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  • Author or Editor: A. Sakaguchi x
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Abstract  

Some attempts were made to examine the practical conditions for uranium recovery from uranium refining waste water. The adsorbent was highly effective in recovering uranium. The uranium adsorption was affected by pH, temperature, and uranium concentration of the uranium refining waste water. The adsorbent also recovered uranium effectively in column system. It aquires better mechanical properties and can be used repeatedly in the uranium adsorption-desorption cycles.

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Abstract  

In order to develop a new adsorbent for uranium, the adsorption of uranium from seawater by immobilized polyhydroxybenzene compounds has been investigated. Polyhydroxybenzene compounds having adjacent hydroxy groups, such as catechol and pyrogallol, form stable five-membered chelate ring with uranyl ion. The immobilized polyhydroxybenzene compounds have an excellent ability to adsorb uranium from seawater. Especially, the immobilized pyrogallol, having two chelating positions for uranyl ion, is the most suitable adsorbent for uranium recovery from seawater. This adsorbent also has a selectivity for uranium.

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Summary  

Hokutolite, and hot spring water and river water collected recently at Peitou Hot Spring in Taiwan were analyzed for U, Th, Ra and 210Pb isotopes. Concentrations of major chemical elements were also measured. Hokutolite had its typical chemical composition make-up for this area. The concentrations of 238U, 234U, 232   Th, 230   Th, 228   Th, 226Ra, 228Ra and 210Pb in samples scrapped into 7 layers from the surface to the bottom of a hokutolite specimen were 0.0021-0.0068, 0.0022-0.0075, 1.47-2.07, 1.00-1.29, 1.56-1.97, 56.7-68.6, 1.46-2.06 and 25.9-36.0 Bq/g, respectively. All the radionuclides exhibited a relatively uniform distribution, and radioequilibrium was confirmed among 232   Th, 228Ra and 228   Th. From the relationship between the decay and growth of Th-series nuclides it was considered that the hokutolite studied was isolated from the stream water at least 70-80 years ago. The U/Th-series radionuclides in the hot spring water were in rather high concentrations and the enrichment of 228Ra and 228   Th to 232   Th was the most prominent feature. Evaluation of the distribution coefficients (K d) using the data on hot spring water or river water and hokutolite indicated that Th (K d = 104-105) in water was likely to be precipitated (and/or co-precipitated) with BaSO4 as Th(SO4)2 with a relatively high concentration into hokutolite, together with Ra (K d = 106-107).

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Abstract  

Sediment cores from Lake Kawaguchi at the foot of Mt. Fuji in Japan were analyzed for U and Th isotopes (238U, 234U, 232Th, 230Th and 228Th) in the light of the linkage to paleoenvironmental changes. These isotopic concentrations and their ratios varied widely with depth of sediment core. A marked disequilibrium (1.1–1.5) higher than the value of 1.0 was observed for 234U/238U activity ratios, indicating that U from lake water with high 234U/238U ratio (ca. 1.6) was transferred to the bottom sediment by adsorption and/or adhesion onto the settling particles. By using model equations, the U found in the sediment core was separated into lithogenous and autogenous U fractions. These depth profiles were compared with parameters such as organic matter and biogenic-SiO2 contents and amount of rainfall. Some variations of selected parameters with depth coincided with those of lithogenous or autogenous U. The results obtained suggest that variation in the lithogenous and/or autogenous U in the sediment with depth might be helpful in tracing the geochemical behavior of U and the past environmental changes in the area surrounding Lake Kawaguchi.

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Abstract  

To estimate the dietary intakes of 210Pb and 210Po for the Japanese adults and their annual effective doses, 210Pb and 210Po were measured for 240 daily diet samples collected at two locations of Ishikawa Prefecture in Japan over three years by duplicate portion studies. No appreciable differences in intake rates of 210Pb and 210Po and their 210Po/210Pb ratios were seen among the years in each district, and between the two districts. The intake rates evaluated using 240 diet samples were 0.20 Bq/d/p for 210Pb and 0.61 Bq/d/p for 210Po as a median, respectively. Annual effective doses of 210Pb and 210Po for Japanese adults were estimated to be 0.050 and 0.053 mSv/y, respectively.

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Summary  

In connection with the investigation of acid depositions, a reliable method for the determination of the cosmogenic radionuclide 35S in precipitation was developed, and atmospheric depositions of 35S and SO4 2- have been measured every ten days at Tatsunokuchi,in a heavy-snowfall area facing to the Sea of Japan for two years during 1998-1999. Consistent seasonal cycles were found for the atmospheric depositions of 35S and non-sea salt sulfate (nss-SO4 2-),   in which both depositions were high in winter and low in other seasons. A similar wet scavenging mechanism was suggested to be involved in the association of 35S and SO4 2-.

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Abstract  

Sediment core samples were collected up to a depth of 25–40 cm from three ponds (P. Korosteli, P. Mihairov and P. Alkat) and two lakes (L. Kanoneruka and L. Semanaika) located in widely separated regions outside the former Semipalatinsk Nuclear Test Site (SNTS) in Kazakhstan. The 137Cs, Pu and U concentrations with depth were determined in samples divided at 1 cm intervals from the top of each core. These sediment cores were dated by the excess 210Pb method. The reservoirs with low sedimentation rates of 0.038–0.41 g·cm–2·y–1 permitted, but not in detail, the estimation of the depositional history of close-in fallout of 137Cs and Pu within these regions. The sediments accumulating an anomalously high 238U concentration of 250–400 Bq/kg were also found for two of the five reservoirs, in which their 234U/238U and 235U/238U activity ratios were 1.3–2.0 and around 0.047 (nearly the same as that of natural U), respectively. Such U enrichment at the subsurface with a thin layer of lower-U sediment at the surface is mainly due to infiltration of lake water containing U from the ground water flowing into the lake or pond, followed by reduction of U(VI) to U(IV) at the redox boundary.

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