MATERIAL AND METHODS The technique used in this work is based on CR-39 nuclear track detectors (Pershore Mouldings which was made in England). The passive radon dosimeter geometry consists of a closed chamber into which radon diffuses (Al-Jarallah et al., 2003). [8] It is made from plastic cup with a hole at the top cover which is covered with a 5 thickness of soft Volume 2, Issue 5, May 2013 Page 455

2 sponge layer. The radon dosimeter containing CR-39 (with an area 1 x 1 and 500 at its bottom. The design of the chamber ensures that the aerosol particles and radon decay products are deposited on the sponge from outside and that only radon diffuses through it to the volume of the chamber (Al-Jarallah et al., 2008). [9] The radon dosimeter was used to determine the indoor radon concentrations as shown in the figure (1). The exposure time was 90 days. At the end of the exposure time, the radon dosimeters were collected and the detectors were removed, and then treated using etching solution NaOH with 6.25N in water bath at 70±1 C for 7 h. Then, the CR-39 detectors were washed with distilled water and dried. The tracks produced were counted using optical microscope with 400x magnification as shown in figure (2). Figure 1 The Radon dosimeter. Figure 2 The tracks counting system.. The radon concentrations were calculated using the following equation (Ajaj, 1999): [10] C Rn = (1) where represents the track density resulting from all alpha particles which are present inside the container, represent the time exposure radon and the calibration factor is given by: where is the critical angle, R is the alpha particle range and is the radius of container. The radon and uranium dosimeters for soil are shown in figures (3) and (4) respectively. CR-39 Detector Cover Plastic Container 15 Soil 6cm Figure 3 The radon dosimeter for soil. Volume 2, Issue 5, May 2013 Page 456

3 Cover Soil Sample CR 3 cm 5 cm Figure 4 The uranium dosimeter for soil. The uranium concentration C U can be determined using a procedure similar to used to determine radon concentration, one can write (Ajaj, 1999, Salama et al., 2006): [10,11] C U K U T (2) C Th K Th T (3) (4) total=c U K U T + C Th K Th T (5) = C U Ku+ C Th K Th (6) C U K U [1+ (C Th / C U ) (K Th / K U )] (7) The ratio C Th / C U = 4 / T = C U K U [1+ 4 (K Th / K U )] -- (8) K U =0.25 A U cos (9) K Th is given by a formula similar to eq. (9). where is the density, e i is the branching ratio, and A U is the radioactivity concentration of 1 ppm (one part per million ) of Uranium. The mass exhalation rate is given by the following equation (K. Kant et al., 2010): [12] E x = (10) where E x is the mass exhalation rate of radon, C Rn is the integrated radon exposure (Bq m -3 h -1 ), M is the mass of the sample, V is the effective volume of radon dosimeter can (figure 1), is the decay constant of radon and T is the exposure time. The annual exposure to potential alpha energy E P (effective dose equivalent) is then related to the average radon concentration C Rn by the expression: E P [WLM.Y -1 ] = --- (11) where, C Rn is in Bq/m 3 ; n is the fraction of time spent indoors; 8760, the number of hours per year; 170, the number of hours per working month and F is the equilibrium factor for radon and was taken as 0.4 as suggested by UNSCEAR, (2000). Radon progeny equilibrium is a very important quantity, where dose calculation are to be made on the basis of the measurement of radon concentration, it may have value 0 < F < 1.Thus, the values of n=0.8 and F=0.4 were used in the present research. From radon exposure the indoor inhalation exposure (radon) effective dose was estimated using the conversion factor of 3.88 by ICRP, (1993) (Mahur, 2012). [13] In addition to the radon and uranium measurements, gamma rays were measured in 75 locations of the University of Baghdad - Jadiriyah site using digital hand-held gamma spectrometer. 3. Results and Discussion A summary of the results are shown in Table (1), it is observed that the concentration of indoor radon and the indoor inhalation exposure (radon) effective dose inside the buildings at the university of Baghdad-Jadiriyah site. The concentrations of indoor radon were varied from ±2.182 to ±1.98 with an average value of ± From the results listed in Table (2), it is observed that the average concentrations of indoor radon in the campus of the university of Baghdad Jadiriyah site were lowest at the Institute of Genetic Engineering with value of ±1.46 while the highest value was ±1.48 in the College of Khwarizmi Engineering because all college buildings located has lacked of ventilation. The indoor radon concentrations are much lower than the recommended ICRP action level of (ICRP 1993). [14] The average indoor inhalation exposure (radon) effective dose in the buildings was ± Table (3) shows the concentration of radon in soil and mass exhalation rate of radon in Jadiriyah site. The average radon concentration in soil samples was Volume 2, Issue 5, May 2013 Page 457

4 66.73±2.62. The radon concentrations in the soil are lower than the allowed limit (800 ) from WHO (WHO,1993). [15] The mass exhalation rate of radon ranged from 2.851± to 4.240± with an overall average value of 3.31±0.13 Table (4) shows the concentrations of uranium in soil samples taken from the university of Baghdad - Jadiriyah site. Its values varied from ±0.623 to ±1.153 with an overall average value of ± The uranium concentration in soil s samples are less than the allowed limit (40 ) from UNSCEAR (UNSCEAR1993). [16] Also the background gamma dose rate was measured in Jadiriyah site, it is equal to It is lower than the recommended Ministry of Environmental in Iraq action level of 0.08±0.008 (Ministry of Environment/Iraq). [17] Table 1: Radon concentrations, E P and indoor inhalation exposure (radon) effective dose in buildings. No. Symbol Radon concentration ( ) E p ( ) Indoor Inhalation exposure (radon) effective dose ( ) 1 A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± A ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± Volume 2, Issue 5, May 2013 Page 458

5 37 B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± B ± ± C ± ± C ± ± C ± ± C ± ± C ± ± C ± ± C ± ± C ± ± C ± ± C ± ± C ± ± D ± ± D ± ± D ± ± D ± ± D ± ± D ± ± D ± ± D ± ± D ± ± D ± ± D ± ± D ± ± E ± ± E ± ± E ± ± E ± ± E ± ± E ± ± E ± ± E ± ± E ± ± E ± ± F ± ± F ± ± F ± ± Volume 2, Issue 5, May 2013 Page 459

6 85 F ± ± F ± ± F ± ± F ± ± F ± ± F ± ± F ± ± F ± ± G ± ± G ± ± G ± ± G ± ± G ± ± G ± ± G ± ± G ± ± H ± ± H ± ± H ± ± K ± ± K ± ± K ± ± K ± ± M ± ± M ± ± N ± ± N ± ± N ± ± where the symbols A s for College of Science, B s for College of Engineering, C s for College of Science for Women, D s for College of Education for Women, E s for College of Media, F s for College of Political Science, G s for College of Khwarizmi Engineering, H s for Institute of Laser, K s for Institute of Accounting and Financial studies, M s for Institute of Genetic Engineering, and N s for Institute of Urban and Regional planning. Table 2: The average radon concentrations in the colleges and institutes in Jadiriyah site No. Name of College or Institute Average Radon concentrations( ) 1 College of Science ± College of Engineering ± College of Science for Women ± College of Education for Women ± College of Media ± College of Political Science ± College of Khwarizmi Engineering ± Institute of Laser ± Institute of Accounting and Financial studies ± Institute of Genetic Engineering ± Institute of Urban and Regional planning ±0.903 Volume 2, Issue 5, May 2013 Page 460

7 Table 3: Radon concentrations and mass exhalation rate in soil samples. No. Symbol Radon concentration Radon mass exhalation rate ( ) ( ) 1 S ± ± S ± ± S ± ± S ± ± S ± ± S ± ±0.011 Table 4: Uranium concentrations in Jadiriyah site. No. Symbol Uranium concentration ( ) Uranium concentration ( ) 1 S ± ± S ± ± S ± ± S ± ± S ± ± S ± ± Conclusions The concentrations of radon gas in soil samples and inside buildings were measured using Cr 39 detectors, and they were found lower than the recommended WHO and ICRP action levels respectively. The concentrations of uranium in soil samples were found lower than the recommended UNSCEAR. The background gamma rays and mass exhalation rates of radon were and ±2.315, respectively. All results of indoor radon showed that no action is required to reduce radon levels inside the buildings. References [1.] F. S. Al- Saleh, "Measurements of indoor gamma radiation and radon concentrations in dwellings of Riyadh city, Saudi Arabia", App. Rad. Isot. 65(2007) [2.] M. A. Misdaq, A. Merzouki, D. Elabboubi, F. Aitnouh, and S. Berrazzouk, "Determination of radon equivalent alpha- dose in different human organs from water ingestion using SSNTD and dosimetric compartmental models", J. Radioanal. Nucl. Chem., Vol.245, No.3 (2000) [3.] M. Wilkening, "Radon in the Environment", Elsevier Science Publishing Company INC., New York, U.S.A [4.] UNSCEAR 1993, "Sources and Effects of Ionizing Radiation", United Nations Scientific Committee on the Effects of Atomic Radiation 1993, Report to the General Assembly. [5.] N. L. Nagda, " Radon: Prevalence, Measurements, Health Risks and Control", American Society for testing and materials, Philadelphia, PA, [6.] R. M. Ramadhan, " Measurement of radon concentration in Iraqi and imported cement", J. Thi- Qar Sci., Vol.3 (2), [7.] WHO, "Handbook on Indoor Radon, A public health perspective" World Health Organization, [8.] M. I. Al-Jarallah and F. Rehman, "Indoor radon measurements in dwellings of four Saudi Arabian cities", Radiat. Meas. 36(2003) [9.] M. I. Al-Jaralla, F. Rehman, and Abdalla K. "Comparative study of short and long term indoor radon measurements", Radiat. Meas. 43(2008) S471-S474. [10.] F. Abdul-Kader, " A study of the nuclear track detectors and the use of them in Natural Radioactivity Measurements in Mekkah ", M.sc thesis, Umm Al- Qura University, [11.] T. A. Salama, U. Seddik, T. M. Dsoky, A. M. Morsy, and R. El-Asser, "Determination of thorium and uranium contents in soil samples using SSNTDs passive method", Pramana J. Phys., Vol. 67, No. 2, 2006, pp [12.] K. Kant, R. Rashmi, S. Kuriakose, R. G. Sonkawade, R. P. Chauhan, S.K. Chakarvarti and G. S. Sharma, " Radon activity and exhalation rates in Indian fly ash samples ", Indian Journal of Pure & Applied Physics, Vol. 48, July 2010, pp Volume 2, Issue 5, May 2013 Page 461

8 [13.] A. K. Mahur, "Comparative study of indoor radon, thoron with radon exhalation rate in soil samples in some historical places at Jaipur, Rajasthan, India", Pelagia Research Library: Advances in Applied Science Research, 2012, 3(2): [14.] International Commission on Radiological Protection (ICRP 65), 1993, "Protection against Rn-222 at home and at work", Pergamon Press, Oxford, [15.] World Health Organization, WHO, " Guidelines for Drinking Water Quality", 2nd. Geneva, [16.] UNSCEAR 1993, "sources and effects of ionizing radiation ", united nations scientific committee effects of atomic radiation, Report to the General Assembly, United Nations, New York,1993. [17.] Ministry of Environment in Iraq, "Indeed Environment Radioactivity for 2007". AUTHOR Shafik S. Shafik received the B.S., M.S. and Ph. D. degrees in Nuclear Physics, from Physics Department, Collage of Science, Baghdad University in 1995, 1999, and 2006 respectively. During , he stayed in Iraqi Radiation Protection Center (ICRC), Ministry of Environment of Iraq. During till now he worked as a lecturer in the Physics Department, Collage of Science, Baghdad University. In addition, he now occupies a deputy Dean of the Collage of Science, Baghdad University Volume 2, Issue 5, May 2013 Page 462