BIBECHANA Vol. 20, No. 3, December 2023, 285-289 ISSN 2091-0762 (Print), 2382-5340 (Online) Journal homepage: http://nepjol.info/index.php/BIBECHANA Publisher:Dept. of Phys., Mahendra Morang A. M. Campus (Tribhuvan University)Biratnagar Measurement of background radiation in Jhapa, Ilam, Panchthar, and Taplejung districts of Nepal Arun Kumar Shrestha1,2, Roshan Nepal1, Kamala Shrestha1 Dijan Regmi1, Ganesh Kumar Shrestha3, Buddha Ram Shah4, Ram Prasad Koirala5,∗ 1Damak Multiple Campus, Tribhuvan University, Jhapa, Nepal 2Central Department of Physics, Tribhuvan University, Nepal 3Pulchowk Engineering Campus, Tribhuvan University, Nepal 4Nepal Academy of Science and Technology, Lalitpur, Nepal 5Mahendra Morang Adarsh Multiple Campus, Tribhuvan University, Biratnagar, Nepal ∗Corresponding author. Email: ramprasadkoirala13@gmail.com Abstract In this study, we investigated the levels of background radiation in different locations across the Eastern part of Koshi province, specifically in Taplejung, Panchthar, Ilam, and Jhapa. We used a portable Geiger Muller counter to collect data from twenty different locations, with five sites taken from each district. The average absorbed dose rate was found to be 0.243±0.035 mSv/y. The highest measured value of absorbed dose was 0.335±0.041 mSv/y at Pathivara temple in Taplejung, and the lowest was found to be 0.197±0.039 mSv/y at Kakarvita, Jhapa. The results suggest that these four districts do not pose any radiation risk because it was below the threshold of risk (1mSv/y). We also measured the variation of absorption dose with altitude which is positively correlated with altitude with a correlation coefficient of +0.57. This might be because of the surge in cosmic radiation with an increase in altitude. Keywords Onizing radiation, Cosmic radiation, Absorbed dose, G.M. Counter, Background radiation. Article information Manuscript received: August 13, 2023; Accepted: October 16, 2023 DOI https://doi.org/10.3126/bibechana.v20i3.57882 This work is licensed under the Creative Commons CC BY-NC License. https://creativecommons. org/licenses/by-nc/4.0/ 1 Introduction Background radiation measurement is an impor- tant task to evaluate dose for general people due to various sources. These sources are categorized into three groups: primordial, cosmogenic, and human-produced, with the most abundant being naturally occurring radionuclides (i.e. Primordial radionuclides) [1–4]. These radionuclides exist in each rock, soil, and water and significantly vary 285 http://nepjol.info/index.php/BIBECHANA ramprasadkoirala13@gmail.com https://doi.org/10.3126/bibechana.v20i3.57882 https://creativecommons.org/licenses/by-nc/4.0/ https://creativecommons.org/licenses/by-nc/4.0/ Arun Kumar Shrestha et al./ BIBECHANA 20 (2023) 285-289 286 depending upon geological and geographical situ- ations. Cosmic radiation is a significant contribu- tor to the radiation entering the earth’s atmosphere from its surroundings. The amount of cosmic ra- diation that reaches the earth’s surface varies de- pending on a number of factors, such as altitude, latitude, and solar activity [5]. In addition to these sources, the background radiation at the local level is also greatly affected by the presence of man-made sources, such as those from nuclear activities and accidents [6]. There are various regulatory bodies such as the Nuclear Regulatory Commission (NRC) and the International Atomic Energy Agency (IAEA) that set standards for radiation exposure to ensure the safety of individuals working with radiation or liv- ing near nuclear facilities. These agencies also mon- itor background radiation levels to ensure they re- main within safe limits [7–9]. There are several international studies reported in the literature for the measurement of background radiation levels both in outdoor and indoor ar- eas, and the global average value for dose rate is 59 nGy/h with the range of 18− 93 nGy/h [10,11]. The first preliminary ground radiometric sur- vey in Nepal was conducted in 1977/1978 and con- firmed the presence of deposition of the mineralized bodies in Tinbhangale, Makawanpur. Pantha et al. (2018), Gautam et al. (2020), Dhami et al. (2020), and Shrestha et al. (2023) conducted the radio- metric survey in Pokhara Valley, Kathmandu, Kan- chanpur, and Morang district, respectively [12–15]. Results showed that these areas are under normal background radiation. In Nepal, there are 77 dis- tricts; therefore, the comprehensive investigation to assess background radiation levels across the coun- try is the most important and immediate concern to the general population [16] because no further works have been obtained in the literature. Simi- larly, people living in high-altitude regions are re- ceiving a higher dose of radiation, but it has a lack of information. Therefore, this study was carried out to provide a map of background radiation us- ing a GM detector in eastern Nepal and to estimate the annual effective dose of residents in these areas. Such works become very useful for locating the high background radiation area. It is also a regulatory prerequisite for installing and operating a research reactor and nuclear power plant and testing nuclear weapons. 2 Materials and Methods 2.1 Description of Instrument The data collection in this study was performed us- ing the GM counter model GMC-300E plus, which employs a GM tube to detect nuclear radiation. The GM tube is designed to detect radiation by producing an electric current pulse when ionization occurs due to the passage of radiation through the tube. The instrument then detects and records each pulse as a count. The GMC-300E plus is a highly portable and battery-operated device that offers three different modes for displaying the counts: counts per minute (CPM), milliroentgen per hour (mR/h), and microsievert per hour (µSv/h). It is worth noting that the GMC-300E plus is capable of detecting high-energy x-rays (0.03 − 3.0MeV), beta particles (0.25 − 3.5MeV), and gamma rays (0.1 − 1.25MeV). This makes it an ideal device for monitoring a wide range of nuclear radiation sources in different settings. The porta- bility of the instrument allows for easy transport, enabling data collection to be performed on-site or in the field. The three different modes of display provide flexibility in the analysis of the collected data, making it easier to compare the results with existing radiation safety standards. For quality con- trol measures, some specifications of the instrument are shown in Table 1. 2.2 Study Area The present study comprises data collected from the Eastern part of Nepal, encompassing four distinct districts, namely Jhapa, Ilam, Panchthar, and Ta- plejung. The total area of the site under considera- tion is approximately 8196 square kilometers. The geographical expanse of the region can be broadly classified into three categories, viz., the mountain- ous terrain, the central hilly region, and the lower terrain (plain) region. The pinnacle of the region is the Kanchenjunga peak, situated in Taplejung, with an altitude of 8586meters, while the lowest is marked by Kechana Kalan, located in Jhapa, with an elevation of merely 60meters. The high- est point of elevation, from where the data has been gathered, is Pathivara, situated at a height of 3780meters. On the other hand, the lowest al- titude, where data collection was undertaken, is an altitude of 92meters, which is at Kakarvita in Jhapa. The study area with the sampling locations in four districts is given in Fig. 1. Arun Kumar Shrestha et al./ BIBECHANA 20 (2023) 285-289 287 Figure 1: Study area with the sampling locations. 2.3 Measurement and Calculations Data was collected in count per minute (CPM) 10 times from a location. For conversion of this data into mSv/y, Eq. (1) is used [17], D(mSv/y) = (M × 0.2× F × 24× 365) 1 100 (1) where, D: absorbed dose rate in mSv/y M : Measured value in Count Per Minute F : Conversion Factor from CPM to µSv/hr 0.2 is the outdoor occupancy factor After the conversion of all data, mean and stan- dard deviation were calculated, and all data were plotted in an error bar graph. 3 Results and Discussion The background radiation of the Taplejung district is presented in Fig. 2. The background radiation in count per minute was converted into an absorbed dose rate using Eq. (1). The lowest value was ob- served to be (0.268∓).03)mSv/y in Phungling and the highest dose rate (0.335∓).041)mSv/y was ob- served in Pathivara. It may be due to the effect of cosmic radiation at higher altitudes. The average background radiation of the Taplejung district was (0.289∓ 0.02)mSv/y. The background radiation of the Panchthar dis- trict is presented in Fig. 3. The lowest dose was found to be in Phidim, and the highest dose was observed in Pauwa Vangang. As a result, the mean background radiation of the Panchthar district was (0.247 ± 0.056)mSv/y. The background radiation of the Ilam district is presented in Fig. 4. The minimum dose rate was in Jorkalash, and the max- imum dose rate was in Ilam Bazar. The aver- age background radiation of the Ilam district was (0.225±0.015)mSv/y. The background radiation of the Jhapa district is presented in Fig. 5. The lowest dose was found to be in Kakarvita, and the high- est equivalent dose rate of was observed in Bhadra- pur. However, the average background radiation of the Jhapa district was (0.209 ± 0.011)mSv/y. All these values were below the recommended value of 1mSv/y set by the International Commission on Radiological Protection (ICRP) for non-radiation workers and the public. The equivalent dose of all districts where the study is conducted is plotted in Fig. 6. The low- est equivalent dose rate (0.209± 0.011)mSv/y was found to be in Jhapa, and the highest equivalent dose rate (0.280 ± 0.026)mSv/y was observed in Taplejung. The average background radiation of the Eastern region of Koshi Province was (0.242 ± 0.034)mSv/y. This result also supports the in- crease in background radiation with altitude. The average altitude of the study areas in Jhapa, Ilam, Panther, and Taplejung is 117, 1003, 1279, and 2110m respectively. Jhapa being at lower altitude has low dose rate, and Taplejung, being at higher altitude, has a high dose rate. Variation of absorbed dose rate with altitude has been shown in Fig. 7. It shows that there is a positive correlation between al- titude and absorbed dose rate, as altitude increases the exposure also increases, this might be due to the increase in cosmic radiation with an increase in altitude. Arun Kumar Shrestha et al./ BIBECHANA 20 (2023) 285-289 288 Figure 2: Background radiation of different parts of Taplejung district. Figure 3: Background radiation of different parts of Panchthar district. Figure 4: Background radiation of different parts of Illam district. Figure 5: Background radiation of different parts of Jhapa district. Figure 6: Comparative study of dose rate at differ- ent districts. Figure 7: Variation of background radiation with altitude. 4 Conclusion The study focused on measuring the natural back- ground radiation dose at different locations in the Taplejung, Panchthar, Ilam, and Jhapa districts. A total of twenty locations were considered for the study, and the average dose rate for four dis- tricts was found to be (0.24 ± 0.25)mSv/y. It is also observed that background radiation also in- creases with increasing altitude. It was determined that the annual effective dose value was lower than the legally prescribed dose limits for non-radiation workers and the general public, as set by the In- ternational Commission on Radiological Protection (ICRP). Therefore, the natural exposure level in Taplejung, Panchthar, Ilam, and Jhapa is not haz- ardous to the people residing in the study region. Arun Kumar Shrestha et al./ BIBECHANA 20 (2023) 285-289 289 Conflicts of Interest The authors declare that there are no conflicts of interest regarding the publication of this paper. Acknowledgment A. K. Shrestha would like to thank the Univer- sity Grants Commission Nepal for providing the Ph.D. fellowship and research support grant (PhD- 078/79-ST-13). References [1] L. Benedick and Z. Jeran. Radiological of nat- ural and mineral drinking water in slovenia. Radiat. Prot. Dosim., 151:306–313, 2012. [2] R.P. Chetri. Background radiation: detec- tion, measurement, and hazards. Himalayan Physics, 627:119–122, 2017. 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Assessment of back- ground radiation level in different locations of bangladesh. Nuclear Science and Applications, 27(12):33–36, 2018. Introduction Materials and Methods Description of Instrument Study Area Measurement and Calculations Results and Discussion Conclusion