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Hashikura, Yasuaki*; Ishijima, Yasuhiro; Nakahara, Masaumi; Sano, Yuichi; Ueno, Fumiyoshi; Abe, Hitoshi
Hozengaku, 19(3), p.95 - 102, 2020/10
A plutonium concentrator was selected, and constant load tensile tests with controlled applied potentials and electrochemical tests were conducted in nitric acid and sodium nitrate solutions. From the results, a map which shows the effect of nitric acid concentration to crack initiation potential was drawn. And, it was pointed out that not only the nitric acid but also the nitrate ion coordinated to the nitrate must be considered in evaluating the possibility of stress corrosion cracking.
Nakahara, Masaumi; Sano, Yuichi; Nomura, Kazunori
Radiochimica Acta, 108(9), p.701 - 706, 2020/09
Times Cited Count：0 Percentile：0.01(Chemistry, Inorganic & Nuclear)To evaluate the corrosion behavior of a Pu evaporator made from Zr in a reprocessing plant, the influence of PuO
was investigated with Pu nitrate solutions in electrochemical experiments. The maximum open circuit potential of Zr in the Pu nitrate solution was approximately 1 V in the Pu nitrate solution containing 7 mol dm
HNO
. However, there were no significant changes at high PuO concentrations, and Zr showed high corrosion resistance under our experimental conditions.
Nakahara, Masaumi; Sano, Yuichi; Abe, Hitoshi
Progress in Nuclear Science and Technology (Internet), 5, p.52 - 55, 2018/11
For evaluating the secular change of Pu evaporator made of Zr in the commercialized nuclear fuel reprocessing plant, electrochemical experiments were carried out with Pu nitrate solutions. The open circuit potentials of Zr increased with increasing Pu, HNO concentrations and temperature. However, these experimental results imply that Zr has high corrosion resistance in Pu nitrate solutions.
Nakahara, Masaumi; Sano, Yuichi; Nomura, Kazunori; Takeuchi, Masayuki
Journal of Chemical Engineering of Japan, 51(3), p.237 - 242, 2018/03
Times Cited Count：2 Percentile：8.98(Engineering, Chemical)For evaluating the Pu partitioning behavior under the condition of high Pu concentration in the feed solution by the acid split method, the counter current experiment was carried out. The Pu content in the U/Pu product was 1.51 times higher than that in the feed solution. In the Pu partitioning section, Pu polymerization and third phase formation were observed, and the operation of centrifugal contactors was stable.
Sano, Yuichi; Watanabe, So; Nakahara, Masaumi; Aihara, Haruka; Takeuchi, Masayuki
Proceedings of International Nuclear Fuel Cycle Conference (GLOBAL 2017) (USB Flash Drive), 4 Pages, 2017/09
JAEA has been promoting MA recycle project using a FR fuel cycle named as SmART cycle concept. The SmART cycle contains the recovery of all actinides, in which total amount of MA is estimated to around 1-2g, at CPF from the FR Joyo spent fuel, the fabrication of MA bearing MOX fuel pellets and pins at AGF with recovered actinides, and the irradiation test of the fabricated fuels at the Joyo. In this paper, recent activities on actinides recovery in CPF, which will make a significant contribution to the SmART cycle, were summarized.
Takeuchi, Masayuki; Sano, Yuichi; Watanabe, So; Nakahara, Masaumi; Aihara, Haruka; Kofuji, Hirohide; Koizumi, Tsutomu; Mizuno, Tomoyasu
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04
Tc-radiopharmaceuticals obtained from 
Mo produced by 
Mo(n,2n)Mo and fission of 
UHashimoto, Kazuyuki; Nagai, Yasuki; Kawabata, Masako; Sato, Nozomi*; Hatsukawa, Yuichi; Saeki, Hideya; Motoishi, Shoji*; Ota, Masayuki; Konno, Chikara; Ochiai, Kentaro; et al.
Journal of the Physical Society of Japan, 84(4), p.043202_1 - 043202_4, 2015/04
Times Cited Count：8 Percentile：52.77(Physics, Multidisciplinary)
to extreme environmentsHorikawa, Daiki*; Yamaguchi, Ayami*; Sakashita, Tetsuya; Tanaka, Daisuke*; Hamada, Nobuyuki*; Yukuhiro, Fumiko*; Kuwahara, Hirokazu*; Kunieda, Takekazu*; Watanabe, Masahiko*; Nakahara, Yuichi*; et al.
Astrobiology, 12(4), p.283 - 289, 2012/04
Times Cited Count：23 Percentile：68.61(Astronomy & Astrophysics)We examined the hatchability of hydrated and anhydrobiotic eggs of the tardigrade to hatch after ionizing irradiation (helium ions), extremely low and high temperatures, and high vacuum. Anhydrobiotic eggs (50% lethal dose; 1690 Gy) were substantially more radioresistant than hydrated ones (50% lethal dose; 509 Gy). Anhydrobiotic eggs also have a broader temperature resistance compared with hydrated ones. Over 70% of the anhydrobiotic eggs treated at high and low temperatures, but all of the hydrated eggs failed to hatch. After exposure to high vacuum conditions, the hatchability of the anhydrobiotic eggs was comparable to that of untreated control eggs.
Gusev, O.*; Nakahara, Yuichi*; Vanyagina, V.*; Malutina, L.*; Cornette, R.*; Sakashita, Tetsuya; Hamada, Nobuyuki*; Kikawada, Takahiro*; Kobayashi, Yasuhiko; Okuda, Takashi*
PLoS ONE (Internet), 5(11), p.e14008_1 - e14008_9, 2010/11
Times Cited Count：52 Percentile：75.63(Multidisciplinary Sciences)Anhydrobiotic chironomid larvae can withstand prolonged complete desiccation as well as other external stresses including ionizing radiation. To understand the cross-tolerance mechanism, we have analyzed the damage and repair in the nuclear DNA using DNA comet assays and gene expression in relation to anhydrobiosis and radiation. We found that dehydration causes alterations in chromatin structure and a severe fragmentation of nuclear DNA in the cells of the larvae despite successful anhydrobiosis. Furthermore, while the larvae have restored physiological activity within an hour following rehydration, nuclear DNA restoration typically took 72 to 96 h.
Nakahara, Masaumi; Sano, Yuichi
Radiochimica Acta, 97(12), p.727 - 731, 2009/12
Times Cited Count：5 Percentile：35.91(Chemistry, Inorganic & Nuclear)The behavior of Np in a simplified solvent extraction process for U, Pu, and Np co-recovery was investigated. Two approaches flow sheets, high HNO concentration of feed solution and high HNO concentration of scrubbing solution, was examined with dissolver solution of an irradiated fast reactor core fuel. It is more effective for the Np recovery under the condition of the feed solution with a high HNO concentration because the inextractable Np(V) is effectively oxidized to extractable Np(VI) in the feed solution and there is less effect of HNO at the extraction section.
Furuta, Etsuko*; Nakahara, Hiromichi*; Hatsukawa, Yuichi; Matsue, Hideaki; Sakane, Hitoshi*
Journal of Radioanalytical and Nuclear Chemistry, 278(3), p.553 - 557, 2008/12
Times Cited Count：6 Percentile：39.98(Chemistry, Analytical)In Japan, cosmetics which declared hormesis effect are available through Internet. The existence of a daughter nuclides of Th and U series, however, were observed by measurements of the 
rays with a high purity Ge detector. In this study, in order to clarify the contents of trace elements, the hormesis cosmetics including radiation sources were analyzed using instrumental neutron activation analysis method (INAA), prompt activation analysis (PGAA) and neutron activation analysis with multiple ray detection (NAAMG). In the conference, we will report the results of analysis data which including heavy metallic and actinide elements. Furthermore, we will evaluate a possibility of uptake of heavy metal elements and radiation sources, and will discuss the influence of them to human body.
concentration at extraction sectionNakahara, Masaumi; Sano, Yuichi; Koizumi, Tsutomu
JAEA-Research 2008-078, 24 Pages, 2008/10
JAEA-Research-2008-078.pdf:0.98MB
Concerning the advanced aqueous reprocessing system, we have been investigating a simplified solvent extraction process using TBP as an extractant for U, Pu and Np co-recovery. The experiment was conducted with low HNO concentration in the feed solution and high HNO concentration in the scrubbing solution, which was expected to bring a high HNO concentration into the extraction section and the efficient Np oxidation and extraction in this section. This experiment had been conducted with the dissolver solution of "JOYO" Mk-I and Mk-II irradiated MOX fuel. The Pu valence was adjusted to Pu(IV) by bubbling NOx gas into the feed solution. It was attempted to oxidize Np(V) to Np(VI) in the extraction section by adjusting HNO concentration of the feed and scrubbing solutions to 3.9M and 10M, respectively. After operation, the Np leakage to the raffinate could be kept under 6.3%. The decontamination factor of total- was 5.1
10
in this experiment.
; A New model animal for astrobiologyHorikawa, Daiki*; Kunieda, Takekazu*; Abe, Wataru*; Watanabe, Masahiko*; Nakahara, Yuichi*; Yukuhiro, Fumiko*; Sakashita, Tetsuya; Hamada, Nobuyuki*; Wada, Seiichi*; Funayama, Tomoo; et al.
Astrobiology, 8(3), p.549 - 556, 2008/06
Times Cited Count：96 Percentile：91.1(Astronomy & Astrophysics)We report the successful rearing of the herbivorous tardigrade, , by supplying the green alga 
as food. The life span was 35 d, deposited eggs required 5.7 d to hatch, and animals began to deposit eggs 9 d after hatching. The reared individuals of this species had an anhydrobiotic capacity throughout their life cycle in egg, juvenile, and adult stages. Furthermore, the reared adults in an anhydrobiotic state were tolerant of temperatures of 90
C and -196C and exposure to 99.8% acetonitrile or irradiation with 4000 Gy He ions. Based on their life history traits and tolerance to extreme stresses, 
might be a suitable model for astrobiological studies of multicellular organisms.
Nakahara, Masaumi; Sano, Yuichi; Nomura, Kazunori; Washiya, Tadahiro; Komaki, Jun
Proceedings of 3rd International ATALANTE Conference (ATALANTE 2008) (CD-ROM), 5 Pages, 2008/05
Among minor actinides, Np has a possibility to be co-recovered with U and Pu by tri-n-butylphosphate (TBP) according to its extractable valences; Np(IV) and Np(VI). Therefore, the Np valence needs to be adjusted to extractable Np(VI). In this process, partitioning section purification section are deleted, and the flow sheet is designed by single cycle. This works using the dissolver solution of irradiated MOX fuel from fast reactor "JOYO" has been carried out with centrifugal contactors, whose residence time is considerably smaller than that of mixer-settler. The feed solution is adjusted to having high HNO concentration. This condition adjusts the Np valence for its extraction. As expected, about 99% of Np was recovered with U and Pu. Through this series of studies, the U, Pu and Np co-recovery process using high HNO concentration feed solution was successfully demonstrated.
Nomura, Kazunori; Hinai, Hiroshi; Nakahara, Masaumi; Kaji, Naoya; Kamiya, Masayoshi; Oyama, Koichi; Sano, Yuichi; Washiya, Tadahiro; Komaki, Jun
Proceedings of 3rd International ATALANTE Conference (ATALANTE 2008) (CD-ROM), 5 Pages, 2008/05
Nakahara, Yuichi*; Watanabe, Masahiko*; Kikawada, Takahiro*; Fujita, Akihiko*; Horikawa, Daiki*; Okuda, Takashi*; Sakashita, Tetsuya; Funayama, Tomoo; Hamada, Nobuyuki*; Wada, Seiichi*; et al.
JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 113, 2008/03
We have shown that anhydrobiotic larvae of have higher tolerance against both high linear energy transfer (LET) radiation than hydrated larvae. We therefore examined effects of high-LET radiation on four kinds of larvae: (1) normal hydrated (intact) larva, (2) intermediates between the anhydrobiotic and normal hydrated state, (3) almost completely dehydrated (anhydrobiotic) larvae, and (4) immediately rehydrated larvae that are assumed to have a similar molecular profile to anhydrobiotic larvae. The intermediates and immediately rehydrated larvae survived longer after high-LET radiation than intact larvae, indicating that radiation tolerance could be enhanced even in hydrated larvae. Physiological changes toward anhydrobiosis, e.g. accumulation of protectants or increasing damage repair capacity, correlate with improved radiation tolerance in hydrated larvae.
Nomura, Kazunori; Nakahara, Masaumi; Yano, Kimihiko; Sano, Yuichi; Shibata, Atsuhiro; Washiya, Tadahiro
Proceedings of International Symposium on EcoTopia Science 2007 (ISETS '07) (CD-ROM), p.1058 - 1061, 2007/11
larvaeWatanabe, Masahiko*; Nakahara, Yuichi*; Sakashita, Tetsuya; Kikawada, Takahiro*; Fujita, Akihiko*; Hamada, Nobuyuki*; Horikawa, Daiki*; Wada, Seiichi*; Kobayashi, Yasuhiko; Okuda, Takashi*
Journal of Insect Physiology, 53(6), p.573 - 579, 2007/06
Times Cited Count：20 Percentile：64.98(Entomology)We examined effects of high-LET radiation on 4 kinds of larvae: (1) normal hydrated (intact) larva, (2) intermediates between the anhydrobiotic and normal hydrated state, (3) almost completely dehydrated (anhydrobiotic) larvae, and (4) immediately-rehydrated larvae that are assumed to have a similar molecular profile to anhydrobiotic larvae. The intermediates and immediately-rehydrated larvae survived longer after high-LET radiation than intact larvae, indicating that radiation tolerance could be enhanced even in hydrated larvae. Physiological changes toward anhydrobiosis, e.g. accumulation of protectants or increasing damage repair capacity, correlate with improved radiation tolerance in hydrated larvae. In addition, almost complete desiccation further enhanced radiation tolerance, possibly in a different way from the hydrated larvae.
Nakahara, Masaumi; Sano, Yuichi; Koma, Yoshikazu; Kamiya, Masayoshi; Shibata, Atsuhiro; Koizumi, Tsutomu; Koyama, Tomozo
Journal of Nuclear Science and Technology, 44(3), p.373 - 381, 2007/03
Times Cited Count：27 Percentile：84.94(Nuclear Science & Technology)Actinides recovery was attempted by the simplified solvent extraction process using TBP as an extractant for U, Pu and Np co-recovery and the SETFICS process for Am and Cm recovery with a view to decreasing the environmental impact. Uranium, Pu and Np co-recovery was conducted under the condition with high nitric acid concentration in the feed solution or scrubbing solution. High nitric acid concentration in the feed solution availed to the Np oxidation not only in the feed solution, but also at the extraction section. This oxidation reaction permitted the Np extraction with U and Pu. In the SETFICS process, a TRUEX solvent of 0.2M CMPO/1.4M TBP was employed to increase the loading of metals. In place of sodium nitrate, HAN was applied to this experimental flow sheet for "salt-free" concept. This experiment was succeeded in Am and Cm product. On high-loading flow sheet, the flow rate of aqueous effluents and spent solvent was expected to decrease in 47% and 54%, respectively.
-ray on the tardigrade 
Horikawa, Daiki*; Sakashita, Tetsuya; Katagiri, Chihiro*; Watanabe, Masahiko*; Kikawada, Takahiro*; Nakahara, Yuichi*; Hamada, Nobuyuki*; Wada, Seiichi*; Funayama, Tomoo; Higashi, Seigo*; et al.
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 116, 2007/02
no abstracts in English
