Measurements of Radon Concentrations in Some Dried Fruit and Grain Samples by (CR-39) Nuclear Track Detector

The purpose of this study was to measure the radon concentration of some dried fruit and grain samples which were consumed as a meal. This is performed by counting the alpha tracks emitted from radon by exposing the CR-39 detector. Measurements indicated that the highest concentration of radon in dried fruit samples was in dried coconut sample 69.89247 Bq/m 3 , and the lowest concentration of radon was in figs 50.40323 Bq/m 3 , while the highest concentration of radon was in grain samples in oats was 61.82796 Bq/m 3 , The lowest concentration of radon was in Iraqi bulgur was 48.3871 Bq/m 3 , These results are due to the type and characteristics of the soil. Also shows that the behavior of the surface exhalation rate is higher than the mass exhalation rate.The concentration of radon gas and the rate of exhalation of radon for samples of Dehydrated fruit and cereals are within the permissible global limit, and eating these foods will be healthy and safety for the public.


Introduction
There are certain concentrations of radionuclide within the human body.These either caused by constant exposure to natural radiation (cosmic rays, terrestrial sources, and radon) and to man-made sources of radiation, or are naturally present within the body from birth, such as 40 K, 14 C and 210 Pb [1]. Nuclei can undergo a variety of processes which result in the emission of radiation. Internal radiation exposure, affecting the respiratory tract is due to the inhalation of radon and its daughters [2,3]. Radon is the decay product of the naturally occurring radionuclide 226 Ra, which in turn is a decay product of 238 U. Since radon is a gas, it can escape from the substance in which it is produced into the air, and since uranium and radium exist commonly in soil, rocks, and water, the inhaled air contains radon Radon gas is pervasive both outdoors and indoors, so it is considered as radiation health hazard that causes excess lung cancer [4,5]. More attention has been paid to the impact of radiation exposure on animals and plants than before [6]. Radiation damage in plants is due to irregular form, low growth or yield, loss of reproductive ability, wilting and death (in high-exposure cases).When inhaled, radionuclides are distributed among body organs in accordance with the metabolism of the part concerned, which typically shows different radiation sensitivities [7][8][9][10].
With increasing of recognition and application of irradiation as a sanitary treatment of food based on the provisions of the Agreement on the Application of sanitary measures of the World Trade Organization, it is therefore important that appropriate dosimetry systems be used, to ensure that the trade in irradiated foodstuffs complies with national and international standards [11,12]. Therefore, the main effect of the particles charged on these detectors such as (CR-39) is their degradation; these effects reflect substantial changes in the properties of the polymer detector. The fall of radiation leads to the irritation and ionization of these molecules in generaland thus severs the bonds between them and damage [13,14,15].

Experimental Work 2.1. Samples Preparation: The practical part
Twelve samples were collected, six samples of dried fruit and six samples of grains , purchased from local Iraqi markets, as shown in the Table (1). These samples were milled, sieved, and placed inside a plastic cans(one sample per can). The can is 13cm high and 8 cm in diameter. A square piece (1 cm x 1 cm) of CR-39 detectors (British made) with a thickness of 500μm 250 gm of NaOH was used in the solution preparation process were positioned on the inner surface of the can covers, as shown in Figure 1. The samples were placed at a height of 3 cm inside these cans which were then sealed for 60 days to achieve the radioactive balance, After this time, the CR-39 detectors were etched in 6.25N NaOH solution at a temperature of 60 ˚C for 5 hours to reveal the alpha particles tracks.  Figure -1 the dimensions of the used cans.

Density of the tracks
The density of the tracks (ρ) on the CR detector was calculated according to the following relation [16,17].

Calculation of Radon Exposure
The radon gas concentration in some dried fruit and grain samples were obtained, using the following relation [18].

C Rn (sample) / ρ Rn (sample) = C s (standard) / ρ s (standard)
Where: C Rn : is the radon gas concentration in unknown sample (Bq/m 3 ). C S : is the radon gas concentration in standard sample (Bq/m 3 ). ρ Rn : is the track density of the unknown sample (track/mm 2 ). ρ S : is the track density of the standard sample (track/mm 2 ). Figure 2 shows the relationship between track density (ρ Rn ) and radon exposure. Therefore, from the slope of the graph k where C Rn = ρ Rn / k

2-4 Determination of Radon Exhalation Rate in Samples
The surface and mass exhalation rate (E A , E m ) can be calculated as follows [19,20]:

Results and Discussion
Radon gas concentration, for the dried fruits and grain samples, was measured and the results are shown in Table (2). The mean radon gas concentration was shown to be higher in the dried fruit samples than in the grain samples, as shown in Figure 3. The concentration of radon gas in some dried fruits samples ranged from 50.40 Bq/m 3 in sample F1 to 69.89 Bq/m 3 in sample F5, while the concentration of radon gas in the grain samples varied from 48.387 Bq/m 3 in sample C11 to 61.827 Bq/m 3 in sample C7.  The exhalation rate of radon was measured where the surface exhalation rate and the mass exhalation rate are shown in Table 2 and Figures 4 and 5.

CONCLUSUONS
The Iraqi figs among the dried fruit samples and Iraqi bulgur among the grain samples showed the lowest concentration of radon gas. Also, they showed the lowest surface exhalation rate and mass radon exhalation rate. The findings showed that all the dried fruit and grain samples under study had radon gas concentration at the acceptable global limit recommended by ICRP.