Rupali Karpe

Spatial distribution and accumulation of 226Ra, 228Ra, 40K and 137Cs in bottom sediments of Mumbai Harbour Bay

The present work shows the activity levels of 226Ra, 228Ra, 40K and 137Cs in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that 40K and 228Ra concentration is nearly uniform throughout the studied area while 226Ra and 137Cs are more concentrated in the southern regions of the bay. The significant variation in the activity levels of radionuclides within the study site might be due to their sorption/desorption processes onto the surface of sediment materials. The low mean value of 226Ra/228Ra ratio (0.72) in the sediments indicates that 238U has relatively greater solubility and mobility than 232Th. Similarly, low activity ratio (0.18) for 137Cs/40K reflects the presence of very high content of 40K in sediment due to presence of primary minerals in sediment. Silt and clay were reported to dominate the composition of the sediment. A significant positive correlation between 226Ra and 228Ra and 137Cs and 40K suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system.

Selective separation of iron from uranium in quantitative determination of traces of uranium by alpha spectrometry in soil/sediment sample

During this work, controlled redox potential methodology was adopted for the complete separation of traces of uranium from the host matrix of mixed hydroxide of Iron. Precipitates of Fe(+2) and Fe(+3) along with other transuranic elements were obtained from acid leached solution of soil by raising the pH to 9 with 14N ammonia solution. The concentration of the uranium observed in the soil samples was 200-600 ppb, whereas in sediment samples, the concentration range was 61-400 ppb.

Grass to cow milk transfer coefficient (Fm ) of Iodine for equilibrium and emergency situations

Radioiodine ( 131 I) is one of the radionuclides likely to get released into the atmosphere in case of a reactor accident, though chances of such an accident are very remote due to stringent engineering safety features. If released to the environment during an accident, 131 I may enter the grass→cow→cow milk pathway, leading to increased thyroid dose to those consuming milk, especially infants and children. The estimation of site-specific grass to milk transfer coefficient (F m ) for iodine is essential for an accurate assessment of the radiological hazard to the population in the region surrounding a nuclear power plant. In this study, a method based on the chemical separation of iodine present in grass and cow milk, and subsequent neutron activation analysis (NAA) has been optimized for the determination of stable iodine concentration in grass and cow milk. The method involves preconcentration of iodine from the sample matrix, and determination of iodine by NAA. The detection limit of stable iodine in milk was found to be 1 ng/mL. For the validation of the result, iodine concentration in NIST reference materials was determined simultaneously. The present study has yielded a F m value of 5.6 × 10−3 d/L for dairy farm cows and 6.3 × 10−3 d/L for local breed cows under equilibrium conditions. These results are similar to the values given in International Atomic Energy Agency report (TRS-472). To simulate a rapid deposition of iodine on grass and for the estimation of F m value for an emergency situation, grass grown in the experimental field was sprayed with stable potassium iodide solution and fed to the adopted cows, and the milk samples were collected regularly and analyzed. The F m value for the simulated accidental situation was found to be 3.9 × 10−3 d/L.