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Journal Articles

Consideration on stress corrosion cracking evaluation of zirconium for Fuel Reprocessing Facilities

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.

Journal Articles

Influence of plutonyl ion on electrochemical characterization of zirconium in plutonium nitrate solutions

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$$_{2}$$$$^{2+}$$ 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$$^{-3}$$ HNO$$_{3}$$. However, there were no significant changes at high PuO$$_{2}$$$$^{2+}$$ concentrations, and Zr showed high corrosion resistance under our experimental conditions.

Journal Articles

Electrochemical properties of zirconium in highly concentrated plutonium nitrate solution

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$$_{3}$$ concentrations and temperature. However, these experimental results imply that Zr has high corrosion resistance in Pu nitrate solutions.

Journal Articles

Partitioning of plutonium by acid split method with dissolver solution derived from irradiated fast reactor fuel with high concentration of plutonium

Nakahara, Masaumi; Sano, Yuichi; Nomura, Kazunori; Takeuchi, Masayuki

Journal of Chemical Engineering of Japan, 51(3), p.237 - 242, 2018/03

 Times Cited Count:1 Percentile:8.18(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.

Journal Articles

Actinides recovery from irradiated fuel for SmART cycle

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.

Journal Articles

Minor actinides recovery from irradiated fuel for SmART cycle test

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

Journal Articles

SPECT imaging of mice with $$^{99m}$$Tc-radiopharmaceuticals obtained from $$^{99}$$Mo produced by $$^{100}$$Mo(n,2n)$$^{99}$$Mo and fission of $$^{235}$$U

Hashimoto, 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:6 Percentile:50.68(Physics, Multidisciplinary)

Journal Articles

Two-mode fission; Experimental verification and characterization of two fission-modes

Nagame, Yuichiro; Nakahara, Hiromichi*

Radiochimica Acta, 100(8-9), p.605 - 614, 2012/08

 Times Cited Count:6 Percentile:48.57(Chemistry, Inorganic & Nuclear)

Journal Articles

Tolerance of anhydrobiotic eggs of the tardigrade ${it Ramazzottius varieornatus}$ to extreme environments

Horikawa, 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:20 Percentile:70.08(Astronomy & Astrophysics)

We examined the hatchability of hydrated and anhydrobiotic eggs of the tardigrade ${it Ramazzottius varieornatus}$ 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.

Journal Articles

Production and chemistry of transuranium elements

Nagame, Yuichiro; Hirata, Masaru; Nakahara, Hiromichi*

Handbook of Nuclear Chemistry, p.817 - 875, 2011/02

Journal Articles

Nuclear-charge polarization at scission in proton-induced fission of $$^{233}$$U

Nishinaka, Ichiro; Tanikawa, Masashi*; Nagame, Yuichiro; Nakahara, Hiromichi*

European Physical Journal A, 47(1), p.1 - 8, 2011/01

 Times Cited Count:16 Percentile:71.99(Physics, Nuclear)

The most probable charges of secondary fragments in the 11.5 MeV proton-induced fission of $$^{233}$$U were determined from the mass yields measured by the double time-of-flight method and the fractional cumulative and independent yields measured radiochemically and reported in literature. The nuclear-charge polarization of primary fragments at scission was obtained by correcting the secondary fragment mass for neutron evaporation. The results show that the nuclear-charge polarization is determined by the minimum potential energy of nuclei at scission and that it is nearly independent not only of mass and excitation energy but also of the neutron-to-proton ratio of the fissioning nucleus.

Journal Articles

Anhydrobiosis-associated nuclear DNA damage and repair in the Sleeping Chironomid; Linkage with radioresistance

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:42 Percentile:73.43(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.

Journal Articles

Uranium, plutonium and neptunium co-recovery with high nitric acid concentration in extraction section by simplified solvent extraction process

Nakahara, Masaumi; Sano, Yuichi

Radiochimica Acta, 97(12), p.727 - 731, 2009/12

 Times Cited Count:4 Percentile:32.89(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$$_{3}$$ concentration of feed solution and high HNO$$_{3}$$ 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$$_{3}$$ concentration because the inextractable Np(V) is effectively oxidized to extractable Np(VI) in the feed solution and there is less effect of HNO$$_{2}$$ at the extraction section.

JAEA Reports

U, Pu and Np co-recovery in simplified solvent extraction process; Extraction behavior of Np using high HNO$$_{3}$$ concentration at extraction section

Nakahara, 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$$_{3}$$ concentration in the feed solution and high HNO$$_{3}$$ concentration in the scrubbing solution, which was expected to bring a high HNO$$_{3}$$ 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$$_{3}$$ 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-$$gamma$$ was 5.1$$times$$10$$^{4}$$ in this experiment.

Journal Articles

Establishment of a rearing system of the extremotolerant tardigrade ${it Ramazzottius varieornatus}$; A New model animal for astrobiology

Horikawa, 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:70 Percentile:89.07(Astronomy & Astrophysics)

We report the successful rearing of the herbivorous tardigrade, ${it Ramazzottius varieornatus}$, by supplying the green alga ${it Chlorella vulgaris}$ 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$$^{circ}$$C and -196$$^{circ}$$C and exposure to 99.8% acetonitrile or irradiation with 4000 Gy $$^{4}$$He ions. Based on their life history traits and tolerance to extreme stresses, ${it R. varieornatus}$ might be a suitable model for astrobiological studies of multicellular organisms.

Journal Articles

Uranium, plutonium and neptunium co-recovery with irradiated fast reactor MOX fuel by single cycle extraction process

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$$_{3}$$ 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$$_{3}$$ concentration feed solution was successfully demonstrated.

Journal Articles

Dissolution of powdered spent fuel and U crystallization from actual dissolver solution for "NEXT" process development

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

Journal Articles

Fluoride complexation of element 104, rutherfordium (Rf), investigated by cation-exchange chromatography

Ishii, Yasuo; Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Tome, Hayato; Nishinaka, Ichiro; Nagame, Yuichiro; Miyashita, Sunao*; Mori, Tomotaka*; Suganuma, Hideo*; et al.

Chemistry Letters, 37(3), p.288 - 289, 2008/03

 Times Cited Count:18 Percentile:54.69(Chemistry, Multidisciplinary)

We have investigated cation-exchange behavior of Rf together with the lighter homologues of the group-4 elements Zr and Hf, and the tetravalent pseudo-homologue Th, in HF/HNO$$_{3}$$ solution using Automated Ion exchange separation apparatus coupled with the Detection system for Alpha spectroscopy (AIDA). The ${it K}$ $$_{d}$$ values of Zr, Hf, Th and Rf in HF/0.1 M HNO$$_{3}$$ were decreased with increasing the concentration of the fluoride ion [F$$^{-}$$], indicating the formation of the fluoride complexes. The sequence of the fluoride complexation strength is Zr $$sim$$ Hf $$>$$ Rf $$>$$ Th.

Journal Articles

Effect of ion beam irradiation for microspores of eggplant (${it Solanum melongena}$ L.)

Saiki, Yumi*; Takata, Kinuko*; Uchimura, Yosuke*; Hirashima, Keita*; Nakahara, Takao*; Hase, Yoshihiro; Yokota, Yuichiro; Tanaka, Atsushi

JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 70, 2008/03

no abstracts in English

Journal Articles

Radiation tolerance linked to anhydrobiosis in ${it Polypedilum vanderplanki}$

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 ${it Polypedilum vanderplanki}$ 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.

109 (Records 1-20 displayed on this page)