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Journal Articles

First isolation and analysis of caesium-bearing microparticles from marine samples in the Pacific coastal area near Fukushima Prefecture

Miura, Hikaru*; Ishimaru, Takashi*; Ito, Yukari*; Kuribara, Yuichi; Otosaka, Shigeyoshi*; Sakaguchi, Aya*; Misumi, Kazuhiro*; Tsumune, Daisuke*; Kubo, Atsushi*; Higaki, Shogo*; et al.

Scientific Reports (Internet), 11, p.5664_1 - 5664_11, 2021/03

 Times Cited Count:0 Percentile:0(Multidisciplinary Sciences)

For the first time, we isolated and investigated seven CsMPs (radioactive caesium-bearing microparticles) from marine particulate matter and sediment. From the elemental composition, the $$^{134}$$Cs/$$^{137}$$Cs activity ratio, and the $$^{137}$$Cs activity per unit volume results, we inferred that the five CsMPs collected from particulate matter were emitted from Unit 2 of the FDNPP, whereas the two CsMPs collected from marine sediment were possibly emitted from Unit 3. The presence of CsMPs can cause overestimation of the solid-water distribution coefficient of Cs in marine sediments and particulate matter and a high apparent radiocaesium concentration factor for marine biota. CsMPs emitted from Unit 2, which were collected from the estuary of a river that flowed through a highly contaminated area, may have been deposited on land and then transported by the river. By contrast, CsMPs emitted from Unit 3 were possibly transported eastward by the wind and deposited directly onto the ocean surface.

Journal Articles

Discovery of a new low energy neutron resonance of $$^{89}$$Y

Katabuchi, Tatsuya*; Toh, Yosuke; Mizumoto, Motoharu*; Saito, Tatsuhiro*; Terada, Kazushi*; Kimura, Atsushi; Nakamura, Shoji; Huang, M.*; Rovira Leveroni, G.; Igashira, Masayuki*

European Physical Journal A, 57(1), p.4_1 - 4_4, 2021/01

 Times Cited Count:0 Percentile:0.03(Physics, Nuclear)

Journal Articles

Direct observation of the magnetic ordering process in the ferromagnetic semiconductor Ga$$_{1-x}$$Mn$$_{x}$$As via soft X-ray magnetic circular dichroism

Takeda, Yukiharu; Oya, Shinobu*; Pham, N. H.*; Kobayashi, Masaki*; Saito, Yuji; Yamagami, Hiroshi; Tanaka, Masaaki*; Fujimori, Atsushi*

Journal of Applied Physics, 128(21), p.213902_1 - 213902_11, 2020/12

 Times Cited Count:1 Percentile:24.67(Physics, Applied)

Journal Articles

Insight into Kondo screening in the intermediate-valence compound SmOs$$_4$$Sb$$_{12}$$ uncovered by soft X-ray magnetic circular dichroism

Saito, Yuji; Fujiwara, Hidenori*; Yasui, Akira*; Kadono, Toshiharu*; Sugawara, Hitoshi*; Kikuchi, Daisuke*; Sato, Hideyuki*; Suga, Shigemasa*; Yamasaki, Atsushi*; Sekiyama, Akira*; et al.

Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

Controlled growth of boron-doped epitaxial graphene by thermal decomposition of a B$$_{4}$$C thin film

Norimatsu, Wataru*; Matsuda, Keita*; Terasawa, Tomoo; Takata, Nao*; Masumori, Atsushi*; Ito, Keita*; Oda, Koji*; Ito, Takahiro*; Endo, Akira*; Funahashi, Ryoji*; et al.

Nanotechnology, 31(14), p.145711_1 - 145711_7, 2020/04

 Times Cited Count:3 Percentile:58.93(Nanoscience & Nanotechnology)

We show that boron-doped epitaxial graphene can be successfully grown by thermal decomposition of a boron carbide thin film, which can also be epitaxially grown on a silicon carbide substrate. The interfaces of B$$_{4}$$C on SiC and graphene on B$$_{4}$$C had a fixed orientation relation, having a local stable structure with no dangling bonds. The first carbon layer on B$$_{4}$$C acts as a buffer layer, and the overlaying carbon layers are graphene. Graphene on B$$_{4}$$C was highly boron doped, and the hole concentration could be controlled over a wide range of 2$$times$$10$$^{13}$$ to 2$$times$$10$$^{15}$$ cm$$^{-2}$$. Highly boron-doped graphene exhibited a spin-glass behavior, which suggests the presence of local antiferromagnetic ordering in the spin-frustration system. Thermal decomposition of carbides holds the promise of being a technique to obtain a new class of wafer-scale functional epitaxial graphene for various applications.

Journal Articles

Corrosion monitoring in humidity-controlled environment simulating gamma ray irradiation

Omori, Atsushi*; Akiyama, Eiji*; Abe, Hiroshi*; Hata, Kuniki; Sato, Tomonori; Kaji, Yoshiyuki; Inoue, Hiroyuki*; Taguchi, Mitsumasa*; Seito, Hajime*; Tada, Eiji*; et al.

Zairyo To Kankyo, 69(4), p.107 - 111, 2020/04

To evaluate the effect of oxidants, which are formed by radiolysis of water under gamma ray irradiation, on the corrosion of a carbon steel in humid environment, ozone was introduced as a model oxidant in to humidity-controlled air at 50$$^{circ}$$C in a thermo-hygrostat chamber. Corrosion monitoring was performed by using an Atmospheric Corrosion Monitor-type (ACM) sensor consisting of a carbon steel anode and an Ag cathode. The output current of the ACM sensor was increased with the increase in relative humidity and it was obviously increased with the increase in the introduced ozone concentration at each relative humidity. The results indicate that ozone accelerates the corrosion of the carbon steel. The effect of ozone on the corrosion acceleration is attributed to the fast reduction reaction and fast dissolution reaction in to water compared to that of oxygen.

Journal Articles

Measurement of the angular distribution of $$gamma$$-rays after neutron capture by $$^{139}$$La for a T-violation search

Okudaira, Takuya; Shimizu, Hirohiko*; Kitaguchi, Masaaki*; Hirota, Katsuya*; Haddock, C. C.*; Ito, Ikuya*; Yamamoto, Tomoki*; Endo, Shunsuke*; Ishizaki, Kohei*; Sato, Takumi*; et al.

EPJ Web of Conferences, 219, p.09001_1 - 09001_6, 2019/12

Parity violating effects enhanced by up to 10$$^6$$ times have been observed in several neutron induced compound nuclei. There is a theoretical prediction that time reversal (T) violating effects can also be enhanced in these nuclei implying that T-violation can be searched for by making very sensitive measurements. However, the enhancement factor has not yet been measured in all nuclei. The angular distribution of the (n,$$gamma$$) reaction was measured with $$^{139}$$La by using a germanium detector assembly at J-PARC, and the enhancement factor was obtained. From the result, the measurement time to achieve the most sensitive T-violation search was estimated as 1.4 days, and a 40% polarized $$^{139}$$La target and a 70% polarized $$^3$$He spin filter whose thickness is 70 atm$$cdot$$cm are needed. Therefore high quality $$^3$$He spin filter is developed in JAEA. The measurement result of the (n,$$gamma$$) reaction at J-PARC and the development status of the $$^3$$He spin filter will be presented.

Journal Articles

Study on evaluation method for entrained gas flow rate by free surface vortex

Ito, Kei*; Ito, Daisuke*; Saito, Yasushi*; Ezure, Toshiki; Matsushita, Kentaro; Tanaka, Masaaki; Imai, Yasutomo*

Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.6632 - 6642, 2019/08

In this paper, a mechanistic model is proposed to calculate the entrained gas flow rate by a free surface vortex. The model contains the theoretical equation of transient gas core elongation and the empirical equation of critical gas core length for gas bubble detachment. Based on those two equations, the entrained gas flow rate is calculated as the portion of the gas core elongated beyond the critical gas core length per unit time. Then, the mechanistic model was applied to the calculation of the entrained gas flow rate in a simple water experiment. As a result, it is confirmed that the entrained gas flow rate grows rapidly when the liquid (water) flow rate, which determine the strength of a free surface vortex, exceeds a certain threshold value.

Journal Articles

Electronic structure of the high-$$T_{rm C}$$ ferromagnetic semiconductor (Ga,Fe)Sb; X-ray magnetic circular dichroism and resonance photoemission spectroscopy studies

Sakamoto, Shoya*; Tu, N. T.*; Takeda, Yukiharu; Fujimori, Shinichi; Hai, P. N.*; Anh, L. D.*; Wakabayashi, Yuki K.*; Shibata, Goro*; Horio, Masafumi*; Ikeda, Keisuke*; et al.

Physical Review B, 100(3), p.035204_1 - 035204_8, 2019/07

Journal Articles

Electronic structure of the high-$$T_{rm C}$$ ferromagnetic semiconductor (Ga,Fe)Sb; X-ray magnetic circular dichroism and resonance photoemission spectroscopy studies

Sakamoto, Shoya*; Tu, N. T.*; Takeda, Yukiharu; Fujimori, Shinichi; Hai, P. N.*; Anh, L. D.*; Wakabayashi, Yuki*; Shibata, Goro*; Horio, Masafumi*; Ikeda, Keisuke*; et al.

Physical Review B, 100(3), p.035204_1 - 035204_8, 2019/07

 Times Cited Count:8 Percentile:67.98(Materials Science, Multidisciplinary)

Journal Articles

Mapping measurement for beam energy position monitor system for RIKEN superconducting acceleration cavity

Watanabe, Tamaki*; Toyama, Takeshi*; Hanamura, Kotoku*; Imao, Hiroshi*; Kamigaito, Osamu*; Kamoshida, Atsushi*; Kawachi, Toshihiko*; Koyama, Ryo*; Sakamoto, Naruhiko*; Fukunishi, Nobuhisa*; et al.

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1105 - 1108, 2019/07

Upgrades for the RIKEN heavy-ion linac (RILAC) involving a new superconducting linac (SRILAC) are currently underway at the RIKEN radioactive isotope beam factory (RIBF). It is crucially important to develop nondestructive beam measurement diagnostics. We have developed a beam energy position monitor (BEPM) system which can measure not only the beam position but also the beam energy simultaneously by measuring the time of flight of the beam. We fabricated 11 BEPMs and completed the position calibration to obtain the sensitivity and offset for each BEPMs. The position accuracy has been achieved to be less than $$pm$$ 0.1 mm by using the mapping measurement.

Journal Articles

Study on analysis method for inert gas behavior in liquid metal flow with considering dissolution and entrainment at free surface

Matsushita, Kentaro; Ito, Kei*; Ezure, Toshiki; Tanaka, Masaaki

Dai-24-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (USB Flash Drive), 5 Pages, 2019/06

In the design study on a sodium-cooled fast reactor (SFR), a numerical simulation code named SYRENA has been developed in Japan Atomic Energy Agency to analyze the behavior of gas bubbles and/or dissolved gas in the primary coolant system. In the present study, the effect of the non-condensable gas entrainment at the free surface on the bubble and the dissolved gas behavior in the primary coolant system were investigated for a typical pool type reactor, and also effect of a dipped-plate (D/P) installed below the free surface in the reactor vessel to suppress the gas bubble entrainment into the primary coolant system was especially investigated. It was clarified that the D/P was influential to the non-condensable gas behavior and the molar flow rate of gas bubbles in the primary coolant system varies depending on the relationship between the gas entrainment rate at the free surface and the exchange flow rate through the D/P.

Journal Articles

Optimization of an isothermal gas-chromatographic setup for the chemical exploration of dubnium (Db, Z = 105) oxychlorides

Chiera, N. M.; Sato, Tetsuya; Tomitsuka, Tomohiro; Asai, Masato; Ito, Yuta; Shirai, Kaori*; Suzuki, Hayato; Tokoi, Katsuyuki; Toyoshima, Atsushi; Tsukada, Kazuaki; et al.

Journal of Radioanalytical and Nuclear Chemistry, 320(3), p.633 - 642, 2019/06

 Times Cited Count:1 Percentile:23.13(Chemistry, Analytical)

An isothermal gas-chromatographic (IGC) device has been developed and tested for on-line gas phase studies of volatile oxychlorides of short-lived group-5 transition metals. Radioisotopes of niobium and tantalum, produced in nuclear fusion evaporation reactions, are directly flushed into the IGC setup by an inert gas-jet. Oxychloride compounds are formed by the addition of SOCl$$_2$$ and O$$_2$$. Parameters influencing the formation and transport of NbOCl$$_3$$ and TaOCl$$_3$$ are investigated. For nuclides with half-lives ($$t_{1/2}$$) of about 30 s, an overall efficiency of 7% is obtained, rendering the IGC setup suitable for the chemical exploration of $$^{262}$$Db($$t_{1/2}$$ = 34s).

Journal Articles

Dry cleaning process test for fuel assembly of fast reactor plant system, 1; Pilot scale test for fuel pin bundle

Kudo, Hideyuki*; Otani, Yuichi*; Hara, Masahide*; Kato, Atsushi; Ishikawa, Nobuyuki; Otaka, Masahiko; Nagai, Keiichi; Saito, Junichi; Ara, Kuniaki; Ide, Akihiro*

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 10 Pages, 2019/05

A next generation SFR in Japan has adopted an advanced dry cleaning system which consists of the argon gas blowing process to reduce the amount of metallic residual sodium remaining on spent fuel assemblies. This paper describes experimental and analytical work focusing on the amount of residual sodium remaining on a fuel pin bundle before and after the argon gas blowing process. The experiments were conducted using a sodium test loop and a short specimen consisting of a 7 pin bundle. The effects of the blowing gas velocity and the blowing time were quantitatively analyzed in the experiments. On the basis of these experimental results, evaluation models predicting the amount of the residual sodium were constructed.

Journal Articles

Dry cleaning process test for fuel assembly of fast reactor plant system, 2; Laboratory scale test for fuel assembly and evaluation of the amount of residual sodium

Ide, Akihiro*; Kudo, Hideyuki*; Inuzuka, Taisuke*; Hara, Masahide*; Kato, Atsushi; Ishikawa, Nobuyuki; Otaka, Masahiko; Nagai, Keiichi; Saito, Junichi; Ara, Kuniaki

Proceedings of 2019 International Congress on Advances in Nuclear Power Plants (ICAPP 2019) (Internet), 10 Pages, 2019/05

A next generation SFR in Japan has adopted an advanced dry cleaning system which consists of the following process of argon gas blowing to reduce the amount of metallic sodium, moist argon gas blowing to deactivate the residual sodium, and direct storage in the SFP without using storage containers. This three-step process increases economic competitiveness and reduces waste products. In this Research and Development work, the amount of residual sodium and performance of the dry cleaning process were investigated. This paper describes experimental and analytical work for all parts of a fuel assembly except for a fuel pin bundle.

Journal Articles

Parametric analysis of bubble and dissolved gas behavior in primary coolant system of sodium-cooled fast reactors

Matsushita, Kentaro; Ito, Kei*; Ezure, Toshiki; Tanaka, Masaaki

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 9 Pages, 2019/05

A numerical simulation code named SYRENA has been developed in JAEA to analyze the behavior of entrained bubbles and dissolved gas in the primary coolant of sodium-cooled fast reactor (SFR). In the present study, a flow network model of SYRENA to a hypothetical pool type reactor was developed and the non-condensable gas behavior was investigated through the comparison with that in the loop type reactor. The effect of the dipped-plate (D/P) tentatively introduced into the pool-type reactor on the gas behavior was investigated through the parametric analyses about the sodium exchange flow rate through the D/P and the gas entrainment rate at the free surface. It was suggested that the increase in the exchange flow rate through the D/P doesn't always work to decrease the bubble volume in the primary coolant system.

Journal Articles

Study on hydrogen generation from cement solidified products loading low-level radioactive liquid wastes at Tokai Reprocessing Plant

Sato, Fuminori; Matsushima, Ryotatsu; Ito, Yoshiyuki

QST-M-16; QST Takasaki Annual Report 2017, P. 60, 2019/03

Hydrogen gas generation by $$gamma$$-radiation from cement solidified products loading low-level radioactive liquid waste generated at LWTF in Tokai Reprocessing Facility was studied.

Journal Articles

Manifestation of electron correlation effect in 5$$f$$ states of uranium compounds revealed by 4$$d$$-5$$f$$ resonant photoelectron spectroscopy

Fujimori, Shinichi; Kobata, Masaaki; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*

Physical Review B, 99(3), p.035109_1 - 035109_5, 2019/01

 Times Cited Count:6 Percentile:51.19(Materials Science, Multidisciplinary)

Journal Articles

Electronic structure of URu$$_2$$Si$$_2$$ studied by photoelectron spectroscopy (INVITED)

Fujimori, Shinichi; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*

Progress in Nuclear Science and Technology (Internet), 5, p.82 - 85, 2018/11

Journal Articles

Local magnetic states of the weakly ferromagnetic iron-based superconductor Sr$$_{2}$$VFeAsO$$_{3-delta}$$ studied by X-ray magnetic circular dichroism

Horio, Masafumi*; Takeda, Yukiharu; Namiki, Hiromasa*; Katagiri, Takao*; Wakabayashi, Yuki*; Sakamoto, Shoya*; Nonaka, Yosuke*; Shibata, Goro*; Ikeda, Keisuke*; Saito, Yuji; et al.

Journal of the Physical Society of Japan, 87(10), p.105001_1 - 105001_2, 2018/10

 Times Cited Count:1 Percentile:16.87(Physics, Multidisciplinary)

515 (Records 1-20 displayed on this page)