308 K . M . Thabayneh and R . J . Shawamreh : Radioprotection 2024 , 59 ( 4 ), 306 – 316
Fig . 1 . West Bank map including the north districts ( Tulkarm , Jenin and Tubas ). depth . Each container was carefully sealed and left undisturbed for a period of 75 days ( Thabayneh , 2015 ). Within each securely sealed container , a CR-39 detector was affixed beneath the cork head . Positioned approximately 1.5 cm from the soil sample ’ s surface , the sensitive part of the detector was oriented towards the emanating radon-222 . This configuration allowed the detector to register alpha particles resulting from the decay of radon-222 across the entire volume of the container . To seal the container tightly , an inverted cylindrical plastic cover was used , as illustrated in Figure 2 . This arrangement upheld the sample ’ s integrity and enabled precise measurements of radon-222 concentration and radon-222 exhalation rates ( Thabayneh , 2015 ).
After the exposure period , during which alpha particles from radon-222 and its daughters bombarded the CR-39 detector , the detectors were gathered for subsequent analysis . These detectors underwent an etching process in a 6.25 M NaOH solution at a temperature of 70 ° C for 4 h . The purpose of this etching process was to unveil the tracks generated by the alpha particles on the detector surface . Post-etching , the detectors were rinsed with distilled water and allowed to air dry . The tracks on the detectors were manually enumerated utilizing an optical microscope with a 160 magnification . For each detector , 10 random fields of view were chosen , and the average number of tracks per field of view was calculated . The area of each field of view was determined to be approximately 0.0133 cm 2 . The resultant average track density per field of view was then employed to compute the track density per square meter ( Jazzar and Thabayneh , 2014 ; Thabayneh , 2016 , 2018 ).
This information , along with other data , was subsequently employed to calculate the concentration of radon-222 in the soil samples . By analyzing the track densities , it was possible to estimate the levels of radon-222 present in the tested soil items or other relevant samples .
3 Theoretical calculations
3.1 Calculations of radon-222 concentrations
To estimate the concentration of radon-222 in secular equilibrium ( C Rn ), the following equation can be used