K. Siddappa

226Ra, 40K and 7Be activity concentrations in plants in the environment of Kaiga, India

Leaves, stem and bark samples from several plant species were collected from tropical forest of Kaiga, in the west coast of India where two nuclear power reactors of 220 MW each have just been commissioned and another two are under construction, and analysed for their (226)Ra, (40)K and (7)Be concentrations. The activities of (226)Ra and (40)K in plants were found to vary in the range BDL-13.2 and 12.0-797.3 Bq kg(-1), respectively. Plants show significant (7)Be activity in leaves, the activity varies in 72.5-1,060.8 Bq kg(-1). Stem and bark of plants show higher levels of (226)Ra and (40)K when compared to leaves. Soil-to-plant transfer factor for (226)Ra and (40)K were found to vary in the range BDL-0.37 and 0.09-5.61, respectively for different plants. The concentration of (226)Ra and (40)K in leaves depends on the age of the leaves.

Experimental effective atomic numbers for the photoelectric process in some alloys at 84 and 145 keV

The total attenuation coefficients are measured for seven alloys at 84 and 145 keV by the transmission method using a good geometry setup employing a NaI(Tl) scintillation spectrometer. The scattering contributions are deduced using the theoretical cross sections taken from the recent literature and are subtracted from the measured total cross sections to get the photoelectric cross sections. Finally, the effective atomic numbers are obtained from the graph of cross section versus the atomic number. Results are compared with semiempirical estimates and are found to be in good agreement. Results are also compared with the available experimental values, some of which are reported at 412 keV and some at 52.5 keV and a good agreement is noted.

Distribution and behaviour of natural radionuclides in soil samples of Goa on the southwest coast of India

Publisher Summary Human beings have always been exposed to natural background radiation. The natural background radiation has two components: one originating from extra terrestrial sources such as cosmic rays and the other from terrestrial sources that derive essentially from the Earths strata. This chapter discusses the program of studies on natural radiation in the environment of Goa that was conducted by the research group in the period 1995–1999 to establish the natural background radiation level and radionuclide distribution in the environment. Soil samples were collected and analyzed for their gamma radionuclides—namely, 226 Ra, 232 Th and 40 K using an HPGe spectrometer. 210 Pb and 210 Po were determined employing radiochemical techniques. Activity ratios and correlation studies of 226 Ra, 210 Pb and 210 Po in surface soil clearly indicate the presence of unsupported 210 Pb and 210 Po in surface soil. Significant correlation observed between the concentrations of 210 Pb and 210 Po and soil organic matter content confirms the adsorption of these radionuclides from atmospheric precipitation, hence causing higher concentrations in surface soil.

Concentration, distribution and transportation of 222Rn and its decay products in the environment of coastal Karnataka and Kaiga in southwest India

Publisher Summary Studies on radon and its decay products in the atmosphere are useful for determining the radiological risk to the general public. Concentrations of 222 Rn and its decay products in ground level air are dependent on its exhalation rate and atmospheric diffusion depending on meteorological parameters. In the present investigation, extensive studies on 222 Rn exhalation rate, 222 Rn and its decay product concentrations in air at ambient temperature and humidity were carried out simultaneously at each sampling location in coastal Karnataka and Kaiga. Correlations of 226 Ra in soil, 222 Rn exhalation rate, equilibrium factors, and annual effective dose to the general public were estimated. The estimated dose to the general public due to inhalation of outdoor 222 Rn and its decay products using the equilibrium factor suggested by UNSCEAR yielded higher values than the dose calculated from the equilibrium factors obtained here. This suggests the need and importance of measurement of individual 222 Rn concentrations and its decay products, and of establishing the equilibrium factor individually for a larger number of areas so that a more realistic equilibrium factor can be derived for global use.

Prominent artificial radionuclide activity in the environment of coastal Karnataka on the southwest coast of India

Studies on radiation level and radionuclide distribution in the environment of coastal Karnataka were undertaken to provide baseline data for the future assessment of the impact of the nuclear and thermal power stations that are being set up in the region and to understand the behaviour of radionuclides in the environment. As part of the programme the concentrations of two important artificial radionuclides, namely 90Sr and 137Cs, have been measured in a number of environmental samples. The concentration of 90Sr is very low in most of the samples. Among the samples analysed for the concentration of 137Cs, soil samples showed elevated levels of activity in some sampling stations. Among the vegetables, brinjal (Solanum melongena. L) showed considerable activity. The internal dose due to intake of 90Sr through diet was 0.42 microSv year(-1) for the vegetarian population and 0.32 microSv year(-1) for the non-vegetarian population. The internal dose due to dietary intake of 137Cs was found to be 0.34 microSv year(-1) and 0.26 microSv year(-1) respectively for the vegetarian and non-vegetarian population. The results are discussed in the light of the literature values reported for other environs of India and abroad and appropriate inferences are drawn.

MEASUREMENT OF PHOTOFISSION CROSS-SECTION OF 238U USING MICROTRON FACILITY

Photofission cross-section of 238U was measured using bremsstrahlung radiation energy 7.4–9.0 MeV with energy step of 0.4 MeV by employing Lexan polycarbonate film as solid state nuclear track detector (SSNTD). The photon intensity from the Microtron accelerator at a distance of 15 cm from the bremsstrahlung converter (tantalum target) facility was estimated to be 1010 photons/sec using the code EGS-4. In this paper, details of the fission fragment angular distribution measurements of 238U target using Lexan polycarbonate have been discussed. The photofission cross-section was calculated using the angular distribution of fission fragments and the results were compared with those obtained using the code EMPIRE-II and various barrier parameters of the RIPL-1, RIPL-2 libraries and with the new analytical fission barrier formula based on the Hugenholtz–Van Hove theorem. The present experimental measurements were in good agreement with the results obtained from the Empire-II code predictions for potential parameter taken from RIPL-1 and a newly developed analytical fission barrier formula.

Caesium-137 concentration in Kaiga environment

Measurement of radioactivity levels in various environmental matrices at the Kaiga nuclear power plant and the surrounding environs has been carried out on a routine basis to establish the baseline background radiation level prevailing in the region. Measurement of the concentration of Cs-137 in environmental matrices is necessary to estimate the amount of fallout of this radionuclide in the region and to assess the long term impact of the nuclear power plant on the environment.