Measurement of Radon Concentration in College of Education for Pure Science / Ibn Al-Haitham Buildings Using CR-39 Detector

In the present work , radon concentration was measured indoor buildings in the College of Education for Pure Science/ Ibn AlHaitham University of Baghdad using detector (CR-39) by counting track of alpha resulting from decay series of uranium on the detectors which have exposure to air inside the rooms for (30) days , have been applied the equation (1) and (2) to calculate concentrations of Radon and the results showed that all samples were within the allowable range globally except two samples F1 and F2 where concentrations were (445.868Bq/m) and (436.791Bq/m) respectively , they were higher than allowable range globally which was (200-300) Bq/m recorded by (ICRP) [1] . Kay word: Radon, reaction, Calibration, detector, Radiation.


Introduction
Radon is a gas that results from the disintegration of 235 Uand 238 U or 232 Th, as both sources of Radon are 232 Th and 235 Uand 238 U which are found in low concentration in rock and soil [2].Its atomic number is (86) and mass number is (222) in the periodic table [3].Radon is a rare natural element as it is found in gas form, noble and radioactive in its isotopes.Radon gas can gather in buildings, especially in closed regions, such as under roofs and basement.It is found in some spring waters and hot springs too [4].But from other opinion, inhalation may be a problem to human's health.Since Radon is noble gas, this guarantees that it cannot be frozen through chemical reactions [5]. 226Ra whose half-life is (1600) years can be formed through Radon decay with 238 U during four intermediate cases in order to form 226 Ra, after that it decays to form 222 Rngas which has half -life (3.82) days, which in turn gives sufficient time to be diffused through soil and into houses, where it then disintegrates in order that it can produce more radiologically active Radon breeds (Radon daughters) [4].The presence of 226  Ra in the ground of the facilities and in the building materials is considered the main radon source [6].The outside air also has a role to Radon concentration indoors, through the air ventilation.Other Radon sources can be existed in tap-water; the domestic gas supplies are generally 229 Rn source.It was noticed that high indoor Radon levels are created from Radon that is in the underlying rocks and soils [7].

Experimental Details
Radon concentration was measured using solid state nuclear track detectors type CR-39 detector with a thickness of (250 µm) and the approximate area (1cm²) were used in this work.The detectors are covered from both sides with plastic and this plastic is removed when the detector is used to prevent detector from radiation background and there are distortions that occur as a result of exposure to external stresses,where detectors were distributed in random buildings inside College of Education , in every room placed two detector .The detectors were placed at hight (160cm) for (30) days.
After it has been collected for the configured to chemical etching process using sodium hydroxide solution (NaOH) , water bath from type (Memmert) German-made used for heating sodium hydroxide solution (NaOH) and the temperature was suitable for etching process of CR -39 detectors (60 C°) for four hours , afterward previewed microscopically to count number of track for alpha per unit area and calculate radon concentrations after the comparison process with standard source as shown in figure (1).Calibration of the CR -39 detector in the present work , four (CR -39) detectors were used standard source ( 226 Ra) .Figure (2) shows the relation between the exposure of Radon (Es) and the density of track (ρs).
The highest value of exposure to radon progeny (EP) as observed in table (1) was found in samples F1and F2 which was (1.987 WLM/Y) and (1.946 WLM/Y) ,the lowest value was found in sample C1 which was (0.077 WLM/Y) , all the results of samples were within allowable limit recorded by (NCRP) which was range of (1-2) WLM/Y [17].The potential Alpha energy concentration (PAEC) as observed from the table (1) ,for samples the values were varied between (0.0018 WL) and (0.0482 WL) , all the result of samples were within allowable limit (53.33mWL) which was recorded by (UNSCEAR) [18] .

): levels concentration of radon indoor college buildings.
[1]30526/31.2.1943The radon concentration (CRn) as observed from table(1), for buildings inside college of education varies from(17.412Bq/m 3 ) to (445.868Bq/m 3 ) with average (123.8652Bq/m 3 ) .The highest value was found in sample F1 which value of radon concentration was (445.868Bq/m 3 ) and the lowest value was found in sample C1 which value of radon concentration(17.412Bq/m 3 ) .All results of radon concentration were lower than the recorded value by [ICRP] except two samples F1and F2 were higher than the recorded value by [ICRP] (200-300)Bq/m 3[1].