Determination of Natural Radionuclides for Ground Shapes in Tar Al-Najaf , Iraq

The natural radioactivity of the earth formations of Tar Al-Najaf region in Al-Najaf Al-Ashraf governorate has been studied , which is considered one of the most important archaeological areas in the province. As Tar Al-Najaf is one of the natural phenomena prominently present in the governorate

The natural radioactivity of the earth formations of Tar Al-Najaf region in Al-Najaf Al-Ashraf governorate has been studied , which is considered one of the most important archaeological areas in the province. As Tar Al-Najaf is one of the natural phenomena prominently present in the governorate, as it cuts sharply to form a rocky cliff, as well as overlooks from the southern end of a plateau Al-Najaf and on the sea of Al-Najaf, in a clear and surprising way, Al-Najaf flew, by selecting 30 sites to take soil samples from the region, and spectral measurements were made using gamma-ray spectroscopy (NaI(Tl)) . It was found that the specific activity of 238 U, 232 Th and 40 K in the studied ranged between to with average , to (

INTRODUCTION
The concentration of radionuclide activity in soil is a major determinant of natural background radiation.
More than 60 radionuclides can be found in nature, and they can be classified into three general categories, Space and human produced. Radionuclides are found naturally or manufactured by man. The radioactive ones are heavy elements. Each element with an atomic number of more than eight has radioactive isotopes and is subject to disintegration. As for the stable, it is indissoluble, and these isotopes are radioactive [1]. Radioactive isotopes have provided countless services in the field of soil research, and other fields such as medicine, agriculture and industry that have benefited humans, and despite their great benefits, they lead to damage to living organisms and the environment [2]. Radioactivity can be defined as the process in which the unstable nucleus gets rid of excess energy by releasing particles and electromagnetic radiation, and familiar radiation is alpha particles, beta particles, and gamma rays [3]. This study aims to estimate the natural radionuclides in the natural formations of Tar Al-Najaf region by taking 30 soil samples from different locations in this region in order to assess the level of radioactive background from which they arise and calculate the external hazard factors that are integrated with current and future studies, and then compare the obtained results with the allowed global average.

STUDY AREA
Tar al-Najaf is considered one of the most important historical archaeological areas in the province, as it is considered one of the natural phenomena prominently present in the province, as it cuts the plateau sharply to form the rocky cliff, as well as overlooking the southern end of the Najaf plateau and the sea of Najaf in a clear and sudden way to be Tar al-Najaf [4]. The study area consisted of rock formations, including the formation of Injanah (Upper Miocene) and the hole formed (Middle Miocene), as well as the tor of Najaf is clearly visible as the tor extends from the eastern, northeastern and northern edge of the al-Najaf sea depression from the west of the city of Abi Sakhir from the intersection of the point ( ) and heads northwest and parallel to the Abu Sakhir -Najaf road to the west of the holy city of Najaf, specifically at the shrine of Safi al-Safa, where it takes the form of an arc heading towards the west at the point )and its length at this point is (21) , and then it descends south at the point( )and its length is , and the road and its hills end at the point , and the total length of the AL Tar is , Figure

Samples Collection and Preparation:
In this research thirty soil samples have been collected during the period from 20 Sep. 2022 to 30 Sep. 2022 were collected distributed along the study area, with a separation distance of (1 km) between one sample and another, and the coordinates of the sites were recorded using the GPS device (G.P.S).The samples have been taken to measure the amount of natural radioactivity in addition to the risk indicators.
Through the specific activity of radioactive elements (238U, 232Th and ).
The samples have been transferred to the research laboratory in the Physics Department-College of Education for Girls-Kufa University. These samples have been dried until a stable weight has reached, crushed, and sieved to (0.5 mm) in order to obtain homogeneous samples, the samples weight ranged between (500 to 600) gm. After that, the soil samples have been packed in plastic bags, and the information on each sample has been recorded. In addition, the samples are filled in special measuring containers (Marinelli beakers), and these containers are tightly wrapped with adhesive tape and the samples have been left stored in these containers for 28 day to obtain a state of radioactive equilibrium between uranium and thorium and their radioactive daughters. Finally, the natural radioactivity of the isotopes , and is measured for (18000sec) by a gamma-ray spectroscopy with scintillation detector 3 from ORTEC with energy resolution and efficiency of at energy

Data analysis and Mathematical equations:
When 238 U and 232 Th is balanced with their radioactive daughters, the activity of all elements of the two radiation chains is in balance, so it is possible to calculate the concentration of an element in any chain in terms of the concentration of another element, the concentration of 232 Th calculating by the activity concentration of thallium 208 Tl radionuclides with energy and 238 U by calculating the activity concentration of bismuth nuclides 214 Bi with energy of , as well as calculating the concentration of potassium radioactive nuclide 40 K with energy of through equation (1) [6].

Radium Equivalent :
The value of the equivalent concentration of radium, which is used to estimate the risk of the concentration caused by the activity of 238 U, 232 Th and 40 K, in units, is calculated from the following equation.

As
, and are the active concentrations of uranium, thorium, and potassium respectively, and the highest value must be less than the internationally permissible limit ( ) [7,8].

Activity Concentration Index ( ):
The Activity Concentration Index refer to the risk arising from gamma rays associated with natural radionuclides (uranium 238 U, thorium 232 Th and potassium 40 K) in the studied material. The Activity Concentration Index (Iγ) calculated from the following equation [9-10].

External Hazard Index ( ):
External hazard index( ) gives the assessment of the health risk associated with the emission of gamma radiation by various natural radionuclides which calculated through the following equation [11,12].

Results and Discussion:
The specific activity of 238 U, 232 Th and 40 K radionuclides in thirty soil samples from Tar al-Najaf ground shapes have been calculated using equation (1) after preparing the samples for measurement with a gamma-ray spectroscopy detector from ORTEC with energy resolution and efficiency of at energy . The soil samples weight ranged between (500 to 800) gm. After that, the samples have been packed in plastic bags, and the information on each sample has been recorded. The samples are filled in special measuring containers (Marinelli beakers), and these containers are tightly wrapped with adhesive tape and the samples have been left stored in these containers for 28 day to obtain a state of radioactive equilibrium between uranium and thorium and their radioactive daughters. The radioactivity of the isotopes are measured for (18000). The specific activity of 238 U, 232 Th and 40 K have been explained in Table (1) and Figure (2), whereas the radium equivalent , activity concentration Index ( ) and external hazard Index ( ) have been shown in Table (2) . The obtained results were compared with the permissible global average they were within the acceptable worldwide limit [13][14][15].

Figure (2):
The specific activity of 238 U, 232 Th and 40 K radionuclides in thirty soil samples from Tar al-Najaf ground shapes.
The concentration of the radionuclides' have been varies from one location to another depending on the natural distribution of radionuclides, i.e. it is of random origin, and that the concentrations are within the global average [13][14][15], meaning that they do not pose a threat to human health, especially as they are considered archaeological and wonderful tourism areas that reflect the history of the formation of landforms within this region of the governorate Najaf, which could continue to be an important area for tourists. It is clear that the highest value of the specific activity of uranium 238 U, was in sample (15), and the lowest value was in sample (8) and the average of these values was It was found that the highest value of the specific activity of thorium 232 Th was in sample (21), and the lowest value was in sample (30), and the average of these values was . For potassium 40 K, the highest value of specific activity was in sample (30), and the lowest value was in sample (8), and the average of these values was . As for the highest value of radium equivalent, it was in sample (16), and the lowest value was in sample (8), and the average of these values was . The highest value of the activity concentration Index ( ) was in sample (16), and the lowest value was in sample (8), and the average of these values was .The highest value of the external Hazard Index ( ) was in sample (16), and the lowest value was in sample (8), and the average of these values was .

Conclusions :
The specific radioactivity values of the uranium, thorium, and potassium isotopes were distributed in varying proportions for the Tar Al-Najaf area, which is within the internationally permitted range, and most of the results of the radioactive hazard coefficients for each of the radium equivalent, activity concentration Index, and external risk coefficient for the soil samples were within the internationally permissible limit. The results do not pose a threat to humans and residents near this area.