Microbially formed Mn(IV) oxide as a novel adsorbent for removal of Radium

Tanaka, Kazuya; Yamaji, Keiko*; Masuya, Hayato*; Tomita, Jumpei; Ozawa, Mayumi*; Yamasaki, Shinya*; Tokunaga, Kohei; Fukuyama, Kenjin*; Ohara, Yoshiyuki*; Maamoun, I.*; et al.

Chemosphere, 355, p.141837_1 - 141837_11, 2024/05

https://doi.org/10.1016/j.chemosphere.2024.141837

In this study, biogenic Mn(IV) oxide was applied to remove Ra from mine water collected from a U mill tailings pond in the Ningyo-toge center. Just 7.6 mg of biogenic Mn(IV) oxide removed more than 98% of the Ra from 3 L of mine water, corresponding to a distribution coefficient of 10 mL/g for Ra at pH 7. The obtained value was convincingly high for practical application of biogenic Mn(IV) oxide in water treatment.

Current status of a JAEA development program on nuclear and radioactive materials detection techniques in major public events

Koizumi, Mitsuo; Takahashi, Tone; Hironaka, Kota; Mochimaru, Takanori*; Yamaguchi, Ikuto*; Kimura, Yoshiki; Tanigaki, Minoru*; Masaki, Hiroko*; Harada, Hiroshi*; Goto, Jun*; et al.

Proceedings of INMM & ESARDA Joint Annual Meeting 2023 (Internet), 7 Pages, 2023/05

Reactor noise power-spectral analysis for a graphite-moderated and -reflected core, 3

Sakon, Atsushi*; Hashimoto, Kengo*; Sano, Tadafumi*; Nakajima, Kunihiro*; Kanda, Shun*; Goto, Masaki*; Fukaya, Yuji; Okita, Shoichiro; Fujimoto, Nozomu*; Takahashi, Yoshiyuki*

KURNS Progress Report 2021, P. 100, 2022/07

https://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2021/ProgRep2021.html

The R&D of reactor noise analysis to obtain HTGR nuclear characteristics have been performed with Kyoto University Critical Assembly (KUCA). In the last study, a neutron detector located about 55 cm away of fuel assembly measured the auto power spectral density. However, the prompt neutron decay constants obtained by this detector was different from that of other detectors. The objective of this study is experimental study of reactor noise analysis by the power spectrum method using neutron detector placed outside reactor core.

Study on plutonium burner high temperature gas-cooled reactor in Japan; Introduction scenario, reactor safety and fabrication tests of the 3S-TRISO fuel

Ueta, Shohei; Mizuta, Naoki; Fukaya, Yuji; Goto, Minoru; Tachibana, Yukio; Honda, Masaki*; Saiki, Yohei*; Takahashi, Masashi*; Ohira, Koichi*; Nakano, Masaaki*; et al.

Nuclear Engineering and Design, 357, p.110419_1 - 110419_10, 2020/02

https://doi.org/10.1016/j.nucengdes.2019.110419

The concept of a plutonium (Pu) burner HTGR is proposed to incarnate highly-effective Pu utilization by its inherent safety features. The security and safety fuel (3S-TRISO fuel) employs the coated fuel particle with a fuel kernel made of plutonium dioxide (PuO) and yttria stabilized zirconia (YSZ) as an inert matrix. This paper presents feasibility study of Pu burner HTGR and R&D on the 3S-TRISO fuel.

Mineralogical control of the size distribution of stable Cs and radiocesium in riverbed sediments

Tanaka, Kazuya; Watanabe, Naoko*; Yamasaki, Shinya*; Sakaguchi, Aya*; Fan, Q.*; Takahashi, Yoshio*

Geochemical Journal, 52(2), p.173 - 185, 2018/00

https://doi.org/10.2343/geochemj.2.0501

We analyzed riverbed sediments collected at two sites, Yamakiya and Kuroiwa, in Fukushima after the Fukushima accident. The size distributions of K, Rb, and Csreflected the mineralogy of sediments, where primary host minerals for these alkali elements would be biotite, K-feldspar, and clay minerals. Silt-size fractions contained high Cs and Cs concentrations possibly due to adsorption on clay minerals. Their concentrations decreased with particle size at the Yamakiya site. In contrast, coarse and very coarse sand fractions from the Kuroiwa site showed higher Cs and Cs concentrations in comparison to fine - medium sand fractions. The coarse sand fractions contained many weathered biotite grains. Overall, the size distributions of Cs and Cs were similar in the sediments, suggesting that the Fukushima-derived radiocesium was distributed into each particle size fraction in response to the distribution of the stable Cs that was controlled by mineralogical composition.

Fabrication of Pt nanoparticle incorporated polymer nanowires by high energy ion and electron beam irradiation

Tsukuda, Satoshi*; Takahashi, Ryota*; Seki, Shuhei*; Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Tanaka, Shunichiro*

Radiation Physics and Chemistry, 118, p.16 - 20, 2016/01

https://doi.org/10.1016/j.radphyschem.2015.05.029

Polyvinylpyrrolidone (PVP)-Pt nanoparticles (NPs) hybrid nanowires were fabricated by high energy ion beam irradiation to PVP thin films including HPtCl. Single ion hitting caused crosslinking reactions of PVP and reduction of Pt ions within local cylindrical area along an ion trajectory (ion track); therefore, the PVP nanowires including Pt NPs were formed and isolated on Si substrate after wet-development procedure. The number of Pt NPs was easily controlled by the mixed ratio of PVP and HPtCl. However, increasing the amount of HPtCl led to decreasing the radial size and separation of the hybrid nanowires during the wet-development. Additional electron beam irradiation after ion beam improved separation of the nanowires and controlled radial sizes due to an increase in the density of crosslinking points inner the nanowires.

Measurement of air dose rates over a wide area around the Fukushima Dai-ichi Nuclear Power Plant through a series of car-borne surveys

Ando, Masaki; Nakahara, Yukio; Tsuda, Shuichi; Yoshida, Tadayoshi; Matsuda, Norihiro; Takahashi, Fumiaki; Mikami, Satoshi; Kinouchi, Nobuyuki; Sato, Tetsuro*; Tanigaki, Minoru*; et al.

Journal of Environmental Radioactivity, 139, p.266 - 280, 2015/01

https://doi.org/10.1016/j.jenvrad.2014.05.014

A series of car-borne surveys using the KURAMA and KURAMA-II systems was conducted in a wide area in eastern Japan from June 2011 to December 2012 to evaluate the distribution of air dose rates around the Fukushima Dai-ichi Nuclear Power Plant, and to determine the time-dependent trend of decrease in air dose rates. An automated data processing system was established, which enables analyses of large amounts of data obtained with the use of about 100 units of the measurement system in a short time. The initial data for studying the migration status of radioactive cesium was obtained in the first survey, followed by the other car-borne surveys having wider measurement ranges. Comparing the measured air dose rates obtained in each survey, it was found that the decreasing trend of air dose rates measured through car-borne surveys was larger than that expected from the physical decay of radioactive cesium and that measured using NaI (Tl) survey meters around the road.

Irradiation performance of HTGR fuel in WWR-K research reactor

Ueta, Shohei; Shaimerdenov, A.*; Gizatulin, S.*; Chekushina, L.*; Honda, Masaki*; Takahashi, Masashi*; Kitagawa, Kenichi*; Chakrov, P.*; Sakaba, Nariaki

Proceedings of 7th International Topical Meeting on High Temperature Reactor Technology (HTR 2014) (USB Flash Drive), 7 Pages, 2014/10

A capsule irradiation test with the high temperature gas-cooled reactor (HTGR) fuel is being carried out using WWR-K research reactor in the Institute of Nuclear Physics of the Republic of Kazakhstan (INP) to attain 100 GWd/t-U of burnup under normal operating condition of a practical small-sized HTGR. This is the first HTGR fuel irradiation test for INP in Kazakhstan collaborated with Japan Atomic Energy Agency (JAEA) in frame of International Science and Technology Center (ISTC) project. In the test, TRISO coated fuel particle with low-enriched UO (less than 10% of U) is used, which was newly designed by JAEA to extend burnup up to 100 GWd/t-U comparing with that of the HTTR (33 GWd/t-U). Both TRISO and fuel compact as the irradiation test specimen were fabricated in basis of the HTTR fuel technology by Nuclear Fuel Industries, Ltd. in Japan. A helium-gas-swept capsule and a swept-gas sampling device installed in WWR-K were designed and constructed by INP. The irradiation test has been started in October 2012 and will be completed up to the end of February 2015. The irradiation test is in the progress up to 69 GWd/t of burnup, and integrity of new TRISO fuel has been confirmed. In addition, as predicted by the fuel design, fission gas release was observed due to additional failure of as-fabricated SiC-defective fuel.

Beam position monitor system of J-PARC RCS

Hayashi, Naoki; Kawase, Masato; Hatakeyama, Shuichiro; Hiroki, Seiji; Saeki, Riuji; Takahashi, Hiroki; Teruyama, Yuzo*; Toyokawa, Ryoji*; Arakawa, Dai*; Hiramatsu, Shigenori*; et al.

Nuclear Instruments and Methods in Physics Research A, 677, p.94 - 106, 2012/06

https://doi.org/10.1016/j.nima.2012.02.013

A beam position monitor (BPM) system at J-PARC RCS is described. The J-PARC RCS is a rapid-cycling proton synchrotron and its designed beam power is 1 MW. A diameter of the BPM detector is larger than 250 mm, however the system has to measure the beam position very accurately. The system should work not only for the high intensity but also for lower intensity. There are 54 BPM around the ring and most of them are placed inside steering magnets because of quite limited space. The BPM detector is an electro static type and it has four electrodes, and a pair of electrode gives a good linear response with diagonal cut shape to detect the charge center precisely. The signal processing unit, which is equipped with 14-bit 40 MSPS ADC and 600 MHz DSP, has been developed. They are controlled via shared memory space and EPICS. It is capable to record full 25 Hz pulse data for averaged mode and it could also store whole waveform data for further analysis, like turn-by-turn position calculation.

Trial visualization of fast reactor design knowledge

Yoshikawa, Shinji; Minami, Masaki*; Takahashi, Tadao*

Journal of Nuclear Science and Technology, 48(4), p.709 - 714, 2011/04

https://doi.org/10.3327/jnst.48.709

In design problems of large-scale systems like fast breeder reactors, inter-relations among design specifications are very important where a selected specification option is transferred to other specification selections as a premise to be taken account in engineering judgments. These inter-relations are also important in design case studies with hypothetical adoption of rejected design options for evaluation of deviation propagations among design specifications. Some of these rejected options have potential worth for future reconsideration by some circumstance changes (e.g., advanced simulations to exclude needs for mock-up tests, etc), to contribute for flexibility in system designs. In this study, a computer software is built to visualize design problem structure by representing engineering knowledge nodes on individual specification selections along with inter-relations of design specifications, to validate the knowledge representation method and to derive open problems.