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Abstract  

Depth profiles of the long-lived radionuclides, 137Cs, 90Sr, Pu isotopes and 241Am were examined in undisturbed sandy, peaty and Podsol soils in the Chernobyl 30 km exclusion zone sampled around 10 years after the accident. Two Podsol soils, which have different radioactive deposition characteristics, have also been examined. Activity ratios of 239,240Pu/137Cs, 90Sr/137Cs, and 241Am/137Cs in the 0-1 cm layer of the two Podsol soils differed very much. Speciation of the radionuclides by sequential selective extraction was examined in the soils. Depth profiles of the soils have been analyzed according to the speciation results and soil characteristics.

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Abstract  

Adsorption and desorption of95Zr−95Nb,99Mo,103Ru,132Te and239Np in a HCl-alumina system were studied in order to purify99Mo and132Te obtained by the cation-exchange separation of fission products and to prepare highly pure99mTc and132I generators.99Mo and132Te, of which radionuclidic purity was over 99.99% and 99.999%, respectively, could be obtained by passing the cation-exchange separated Mo and Te fractions through alumina columns, by washing with HCl and finally by eluting99Mo with 1M NH4OH and132Te with 3M NaOH. In order to raise the recovery of99Mo and132Te from the alumina columns, they should be eluted as quickly as possible after the adsorption. The direct use of the alumina column containing99Mo or132Te as the generator allowed milking of99mTc or132I, of which radionuclidic purity was over 99.999%. Milking yields of99mTc with 0.1M HCl and132I with 0.01M NH4OH were 77% and 90%, respectively. The latter value was much higher than that in usual performance of the generator.

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Abstract  

Environmental factors (nutrients and pH) influence the retention of Sr, Cs, and Ba as analogue of long-lived radionuclides by the microorganism. The effect of pH and concentration of organic nutrients are proved to be significant factors for retention of cations (Sr, Cs and Ba) by the microorganisms inoculated from surface soil. Microorganisms can affect the speciation of Sr, Cs, and Ba in the environment. Concentration of organic nutrients and pH are indicated to be the important environmental factors in the consideration of the migration of the radionuclides through microbial processes in the terrestrial environment.

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Abstract  

Macro-porous cation exchange resin Diaion CPK-08 and gel type cation exchange resin Dowex 50WX8 were irradiated with γ-rays from60Co, while soaked in distilled water, 0.5M HNO3 or 4M HNO3, and the ion-exchange properties, such as strong- and weak-acid capacities, moisture content and wet resin volume, were examined in relation to absorbed dose. There was no appreciable difference between the radiation stabilities of the two cation exchangers. Increase of HNO3 concentration reduced the loss of strong-acid capacity and increased the decross-linkage and the weak-acid capacity. Elution characteristics of137Cs and90Sr from columns packed with γ-irradiated resin were examined and the column distribution ratio of these radionuclides and the theoretical plate number were calculated. These values decreased with the increase of absorbed dose. Diaion CPK-08 was packed into a pressurized column and irradiated with γ-rays at a dose rate of 2·106 R/hr, while water was passed through the column at a constant flow rate. The greatest change of the resin properties was observed at an upper stream position from the position of the highest radiation dose of 2·106 R/hr.

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Abstract  

In Japan, about 70% of land area is covered by forest. Therefore, forest ecosystem plays a vital role in ultimate fate of radionuclides and carbon cycle in terrestrial environment. In this study, three undisturbed forest soil profiles were collected from Ibaraki Prefecture, Japan. The 137Cs data illustrate that maximum fallout deposition of 137Cs took place around 1964. 14C determination shows that 14C also has peak values in the top 10 cm of the soil profiles ascribed to the highest bomb 14C level in 1960's. The 13C data show that the turnover dynamics of soil organic carbon could be described very well by progressive enrichment values of d13C.

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Abstract  

A simultaneous sampling system for the speciation of atmospheric T and 14C has been developed. Firstly tritiated moisture together with all water vapor in air is adsorbed on Drierite after coagulation using an electric cooler. Then 14CO2 plus stable CO2 in the dried air is adsorbed on molecular sieve 4A. Elemental tritium gas (HT) plus hydrogen gas (H2) in the atmosphere along with H2 gas generated from electrolysis of groundwater which does not contain any T, are oxidized on Pd catalyst to water and adsorbed on molecular sieve 3A. Tritiated methane (CH3T) and 14CH4 plus stable methane in the atmosphere are oxidized on Pt catalyst to water and CO2 under 400 °C. Then, Drierite and molecular sieve 4A adsorb the oxidized T (HTO) and C-14 (14CO2), respectively. Tritium and C-14 in surface and soil air have been measured using this system

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
H. Natsume
,
H. Umezawa
,
T. Suzuki
,
F. Ichikawa
,
T. Sato
,
S. Baba
, and
H. Amano

Abstract  

A scheme for the sequential separation of fission products has been developed on the basis of ion-exchange techniques. It consists of a main cation-exchange process for group separation and subsidiary processes of cation or anion exchange for further separations or purifications of the individual fission products. By the present method, Zn, Rb, Sr, Y, (Zr), Mo, Pd, Cd, Te, Cs, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu and Tb can be separated simultaneously from an irradiated uranium sample. Of these, alkali, alkaline earth and rare earth metal ions are separated quantitatively. A polarographic method was applied to determine the recoveries of Zn, Mo, Pd, Cd and Te, which were not separated quantitatively.

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Abstract  

The concentration of pore water uranium in six sediments from oligotrophic, mesotrophic, acidotrophic and dystrophic lakes was measured by inductively coupled plasma-mass spectrometry. Profiles of pore water U can be divided into two groups such as low (17±7 ng/l) and high concentration (69±30 ng/l). These values were 1–2 orders of magnitude higher than that of lake waters (6±4 ng/l) due to the release of U from the sediments by decomposition of organic materials. Variations in pore water U concentrations seem to relate to the differences in pore water pH, the association forms, and their contents of U in the lake sediments.

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Abstract  

Surface soil samples (0–1 cm) were collected to understand the role of hot particle (HP) in migration of radionuclide approximately 11 years after the Chernobyl accident. Three types of HPs were found by the analyses using alpha-track technique and scanning electron microscopy/energy dispersive X-ray spectrometer (SEM/EDX). The dissolution of HPs has been affected by the existing type of HPs. Six-stage sequential selective extraction procedure was carried out to define the chemical forms of uranium, 241Am and 137Cs. The chemical form of radionuclides in surface soil is significantly different between the west and the north traces of radioactive plumes approximately 11 years after the accident.

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Abstract  

Carrier-free99mTcO4 eluated from clinical99Mo/99mTc generators was examined to determine its specific activity. The observed specific activity was found to be always lower than the calculated value based on the99Mo–99mTc–99Tc decay scheme data. These results could be explained in terms of existence of excess Tc loaded onto generator column.

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