نتایج جستجو برای: 238u
تعداد نتایج: 745 فیلتر نتایج به سال:
The second point makes the matrix matching of standards to samples for direct analysis impossible and, in order to normalize all samples to a similar matrix, the analysis of a diluted (or digested) solution is preferable. High instrumental sensitivity is then required to reliably measure the resulting single digit pg g-1 uranium concentrations. While the quantification of uranium is therefore d...
A new theory is described for the uptake of U in an open system applied to the dating of archaeological bones. Analytical solutions are obtained for the rate of radioactive decay of 238U, 234U and 230Th as a function of position for the case where both 238U and 234U diffuse across a bone, and where external supply of 234U is not in equilibriumwith 238U. The new theory constitutes a forward mode...
Pre-operational survey at Kalpakkam coast, indicated elevated gamma background radiation levels in the range of 100-4000 nGy h(-1) over the large tracts of the coastal sands due to the presence of pockets of monazite mineral in beach sands. In view of the prevalence of monazite, a systematic gamma spectrometric study of distribution of natural radionuclides in soil and beach sand samples collec...
The aim of this work was to calculate the values of the 234U/238U activity ratio in natural environment (water, sediments, Baltic organisms and marine birds from various regions of the southern Baltic Sea; river waters (the Vistula and the Oder River); plants and soils collected near phosphogypsum waste heap in Wiślinka (Northern Poland) and deer-like animals from Northern Poland. On the basis ...
The Red Sea is a deep semi-enclosed and narrow basin connected to the Indian Ocean by a narrow sill in the south and to the Suez Canal in the north. Oil industries in the Gulf of Suez, phosphate ore mining activities in Safaga-Quseir region and intensified navigation activities are non-nuclear pollution sources that could have serious radiological impacts on the marine environment and the coast...
Reaction mechanism analyses performed with a 4pi detector for the systems 208Pb + Ge, 238U + Ni and 238U + Ge, combined with analyses of the associated reaction time distributions, provide us with evidence for nuclei with Z=120 and 124 living longer than 10(-18) s and arising from highly excited compound nuclei. By contrast, the neutron deficient nuclei with Z=114 possibly formed in 208Pb + Ge ...
Phosphate and environmental samples were collected from Abu Tartor phosphate mine and the surrounding region. The activity concentration of 226Ra (238U) series, 232Th series and 40K were measured using a gamma-ray spectrometer. The activities of uranium isotopes (238U, 235U and 234U) and 210Pb were measured using an alpha spectrometer and a low-background proportional gas counting system, respe...
Large amounts of uranium waste rocks and tailings resulting from the exploitation and treatment of uranium ore at the Northern Guangdong mine (South China) have been accumulated in dams (tailing ponds). To reduce the dispersion of natural radionuclides into the environment, some dams were revegetated with arbor, bush and sward. Besides these plants, Miscanthus floridulu is the dominant plant gr...
-We present new precise U-Th ages of well-preserved coral specimens collected from the island of Barbados, West Indies, and the atoll of Mururoa, French Polynesia. Our new data confirm the ages attributed to oxygen isotope stage 7 in the framework of the Milankovitch theory (BERGER, 1978; MARTINSON et al., 1987). By using thermal ionization mass spectrometry (TIMS), it is also possible to quant...
While the quantification of uranium is therefore demanding in the diluted sample, uranium isotope ratio determination requires the ultimate in instrumental performance as good precisions for large isotope ratios are required at low concentrations. The abundances of the three naturally occurring U isotopes are shown in Table 1, together with the 234U/238U and 235U/238U ratios. The nuclear indust...
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