Raj Mangal Tripathi

Assessment of environmental radioactivity at uranium mining, processing and tailings management facility at Jaduguda, India.

The uranium mines at Jaduguda and nearby areas of the Singhbhum thrust belt of Jharkhand State are the only operating mines in India, which supply fuel to nuclear power plants. The gamma radiation dose rates observed at different locations 1m above the tailings surface vary from 0.8 to 3.3 microGy h(-1). The geometric mean activity concentration of (222)Rn in air over the tailings ponds I and II were found to be 30 and 23 Bq m(-3), respectively, but reduces to the local background level at the boundaries of the tailings ponds. The uranium and (226)Ra levels in the ground water sources in the vicinity of the tailings pond are very similar to the regional average of 3.6 microg L(-1) and 23 mBq L(-1), respectively, indicating that there is no ground water migration of radioactive material from the tailings pond. This paper gives a brief account of the environmental radioactivity monitoring during uranium mining, ore processing and waste management operations.

Distribution of uranium in drinking water and associated age-dependent radiation dose in India

Exposure due to natural radiation is of particular importance because it accounts for the largest contribution (nearly 85 %) to the total collective dose of the world population. An attempt has been made to present the feasibility of uranium occurrence in drinking water samples from different states of India, by laser-induced fluorimetry. The associated age-dependent radiation dose was estimated by taking the prescribed water intake values of different age groups. The concentration of uranium obtained, i.e. 0.1 +/- 0.01 to 19.6 +/- 1.8 microg l(-1), is well below the drinking water guideline value of 30 microg l(-1). The annual ingestion dose due to uranium in drinking water for various age groups is found to vary from 0.14 to 48 microSv y(-1).

Study on speciation and salinity-induced mobility of uranium from soil

AbstractA study was ncarried out to investigate the impact of salinity on mobility of uranium (U) in soil and the mechanism involved. In order to explore the involved process, speciation study was carried out and it confirmed that U was present in the moderately reduced soil as a mixture of U(IV) and U(VI) with U(IV) as dominating (71xa0%) state. Sequential extraction of soil samples showed that major fraction is bound to clay mineral (49.31xa0%) followed by oxides and hydroxide of Fe/Mn (19.58xa0%), organic phase (10.75xa0%), exchangeable (10.41xa0%) and remaining to carbonate phase (9.96xa0%). The speciation study of U(VI) in soil solution revealed that UO2CO3, (UO2)2CO3(OH)3−, UO2(CO3)22−, UO2OH+ and UO2(OH)2 are predominate species in the ambient condition. The effect of salinity induced by CaCl2, MgCl2, NaCl, NaNO3 and Na2SO4 on the mobility of uranium elucidates that increases in ionic strength mobilize U(VI) from soil exchange sites forcing it into solution. Although the desorption capacity of cations is directly proportional to ionic radius (Ca2+xa0>xa0Mg2+xa0>xa0Na+) and strength of solution it fails in case of Na2SO4 and NaNO3. It was observed that at high salinity, U is removed from solution as Na2U2O7 (s) at near neutral pH. At high salinity NaNO3 induces highest desorption of U from soil subjected to its oxidizing properties. The study confirms that ion exchange mechanism is involved in the desorption of U from soil CaCl2, MgCl2, NaCl, Na2SO4 whereas NaNO3-induced uranium desorption involves both ion exchange mechanism as well as oxidative dissolution of U(IV) bound to Fe/Mn− oxides and organic matter.

DISTRIBUTION, ENRICHMENT AND PRINCIPAL COMPONENT ANALYSIS FOR POSSIBLE SOURCES OF NATURALLY OCCURRING AND ANTHROPOGENIC RADIONUCLIDES IN THE AGRICULTURAL SOIL OF PUNJAB STATE, INDIA

Enrichment factor (EF) of elements including geo-accumulation indices for soil quality and principal component analysis (PCA) were used to identify the contributions of the origin of sources in the studied area. Results of (40)K, (137)Cs, (238)U and (232)Th including their decay series isotopes in the agricultural soil of Mansa and Bathinda districts in the state of Punjab were presented and discussed. The measured mean radioactivity concentrations for (238)U, (232)Th and (40)K in the agricultural soil of the studied area differed from nationwide average crustal abundances by 51, 17 and 43 %, respectively. The sequence of the EFs of radionuclides in soil from the greatest to the least was found to be (238)U > (40)K > (226)Ra > (137)Cs > (232)Th > (228)Ra. Even though the enrichment of naturally occurring radionuclides was found to be higher, they remained to be in I(geo) class of 0, indicating that the soil is uncontaminated with respect to these radionuclides. Among non-metals, N showed the highest EF and belonged to I(geo) class of 2, indicating that soil is moderately contaminated due to intrusion of fertiliser. The resulting data set of elemental contents in soil was also interpreted by PCA, which facilitates identification of the different groups of correlated elements. The levels of the (40)K, (238)U and (232)Th radionuclides showed a significant positive correlation with each other, suggesting a similar origin of their geochemical sources and identical behaviour during transport in the soil system.

An evaluation of radiation exposures in a tropical phosphogypsum disposal environment.

Environmental radiological aspects of phosphatic fertiliser production with particular reference to disposal of phosphogypsum at two sites in India are examined. Concentration of uranium and its decay products in the rock phosphate and products are presented. External gamma exposure and inhalation of radon and progeny are found to be the major routes of exposure to public in phosphogypsum disposal environment. An estimate of the committed effective dose to a representative person gives an average additional dose of 0.6 mSv annually in the study sites.

Equilibrium isotherm and kinetics modeling of U(VI) adsorption by natural soil systems

This research examined the adsorption capability of natural soils of different origin for U(VI) at soil–water interface and the mechanism involved. Adsorption kinetics study indicates that adsorption followed the pseudo-second order kinetics irrespective of soil types and was not solely controlled by the diffusion step rather surface complexation and ion-exchange plays major role. Study of adsorption isotherms indicates adsorption involves chemisorption and soil with high Fe and Mn content better fit to Langmuir model. The study provides a better insight for site selection for radioactive waste (uranium) disposal facilities as well as soil suitable for back fill or permeable reactive barrier to inhibit migration of U(VI).

Occupational radiation exposure due to norm in a rare-earth compounds production facility

In India, rare-earth compounds are produced from the beach sand mineral monazite. Caustic digestion of the mineral followed by selective acid extraction is the method used to separate composite rare-earth fraction. The composite rare-earth chloride contains low levels of natural radionuclides and is the starting material for individual rare-earth compounds which have wide applications. Activity concentrations in composite rare-earth compounds such as chlorides, fluorides, carbonates and oxides of Ce, Nd, Pr, Sm, Gd, etc. are presented in this paper. The external gamma exposure rates and airborne activity due to thorium and thoron progeny in the occupational environment are studied. The activity levels in liquid effluent are presented. The potential individual occupational dose is estimated to be 1.9 mSv per annum.

Inventory, fluxes and residence times from the depth profiles of naturally occurring 210Pb in marine sediments of Mumbai Harbor Bay

AbstractMeasurements of the vertical concentration profile of deposited 210Pb and its parent (226Ra) in cores of recent marine sediment of Mumbai Harbor Bay (MHB) were made to determine the various depth distribution parameters n(sedimentation rate, age of sediment, total inventory, fluxes, residence times, scavenging rate, linear attenuation coefficient and relaxation mass depth). Overall, the profile distributions of 226Ra and 210Pb showed a decreasing trend with increasing the depth. The mean of sedimentation rate in the studied area was obtained to be about 0.76xa0cmxa0year−1 which corresponds to average age of sediment of about 56xa0years. The average total deposited 210Pb for the studied sediment profile was 9.68xa0kxa0Bqxa0m−2 and correspondingly the average value of fluxes of total 210Pb and excess 210Pb (atmospheric flux) were 0.59 and 0.32xa0kxa0Bqxa0m−2xa0year−1, respectively. The residence time of 210Pb was in the range of 26–226xa0years throughout the sediment profile and showed generally an increasing trend from top to bottom. The mean relaxation mass depth (h0) derived from the depth profile of 210Pb at the studied area was about 190xa0kgxa0m−2. The negative association between clay content of cores and the h0 of 210Pb indicates that as the clay content increases, the penetration depth of deposited 210Pb in sediment profile decreases.

Metal characterization of airborne particulate matters in a coastal region

ABSTRACT The concentrations of suspended particulate matter in the air of the Orissa Sand Complex had an average value of 128 ± 10 µg m−3 in residential areas and 170 ± 8 µg m−3 in mining areas. PM10 levels in residential areas were found to have an average of 35 ± 10 µg m−3, in mining areas 45 ± 10 µg m−3. The distribution of some elements is also discussed here. Inhalation doses were observed to be higher in summer than in winter and the rainy season. The highest dose rate was for the age group of 1 year, and health risks were found to be highest for the same. For adults, inhalation dose and health risk are 1.3 times higher in mining than in residential areas.

A study of disequilibrium between 220Rn and 216Po for 220Rn measurements using a flow-through Lucas scintillation cell.

Lucas-type scintillation cells (LSCs) are commonly used for rapid measurements of (220)Rn concentrations in flow-through mode in field and for calibration experiments in laboratories. However, in those measurements, equilibrium between (220)Rn and (216)Po is generally assumed and two alpha particles are considered to be emitted per (220)Rn decay due to very short half-life of (216)Po. In this paper, a small, yet significant disequilibrium existing between (220)Rn and (216)Po has been examined and shown that less than two alpha particles are actually emitted per (220)Rn decay in the cell when flow is maintained. A theoretical formula has been derived for the first time for a correction factor (CF) to be applied to this measured concentration to account for the disequilibrium. The existence of this disequilibrium has been verified experimentally and is found to increase with the increase in the ratio of flow rate to cell volume. The reason for the disequilibrium is attributed to the flushing out of (216)Po formed in the cell before its decay due to the flow. Uncertainties in measured concentrations have been estimated and the estimated CF values have been found to be significant for the flow rates considered above 5 dm(3) min(-1) for a cell of volume 0.125 dm(3). The calculated values of the CF are about 1.055 to 1.178 in the flow rate range of 4 to 15 dm(3) min(-1) for the cell of volume 0.125 dm(3), while the corresponding experimental values are 1.023 to 1.264. This is a systematic error introduced in (220)Rn measurements using a flow-through LSC, which can be removed either by correct formulation or by proper design of a measurement set-up.