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Sorption of Np(IV) on MX-80 in Ca-Na-Cl Type Reference Water of Crystalline Rock
Nagasaki, Shinya Korean Radioactive Waste Society 2021 방사성폐기물학회지 Vol.19 No.1
The pH dependence of sorption distribution coefficient (Kd) of Np(IV) on MX-80 in Ca-Na-Cl type solution with the ionic strength of 0.3 M, which was similar to one of the reference groundwaters in crystalline rock, was experimentally investigated under the reducing conditions. The overall trend of Kd on MX-80 was independent of pH at 5 ≤ pH ≤ 10 but increased as pH increased at pH ≤ 5. The 2-site protolysis non-electrostatic surface complexation and cation exchange model was applied to the experimentally measured pH dependence of Kd and the optimized surface complexation constants of Np(IV) sorption on MX-80 were estimated. The values of surface complexation constants in this work agreed relatively well with those in the Na-Ca-Cl solution previously evaluated, suggesting that compared to Na+, the competition of Ca2+ with Np(IV) for surface complexation on MX-80 was not much strong in Ca-Na-Cl solution. The sorption model well predicted the pH dependence of Kd values but slightly overestimated the sorption at the low pH region.
Plasma Breakdown using Second Harmonic EC Waves in Helical Devices
Kazunobu Nagasaki,A. Cappa,A. Fernandez,D. Tafalla,E. de la Cal,F. Tabares,F. Sano,F. Castejon,H. Shidara,H. Okada,K. Kondo,K. Takahashi,S. Kobayashi,T. Mizuuchi,T. Estrada,V. Tribaldos,Y. Yoshimura 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
Plasma breakdown using second-harmonic electron cyclotron (EC) waves has been studied experimentally in three helical devices, Heliotron J, TJ-II and CHS. Recent technological progress on electron cyclotron heating (ECH) systems enables us to determine what the important factors for second-harmonic plasma breakdown are. Comparison of the experimental results among three devices shows a common feature that the plasma starts up from the good confinement region and strongly depends on the nonlinear interactions with the electric field of the local beam rather than the multi-reflected field. This suggests that the confinement of high energy electrons generated by ECH has a dominant role in second-harmonic plasma breakdown.
Shinya Nagasaki,Xiaopan Wang,Adriaan Buijs 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.5
The proliferation resistance (PR) of Th/U and Th/Pu fuels used in CANada Deuterium Uranium for thedeep geological repository was assessed by combining the multiattribute utility analysis proposed byChirayath et al., 2015 [1] with the transport model of radionuclides in the repository and comparing withthat of the used natural U fuel case. It was found that there was no significant advantage for Th/U and Th/Pu fuels from the viewpoint of the PR in the repository. It was also found that the PR values for usednuclear fuels in the repository of Th/U, Th/Pu, and natural U was comparable with those for enrichmentand reprocessing facilities in the pressurized water reactor (PWR) nuclear fuel cycle. On the other hand,the PR values considering the transport of radionuclides in the repository were found to be slightlysmaller than those without their transport after the used nuclear fuels started dissolving after 1,000years.
Dinoflagellates, Diatoms, and Their Viruses
Keizo Nagasaki 한국미생물학회 2008 The journal of microbiology Vol.46 No.3
Since the first discovery of the very high virus abundance in marine environments, a number of researchers were fascinated with the world of “marine viruses”, which had previously been mostly overlooked in studies on marine ecosystems. In the present paper, the possible role of viruses infecting marine eukaryotic microalgae is enlightened, especially summarizing the most up-to-the-minute information of marine viruses infecting bloom-forming dinoflagellates and diatoms. To author’s knowledge, ~40 viruses infecting marine eukaryotic algae have been isolated and characterized to different extents. Among them, a double-stranded DNA (dsDNA) virus “HcV” and a single-stranded RNA (ssRNA) virus “HcRNAV” are the only dinoflagellate-infecting (lytic) viruses that were made into culture; their hosts are a bivalve-killing dinoflagellate Heterocapsa circularisquama. In this article, ecological relationship between H. circularisquama and its viruses is focused. On the other hand, several diatom-infecting viruses were recently isolated and partially characterized; among them, one is infectious to a pen-shaped bloom-forming diatom species Rhizosolenia setigera; some viruses are infectious to genus Chaetoceros which is one of the most abundant and diverse diatom group. Although the ecological relationships between diatoms and their viruses have not been sufficiently elucidated, viral infection is considered to be one of the significant factors affecting dynamics of diatoms in nature. Besides, both the dinoflagellate-infecting viruses and diatom-infecting viruses are so unique from the viewpoint of virus taxonomy; they are remarkably different from any other viruses ever reported. Studies on these viruses lead to an idea that ocean may be a treasury of novel viruses equipped with fascinating functions and ecological roles.
Shinya Nagasaki,Takumi Saito,Satoru Tsushima,Jared Goguen,Tammy Yang 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.8
The interaction of NpO+ 2 with Cl- was studied using visibleenear-infrared spectroscopy in NaCl-Ca- Cl2-NaClO4, NaCl-NaClO4, and CaCl2-NaClO4 solutions with ionic strength (I) of 6M. The spectra of NpO+2 around 980 nm varied with Cl- concentration in the NaCl-CaCl2-NaClO4 and NaCl-NaClO4 solutions at [Cle] ≥ 3.5M, but not in the CaCl2-NaClO4 solution. Assuming the 1:1 interaction between NpOþ+ and Cl-, the apparent equilibrium constants at I = 6M were evaluated. The presence of Ca2+ was found to destabilize overall interaction between NpOþ 2 and Cle. The observations were consistent with the density functional theory calculation.