Authors:M. Yamamoto, S. Igarashi, K. Chatani, K. Komura, and K. Ueno
This paper describes the analytical methods for the determination of237Np, Pu isotopes, and241Am, with particular emphasis on237Np by alpha-ray spectrometry and241Pu by liquid scintillation technique. Results are also presented for the sediment cores collected from Mikata Five Lakes in Fukui Prefecture, Japan.
Authors:M. Yamamoto, K. Shiraishi, K. Komura, and K. Ueno
Diet samples were collected by a duplicate portion study of Japanese adults in two districts, a newly-rising town and an established seaside village, of Ishikawa Prefecture, which faces the Sea of Japan. Uranium concentrations in a total of 80 diet samples were determined by -spectrometry after chemical separation. No marked differences between the two districts were found regarding characteristics of food consumption in thirteen categories and in daily intake of238U per person. The daily intake of238U per person ranged from 1.1 to 40 mBq with a geometric mean value of 9.6±2.1 mBq. The234U/238U activity ratios ranged from 0.7–1.5, with most being from 1.0–1.2. The internal dose estimation system (IDES) was completed with Japanese physical parameters and other parameters of ICRP Publication 30, and then the annaul effective dose equivalent was estimated as 3·10–7 Sv for238U in a Japanese adult.
Authors:Y. Yamada, M. Itoh, N. Kiriyama, K. Komura, and K. Ueno
All of the combustion water samples extracted from cellulose in pine tree rings corresponding to the 1983–1987 period showed elevated tritium concentrations of approximately 65 pCi/dm3, which were 30 to 35 pCi/dm3 higher than those for precipitation and atmospheric vapor in recent years. In addition, other environmental samples, viz. the tissue-free water in tree rings, and of combustion and tissue-free water in pine needles and spring water near the pine tree site also showed concentrations similar to the combustion water of cellulose. These findings suggest that most of the tritium in tree rings was supplied from underground water containing a high tritium concentration in the root zone of the pine tree.
Authors:M. Yamamoto, Y. Yamauchi, K. Komura, K. Ueno, and D. Assinder
Chemical leaching experiments of237Np in the sediments from the Esk Estuary and the Ribble Estuary in the Irish Sea, U. K., have been carried out, in comparison with those of239, 240Pu and241Am, to understand the geochemical associations of these long-lived radionuclides with sediment. Experimental results show that partitioning behavior of237Np is obviously different from those of239, 240Pu and241Am.
Authors:M. Yamamoto, Y. Yamauchi, H. Kawamura, K. Komura, and K. Ueno
210Pb and210Po in human hair have been measured to serve as an aid in order to estimate the dietary intake and body burden of these radionuclides of Japanese. The210Po concentrations found in 83 hair samples were ranging from 4.0 to 59.3 mBq/g with a mean (median) value of 18.2±12.2 (14.9) mBq/g as compared to the210Pb concentrations from 0.7 to 6.5 mBq/g with a mean (median) value of 2.3±1.1 (2.0) mBq/g. The210Po/210Pb activity ratios (mean: 8.7±5.1, median: 7.1) were surprisingly higher compared with the available literature value of about 2. The high concentration of210Po in human hair of Japanese may be due to the ingestion of animal protein mainly in the form of seafood.
Authors:L. Sha, M. Yamamoto, K. Komura, and K. Ueno
This paper gives the first data on239,240Pu and241Am in Chinese soils. Surface soil samples with a set of 0–5 cm and 5–20 cm depth were collected from Beijing, Taiyuan, Shijiazhuang and Jinang of China in 1990, and239,240Pu,241Am and137Cs, including naturally occurring radionuclides, in these samples were measured to evaluate their present levels and distributions. From these results, the average accumulated depositions were estimated roughly to be 24±13 MBq/km2 for239,240Pu, 10±5 MBq/km2 for241Am and 1.2±0.7 GBq/km2 for137Cs. The activity ratios of239,240Pu/137Cs and241Am/239,240Pu ranged from 0.016 to 0.026 with a mean value of 0.020±0.004 and 0.35 to 0.49 with a mean value of 0.43±0.05, respectively.
Authors:Y. Takizawa, L. Zhao, M. Yamamoto, T. Abe, and K. Ueno
To determine the levels of210Pb and210Po in human tissues of people in Japan, various tissue samples were obtained at autopsy from the cadavers of 22 oncologic cases, mainly in Niigata Prefecture in northern Japan, from 1986 to 1988.Wet ashing, followed by electrochemical deposition and alpha spectrometry were used to separate and determine the210Pb and210Po present. Among the tissues analyzed, the highest concentrations of210Pb and210Po were observed in bone (sternum), liver, and kidneys. The total body burden of210Pb and210Po was found to be approximately 427 pCi and 514 pCi, respectively. This estimated210Po value did not differ significantly from values found in populations in the U.S.A. and European countries.
Authors:L. Zhang, S. Ueno, K. Sato, R. Adlof, and G. List
We have conducted thermal and X-ray diffraction experiments on binary mixtures of symmetric stearic-oleic mixed-acid triacylglycerol
(TAG) (1,3-distearoyl-2-oleoyl-glycerol: SOS) and asymmetric stearic-oleic mixed-acid TAG (1,2-dioleoyl-3-stearoyl-sn-glycerol: OOS), in which optically active sn-OOS was employed. We found that SOS–OOS mixtures exhibited immiscible monotectic or peritectic mixing behavior. This result
was consistent with previous study on binary mixtures of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP) and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP), in which racemic rac-OOP molecules were employed. The differences between the SOS–OOS and POP–OOP mixtures were in the polymorphic behavior of
the fractions of POP and SOS. No effect was found from using an optically active (sn-OOS) or racemic mixture (rac-OOP) as an asymmetric oleic–oleic-saturated acid TAG. From the two results, we may conclude that an immiscible phase was
formed in the binary mixtures of symmetric saturated-oleic-saturated TAGs and asymmetric oleic–oleic-saturated TAGs, of both
racemic and optically active types. This result stands in contrast to mixtures of SOS–OSO (1,3-dioleoyl-2-stearoyl-glycerol),
SOS–SSO (1,2-distearoyl-3-oleoyl-rac-glycerol), POP–OPO (1,3-dioleoyl-2-palmitoyl-glycerol), and POP–PPO (1,2-dipalmitoyl-3-oleoyl-rac-glycerol), all of which exhibited molecular-compound-forming behavior with molecular compound crystals at an equal ratio
of the binary mixtures. Molecular-level mechanisms to explain this difference are discussed, based on possible roles of glycerol
groups acting during the mixing processes of saturated–unsaturated mixed-acid TAGs.
Authors:M. Yamamoto, Syarbaini, K. Kofuji, A. Tsumura, K. Komura, K. Ueno, and D. Assinder
An analytical method has been developed for the determination of low-level99Tc in environmental samples by High Resolution ICP-MS. The method consists of leaching of99Tc by HNO3 and separation by three different solvent extractions with 30% TOA-xylene, MEK, and cyclohexanone. Finally, purification of99Tc was made by using an anion exchange resin column to reduce dissolved solids content. The final solution was adjusted to 1M HNO3 for introducing into the HR-ICP-MS. The accuracy and precision of the method was confirmed to be satisfactory by applying this technique to the determination of99Tc in IAEA marine algae sample (AG-B-1). Measurements of99Tc using 0.5–2.5 g of sediment samples from the Irish Sea, UK, were successfully performed by the present method.
Authors:M. Yamamoto, Y. Yamauchi, K. Chatani, S. Igarashi, K. Komura, K. Ueno, and M. Sakanoue
In order to investigate the sedimentary behaviour of neptunium,237Np together with Pu isotopes and241Am have been measured for the sediment cores collected from Lake Mikata (freshwater) and from Lake Kugushi (brakish water) both belonging to the Mikata Five Lakes, and from Nyu Bay (sea water). In all sediment core samples237Np was detected, and its concentrations were far below those of239,240Pu and241Am measured for the same samples. Inventories of237Np in Lake Mikata, Lake Kugushi and Nyu Bay were estimated to be 0.53, 0.29 and 0.34 MBq/km2, respectively. The activity ratio of237Np/239,240Pu calculted from the inventories in each sediment core was 0.29% for Lake Mikata, 0.15% for Lake Kugushi and 0.10% for Nyu Bay. These values except for the value for Lake Mikata are two or three times lower than the value of 0.3–0.4% observed for surface soils of 0–20 cm depth, suggesting that Np is more soluble compared with Pu.