Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2017

Nakano, Masanao; Fujita, Hiroki; Mizutani, Tomoko; Nemoto, Masashi; Tobita, Keiji; Kono, Takahiko; Hosomi, Kenji; Hokama, Tomonori; Nishimura, Tomohiro; Matsubara, Natsumi; et al.

JAEA-Review 2018-025, 171 Pages, 2019/02

JAEA-Review-2018-025.pdf:3.81MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2016 to March 2017. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Station of Electric Power Company Holdings, Inc. in March 2011. Appendices present comprehensive information, such as monitoring programs, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data which were influenced by the accidental release and were exceeded the normal range of fluctuation in the monitoring, were evaluated.

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2015

Nakano, Masanao; Fujita, Hiroki; Mizutani, Tomoko; Hosomi, Kenji; Nagaoka, Mika; Hokama, Tomonori; Yokoyama, Hiroya; Nishimura, Tomohiro; Matsubara, Natsumi; Maehara, Yushi; et al.

JAEA-Review 2016-035, 179 Pages, 2017/03

JAEA-Review-2016-035.pdf:4.2MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2015 to March 2016. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Station of Electric Power Company Holdings, Inc. in March 2011. Appendices present comprehensive information, such as monitoring programs, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data which were influenced by the accidental release and were exceeded the normal range of fluctuation in the monitoring, were evaluated.

Titanium alloy as a potential low radioactivation vacuum material

Kamiya, Junichiro; Hikichi, Yusuke; Kinsho, Michikazu; Ogiwara, Norio; Fukuda, Mitsuhiro*; Hamatani, Noriaki*; Hatanaka, Kichiji*; Kamakura, Keita*; Takahisa, Keiji*

Journal of Vacuum Science and Technology A, 33(3), p.031605_1 - 031605_8, 2015/05

https://doi.org/10.1116/1.4916934

For the vacuum systems of high-intensity beam accelerators, low radioactivation materials with good vacuum characteristics and high mechanical strength are required. The titanium alloy Ti-6Al-4V was investigated as a potential low activation vacuum material with high mechanical strength for the fabrication of vacuum components, particularly the flanges of beam pipes, in the J-PARC 3 GeV synchrotron. The dose rate of Ti-6Al-4V when irradiated by a 400 MeV proton was observed to decrease more rapidly than that of stainless steel. Furthermore, the generated radioactive isotopes were nuclides with relatively short half-lives. The outgassing rate of Ti-6Al-4V was the same as the typical value for stainless steel. Additionally, the hydrogen concentration in bulk Ti-6Al-4V was reduced to approximately 1 ppm by vacuum firing. These results indicate that Ti-6Al-4V is a good candidate for use as a low activation vacuum material with high mechanical strength.

Development of radiation-resistant optical fiber for application to observation and laser spectroscopy under high radiation dose

Ito, Chikara; Naito, Hiroyuki; Nishimura, Akihiko; Oba, Hironori; Wakaida, Ikuo; Sugiyama, Akira; Chiyatani, Keiji

Journal of Nuclear Science and Technology, 51(7-8), p.944 - 950, 2014/07

https://doi.org/10.1080/00223131.2014.924883

In the Fukushima Daiichi Nuclear Power Station, it is necessary to survey the locations and conditions of fuel debris inside reactor pressure vessels or primary containment vessels under water and radiation environment in preparation for removing fuel debris. An optical fiber is well known for features such as signal transmission, light weight, superior insulation performance, water resistance and electromagnetic noise resistance. These features allow the optical fiber to simplify the instrumentation systems for in-vessel inspection, as long as provide that the optical fiber can be used under high radiation dose environment. The radiation resistance of an optical fiber was improved by increasing the amount of hydroxyl up to 1000 ppm in pure silica fiber. The improved optical fibers were irradiated with -ray up to 1 10 Gy using a Co source. They indicated a large peak around 600 nm and a peak tail from ultraviolet region, but no large absorption in infrared region except a hydroxyl absorption peak of 945 nm. We have confirmed that the optical fiber containing 1000 ppm hydroxyl has enough radiation resistance for radiation induced transmission losses and the infrared imaging is effective for observation under high radiation doses.

Effects of rippled fields due to ferritic inserts and ELM mitigation coils on energetic ion losses in a 15 MA inductive scenario in ITER

Shinohara, Koji; Tani, Keiji*; Oikawa, Toshihiro*; Putvinski, S.*; Schaffer, M.*; Loarte, A.*

Nuclear Fusion, 52(9), p.094008_1 - 094008_12, 2012/09

https://doi.org/10.1088/0029-5515/52/9/094008

Effects of complex symmetry-breakings on alpha particle power loads on first wall structures and equilibrium in ITER

Shinohara, Koji; Kurki-Suonio, T.*; Spong, D. A.*; Asunta, O.*; Tani, Keiji*; Strumberger, E.*; Briguglio, S.*; Koskela, T.*; Vlad, G.*; Gnter, S.*; et al.

Nuclear Fusion, 51(6), p.063028_1 - 063028_12, 2011/06

https://doi.org/10.1088/0029-5515/51/6/063028

Thirty years experience at the experimental fast reactor Joyo; High quality core management and irradiation field characterization technique

Maeda, Shigetaka; Ito, Chikara; Aoyama, Takafumi; Maeda, Yukimoto; Chatani, Keiji

Transactions of the American Nuclear Society, 103(1), p.581 - 582, 2010/11

The experimental fast reactor Joyo of the Japan Atomic Energy Agency is the first liquid sodium fast reactor in Japan. Thirty years of successful operation of Joyo has shown excellent safety and reliability, and has contributed much to the LMFBR development program. Many kinds of irradiation experience have been accumulated to develop the fuels and materials for the prototype reactor Monju and future fast reactors. Accumulated data have been registered with OECD/NEA database with expectation that these data will be widely used. Joyo is presently temporary shutdown because of periodical inspection including in-vessel inspection and repair. After restart, Joyo will play a key role for a wide variety of science and technology fields as fast neutron irradiation bed.

Numerical study of the ripple resonance diffusion of alpha particles in tokamaks

Mimata, Hideyuki*; Tani, Keiji*; Tsutsui, Hiroaki*; Tobita, Kenji; Iio, Shunji*; Shimada, Ryuichi*

Plasma and Fusion Research (Internet), 4, p.008_1 - 008_8, 2009/04

https://doi.org/10.1585/pfr.4.008

The energy dependence of the diffusion coefficients of alpha particles in rippled magnetic fields of tokamaks are numerically investigated with an orbit following Monte Carlo code. The diffusion coefficients are enhanced around the ripple resonance energy while they are reduced and has a minimum near the resonance energy, and hence they have an M-shaped dependence on the energy. The ripple resonance is caused by a radial change of the toroidal precession of banana particles, and creates islands in the phase space related with the toroidal and poloidal angles. Since the particles outside the separatrix mainly contribute to the diffusion, the M-shaped energy dependence is explained by both island structure and initial distribution of particles in the phase space. Such a ripple resonant diffusion is dominant for fusion-produced alpha particles in the slowing down process.

Hexafluoro complex of rutherfordium in mixed HF/HNO solutions

Toyoshima, Atsushi; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Akiyama, Kazuhiko*; Goto, Shinichi*; Ishii, Yasuo; Nishinaka, Ichiro; Sato, Tetsuya; Nagame, Yuichiro; et al.

Radiochimica Acta, 96(3), p.125 - 134, 2008/03

https://doi.org/10.1524/ract.2008.1474

Formation of an anionic fluoride-complex of element 104, rutherfordium (Rf) produced in the Cm(O,5n)Rf reaction was studied by an anion-exchange method based on an atom-at-a-time scale. It was found that the hexafluoro complex of Rf, [RfF], was formed in the studied fluoride ion concentrations of 0.0005 - 0.013 M. Formation of [RfF] was significantly different from that of the homologues Zr and Hf, [ZrF] and [HfF]; the evaluated formation constant of [RfF] is at least one-order of magnitude smaller than those of [ZrF] and [HfF].

FBR cycle development

Negishi, Hitoshi; Chatani, Keiji; Tanigawa, Shingo

Genshiryoku Nenkan 2008, p.53 - 61, 2007/09

The Japanese government assessed the result of "Feasibility Study on Commercialized FR Cycle System 2nd Phase" and a major concept that is the combination of a sodium cooled FBR (oxide fuel), an advanced aqueous reprocessing and a simplified pelletizing was selected. From now on, the JAEA invests the development resource to a major concept intensively, and aims to put it to practical use by new project, "FaCT". In "Monju", the plant improvement construction have been working on schedule, and the various tests for restart are advanced. The R&D results in "Monju" will be applied to FBR development near future. "Joyo" has been operated over 70,000 hours, and has provided the fields to develop FBR fuel & material. In addition, the external utilization of "Joyo" is enhancing now. FBR development is activating worldwide. The international cooperation under GIF, GNEP and INPRO and the research collaboration with America/France are carrying.