An exposure to natural background radiation in Eastern Nepal

Terrestrial and cosmic radiation are the major contributors to natural background radiation. On accounting it, cosmic radiation exposure is around 0.39 mSv/y, terrestrial radiation is 0.48 mSv/y, radiation from water and food is 0.29 mSv/y, radiation from the air is 1.26 mSv/y and artificial radiation is approximately 0.5mSv/year. As a result, the average human receives roughly 2.4mSv/year from natural sources and 0.5mSv/y from man-made sources. Monitoring the natural background radiation is important to locate the high background area. The main objective of the work is to find the average background radiation in the Morang district and to observe the variation of cosmic radiation at high altitudes. In this study, background radiation was measured in 17 different municipalities of Morang with the help of a GM counter of model GMC-300E plus. Overall, 41 measurements had been carried out for 10 minutes in every 20 seconds interval time. The result showed that the annual effective dose of Morang was 0.24±0.02 and was below the recommended value of 1 mSv/y set by ICRP for public health. Similarly, the variation of background radiation with an altitude from 381 to 2550m showed an increasing trend. The best-fitted line depicted that background radiation increased by 16% with 1000m and it was slightly higher than the literature's result of 10-12%. The comparative study showed that the effective dose (0.24) in the study area was relatively low as compared to other places and the highest dose (0.81) was monitored in Pokhara Valley. The background radiation in the Morang district has been evaluated and found to have 0.24±0.02 below the recommended value. Similarly, there is an increasing trend of radiation with altitude. (author)