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Journal Articles

Rabi-oscillation spectroscopy of the hyperfine structure of muonium atoms

Nishimura, Shoichiro*; Torii, Hiroyuki*; Fukao, Yoshinori*; Ito, Takashi; Iwasaki, Masahiko*; Kanda, Sotaro*; Kawagoe, Kiyotomo*; Kawall, D.*; Kawamura, Naritoshi*; Kurosawa, Noriyuki*; et al.

Physical Review A, 104(2), p.L020801_1 - L020801_6, 2021/08

 Times Cited Count:0 Percentile:0.01(Optics)

JAEA Reports

Soundness survey of cooling tower of Utility Cooling Loop (UCL Cooling Tower) in JMTR

Oto, Tsutomu; Asano, Norikazu; Kawamata, Takanori; Yanai, Tomohiro; Nishimura, Arashi; Araki, Daisuke; Otsuka, Kaoru; Takabe, Yugo; Otsuka, Noriaki; Kojima, Keidai; et al.

JAEA-Review 2020-018, 66 Pages, 2020/11


A collapse event of the cooling tower of secondary cooling system in the JMTR (Japan Materials Testing Reactor) was caused by the strong wind of Typhoon No.15 on September 9, 2019. The cause of the collapse of the cooling tower was investigated and analyzed. As the result, it was identified that four causes occurred in combination. Thus, the soundness of the cooling tower of Utility Cooling Loop (UCL cooling tower), which is a wooden cooling tower installed at the same period as the cooling tower of secondary cooling system, was investigated. The items of soundness survey are to grasp the operation conditions of the UCL cooling tower, to confirm the degradation of structural materials, the inspection items and inspection status of the UCL cooling tower, and to investigate the past meteorological data. As the results of soundness survey of the UCL cooling tower, the improvement of inspection items of the UCL cooling tower was carried out and the replacement and repair of the structural materials of the UCL cooling tower were planned for safe maintenance and management of this facility. And the renewal plan of new cooling tower was created to replace the existing UCL cooling tower. This report is summarized the soundness survey of the UCL cooling tower.

Journal Articles

Radiocesium distribution in aggregate-size fractions of cropland and forest soils affected by the Fukushima nuclear accident

Koarashi, Jun; Nishimura, Shusaku; Atarashi-Andoh, Mariko; Matsunaga, Takeshi*; Sato, Tsutomu*; Nagao, Seiya*

Chemosphere, 205, p.147 - 155, 2018/08

 Times Cited Count:14 Percentile:65.6(Environmental Sciences)

There is little understanding of how soil aggregation can affect the mobility and bioavailability of $$^{137}$$Cs in soils. To explore this, soil samples were collected at seven sites under different land-use conditions in Fukushima and were separated into four aggregate-size fractions. The fractions were then analyzed for $$^{137}$$Cs content and extractability and mineral composition. In forest soils, aggregate formation was significant, and $$^{137}$$Cs was largely associated with large-sized aggregates. In contrast, there was less aggregation in agricultural field soils, and most of $$^{137}$$Cs was in the clay- and silt-sized fractions. Across all sites, the $$^{137}$$Cs extractability was higher in the large-sized aggregate fractions than in the clay-sized fractions. The results demonstrate that large-sized aggregates are a significant reservoir of potentially mobile and bioavailable $$^{137}$$Cs in organic-rich (forest and orchard) soils.

Journal Articles

Demonstration of $$gamma$$-ray pipe-monitoring capabilities for real-time process monitoring safeguards applications in reprocessing facilities

Rodriguez, D.; Tanigawa, Masafumi; Nishimura, Kazuaki; Mukai, Yasunobu; Nakamura, Hironobu; Kurita, Tsutomu; Takamine, Jun; Suzuki, Satoshi*; Sekine, Megumi; Rossi, F.; et al.

Journal of Nuclear Science and Technology, 55(7), p.792 - 804, 2018/07

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Nuclear material in reprocessing facilities is safeguarded by random sample verification with additional continuous monitoring applied to solution masses and volume in important tanks to maintain continuity-of-knowledge of process operation. Measuring the unique $$gamma$$ rays of each solution as the material flows through pipes connecting all tanks and process apparatuses could potentially improve process monitoring by verifying the compositions in real time. We tested this $$gamma$$ ray pipe-monitoring method using plutonium-nitrate solution transferred between tanks at the PCDF-TRP. The $$gamma$$ rays were measured using a lanthanum-bromide detector with a list-mode data acquisition system to obtain both time and energy of $$gamma$$-ray. The analysis and results of this measurement demonstrate an ability to determine isotopic composition, process timing, flow rate, and volume of solution flowing through pipes, introducing a viable capability for process monitoring safeguards verification.

Journal Articles

Completion of solidification and stabilization for Pu nitrate solution to reduce potential risks at Tokai Reprocessing Plant

Mukai, Yasunobu; Nakamichi, Hideo; Kobayashi, Daisuke; Nishimura, Kazuaki; Fujisaku, Sakae; Tanaka, Hideki; Isomae, Hidemi; Nakamura, Hironobu; Kurita, Tsutomu; Iida, Masayoshi*; et al.

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 8 Pages, 2017/04

TRP has stored the plutonium in solution state for long-term since the last PCDF operation in 2007 was finished. After the great east Japan earthquake in 2011, JAEA had investigated the risk against potential hazard of these solutions which might lead to make hydrogen explosion and/or boiling of the solution accidents with the release of radioactive materials to the public when blackout. To reduce the risk for storing Pu solution (about 640 kg Pu), JAEA planned to perform the process operation for the solidification and stabilization of the solution by converted into MOX powder at PCDF in 2013. In order to perform PCDF operation without adaption of new safety regulation, JAEA conducted several safety measures such as emergency safety countermeasures, necessary security and safeguards (3S) measures with understanding of NRA. As a result, the PCDF operation had stared on 28th April, 2014, and successfully completed to convert MOX powder on 3rd August, 2016 for about 2 years as planned.

Journal Articles

New muonium HFS measurements at J-PARC/MUSE

Strasser, P.*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Keiichi*; Ito, Takashi; Iwasaki, Masahiko*; et al.

Hyperfine Interactions, 237(1), p.124_1 - 124_9, 2016/12

 Times Cited Count:6 Percentile:92.96

Journal Articles

Year-round variations in the fluvial transport load of particulate $$^{137}$$Cs in a forested catchment affected by the Fukushima Daiichi Nuclear Power Plant accident

Matsunaga, Takeshi; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Muto, Kotomi; Tsuzuki, Katsunori; Nishimura, Shusaku; Koarashi, Jun; Otosaka, Shigeyoshi; Sato, Tsutomu*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 310(2), p.679 - 693, 2016/11


 Times Cited Count:5 Percentile:54.39(Chemistry, Analytical)

Particulate $$^{137}$$Cs in stream water was collected continuously for two years in order to assess the long-term trend of the $$^{137}$$Cs discharge from the forest environment. Sampling was conducted from December 2011 to December 2013 in a mountainous stream, which received the $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Plant accident. A seasonal increase in fluvial transport load of particulate $$^{137}$$Cs associated with suspended solids (SS) was observed in August and September when rainfall was abundant. The particulate $$^{137}$$Cs concentration decreased at a faster rate than the rate due to radioactive decay. This decrease might be resulted from redistribution of the easily eroded and polluted soil surface due to heavy rain events such as typhoons. These findings indicate that the particulate $$^{137}$$Cs load was subject to the inter-annual variations in rainfalls, and decreased gradually over a long period of time due to a decrease in $$^{137}$$Cs concentration in SS.

Journal Articles

A Passive collection system for whole size fractions in river suspended solids

Matsunaga, Takeshi; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Tsuzuki, Katsunori; Nishimura, Shusaku; Koarashi, Jun; Otosaka, Shigeyoshi; Sato, Tsutomu*; Nagao, Seiya*

Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1291 - 1295, 2015/02

 Times Cited Count:3 Percentile:32.14(Chemistry, Analytical)

An innovative, yet simple method for the passive collection of radioactive materials in river water has been developed and validated. The method employes large filter vessels, containing multiple cartridge filters. River water is led to the system naturally using a drop of the riverbed by hose from upstream. This method makes long-term, unmanned monitoring possible. In addition to regular radioactivity analyses, this method provides an opportunity for the characterization of suspended materials based on its ample collection quantities (more than several tens of grams). This method may also be applicable to sediment-bound chemicals.

Journal Articles

Evaluation of inter-laminar shear strength of GFRP composed of bonded glass/polyimide tapes and cyanate-ester/epoxy blended resin for ITER TF coils

Hemmi, Tsutomu; Nishimura, Arata*; Matsui, Kunihiro; Koizumi, Norikiyo; Nishijima, Shigehiro*; Shikama, Tatsuo*

AIP Conference Proceedings 1574, p.154 - 161, 2014/01

 Times Cited Count:3 Percentile:86.67

Japan Atomic Energy Agency (JAEA), as Japan Domestic Agency, has responsibility to procure 9 ITER Toroidal Field (TF) coils. The insulation system of the ITER TF coils consists of 3 layers of insulations, which are a conductor insulation, a double-pancake (DP) insulation and a ground insulation, composed of multi-layer glass/polyimide tapes impregnated a resin. The ITER TF coils are required to withstand an irradiation of 10 MGy from $$gamma$$-ray and neutrons since the ITER TF coils is exposed by first neutron ($$>$$ 0.1 MeV) of 10$$^{22}$$ n/m$$^{2}$$ during the operation of 20 years in the ITER. Cyanate-ester/epoxy blended resins and bonded glass/polyimide tapes are developed as insulation materials to realize the required radiation-hardness for the insulation of the ITER TF coils. To evaluate the radiation-hardness of the developed insulation materials, the inter-laminar shear strength of glass-fiber reinforced plastics (GFRP) fabricated using developed insulation materials is measured as one of most important mechanical properties before/after the irradiation in a fission reactor of JRR-3. As a result, it is demonstrated that the GFRPs using the developed insulation materials have a sufficient performance to apply the ITER TF coil insulation.

Journal Articles

Fission neutron irradiation effect on interlaminar shear strength of cyanate ester resin GFRP at RT and 77 K

Nishimura, Arata*; Izumi, Yoshinobu*; Nishijima, Shigehiro*; Hemmi, Tsutomu; Koizumi, Norikiyo; Takeuchi, Takao*; Shikama, Tatsuo*

AIP Conference Proceedings 1219, p.127 - 134, 2010/04

 Times Cited Count:1 Percentile:53.11

A GFRP with cyanate ester resin was fabricated and neutron irradiation tests up to 1$$times$$10$$^{22}$$ n/m$$^{2}$$ of fast neutron with over 0.1 MeV energy were carried out in fission reactor. The fabrication process of cyanate ester GFRP was established and a collaboration network to perform investigations on irradiation effect of superconducting magnet materials was constructed. Three kinds of samples were fabricated. The first was CTD403 GFRP made by NIFS, the second was (cyanate ester + epoxy) GFRP provided by Toshiba, and the last was CTD403 GFRP made by Toshiba. The irradiation was carried out at JRR-3 in Japan Atomic Energy Agency using Rabbit capsules. After the irradiation, short beam tests were conducted at room temperature and 77 K and interlaminar shear strength (ILSS) was evaluated. The irradiation of 1$$times$$10$$^{21}$$ n/m$$^{2}$$ increased ILSS a little but 1$$times$$10$$^{22}$$ n/m$$^{2}$$ irradiation decreased ILSS to around 50 MPa. These tendencies were observed in all three kinds of GFRPs.

JAEA Reports

Fuel and core design studies on metal fuel sodium-cooled fast reactor, 3; Joint research report for JFY2007&2008

Okano, Yasushi; Kobayashi, Noboru*; Ogawa, Takashi; Oki, Shigeo; Naganuma, Masayuki; Okubo, Tsutomu; Mizuno, Tomoyasu; Ogata, Takanari*; Ueda, Nobuyuki*; Nishimura, Satoshi*

JAEA-Research 2009-025, 105 Pages, 2009/10


A metal fuel core has specific features on high heavy metal density, hard neutron spectrum, and efficient neutron utilization. Enlarged applicable design envelops would improve core performances and features: higher breeding ratio, compacted reactor core, and, smaller amount of Pu-fissile inventory. A joint study on "Reactor Core and Fuel Design of Metal Fuel Core of Sodium Cooled Fast Reactor" by Japan Atomic Energy Agency and Central Research Institute of Electric Power Industry has been conducted during Japanese fiscal years of 2007 and 2008. This report shows the results on (1) the study on applicable design ranges of metal fuel specifications, (2) the study on conceptual core designs for high breeding ratio, and (3) the safety study on metal fuel core designed in the Fast Reactor Cycle Technology Development (FaCT) Project.

Journal Articles

Development of insulation technology with cyanate ester resins for ITER TF coils

Hemmi, Tsutomu; Koizumi, Norikiyo; Matsui, Kunihiro; Okuno, Kiyoshi; Nishimura, Arata*; Sakai, Masahiro*; Asano, Shiro*

Fusion Engineering and Design, 84(2-6), p.923 - 927, 2009/06

 Times Cited Count:14 Percentile:70.47(Nuclear Science & Technology)

The insulation for ITER-TF coils is required to withstand a total radiation dose of 10$$^{22}$$ fast n/m$$^{2}$$. For this purpose, cyanate ester resins with high radiation-resistant have been considered instead of epoxy resins. In order to evaluate an applicability of cyanate ester resins for ITER-TF coils, the developments of the vacuum pressure impregnation technology and evaluation of the high radiation-resistant properties have been carried out. This paper presents results of these developments with the cyanater ester resin.

Journal Articles

Modeling of chemical transition of nitrate accompanied with corrosion of carbon steel under alkaline conditions

Honda, Akira; Masuda, Kaoru*; Imakita, Tsuyoshi*; Kato, Osamu*; Nishimura, Tsutomu*

Zairyo To Kankyo, 58(5), p.182 - 189, 2009/05

Interaction between carbon steel and nitrate was modeled using the mixed potential concept. Carbon steel was selected as an example of metal components in the repository of radioactive waste. The nitrate reduction accompanied by the corrosion of carbon steel was modeled as a reaction series such as nitrate - nitrite - ammonia. The sum of the current of the reaction series of nitrate - nitrite - ammonia and that of water reduction was assumed to balance with the corrosion current of carbon steel. The input parameters for this kinetic model were determined by electrochemical measurement and immersion test. The results of the immersion test can be interpreted by the analyses of the model.

JAEA Reports

Development of fuel microspheres fabrication by the external gelation process

Tomita, Yutaka; Morihira, Masayuki; Tamaki, Yoshihisa*; Nishimura, Kazuhisa*; Shoji, Shuichi*; Kihara, Yoshiyuki; Kase, Takeshi; Koizumi, Tsutomu

JAEA-Research 2006-088, 95 Pages, 2007/01


JAEA has developed sphere-pac fuels in the feasibility study on commercialized FBR cycle systems as one of the candidates for low decontamination TRU fuels. Optimization of the fabrication condition for coarse spheres, development of an improved external gelation process, and examination of peculiar problems for the low decontamination fuel were carried out in Phase II. The results are shown as follows. (1) Fabrication condition of coarse spheres was optimized. (2) Feasibility of the improved external gelation process was confirmed. (3) Rare earth elements did not bring any problem for the characteristic of spheres and fabrication condition. (4) Radiation resistant data of the feed solution was acquired. Results of tests show the feasibility of the external gelation process for the low decontamination TRU fuel microsphere fabrication.

Journal Articles

Chemical transition of nitrate ions accompanied with corrosion of carbon steel under alkaline conditions

Honda, Akira; Kato, Takashi; Tateishi, Tsuyoshi*; Imakita, Tsuyoshi*; Masuda, Kaoru*; Kato, Osamu*; Nishimura, Tsutomu*

Zairyo To Kankyo, 55(10), p.458 - 465, 2006/10

Migration of radioactive material can be affected by the redox condition and the concentration of ligands in the repository of radioactive waste. It is possible that radioactive waste contains nitrate which can affect the migration behavior of radioactive nuclides by both changing the redox condition of the environment and acting as a ligand. On the other hand, several researchers observed the reduction of nitrate ions in ammonia due to the iron. Ammonia has a potential to ligand for radioactive nuclides. Nitrate can also affect the rate of hydrogen gas evolution accompanied by metal corrosion through changing the rest potential of metal by its oxidizing nature. Carbon steel was, therefore, immersed in an aqueous solution of sodium nitrate in a closed system for observing both the chemical interaction between metal and nitrate, and the effect of nitrate on the hydrogen gas evolution rate. The experimental pH range of the solution was 10.0-13.5 which corresponds to the pH range of pore fluid of cementitious material. The cathodic current density shows a Tafel equation type potential dependency in the aqueous solution containing nitrate or nitrite. In spite of the acceleration of cathodic reaction due to the existence of nitrate, the corrosion rates of carbon steel were not accelerated in the nitrate solutions. This fact suggests that the system is controlled by the anodic reaction. The nitrate reduction accompanied by the corrosion of carbon steel is considered to be a series reaction such as nitrate nitrite ammonia. The nitrate reduction reaction compete with the water reduction reaction within the anodic controlled condition, therefore nitrate strongly reduced the hydrogen evolution rate. The generation rates of ammonia were independent of the concentration of nitrate.

JAEA Reports

A Modeling study for the chemical evolution of nitrate accompanied with the corrosion of carbon steel

Honda, Akira; Masuda, Kaoru*; Kato, Osamu*; Nishimura, Tsutomu*; Tateishi, Tsuyoshi*; Imakita, Tsuyoshi*

JNC TN8400 2005-023, 40 Pages, 2005/09


Uranium and Plutonium are planed to be recovered from spent fuel by the reprocessing in Japan. PUREX method is internationally dominant among the commercial reprocessing plants. PUREX method has been also employed in Japan. The low level liquid waste from PUREX process would contain NO3- as forms of soluble salts, if the special process for decomposing NO3- were not adopted. The nitrate is possibly brought within the repository for TRU waste. The specie of NO3- is an oxidizing agent which can be reduced to NO2- and NH3/NH4+ by the coexistence of reducing materials such as metals.In order to estimate the safety of the repository for TRU waste, the impacts of nitrate on the disposal system for TRU waste have to be estimated. Especially, NH3 can elevate the solubility and reduce Rd value through the formation of ammine complexes. The quantitative information of chemical evolution of nitrate is necessary for evaluating the impact of nitrate and the chemical species arising from nitrate on the safety of the repository of TRU waste. The evolution of chemical form of NO3- by the reducing reaction accompanied with metal corrosion was experimentally examined. The reduction of NO3- was considered to be a serial reaction, that is, NO3- - NO2- - NH3. The rate equations of cathodic reactions (water reduction and reduction of nitrate and nitrite) were experimentally determined through the electrochemical measurements. The rate equation of metal dissolution (anodic reaction) which must be balanced to the cathodic reactions in charge transfer is determined from the results of immersion tests without nitrate. The combination of the rate equations forms an assessment model of chemical evolution of NO3-. The model provided the interpretation of the results of immersion tests with nitrate.

JAEA Reports

Hydrogen Evolution Behavior in the Corrosion of Carbon Steel in Contact with Magnetite

Taniguchi, Naoki; Tateishi, Tsuyoshi*; Fukudome, Kazuyuki*; Nishimura, Tsutomu*; Kawakami, Susumu

JNC TN8400 2005-014, 36 Pages, 2005/07


It has been reported that the corrosion of carbon steel is accelerated by a contact with magnetite, which is a representative corrosion product in low oxygen environment. It is important to clear the corrosion mechanism in the presence of magnetite for long term prediction of overpack corrosion. There are two possible cathodic reactions in the presence of magnetite coupled with anodic reaction. One is reduction of Fe(III) in magnetite, and the other is hydrogen evolution reaction. If the former dominate the cathodic reaction, corrosion acceleration will be stopped with the consumption of Fe(III). While, if the latter is the main cathodic reaction, corrosion acceleration is possible to be continued for a long time. In this study, corrosion rate and hydrogen evolution behavior were investigated by the immersion test of carbon steel in contact with dummy corrosion product to contribute to understanding the corrosion mechanism.

JAEA Reports

Influence of Fe(III)/Fe(II) Ratio in Dummy Corrosion Product on the Corrosion Behavior of Carbon Steel

Taniguchi, Naoki; Tateishi, Tsuyoshi*; Nishimura, Tsutomu*; Kawakami, Susumu

JNC TN8400 2003-049, 23 Pages, 2004/03


The corrosion rate and hydrogen evolution behavior of carbon steel were investigated by immersion test of carbon steel in contact with dummy corrosion product. According to this result, the severe corrosion acceleration occurs when the corrosion product contains excessive Fe(III), and the main cathodic reaction is Fe(III) reduction.

JAEA Reports

Study on Long-Term Corrosion Behavior of High Corrosion Resistant Metal Overpack under Reducing Condition

Wada, Ryutaro*; Nishimura, Tsutomu*; Nakanishi, Tomoaki*; Nakayama, Takenori*; Sakashita, Shinji*; Fujiwara, Kazuo*; Tateishi, Tsuyoshi*

JNC TJ8400 2005-001, 224 Pages, 2004/02


For repository container material of high-level radioactive waste, titanium and nickel-base alloys have been investigated as high corrosion resistance metal. In this study, the effects of environmental and material factors on hydrogen absorption of titanium were investigated experimentally. As for nickel-base allys, previous studies on corrosion behavior were serched.

JAEA Reports

Research on Changes of Nitrate by Interactions with Metals under the Wastes Disposal Environment Containing TRU Nuclide (2) -Summary Report-

Wada, Ryutaro*; Nishimura, Tsutomu*; Masuda, Kaoru*; Fujiwara, Kazuo*; Imakita, Tsuyoshi*; Tateishi, Tsuyoshi*

JNC TJ8400 2004-017, 71 Pages, 2004/02


Research on changes of nitrate by interactions with metals under the wastes disposal environment containing TRU nuclide

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