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Journal Articles

Discriminative measurement of absorbed dose rates in air from natural and artificial radionuclides in Namie Town, Fukushima Prefecture

Ogura, Koya*; Hosoda, Masahiro*; Tamakuma, Yuki*; Suzuki, Takahito*; Yamada, Ryohei; Negemi, Ryoju*; Tsujiguchi, Takakiyo*; Yamaguchi, Masaru*; Shiroma, Yoshitaka*; Iwaoka, Kazuki*; et al.

International Journal of Environmental Research and Public Health, 18(3), p.978_1 - 978_16, 2021/02

Journal Articles

A Unique high natural background radiation area; Dose assessment and perspectives

Hosoda, Masahiro*; Nugraha, E. D.*; Akata, Naofumi*; Yamada, Ryohei; Tamakuma, Yuki*; Sasaki, Michiya*; Kelleher, K.*; Yoshinaga, Shinji*; Suzuki, Takahito*; Rattanapongs, C. P.*; et al.

Science of the Total Environment, 750, p.142346_1 - 142346_11, 2021/01

 Times Cited Count:1 Percentile:100(Environmental Sciences)

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h$$^{-1}$$ and 1109 nGy h$$^{-1}$$. Indoor radon concentrations ranged from 124 Bq m$$^{-3}$$ to 1015 Bq m$$^{-3}$$. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m$$^{-3}$$ recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.

Journal Articles

Reconstruction of residents' thyroid equivalent doses from internal radionuclides after the Fukushima Daiichi Nuclear Power Station accident

Oba, Takashi*; Ishikawa, Tetsuo*; Nagai, Haruyasu; Tokonami, Shinji*; Hasegawa, Arifumi*; Suzuki, Gen*

Scientific Reports (Internet), 10(1), p.3639_1 - 3639_11, 2020/02

 Times Cited Count:1 Percentile:33.18(Multidisciplinary Sciences)

Internal doses of residents after the Fukushima Daiichi Nuclear Power Station accident have been reconstructed. In total 896 behaviour records in the Fukushima Health Management Survey were analysed to estimate thyroid doses via inhalation, using a spatiotemporal radionuclides concentration database constructed by atmospheric dispersion simulations. After a decontamination factor for sheltering and a modifying factor for the dose coefficient were applied, estimated thyroid doses were close to those estimated on the basis of direct thyroid measurement. The median and 95th percentile of thyroid doses of 1-year-old children ranged from 1.2 to 15 mSv and from 7.5 to 30 mSv, respectively.

Journal Articles

Cesium concentrations in various environmental media at Namie, Fukushima

Heged$"u$s, M.*; Shiroma, Yoshitaka*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Suzuki, Takahito*; Tamakuma, Yuki*; Yamada, Ryohei; Tsujiguchi, Takakiyo*; Yamaguchi, Masaru*; Ogura, Koya*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 323(1), p.197 - 204, 2020/01

 Times Cited Count:1 Percentile:65.13(Chemistry, Analytical)

The radioactivity of cesium in the water and sediments of two major rivers was measured along with airborne radioactivity in Namie Town, after the recent partial lift on the evacuation order in 2017. The observed concentrations were up to 384 $$pm$$ 11 mBq/L for $$^{137}$$Cs in unfiltered water and 1.28 $$pm$$ 0.09 mBq/m$$^{3}$$ for $$^{137}$$Cs in air, while the sediment had a maximum of 44900 $$pm$$ 23.4 Bq/kg for $$^{137}$$Cs. The $$^{134}$$Cs/$$^{137}$$Cs ratios indicate the main origin of the cesium in the sediment to be Unit 1 in good agreement with previous reports on the accident.

Journal Articles

Comparative study on performance of various environmental radiation monitors

Tamakuma, Yuki*; Yamada, Ryohei; Suzuki, Takahito*; Kuroki, Tomohiro*; Saga, Rikiya*; Mizuno, Hiroyuki*; Sasaki, Hiroyuki*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Tokonami, Shinji*

Radiation Protection Dosimetry, 184(3-4), p.307 - 310, 2019/10

 Times Cited Count:1 Percentile:65.13(Environmental Sciences)

After the Fukushima Daiichi Nuclear Power Plant accident, the radiation dose for first responders was not evaluated accurately due to lack of the monitoring data. It has been important to evaluate a radiation dose for workers in emergency response at a nuclear accident. In this study, a new device which can evaluate both of external and internal exposure doses was developed and the performance of various environmental radiation monitors including commercially available monitors were tested and compared from the viewpoint of an environmental monitoring at emergency situation. Background counts of the monitors and the ambient dose equivalent rate were measured in Fukushima Prefecture. The detection limit for beta particles was evaluated by the method of ISO11929. The sensitivity for gamma-rays of the dust monitor using a ZnS(Ag) and a plastic scintillator was high, but that of the external exposure monitor using a silicon photodiode with CsI(Tl) crystal was relatively low. The detection limit ranged 190-280 Bq m$$^{-3}$$ at 100 $$mu$$Sv h$$^{-1}$$, exceeding the detection limit of 100 Bq m$$^{-3}$$ in the minimum requirement by the National Regulation Authority in Japan. Use of the shielding with lead is necessary to achieve the minimum requirement. These results indicate that the dust monitor using a ZnS(Ag) scintillator and a plastic scintillator is suitable for the external exposure monitor and the developed internal exposure monitor is for the internal exposure monitor at emergency situation among the evaluated monitors. In the future study, the counting efficiency, the relative uncertainty and the performance of the detection for alpha particles will be evaluated, and it will be considered which type of a monitor is suitable after taking the portability into account.

Journal Articles

Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment

Ekawa, Hiroyuki; Ashikaga, Sakiko; Hasegawa, Shoichi; Hashimoto, Tadashi; Hayakawa, Shuhei; Hosomi, Kenji; Ichikawa, Yudai; Imai, Kenichi; Kimbara, Shinji*; Nanamura, Takuya; et al.

Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.021D02_1 - 021D02_11, 2019/02

 Times Cited Count:2 Percentile:52.32(Physics, Multidisciplinary)

Journal Articles

The Hydrogen gas generation by electron-beam irradiation from ALPS adsorbents solidified by several inorganic materials

Sato, Junya; Suzuki, Shinji*; Kato, Jun; Sakakibara, Tetsuro; Meguro, Yoshihiro; Nakazawa, Osamu

QST-M-2; QST Takasaki Annual Report 2015, P. 87, 2017/03

no abstracts in English

Journal Articles

The Hydrogen gas generation by gamma-ray irradiation from ALPS adsorbents solidified by several inorganic materials

Sato, Junya; Suzuki, Shinji*; Kato, Jun; Sakakibara, Tetsuro; Meguro, Yoshihiro; Nakazawa, Osamu

QST-M-2; QST Takasaki Annual Report 2015, P. 88, 2017/03

no abstracts in English

Journal Articles

Irradiation test of semiconductors components on the shelf for nuclear robots based on Fukushima Accidents

Kawatsuma, Shinji; Nakai, Koji; Suzuki, Yoshiharu; Kase, Takeshi

QST-M-2; QST Takasaki Annual Report 2015, P. 81, 2016/12

Radiation Tolerance of semiconductor components on the shelf, utilized on the robots for emergency response or decommissioning in nuclear facilities, should be estimated. Just after the Fukushima Daiichi NPPs accidents occurred, a guideline, of irradiation tolerance estimation and management method of semiconductor components on the shelf, was tried to be made based on the old database developed in the course of Bilateral Servo Manipulator under the high radiation and high contamination environments. The estimation was conservative, because the data in the database were old and mainly based on the test results of silicon semiconductors. Ga-As Semiconductors are coming major recently, and expected to be higher radiation tolerance. For those reason, present semiconductor devices have irradiated and the irradiation tolerance have estimated.

Journal Articles

Development of an unstable failure analysis procedure considering change of compliance at a crack part of SFR pipes

Wakai, Takashi; Machida, Hideo*; Yoshida, Shinji*; Yanagihara, Seiji*; Suzuki, Ryosuke*; Matsubara, Masaaki*; Enuma, Yasuhiro

Engineering Failure Analysis, 56, p.484 - 500, 2015/10

 Times Cited Count:1 Percentile:84.05(Engineering, Mechanical)

Journal Articles

Development of residual thermal stress-relieving structure of CFC monoblock target for JT-60SA divertor

Tsuru, Daigo; Sakurai, Shinji; Nakamura, Shigetoshi; Ozaki, Hidetsugu; Seki, Yohji; Yokoyama, Kenji; Suzuki, Satoshi

Fusion Engineering and Design, 98-99, p.1403 - 1406, 2015/10

 Times Cited Count:3 Percentile:64.5(Nuclear Science & Technology)

Journal Articles

In-vessel coils for magnetic error field correction in JT-60SA

Matsunaga, Go; Takechi, Manabu; Sakurai, Shinji; Suzuki, Yasuhiro*; Ide, Shunsuke; Urano, Hajime

Fusion Engineering and Design, 98-99, p.1113 - 1117, 2015/10

 Times Cited Count:11 Percentile:19.99(Nuclear Science & Technology)

JAEA Reports

User's guide of cement solidification test for incinerated ash

Nakayama, Takuya; Kawato, Yoshimi; Osugi, Takeshi; Shimazaki, Takejiro; Hanada, Keiji; Suzuki, Shinji; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro

JAEA-Technology 2014-046, 56 Pages, 2015/03

JAEA-Technology-2014-046.pdf:7.61MB

The combustible and flame-retardant radioactive wastes generated as a result of the research activities in Japan Atomic Energy Agency (JAEA) are incinerating to reduce their volume. The incinerated ash is planned to be solidified using cement for disposal. Since the properties of ashes generated in each institute of JAEA are varied with the type of incinerator and the wastes to be incinerated, it is necessary to do fundamental solidification tests in each institute to decide operating conditions of the planning cement solidification facility. It is important to standardize evaluating methods of cement and solidified waste because some characters depend on measuring method. This user's guide have been prepared how to decide the cement solidifying conditions of ash to design the cement solidification facility in JAEA. Requirements on the regulations of solidified radioactive waste have been examined and seven technical criteria, e.g. compressive strength, fluidity, have been selected as characters to be evaluated. Some empirical notes about selection of cement, admixtures, procedure on making a test piece, evaluation of expanding, compressive strength, solubility have been described. The strategy of tests and tips for finding optimized solidification condition has been summarized. Finally the example of optimized conditions satisfied the requirements and some problems to be solved have been described.

JAEA Reports

Investigation of the site selection examples adopted local participation; The Site selection processes in Belgium, UK and Switzerland

Kageyama, Hitoshi; Suzuki, Shinji; Hirose, Ikuro; Yoshioka, Tatsuji

JAEA-Review 2014-019, 79 Pages, 2014/06

JAEA-Review-2014-019.pdf:9.93MB

In late years, local participation policies are being adopted in foreign countries at site selection for the disposal of the radioactive waste. We performed documents investigation about the examples of the site selection processes of Belgium, the U.K., and Switzerland to establish the site selection policy in Japan. Reviewing the merits and demerits of each example through this investigation, we confirmed if we are to adopt local participation policy in our country in future, further prudent study would be necessary, considering current and future social conditions in Japan.

Journal Articles

Expansion control for cementation of incinerated ash

Nakayama, Takuya; Suzuki, Shinji; Hanada, Keiji; Tomioka, Osamu; Sato, Junya; Irisawa, Keita; Kato, Jun; Kawato, Yoshimi; Meguro, Yoshihiro

Proceedings of 2nd International Symposium on Cement-based Materials for Nuclear Wastes (NUWCEM 2014) (CD-ROM), 12 Pages, 2014/06

Journal Articles

High-magnetic-field X-ray absorption and magnetic circular dichroism spectroscopy in the mixed-valent compound YbAgCu$$_4$$

Nakamura, Toshiyuki*; Matsuda, Yasuhiro*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(11), p.114702_1 - 114702_11, 2012/11

 Times Cited Count:11 Percentile:38.03(Physics, Multidisciplinary)

The X-ray absorption and magnetic circular dichroism (MCD) spectra at the Yb L$$_3$$ edge were measured in the mixed-valent heavy fermion compound YbAgCu$$_4$$ at high magnetic fields and low temperatures. The magnetic-field-temperature (H-T) phase boundary determined by the valence state is in very good agreement with that determined by the magnetization. It is clearly found that the metamagnetism of this compound is due to the field induced valence transition. A distinctive positive peak of the XMCD spectra appears in the vicinity of the white line of the absorption due to Yb$$^{3+}$$ state, while no feature is observed in the XMCD spectra corresponding to the Yb$$^{2+}$$ state. A small negative XMCD peak was observed at a lower energy and was attributed to the quadrupole trasition from theoretical calcuration, which explains its peculicar magnetic field dependence.

Journal Articles

Valence fluctuation in YbAgCu$$_4$$ at high Magnetic fields

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(1), p.015002_1 - 015002_2, 2012/01

 Times Cited Count:10 Percentile:40.34(Physics, Multidisciplinary)

The valence change of Yb ion in YbAgCu$$_4$$ was measured by means of X-ray absorption spectroscopy under high magnetic fields up to 35T. The valence state of Yb in YbAgCu$$_4$$ at 4.8K significantly increases at the metamagnetic transition. The saturation value of $$v$$ at 55T is evaluated as 2.97 using the relation $$Delta M/Delta v$$ at 35T. This value is in good agreement with $$v$$ for the related compound YbInCu$$_4$$ at high temperatures and the Yb valence in the localized high-field phase. We conclude that the metamagnetic transition in YbAgCu$$_4$$ arises from the valence transition, as theoretically predicted.

Journal Articles

Orbital magnetism in Cd$$_2$$Os$$_2$$O$$_7$$ studied by X-ray magnetic circular dichroism

Matsuda, Yasuhiro*; Her, J.-L.*; Michimura, Shinji*; Inami, Toshiya; Suzuki, Motohiro*; Kawamura, Naomi*; Mizumaki, Masaichiro*; Kindo, Koichi*; Yamaura, Junichi*; Hiroi, Zenji*

Physical Review B, 84(17), p.174431_1 - 174431_5, 2011/11

 Times Cited Count:20 Percentile:31.84(Materials Science, Multidisciplinary)

X-ray magnetic circular dichroism (XMCD) at the $$L$$$$_{2,3}$$-edge of Os has been investigated in the antiferromagneticphase of Cd$$_2$$Os$$_2$$O$$_7$$, which exhibits a metal-insulator transition around 227 K. According to the sum rule, the XMCD spectra at 10 and 37 T clearly show that the ratio between the orbital magnetic moment ($$m_{rm L}$$) and spinmagnetic moment ($$m_{rm S}$$) is $$m_{rm L}/m_{rm S} = 0.16 pm 0.02$$, and that $$m_{rm L}$$ and $$m_{rm S}$$ are coupled in parallel ($$m_{rm L}parallel m_{rm S}$$). These phenomena are unusual in that the expected ground state of Os$$^{5+}$$ (5$$d^3$$) is an orbital singlet in a cubic crystal field, and $$m_{rm L}$$and $$m_{rm S}$$ should be antiparallel for a less than half-filled system in accordance with Hund's third rule. It is likely that the spin-orbit coupling is important for explaining the observed orbital magnetism.

Journal Articles

Plasma regimes and research goals of JT-60SA towards ITER and DEMO

Kamada, Yutaka; Barabaschi, P.*; Ishida, Shinichi; Ide, Shunsuke; Lackner, K.*; Fujita, Takaaki; Bolzonella, T.*; Suzuki, Takahiro; Matsunaga, Go; Yoshida, Maiko; et al.

Nuclear Fusion, 51(7), p.073011_1 - 073011_11, 2011/07

 Times Cited Count:53 Percentile:6.87(Physics, Fluids & Plasmas)

Journal Articles

Heat transfer characteristics of the first wall with graphite sheet interlayer

Masaki, Kei; Miyo, Yasuhiko; Sakurai, Shinji; Ezato, Koichiro; Suzuki, Satoshi; Sakasai, Akira

Fusion Engineering and Design, 85(10-12), p.1732 - 1735, 2010/12

 Times Cited Count:1 Percentile:88.63(Nuclear Science & Technology)

Steady-state research is indispensable to establish scientific and technological basis for the next fusion devices. In JT-60, long pulse operation of up to 65s (OH) with a neutral beam heating power of $$sim$$12 MW (30s) was conducted to investigate the plasma behavior in several tens of seconds. However, the structure of the JT-60U first wall, which was composed of bolted graphite tiles and backings, restricted the flexibility of the plasma operation, because the first wall was not actively cooled. To improve the heat transfer characteristics of the first wall taking into account the cost, a candidate is to insert a graphite sheet between the graphite tile and the backing plate. Aiming at a design study for next fusion devices, the heat transfer characteristics of the first wall structure were investigated with a variety of graphite sheets and fixing-bolt torque conditions. The first wall mockup used for the experiment was composed of three CFC tiles (125(L) $$times$$110(W)$$times$$24(T) mm for each tile) and a cupper-alloy heat sink (377(L)$$times$$100(W)$$times$$20(T) mm) with two cooling channels of 10 mm diameter. Four types of the graphite sheets, 0.1-mm thickness PGS (Pyrolytic Graphite Sheet; Panasoic Co., Ltd), 0.2-mm PF (Perma Foil; Toyo Tanso Co., Ltd) 0.38-mm PF, 0.6-mm PF, were examined in the experiment. The heat load tests of the mockup were performed with the heat fluxes of 1 and 3 MW/m$$^{2}$$ on the JAERI electron beam irradiation stand. The experimental results showed that the structure with 0.1-mm thickness $$times$$ 3 PGSs had the highest heat transfer performance in the experiment. The first wall structure with the PGS sheets withstood the heat flux of 1 MW/m$$^{2}$$$$times$$100s. The maximum surface temperature of the CFC tile was 500$$^{circ}$$C. Furthermore, the results indicated that the structure could be used at the steady-state condition with the heat flux of $$sim$$1 MW/m$$^{2}$$. In the paper, detail of the results will be presented and discussed.

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