Radiation mapping of Jaipur city using compact aerial radiation monitoring system (CARMS) installed in mobile platform

Full text: Widespread use of radioisotopes for social benefits through industrial, scientific and medical applications poses a potential for occurrence of radiological emergencies due to loss or misuse of the radioactive sources. Besides, as there is increased societal concern for radiation safety of man and environment, monitoring is needed as a confidence building measure. It is necessary to assess any possible increase in background radiation due to the operation of nuclear facilities or any other man made events. Any observable increase in normal radiation background is a precursor for the abnormal presence of radioactivity. As a part of emergency preparedness for response to radiological emergencies, BARC has taken up radiation mapping of all major cities. A mobile ground based radiation monitoring has been conducted around Jaipur city using state-of-the-art radiation monitoring systems and instruments. The systems were mounted in a vehicle at a height of 1.0 meter from the ground and the GPS antenna was mounted on top for clear satellite visibility. It was ensured that the gamma attenuation due to the body of the vehicle was minimal. The average speed of the vehicle was maintained at 30 km/h to ensure uniformity in distance during the data acquisition interval. The monitoring was carried out over two days and resulted in establishment of baseline dose rate data of the city, which will be useful in case of any radiological emergency. The detailed environmental radiation monitoring demonstrated the utility of the systems and the methodology for the assessment of large area ground contamination and also search and detection of any orphan radioactive sources through variations in background gamma radiation observations. The methodology adopted for analysis of the surveyed data is based on the interpretation of the changes in the mean value and standard deviation in the values in different regions of the surveyed area. During this monitoring exercise, total road length of 100 km was covered and the average gamma dose rate recorded was 66.6 nGy/h with standard deviation of ± 4.4 nGy/h. The background gamma levels have been substantially constant in the area of survey. A small difference of 10 nSv/h in average values between CARMS and Gamma Tracer is observed. This is due to different energy compensation technique used and calibration methods related to mounting of detectors and their size. It can be said that through such exercises by mobile radiation monitoring being carried out periodically are very useful in generation of nationwide baseline radiation dose rate and any future deviations due to industrial/malevolent activities can be identified and emergency measures can be implemented