Low Cs retention capability of organic layers in Japanese forest ecosystems affected by the Fukushima nuclear accident

Koarashi, Jun; Atarashi-Andoh, Mariko

Journal of Radioanalytical and Nuclear Chemistry, 320(1), p.179 - 191, 2019/04

https://doi.org/10.1007/s10967-019-06435-7

To quantify the Cs retention behavior in forest-floor organic layers in relation to the litter dynamics, litter samples were collected at five forest sites in Fukushima in 2011 and 2015, and separated into eight fractions with different precursor species and degrees of degradation; afterward, Cs inventory was determined in each litter fraction. The ecological half-lives of Cs in the litter fractions were estimated to be from 0.7 to 4.4 years and found to depend not on the sampling site but rather on the precursor species of the litter materials. Broadleaf- and pine-needle-originated litter fractions exhibited shorter ecological half-lives of Cs, while those of cedar-originated and finely fragmented litter fractions were longer. The results suggested that the organic layers in Japanese forest ecosystems have a low Cs retention capability, although it differs depending on the forest type.

Correlation between Am(III)/Eu(III) selectivity and covalency in metal-chalcogen bonds using density functional calculations

Kaneko, Masashi; Watanabe, Masayuki

Journal of Radioanalytical and Nuclear Chemistry, 316(3), p.1129 - 1137, 2018/06

https://doi.org/10.1007/s10967-017-5683-2

We applied density functional theory calculations to Am(III) and Eu(III) complexes with chalcogen-donor ligands of the formula N(EPMe) (E = O, S, Se, Te). We calculated the equilibrium structures and relative stabilities of the complexes in the complexation reaction. The results indicated that the tendency of the relative stability is O S Se Te, which is consistent with the trend of soft acid classification. Molecular orbital overlap population analysis suggested that this tendency can be correlated with the bonding type in the covalent interaction between the f-orbitals of the metal atom and the chalcogen-donor atoms.

Radiation-induced degradation of aqueous 2-chlorophenol assisted by zeolites

Kumagai, Yuta; Kimura, Atsushi*; Taguchi, Mitsumasa*; Watanabe, Masayuki

Journal of Radioanalytical and Nuclear Chemistry, 316(1), p.341 - 348, 2018/04

https://doi.org/10.1007/s10967-018-5762-z

We studied effect of adsorption and condensation by zeolites on radiation-induced degradation of aqueous 2-chlorophenol (2-ClPh). This study aims to demonstrate that the solid-phase extraction using zeolites has potential advantage in treatments of aqueous organic pollutants. Among three zeolites examined in this study, a mordenite type zeolite (HMOR) that has a high Si to Al ratio (127 3) exhibited preferable performance as the matrix for the 2-ClPh degradation. HMOR adsorbed far more 2-ClPh than the other zeolites, which have lower Si/Al ratios. The irradiation of HMOR induced degradation of adsorbed 2-ClPh into Cl and organic by-products. We found a significant increase in Cl production by HMOR. The yield of Cl production in the presence of HMOR was as high as the yield in aqueous solution of 2-ClPh at a concentration 10 times higher. The increased Cl production indicates that the high concentration of adsorbed 2-ClPh led to effective use of the adsorbed energy of HMOR.

The Application of radiochronometry during the 4th collaborative materials exercise of the nuclear forensics international technical working group (ITWG)

Kristo, M. J.*; Williams, R.*; Gaffney, A. M.*; Kayzar-Boggs, T. M.*; Schorzman, K. C.*; Lagerkvist, P.*; Vesterlund, A.*; Ramebck, H.*; Nelwamondo, A. N.*; Kotze, D.*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 315(2), p.425 - 434, 2018/02

https://doi.org/10.1007/s10967-017-5680-5

In a recent international exercise, 10 international nuclear forensics laboratories successfully performed radiochronometry on three low enriched uranium oxide samples, providing 12 analytical results using three different parent-daughter pairs serving as independent chronometers. The vast majority of the results were consistent with one another and consistent with the known processing history of the materials. In general, for these particular samples, mass spectrometry gave more accurate and more precise analytical results than decay counting measurements. In addition, the concordance of the U-Pa and U-Th chronometers confirmed the validity of the age dating assumptions, increasing confidence in the resulting conclusions.

Development of determination method of Mo content in metal waste generated at the Japan Power Demonstration Reactor

Shimada, Asako; Omori, Hiroyuki*; Kameo, Yutaka

Journal of Radioanalytical and Nuclear Chemistry, 314(2), p.1361 - 1365, 2017/11

https://doi.org/10.1007/s10967-017-5440-6

A separation method of Mo from Nb, Zr, and the matrix elements of rubble waste was modified to determine the content of Mo in metal waste. A separation scheme to treat 1 g of metal waste was established by optimizing the amount of ascorbic acid, the rinsing solution, and repeating of the procedure. A thin-layer source was prepared using direct drop deposition and evaporation to measure Mo content. Finally, Mo content in the metal waste generated at the Japan Power Demonstration Reactor was analyzed using the developed method.

Uranium age-dating using in-situ isotope ratios by thermal ionization mass spectrometry for nuclear forensics

Okubo, Ayako; Shinohara, Nobuo; Magara, Masaaki

Journal of Radioanalytical and Nuclear Chemistry, 314(1), p.231 - 234, 2017/10

https://doi.org/10.1007/s10967-017-5379-7

The model date of two enriched uranium materials were determined using a new method for nuclear forensics investigation. In this method, the Th/U ratio was calculated without spike addition from measured ratios of Th/Th and U/U, and calculated Th/U ratio in secular equilibrium. The obtained model date for the low-enriched uranium material was agreed with the known production date within uncertainty. For the highly enriched uranium material, slightly younger model date than the known production date was obtained. The U interference on Th counting in thermal ionization mass spectrometry measurement was suspected as a potential cause.

Dissolved radiocaesium in seawater off the coast of Fukushima during 2013-2015

Fukuda, Miho*; Aono, Tatsuo*; Yamazaki, Shinnosuke*; Nishikawa, Jun*; Otosaka, Shigeyoshi; Ishimaru, Takashi*; Kanda, Jota*

Journal of Radioanalytical and Nuclear Chemistry, 311(2), p.1479 - 1484, 2017/02

https://doi.org/10.1007/s10967-016-5009-9

In order to investigate processes affecting distribution of radiocaesium in seawater in the adjacent region of Fukushima Daiichi Nuclear Power Plant (FDNPP), relationships between Cs activity in seawater and physical properties of seawater (salinity, temperature, and potential density) were observed in seven stations within 10 km radius from the FDNPP. As a whole, Cs concentrations in seawater were higher in the vicinity of the FDNPP, and were negatively correlated with potential density. From these results, it can be considered that river water discharge or export of seawater from the FDNPP's harbor has affected the higher activity levels of Cs in seawater. It was also observed that the Cs-elevated seawater can be advected to the 2050 m depths.

Applicability of polyvinylpolypyrrolidone adsorbent to treatment process of wastes containing uranium

Ohashi, Yusuke; Harada, Masayuki*; Asanuma, Noriko*; Ando, Shion; Tanaka, Yoshio; Ikeda, Yasuhisa*

Journal of Radioanalytical and Nuclear Chemistry, 311(1), p.491 - 502, 2017/01

https://doi.org/10.1007/s10967-016-5017-9

In order to assess the feasibility of method for recovering U from wastes containing uranium (scrap uranium) using polyvinylpolypyrrolidone (PVPP) adsorbent, we have examined the adsorption and desorption behavior of metal species in HCl aqueous solutions dissolving scrap uranium. It was found that the U(VI) species are selectively adsorbed onto PVPP regardless of the presence of a large amount of Na(I) and Al(III), that the adsorbed U(VI) species are desorbed from PVPP column selectively by water. Pure uranium was efficiently recovered from the eluates. From these results, the PVPP resin is expected to be used as the adsorbent in the treatment process of scrap uranium.

Year-round variations in the fluvial transport load of particulate Cs in a forested catchment affected by the Fukushima Daiichi Nuclear Power Plant accident

Matsunaga, Takeshi; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Muto, Kotomi; Tsuzuki, Katsunori; Nishimura, Shusaku; Koarashi, Jun; Otosaka, Shigeyoshi; Sato, Tsutomu*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 310(2), p.679 - 693, 2016/11

AA2015-0821.pdf:3.78MB

https://doi.org/10.1007/s10967-016-4840-3

Particulate Cs in stream water was collected continuously for two years in order to assess the long-term trend of the Cs discharge from the forest environment. Sampling was conducted from December 2011 to December 2013 in a mountainous stream, which received the Cs from the Fukushima Daiichi Nuclear Power Plant accident. A seasonal increase in fluvial transport load of particulate Cs associated with suspended solids (SS) was observed in August and September when rainfall was abundant. The particulate Cs concentration decreased at a faster rate than the rate due to radioactive decay. This decrease might be resulted from redistribution of the easily eroded and polluted soil surface due to heavy rain events such as typhoons. These findings indicate that the particulate Cs load was subject to the inter-annual variations in rainfalls, and decreased gradually over a long period of time due to a decrease in Cs concentration in SS.

Studies on electrochemical behavior of uranium species in choline chloride-urea eutectic for developing electrolytically treating method of uranium-bearing wastes

Ohashi, Yusuke; Asanuma, Noriko*; Harada, Masayuki*; Tanaka, Yoshio; Ikeda, Yasuhisa*

Journal of Radioanalytical and Nuclear Chemistry, 309(2), p.627 - 636, 2016/08

https://doi.org/10.1007/s10967-015-4625-0

As one of methods for recovering uranium from the uranium-bearing wastes, we have proposed the electrolytic deposition method using choline chloride-urea (CCU) which is known as an ambient temperature molten salt. More than 92% of uranium components in inactivated alumina and spent sodium fluoride adsorbent was dissolved into CCU solution. Cyclic voltammograms (CVs) of the solutions prepared by dissolving uranium-bearing wastes in CCU were measured in the potential range of -2.0 to 1.1 V (vs. Ag/AgCl). The one reduction peak was observed around -0.7 V for all solutions. Based on the results of CVs, bulk electrolyses of the solutions dissolving uranium-bearing wastes were also carried out at -1.5V at 80 C. The deposits were formed on a carbon electrode as cathode. Consequently, we confirmed that CCU is effective media for recovering uranium selectively from uranium-bearing waste.