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Journal Articles

Current location of fuel debris chemistry

Sato, Nobuaki*; Kirishima, Akira*; Sasaki, Takayuki*; Takano, Masahide; Kumagai, Yuta; Sato, Soichi; Tanaka, Kosuke

Current Location of Fuel Debris Chemistry, 178 Pages, 2023/11

Considerable efforts have been devoted to the decommissioning of the TEPCO's Fukushima Daiichi Nuclear Power Station (1F) and now the retrieval of fuel debris is being proceeded on a trial basis. It can be said that the succession of science and technology related to debris, that is, human resource development, is important and indispensable. For that reason, we thought that a specific textbook on decommissioning is necessary. Regarding the 1F fuel debris, we still do not know enough, and it would be difficult to describe the details. However, 12 years have passed since the accident, and we have come to understand the situation of 1F to a certain extent. At this stage, it is essential for future development to organize the current situation by combining examples of past severe accidents. Therefore, we presented in this book the current state of fuel debris chemistry research from the perspectives of solid chemistry, solution chemistry, analytical chemistry, radiochemistry, and radiation chemistry.

JAEA Reports

Experimental study on prevention of high cycle thermal fatigue at the core outlet of advanced sodium-cooled fast reactor; Characteristics of temperature fluctuations and countermeasures to mitigate temperature fluctuations at a bottom of upper internal structure

Kobayashi, Jun; Aizawa, Kosuke; Ezure, Toshiki; Nagasawa, Kazuyoshi*; Kurihara, Akikazu; Tanaka, Masaaki

JAEA-Research 2022-009, 125 Pages, 2023/01

JAEA-Research-2022-009.pdf:29.22MB

The design studies of an advanced loop-type sodium-cooled fast reactor (Advanced- SFR) have been carried out by the Japan Atomic Energy Agency (JAEA). At the core outlet, temperature fluctuations occur due to mixing of hot sodium from the fuel assembly with cold sodium from the control rod channels and radial blanket assembly. These temperature fluctuations may cause high cycle thermal fatigue around a bottom of Upper Internal Structure (UIS) located above the core. Therefore, we conducted a water experiment using a 1/3 scale 60 degree sector model that simulated the upper plenum of the advanced loop-type sodium-cooled reactor. And we proposed some countermeasures against large temperature fluctuations that occur at the bottom of the UIS. In this report, we have summarized that the effect of the countermeasure structure to mitigate the temperature fluctuation generated at the bottom of UIS is confirmed, and the Reynolds number dependency of the countermeasure structure and the characteristics of the temperature fluctuation on the control rod surface.

Journal Articles

Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

Journal Articles

Water experiments on thermal striping phenomena at the core outlet of an advanced sodium-cooled fast reactor, 1; Proposal of countermeasures to mitigate temperature fluctuations around control rods

Kobayashi, Jun; Aizawa, Kosuke; Ezure, Toshiki; Kurihara, Akikazu; Tanaka, Masaaki

Hozengaku, 20(3), p.89 - 96, 2021/10

Hot sodium from the fuel assembly can mix with cold sodium from the control rod (CR) channel and the blanket assemblies at the bottom plate of the Upper Internal Structure (UIS) of Advanced-SFR. Temperature fluctuation due to mixing of the fluids at different temperature between the core outlet and cold channel may cause high cycle thermal fatigue on the structure around the bottom of UIS. A water experiment using a 1/3 scale 60 degree sector model simulating the upper plenum of the Advanced-SFR has been conducted to examine countermeasures for the significant temperature fluctuation generated around the bottom of UIS. We focused on the temperature fluctuations near the primary and backup control rod channels, and studied the countermeasure structure to mitigate the temperature fluctuation through temperature distribution and flow velocity distribution measurements. As a result, effectiveness of the countermeasure to mitigate the temperature fluctuation intensity was confirmed.

Journal Articles

Water experiments on thermal striping phenomena at the core outlet of an advanced sodium-cooled fast reactor, 2; Proposal of countermeasures to mitigate temperature fluctuations around radial blanket fuel assemblies

Kobayashi, Jun; Aizawa, Kosuke; Ezure, Toshiki; Kurihara, Akikazu; Tanaka, Masaaki

Hozengaku, 20(3), p.97 - 101, 2021/10

Focusing on the thermal striping phenomena that occurs at a bottom of the internal structure of an advanced sodium-cooled fast reactor (Advanced-SFR) that has been designed by the Japan Atomic Energy Agency, a water experiment using a 1/3 scale 60 degree sector model simulating the upper plenum of the Advanced-SFR has been conducted to examine countermeasures for the significant temperature fluctuation generated around the bottom of Upper Internal Structure (UIS). In the previous paper, we reported the effect of measures to mitigate temperature fluctuations around the control rod channels. In this paper, the same test section was used, and a water experiment was conducted to obtain the characteristics of temperature fluctuations around the radial blanket fuel assembly. And the shape of the Core Instrumentation Support Plate (CIP) was modified, and it was confirmed that it was highly effective in alleviating temperature fluctuations around the radial blanket fuel assembly.

Journal Articles

Release behavior of radionuclides from MOX fuels irradiated in a fast reactor during heating tests

Tanaka, Kosuke; Sato, Isamu*; Onishi, Takashi; Ishikawa, Takashi; Hirosawa, Takashi; Katsuyama, Kozo; Seino, Hiroshi; Ohno, Shuji; Hamada, Hirotsugu; Tokoro, Daishiro*; et al.

Journal of Nuclear Materials, 536, p.152119_1 - 152119_8, 2020/08

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

In order to obtain the release rate coefficients from fuels for fast reactors (FRs), heating tests and the subsequent analyses of the fission products (FPs) and actinides that are released were carried out using samples of uranium-plutonium mixed oxide (MOX) fuel pellets irradiated at the experimental fast reactor Joyo. Three heating tests targeting temperatures of 2773, 2973 and 3173 K were conducted using an FP release behavior test apparatus equipped with a high-frequency induction furnace and solid FP sampling systems consisting of a thermal gradient tube (TGT) and filters. Irradiated fuel pellets were placed into a tungsten crucible, then loaded into the induction furnace. The temperature was raised continuously at a heating rate of 10 K/s to the targeted temperature and maintained for 500 s in a flowing argon gas atmosphere. The FPs and actinides released from the MOX fuels and deposited in the TGT and filters were quantified by gamma-ray spectrometry and inductively coupled plasma mass spectrometry (ICP-MS) analysis. Based on the analysis, the release rates of radionuclides from MOX fuels for FR were obtained and compared with literature data for light water reactor (LWR) fuels. The release rate coefficients of FPs obtained in this study were found to be similar to or lower than the literature values for LWR fuels. It was also found that the release rate coefficient data for actinides were within the range of variation of literature values for LWR fuels.

Journal Articles

Production of $$^{266}$$Bh in the $$^{248}$$Cm($$^{23}$$Na,5$$n$$)$$^{266}$$Bh reaction and its decay properties

Haba, Hiromitsu*; Fan, F.*; Kaji, Daiya*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Komori, Yukiko*; Kondo, Narumi*; Kudo, Hisaaki*; Morimoto, Koji*; Morita, Kosuke*; et al.

Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08

 Times Cited Count:6 Percentile:60.4(Physics, Nuclear)

Journal Articles

Post-irradiation examinations of annular mixed oxide fuels with average burnup 4 and 5% FIMA

Cappia, F.*; Tanaka, Kosuke; Kato, Masato; McClellan, K.*; Harp, J.*

Journal of Nuclear Materials, 533, p.152076_1 - 152076_14, 2020/05

 Times Cited Count:6 Percentile:61.45(Materials Science, Multidisciplinary)

Journal Articles

Study of quasielastic barrier distributions as a step towards the synthesis of superheavy elements with hot fusion reactions

Tanaka, Taiki*; Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Boll, R. A.*; Brewer, N. T.*; Van Cleve, S.*; Dean, D. J.*; Ishizawa, Satoshi*; et al.

Physical Review Letters, 124(5), p.052502_1 - 052502_6, 2020/02

 Times Cited Count:15 Percentile:80.61(Physics, Multidisciplinary)

Journal Articles

Observation of the competing fission modes in $$^{178}$$Pt

Tsekhanovich, I.*; Andreyev, A. N.; Nishio, Katsuhisa; Denis-Petit, D.*; Hirose, Kentaro; Makii, Hiroyuki; Matheson, Z.*; Morimoto, Koji*; Morita, Kosuke*; Nazarewicz, W.*; et al.

Physics Letters B, 790, p.583 - 588, 2019/03

 Times Cited Count:30 Percentile:94.76(Astronomy & Astrophysics)

Journal Articles

Measurement of Velocity Field in Five Jets Water Test (FIWAT) for thermal striping in sodium-cooled fast reactor

Aizawa, Kosuke; Kobayashi, Jun; Tanaka, Masaaki; Kurihara, Akikazu; Ishida, Katsuji*; Nagasawa, Kazuyoshi*

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 10 Pages, 2018/11

A conceptual design of an advanced loop type sodium cooled reactor has been carried out in the Japan Atomic Energy Agency (JAEA). Temperature fluctuation is caused by mixing of fluids at different temperature from the control rod channels and the core fuel assemblies, high cycle thermal fatigue may arise on the Core Instrument Plane (CIP) at bottom of the Upper Internal Structure (UIS). In JAEA, 1/3-scaled five jets water tests (FIWAT) have been performed in order to investigate thermal striping phenomena around the CIP. In this study, the velocity field was measured in the mixing area between the jet outlet and the bottom of the structure by using particle image velocimetry (PIV) to compare with the temperature fluctuation characteristics.

Journal Articles

First direct mass measurements of nuclides around $$Z$$ = 100 with a multireflection time-of-flight mass spectrograph

Ito, Yuta*; Schury, P.*; Wada, Michiharu*; Arai, Fumiya*; Haba, Hiromitsu*; Hirayama, Yoshikazu*; Ishizawa, Satoshi*; Kaji, Daiya*; Kimura, Sota*; Koura, Hiroyuki; et al.

Physical Review Letters, 120(15), p.152501_1 - 152501_6, 2018/04

 Times Cited Count:56 Percentile:93.55(Physics, Multidisciplinary)

Masses of $$^{246}$$Es, $$^{251}$$Fm and the transfermium nuclei $$^{249-252}$$Md, and $$^{254}$$No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed $$N=152$$ neutron shell closure, have been directly measured using a multi-reflection time-of-flight mass spectrograph. The masses of $$^{246}$$Es and $$^{249,250,252}$$Md were measured for the first time. Using the masses of $$^{249,250}$$Md as anchor points for $$alpha$$ decay chains, the masses of heavier nuclei, up to $$^{261}$$Bh and $$^{266}$$Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter $$delta_{2n}$$ derived from three isotopic masses was updated with the new masses and corroborate the existence of the deformed $$N=152$$ neutron shell closure for Md and Lr.

Journal Articles

Determination of fusion barrier distributions from quasielastic scattering cross sections towards superheavy nuclei synthesis

Tanaka, Taiki*; Narikiyo, Yoshihiro*; Morita, Kosuke*; Fujita, Kunihiro*; Kaji, Daiya*; Morimoto, Koji*; Yamaki, Sayaka*; Wakabayashi, Yasuo*; Tanaka, Kengo*; Takeyama, Mirei*; et al.

Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01

 Times Cited Count:16 Percentile:73.53(Physics, Multidisciplinary)

Excitation functions of quasielastic scattering cross sections for the $$^{48}$$Ca + $$^{208}$$Pb, $$^{50}$$Ti + $$^{208}$$Pb, and $$^{48}$$Ca + $$^{248}$$Cm reactions were successfully measured by using the gas-filled recoil-ion separator GARIS. Fusion barrier distributions were extracted from these data, and compared with the coupled-channels calculations. It was found that the peak energies of the barrier distributions for the $$^{48}$$Ca + $$^{208}$$Pb and $$^{50}$$Ti + $$^{208}$$Pb systems coincide with those of the 2n evaporation channel cross sections for the systems, while that of the $$^{48}$$Ca + $$^{248}$$Cm is located slightly below the 4n evaporation ones. This results provide us helpful information to predict the optimum beam energy to synthesize superheavy nuclei.

Journal Articles

Adsorption of platinum-group metals and molybdenum onto aluminum ferrocyanide in spent fuel solution

Onishi, Takashi; Sekioka, Ken*; Suto, Mitsuo*; Tanaka, Kosuke; Koyama, Shinichi; Inaba, Yusuke*; Takahashi, Hideharu*; Harigai, Miki*; Takeshita, Kenji*

Energy Procedia, 131, p.151 - 156, 2017/12

 Times Cited Count:10 Percentile:98.37

no abstracts in English

Journal Articles

Fabrication and short-term irradiation behaviour of Am-bearing MOX fuels

Kihara, Yoshiyuki; Tanaka, Kosuke; Koyama, Shinichi; Yoshimochi, Hiroshi; Seki, Takayuki; Katsuyama, Kozo

NEA/NSC/R(2017)3, p.341 - 350, 2017/11

In order to investigate the effect of the addition of americium to MOX fuels on the irradiation behaviour, the "Am-1" program is being conducted at the JAEA. The Am-1 program consists of two short-term irradiation tests of 10-min and 24-h irradiation periods, and a steady-state irradiation test. The short-term irradiation tests and their post irradiation examinations (PIEs) have been successfully completed. To date, the data for PIE of the Am-MOX fuels focused on the microstructural evolution and redistribution behaviour of Am at the initial stage of irradiation have been obtained and reported. In this paper, the results obtained from the Am-1 program are reviewed and detailed descriptions of the fabrication and inspection techniques for the Am-MOX fuels prepared for the program are provided. PIE data for the Am-MOX fuels at the initial stage of irradiation have been accumulated. In this paper, unpublished PIE data for the Am-MOX fuels are also presented.

Journal Articles

Effects of $$gamma$$ irradiation on the adsorption characteristics of xerogel microcapsules

Onishi, Takashi; Tanaka, Kosuke; Koyama, Shinichi; Ou, L. Y.*; Mimura, Hitoshi*

NEA/NSC/R(2017)3, p.463 - 469, 2017/11

no abstracts in English

Journal Articles

Observation of doubly-charged ions of francium isotopes extracted from a gas cell

Schury, P.*; Wada, Michiharu*; Ito, Yuta*; Kaji, Daiya*; Haba, Hiromitsu*; Hirayama, Yoshikazu*; Kimura, Sota*; Koura, Hiroyuki; MacCormick, M.*; Miyatake, Hiroari*; et al.

Nuclear Instruments and Methods in Physics Research B, 407, p.160 - 165, 2017/06

 Times Cited Count:13 Percentile:78.46(Instruments & Instrumentation)

Various isotopes of Ac, Ra, Fr, and Rn were produced by fusion-evaporation reactions using a $$^{48}$$Ca beam. The energetic ions were stopped in and extracted from a helium gas cell. The extracted ions were identified using a multi-reflection time-of-fight mass spectrograph. In all cases, it was observed that the predominant charge state for the extracted ions, including the alkali Fr, was 2+.

Journal Articles

Study of the reaction $$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$Lv$$^{ast}$$ at RIKEN-GARIS

Kaji, Daiya*; Morita, Kosuke*; Morimoto, Koji*; Haba, Hiromitsu*; Asai, Masato; Fujita, Kunihiro*; Gan, Z.*; Geissel, H.*; Hasebe, Hiroo*; Hofmann, S.*; et al.

Journal of the Physical Society of Japan, 86(3), p.034201_1 - 034201_7, 2017/03

 Times Cited Count:24 Percentile:81.66(Physics, Multidisciplinary)

The fusion reaction of $$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$Lv$$^{ast}$$ was studied using the gas-filled recoil-ion separator GARIS at RIKEN. A total of seven $$alpha$$ and spontaneous-fission decay chains were observed, which would originate from the reaction products of the element 116, $$^{292}$$Lv and $$^{293}$$Lv. Decay properties observed in the chains are in good agreement with the previously published ones. However, one of the chains showed a discrepancy, indicating the new spontaneous-fission branch in $$^{285}$$Cn or the production of the new isotope $$^{294}$$Lv.

Journal Articles

First online multireflection time-of-flight mass measurements of isobar chains produced by fusion-evaporation reactions; Toward identification of superheavy elements via mass spectroscopy

Schury, P.*; Wada, Michiharu*; Ito, Yuta*; Kaji, Daiya*; Arai, Fumiya*; MacCormick, M.*; Murray, I.*; Haba, Hiromitsu*; Jeong, S.*; Kimura, Sota*; et al.

Physical Review C, 95(1), p.011305_1 - 011305_6, 2017/01

AA2016-0638.pdf:0.71MB

 Times Cited Count:41 Percentile:96.14(Physics, Nuclear)

Using a multireflection time-of-flight mass spectrograph located after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the masses of several $$alpha$$-decaying heavy nuclei were directly and precisely measured. The nuclei were produced via fusion-evaporation reactions and separated from projectilelike and targetlike particles using GARIS-II before being stopped in a helium-filled gas cell. Time-of-flight spectra for three isobar chains, $$^{204}$$Fr-$$^{204}$$Rn-$$^{204}$$At-$$^{204}$$Po, $$^{205}$$Fr- $$^{205}$$Rn-$$^{205}$$At-$$^{205}$$Po-$$^{205}$$Bi, and $$^{206}$$Fr-$$^{206}$$Rn-$$^{206}$$At, were observed. Precision atomic mass values were determined for $$^{204-206}$$Fr, $$^{204,205}$$Rn, and $$^{204,205}$$At. Identifications of $$^{205}$$Bi, $$^{204,205}$$Po, $$^{206}$$Rn, and $$^{206}$$At were made with N$$leq$$10 detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy element ions.

Journal Articles

High temperature physicochemical properties of irradiated fuels

Ishikawa, Takashi; Onishi, Takashi; Hirosawa, Takashi; Tanaka, Kosuke; Katsuyama, Kozo

Proceedings of 54th Annual Meeting of Hot Laboratories and Remote Handling (HOTLAB 2017) (Internet), 10 Pages, 2017/00

174 (Records 1-20 displayed on this page)