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Journal Articles

Integrated radiation air dose rate maps over the 80 km radius of the Fukushima Daiichi Nuclear Power Plant and the entire Fukushima Prefecture during 2011-2022

Sakuma, Kazuyuki; Kurikami, Hiroshi; Wainwright, Haruko*; Tanimori, Soichiro*; Nagao, Fumiya; Ochi, Kotaro; Sanada, Yukihisa; Saito, Kimiaki

Journal of Environmental Radioactivity, 280, p.107554_1 - 107554_11, 2024/12

 Times Cited Count:2 Percentile:53.16(Environmental Sciences)

In this study, we created the integrated radiation air dose rate maps in the Fukushima region during 2011-2022 using multiple types of surveys such as air-borne, car-borne and walk surveys as well as fixed-location measurements. We applied the Bayesian geostatistical method developed by Wainwright et al. (2017, 2019) to the 80 km radius of the Fukushima Daiichi Nuclear Power Plant and the whole of Fukushima Prefecture while considering the history of the lifting of the evacuation zone in Fukushima. The integrated maps fixed the bias to underestimate air dose rates in forest areas, and successfully created more reproducible integrated maps with a wider area and time series than the previous studies. It is highly expected that the results of this study will be used to evaluate detailed exposure doses to the general public.

Journal Articles

${it In situ}$ spectrometry of terrestrial gamma rays using portable germanium detectors in area of 80 km radius around the Fukushima Daiichi Nuclear Power Plant

Mikami, Satoshi; Tanaka, Hiroyuki*; Okuda, Naotoshi*; Sakamoto, Ryuichi*; Ochi, Kotaro; Uno, Kiichiro*; Matsuda, Norihiro; Saito, Kimiaki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 20(4), p.159 - 178, 2021/12

In order to know the background radiation level where the area affected by the Fukushima Daiichi Nuclear Power Plant accident in 2011, terrestrial gamma rays had been measured by using portable germanium detectors repeatedly from 2013 through 2019, at 370 locations within 80 km radius area centered on the Fukushima Daiichi Nuclear Power Plant. Radioactive concentrations of Uranium 238, Thorium 232, Potassium 40 and kerma rates in air due to terrestrial gamma rays were obtained at those locations based on the method of ICRU report 53. Averaged concentrations of $$^{238}$$U, $$^{232}$$Th and $$^{40}$$K were 18.8, 22.7, 428 Bq/kg, respectively, and kerma rate in air over the area was found to be 0.0402 $$mu$$Gy/h. The obtained kerma rates in air were compared to those reported in literatures. It was confirmed that the data were correlated with each other, and were agreed within the range of their uncertainty. This is because the kerma rate in air due to terrestrial gamma rays is depend on geology. The similar trend to previous findings was observed that the kerma rate in air at locations geologically classified as Mesozoic era, Granite and Rhyolite were statistically significantly higher than the others.

Journal Articles

Isotope-selective microscale imaging of radioactive Cs without isobaric interferences using sputtered neutral mass spectrometry with two-step resonant ionization employing newly-developed Ti:Sapphire lasers

Sakamoto, Tetsuo*; Morita, Masato*; Kanenari, Keita*; Tomita, Hideki*; Sonnenschein, V.*; Saito, Kosuke*; Ohashi, Masaya*; Kato, Kotaro*; Iguchi, Tetsuo*; Kawai, Toshihide*; et al.

Analytical Sciences, 34(11), p.1265 - 1270, 2018/11

 Times Cited Count:10 Percentile:33.86(Chemistry, Analytical)

Journal Articles

Mn$$_{2}$$VAl Heusler alloy thin films; Appearance of antiferromagnetism and exchange bias in a layered structure with Fe

Tsuchiya, Tomoki*; Kobayashi, Ryota*; Kubota, Takahide*; Saito, Kotaro*; Ono, Kanta*; Ohara, Takashi; Nakao, Akiko*; Takanashi, Koki*

Journal of Physics D; Applied Physics, 51(6), p.065001_1 - 065001_7, 2018/02

 Times Cited Count:10 Percentile:40.52(Physics, Applied)

Journal Articles

2016 Professional Engineer (PE) test preparation course "Nuclear and Radiation Technical Disciplines"

Takahashi, Naoki; Yoshinaka, Kazuyuki; Harada, Akio; Yamanaka, Atsushi; Ueno, Takashi; Kurihara, Ryoichi; Suzuki, Soju; Takamatsu, Misao; Maeda, Shigetaka; Iseki, Atsushi; et al.

Nihon Genshiryoku Gakkai Homu Peji (Internet), 64 Pages, 2016/00

no abstracts in English

Journal Articles

Influence of electron doping on magnetic order in CeRu$$_2$$Al$$_{10}$$

Kobayashi, Riki*; Kaneko, Koji; Saito, Kotaro*; Mignot, J.-M.*; Andr$'e$, G.*; Robert, J.*; Wakimoto, Shuichi; Matsuda, Masaaki*; Chi, S.*; Haga, Yoshinori; et al.

Journal of the Physical Society of Japan, 83(10), p.104707_1 - 104707_5, 2014/10

 Times Cited Count:17 Percentile:68.22(Physics, Multidisciplinary)

Journal Articles

Identified charged hadron production in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

 Times Cited Count:193 Percentile:99.41(Physics, Nuclear)

Transverse momentum distributions and yields for $$pi^{pm}, K^{pm}, p$$, and $$bar{p}$$ in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different $$sqrt{s}$$ collisions. We also present the scaling properties such as $$m_T$$ and $$x_T$$ scaling and discuss the mechanism of the particle production in $$p + p$$ collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

Journal Articles

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in $$p+p$$ and Au+Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.

Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04

 Times Cited Count:10 Percentile:54.53(Physics, Nuclear)

Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled $$p+p$$ collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to $$p+p$$ collisions.

Journal Articles

Basic vacuum test of 500-kV photocathode DC gun components at KEK

Yamamoto, Masahiro*; Uchiyama, Takashi*; Miyajima, Tsukasa*; Honda, Yosuke*; Sato, Kotaro*; Matsuba, Shunya*; Saito, Yoshio*; Kobayashi, Masanori*; Kurisu, Hiriki*; Hajima, Ryoichi; et al.

Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.717 - 720, 2010/08

A 500-kV photocathode DC electron gun which can supply the beam of a low emittance and a high average current has been developed in collaboration with KEK, JAEA, Hiroshima Univ., Nagoya Univ. and Yamaguchi Univ. The vacuum of the gun chamber has to be lower Extreme High Vacuum for maintain cathode-life time. A titanium chamber and new material of ceramic were employed to reduce outgassing rate. The result of outgassing rate of the gun chamber is described in this report.

Journal Articles

Design of a 500kV electron gun for ERL light source at KEK

Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Uchiyama, Takashi*; Kobayashi, Masanori*; Muto, Toshiya*; Matsuba, Shunya*; Sakanaka, Shogo*; Sato, Kotaro*; Saito, Yoshio*; et al.

Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.860 - 862, 2009/08

A newly 500 kV electron gun (2nd - 500 kV gun) for an ERL light source is designed at KEK. A new concept and state of-the-art technologies of vacuum system, ceramic insulators, high voltage power supply, photocathode and preparation system will be employed. The details are described in this report.

Oral presentation

Activity report of the emergency monitoring committee

Hosoda, Masahiro*; Saito, Kimiaki; Mikami, Satoshi; Sanada, Tetsuya*; Omori, Yasutaka*; Takeda, Hikaru*; Yamada, Takahiro*; Hirao, Shigekazu*; Tani, Kotaro*; Orita, Makiko*; et al.

no journal, , 

no abstracts in English

Oral presentation

R&D on mercury target for spallation neutron source to improve the durability under high power operation, 4; Development of technique on radiation damage evaluation on the mercury target to estimate the residual lifetime

Wakui, Takashi; Saito, Shigeru; Wakai, Eiichi; Sakai, Tomoki*; Mori, Kotaro*; Futakawa, Masatoshi

no journal, , 

One of dominant factors to determine the lifetime of the mercury target in J-PARC is the radiation damage. Authors suggested the tensile properties evaluation technique from numerical tensile tests using material properties estimated from inverse analyses on indentation tests. The technique was applied to ion-irradiated materials, and the validity of the technique was investigated by comparing the result with results of the PIE on the targets of SNS. By conducting indentation tests on samples cut out from used targets, it is expected that the residual lifetime estimation can be conducted considering various effects; fatigue, temperature, LME, etc. superimposed on the radiation damage from evaluating hardness and tensile properties obtained by the technique. The technique and comparison results will be discussed.

Oral presentation

Mechanical properties evaluation technique on radiation damaged materials using indentation test combined with numerical experiment

Wakui, Takashi; Saito, Shigeru; Futakawa, Masatoshi; Sakai, Tomoki*; Mori, Kotaro*

no journal, , 

One of dominant factors to determine the lifetime of the structural components used under high irradiation environment is radiation damage. The indentation test will be applied to understand the degradation in mechanical properties. In this study, the technique evaluating mechanical properties from the combination of the indentation test with inverse analysis and the numerical tensile experiment is proposed. In order to confirm that this technique can evaluate changes in mechanical properties, it was applied to ion irradiated 316L stainless steels. The numerical model consists of multi layers whose mechanical properties are dependent on the DPA distribution. The material constants of each layer were identified. The numerical tensile experiments were conducted by using identified material constants. These results are compared with the PIE results of SNS. As the results, it was confirmed that this technique is effective to evaluate the mechanical property degradation due to irradiation.

Oral presentation

Analysis and prediction of microstructure of heat resistant steels based on system free energy

Murata, Yoshinori*; Shiraki, Atsuhiro*; Takeda, Kotaro*; Tsukada, Yuki*; Saito, Yoshihiro*; Morinaga, Masahiko*; Koyama, Toshiyuki*; Takaya, Shigeru

no journal, , 

no abstracts in English

Oral presentation

Investigation on distribution of radioactive substances in Fukushima, 14; Modeling on the integrated radiation air dose rate maps during 2011-2022

Sakuma, Kazuyuki; Kurikami, Hiroshi; Wainwright, Haruko*; Tanimori, Soichiro*; Nagao, Fumiya; Ochi, Kotaro; Sanada, Yukihisa; Saito, Kimiaki

no journal, , 

no abstracts in English

Oral presentation

Mechanical property evaluation on irradiated materials with gradient damage distribution

Sakai, Tomoki*; Wakui, Takashi; Saito, Shigeru; Futakawa, Masatoshi; Mori, Kotaro*

no journal, , 

One of dominant factors to determine the lifetime of components used under the high-radiation environment is the radiation damage of materials and then understanding of the radiation damage is very important. Although ion irradiation has been conducted as the method simulating the radiation damage, the damaged area is limited to the surface layer of the specimen and has the gradient damage distribution. Micro-indentation tests with a Berkovich indenter were conducted in irradiated and unirradiated area on ion irradiated specimens and the micro-hardness was estimated from load and depth curve. The micro-hardness increased by the irradiation. The micro-hardness increased further under the irradiation condition that hydrogen ion and helium ion were added. On the other hand, the micro-hardness decreased with increasing irradiated temperature.

Oral presentation

Emergency drills at J-PARC

Saito, Fumihiro; Kasugai, Yoshimi; Seki, Kazunari; Nakane, Yoshihiro; Tani, Norio; Sato, Koichi; Yamazaki, Hirohito*; Bessho, Kotaro; Numajiri, Masaharu

no journal, , 

no abstracts in English

Oral presentation

Ferri-electricity in (Bi$$_{1/2}$$K$$_{1/2}$$)TiO$$_3$$-(Bi$$_{1/2}$$Li$$_{1/2}$$)TiO$$_3$$ solid solution

Saito, Kotaro*; Yoneda, Yasuhiro; Matsuo, Hiroki*; Noguchi, Yuji*

no journal, , 

In addition to excellent piezoelectricity and dielectric properties, ferri-dielectric phases exhibit giant electric-field-induced strain due to the electric-field-induced phase transition. The presence of ferri-dielectric phase and its properties were investigated for (Bi$$_{1/2}$$K$$_{1/2}$$)TiO$$_3$$-(Bi$$_{1/2}$$Li$$_{1/2}$$)TiO$$_3$$ (BKT-BLT) solid solution ceramics by searching for compositional phase boundaries and evaluating the composition dependence of polarization properties through crystal structure analysis. This study revealed that a ferri-dielectric phase exists around $$x$$ = 8% in the BKT-BLT solid solution system, and that a specifically high relative permittivity can be obtained at this composition.

Oral presentation

On J-PARC Safety Day

Saito, Fumihiro; Kasugai, Yoshimi; Bessho, Kotaro; Nakane, Yoshihiro

no journal, , 

"Safety day", on which all staff members put their safety-related efforts first, has been assigned on a certain day in late May every year in J-PARC. This is an approach to make a safer environment in J-PARC, learning from the radioactive material leak accident happened on May 23, 2013, to raise the safety consciousness of every staff and foster a safety culture at J-PARC. There are four main programs that have been held on "Safety Day" so far: meeting for sharing safety information, safety awards, lectures on safety matters, and watching the documentary video on the material leak accident. The details will be shown in the presentation.

Oral presentation

Resonant laser secondary neutral mass spectrometry for micro imaging of radioactive isotopes, 2

Tomita, Hideki*; Saito, Kosuke*; Ohashi, Masaya*; Sonnenschein, V.*; Kato, Kotaro*; Suzuki, So*; Iguchi, Tetsuo*; Morita, Masato*; Sakamoto, Tetsuo*; Kanenari, Keita*; et al.

no journal, , 

no abstracts in English

24 (Records 1-20 displayed on this page)