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Journal Articles

Radiation monitoring in the residential environment; Time dependencies of air dose rate and $$^{137}$$Cs inventory

Yoshimura, Kazuya; Nakama, Shigeo; Fujiwara, Kenso

Journal of Radiation Protection and Research, 47(1), p.30 - 38, 2022/03

Journal Articles

Impacts of freeze-thaw processes and subsequent runoff on $$^{137}$$Cs washoff from bare land in Fukushima

Igarashi, Yasunori*; Onda, Yuichi*; Wakiyama, Yoshifumi*; Yoshimura, Kazuya; Kato, Hiroaki*; Kozuka, Shohei*; Manome, Ryo*

Science of the Total Environment, 769, p.144706_1 - 144706_9, 2021/05

 Times Cited Count:0 Percentile:0(Environmental Sciences)

Journal Articles

Calculations for ambient dose equivalent rates in nine forests in eastern Japan from $$^{134}$$Cs and $$^{137}$$Cs radioactivity measurements

Malins, A.; Imamura, Naohiro*; Niizato, Tadafumi; Takahashi, Junko*; Kim, M.; Sakuma, Kazuyuki; Shinomiya, Yoshiki*; Miura, Satoru*; Machida, Masahiko

Journal of Environmental Radioactivity, 226, p.106456_1 - 106456_12, 2021/01

 Times Cited Count:0 Percentile:0(Environmental Sciences)

Journal Articles

Simulation analysis of the Compton-to-peak method for quantifying radiocesium deposition quantities

Malins, A.; Ochi, Kotaro; Machida, Masahiko; Sanada, Yukihisa

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.147 - 154, 2020/10

Journal Articles

Measurement of cesium isotopic ratio by thermal ionization mass spectrometry for neutron capture reaction studies on $$^{135}$$Cs

Shibahara, Yuji*; Nakamura, Shoji; Uehara, Akihiro*; Fujii, Toshiyuki*; Fukutani, Satoshi*; Kimura, Atsushi; Iwamoto, Osamu

Journal of Radioanalytical and Nuclear Chemistry, 325(1), p.155 - 165, 2020/07

 Times Cited Count:0 Percentile:0.01(Chemistry, Analytical)

The measurements of isotopic ratios of Cs samples by thermal ionization mass spectrometry were performed for the analysis of their samples used to evaluate nuclear data obtained for $$^{135}$$Cs. To obtain a high intensity and stable ion beam, the effects of additive agents on the ionization of Cs were examined. The effect of silicotungstic acid on the ionization of Cs was the largest among the additive agents studied in the present study, while the silicotungstic acid also showed the largest isobaric interference of polyatomic ions. It was demonstrated that as small as 2$$times$$10$$^{-13}$$ g of a Cs sample was sufficient to achieve the analytical precision required to measure the $$^{135}$$Cs/$$^{137}$$Cs ratio in the case where an additive agent of TaO/glucose was employed. After examining of the analytical conditions, such as the interference effect due to Ba, the measurements of the isotopic ratios of two Cs samples used in our study using TIMS were conducted, and it was discussed how much the ratios contributed to evaluation of the neutron capture cross-section of $$^{135}$$Cs.

Journal Articles

Vertical and horizontal distributions of $$^{137}$$Cs on paved surfaces affected by the Fukushima Dai-ichi Nuclear Power Plant accident

Yoshimura, Kazuya; Watanabe, Takayoshi; Kurikami, Hiroshi

Journal of Environmental Radioactivity, 217, p.106213_1 - 106213_6, 2020/06

 Times Cited Count:3 Percentile:39.03(Environmental Sciences)

Journal Articles

Measurements of thermal-neutron capture cross-section of cesium-135 by applying mass spectrometry

Nakamura, Shoji; Shibahara, Yuji*; Kimura, Atsushi; Iwamoto, Osamu; Uehara, Akihiro*; Fujii, Toshiyuki*

Journal of Nuclear Science and Technology, 57(4), p.388 - 400, 2020/04

 Times Cited Count:1 Percentile:23.13(Nuclear Science & Technology)

The thermal-neutron capture cross-section ($$sigma_{0}$$) and resonance integral(I$$_{0}$$) were measured for the $$^{135}$$Cs(n,$$gamma$$)$$^{136}$$Cs reaction by an activation method and mass spectrometry. We used $$^{135}$$Cs contained as an impurity in a normally available $$^{137}$$Cs standard solution. An isotope ratio of $$^{135}$$Cs and $$^{137}$$Cs in a standard $$^{137}$$Cs solution was measured by mass spectrometry to quantify $$^{135}$$Cs. The analyzed $$^{137}$$Cs samples were irradiated at the hydraulic conveyer of the research reactor in Institute for Integral Radiation and Nuclear Science, Kyoto University. Wires of Co/Al and Au/Al alloys were used as neutron monitors to measure thermal-neutron fluxes and epi-thermal Westcott's indices at an irradiation position. A gadolinium filter was used to measure the $$sigma_{0}$$, and a value of 0.133 eV was taken as the cut-off energy. Gamma-ray spectroscopy was used to measure induced activities of $$^{137}$$Cs, $$^{136}$$Cs and monitor wires. On the basis of Westcott's convention, the $$sigma_{0}$$ and I$$_{0}$$ values were derived as 8.57$$pm$$0.25 barn, and 45.3$$pm$$3.2 barn, respectively. The $$sigma_{0}$$ obtained in the present study agreed within the limits of uncertainties with the past reported value of 8.3$$pm$$0.3 barn.

Journal Articles

Land use types control solid wash-off rate and entrainment coefficient of Fukushima-derived $$^{137}$$Cs, and their time dependence

Wakiyama, Yoshifumi*; Onda, Yuichi*; Yoshimura, Kazuya; Igarashi, Yasunori*; Kato, Hiroaki*

Journal of Environmental Radioactivity, 210, p.105990_1 - 105990_12, 2019/12

 Times Cited Count:9 Percentile:62.46(Environmental Sciences)

Journal Articles

Activation measurement for thermal-neutron capture cross-section of Cesium-135

Nakamura, Shoji; Kimura, Atsushi; Iwamoto, Osamu; Shibahara, Yuji*; Uehara, Akihiro*; Fujii, Toshiyuki*

KURNS Progress Report 2018, P. 106, 2019/08

Under the ImPACT project, the neutron capture cross-section measurements of Cesium-135 ($$^{135}$$Cs) among the long-lived fission products have been performed at Kyoto University. This paper reports measurements of the thermal-neutron capture cross-section of $$^{135}$$Cs at the Kyoto University Research Reactor (KUR).

Journal Articles

Modelling the effect of mechanical remediation on dose rates above radiocesium contaminated land

Malins, A.; Kurikami, Hiroshi; Kitamura, Akihiro; Machida, Masahiko

Remediation Measures for Radioactively Contaminated Areas, p.259 - 272, 2019/00

Journal Articles

Analysis of $$^{135}$$Cs/$$^{137}$$Cs isotopic ratio for samples used for neutron capture cross section measurement project by thermal ionization mass spectrometry

Shibahara, Yuji*; Uehara, Akihiro*; Fujii, Toshiyuki*; Nakamura, Shoji; Kimura, Atsushi; Hales, B. P.; Iwamoto, Osamu

JAEA-Conf 2018-001, p.205 - 210, 2018/12

In the ImPACT project, high-precision mass analysis was performed on a $$^{137}$$Cs standard solution for using $$^{135}$$Cs included in the standard solution as an impurity to measure the $$^{135}$$Cs cross-sections. A $$^{137}$$Cs standard solution of only 10Bq (pg order) was analyzed, and the isotope ratio of $$^{135}$$Cs and $$^{137}$$Cs was obtained with an accuracy of 0.5%.

Journal Articles

Model intercomparison of atmospheric $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input data

Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qu$'e$lo, D.*; et al.

Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10

 Times Cited Count:19 Percentile:80.33(Meteorology & Atmospheric Sciences)

A model intercomparison of the atmospheric dispersion of $$^{137}$$Cs emitted following the Fukushima Daiichi Nuclear Power Plant accident was conducted by 12 models to understand the behavior of $$^{137}$$Cs in the atmosphere. The same meteorological data, horizontal grid resolution, and an emission inventory were applied to all the models to focus on the model variability originating from the processes included in each model. The multi-model ensemble captured 40% of the observed $$^{137}$$Cs events, and the figure-of-merit in space for the total deposition of $$^{137}$$Cs exceeded 80. Our analyses indicated that the meteorological data were most critical for reproducing the $$^{137}$$Cs events. The results also revealed that the differences among the models were originated from the deposition and diffusion processes when the meteorological field was simulated well. However, the models with strong diffusion tended to overestimate the $$^{137}$$Cs concentrations.

Journal Articles

Secondary radiocesium contamination of agricultural products by resuspended matter

Nihei, Naoto*; Yoshimura, Kazuya; Okumura, Taiga*; Tanoi, Keitaro*; Iijima, Kazuki; Kogure, Toshihiro*; Nakanishi, Tomoko*

Journal of Radioanalytical and Nuclear Chemistry, 318(1), p.341 - 346, 2018/10

 Times Cited Count:1 Percentile:17.98(Chemistry, Analytical)

Journal Articles

Examination of $$^{131}$$I and $$^{137}$$Cs releases during late phase of Fukushima Daiichi NPP accident by using $$^{131}$$I/$$^{137}$$Cs ratio of source terms evaluated reversely by WSPEEDI code with environmental monitoring data

Hidaka, Akihide; Yokoyama, Hiroya

Journal of Nuclear Science and Technology, 54(8), p.819 - 829, 2017/08


 Times Cited Count:9 Percentile:75.2(Nuclear Science & Technology)

To clarify what happened during the Fukushima accident, the phenomena within RPV and the discussion of ties with the environmental monitoring are very important. However, the previous study has not necessarily advanced until the present that passed almost six years from the accident. The present study investigated $$^{131}$$I and $$^{137}$$Cs release behaviors during the late phase of the accident based on $$^{131}$$I/$$^{137}$$Cs ratio of the source terms that were recently evaluated backward by WSPEEDI code based on environmental monitoring data. The $$^{131}$$I release from the contaminated water in the basement of 1F2 and 1F3 reactor buildings was evaluated to be about 10% of $$^{131}$$I source term. The increase in $$^{137}$$Cs release from March 21 to 23 and from March 30 to 31 could be explained by the release of CsBO$$_{2}$$ which is formed as a result of chemical reactions of Cs with B$$_{4}$$C due to re-ascension of the core temperature caused by slight shortage of the core cooling water.

Journal Articles

High-precision mass analysis of RI sample for cross-section measurements

Nakamura, Shoji; Shibahara, Yuji*; Uehara, Akihiro*; Fujii, Toshiyuki*; Kimura, Atsushi; Hales, B. P.; Iwamoto, Osamu

KURRI Progress Report 2016, P. 66, 2017/07

In the ImPACT project, high-precision mass analysis was performed on a $$^{137}$$Cs standard solution for using $$^{135}$$Cs included in the standard solution as an impurity to measure the $$^{135}$$Cs cross-sections. A $$^{137}$$Cs standard solution of only 10Bq (pg order) was analyzed, and the isotope ratio of $$^{135}$$Cs and $$^{137}$$Cs was obtained with an accuracy of 0.5%.

Journal Articles

Distribution of $$^{137}$$Cs on surfaces of buildings and building lots

Yoshimura, Kazuya; Fujiwara, Kenso; Saito, Kimiaki

KEK Proceedings 2016-8, p.67 - 71, 2016/10

This study evaluated the $$^{137}$$Cs inventory (Bq m$$^{-2}$$) on urban surfaces for eleven buildings and building lots in evacuation zone, and relative $$^{137}$$Cs inventory was obtained by dividing with the initial inventory on plane permeable field around the studied building. The relative $$^{137}$$Cs inventory was highest at plane permeable field (0.92), followed by paved ground (0.28) on January 13, 2015. Other surfaces such as roof, wall and window showed obviously small values less than 0.1, indicating that the contamination level of buildings was limited four years after the Fukushima Dai-ichi Nuclear Power Plant accident. Roof and paved ground showed different relative $$^{137}$$Cs inventories from those in the case of Europe after the Chernobyl Nuclear Power Plant accident, suggesting the importance of local parameterization considering the factors affects to the variation of relative $$^{137}$$Cs inventory.

Journal Articles

Migration behavior of particulate radioactive cesium species generated at ground surface

Tanaka, Tadao

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05

It is necessary to confirm that there is no significant radioactivity remaining on NPP site, for the site release beforehand. Cesium 137 ($$^{137}$$Cs) is the typical radionuclide caused from NPP. In this research, generation of particulate $$^{137}$$Cs species at ground surface and its migration behavior were examined. Migration experiments were carried out by a column method, in which deionized water was fed intermittently at the drying interval for 7 days into a sand layer contaminated with $$^{137}$$Cs. A portion of the $$^{137}$$Cs in the upper surface region, which formed particulate species by sorbing on fine particles, migrated into the deeper layer. Fine particle itself also was generated at the sand surface by weathering. The sand was weathered during the drying period, so that small amount of fine particles including $$^{137}$$Cs was newly dissociated from the sand. Such particulate $$^{137}$$Cs species may be accumulated slowly by repeated cycles of rainfall and drying, during long term.

Journal Articles

Development of a long-range atmospheric transport model for nuclear emergency and its application to the Chernobyl nuclear accident

Terada, Hiroaki; Chino, Masamichi

Proceedings of 2nd International Conference on Radioactivity in the Environment, p.15 - 18, 2005/10

The previous version of Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI) has been composed of mass-consistent wind field model WSYNOP and particle dispersion model GEARN. Because WSYNOP has no capability to predict meteorological fields, its accuracy and resolution depends on meteorological input data, and it is impossible to treat physical processes realistically. To improve these problems, an atmospheric dynamic model MM5 is introduced and applied to the Chernobyl accident for the verification. Two calculation cases are conducted, CASE-1 a calculation for European region Domain-1, and CASE-2 a domain nesting calculation for Domain-1 and the region around Chernobyl Domain-2. The air concentration and surface deposition of $$^{137}$$Cs calculated by CASE-1 agree well with the measurements by statistical analysis and comparison for the horizontal distribution. In the result of CASE-2, the detailed distribution of surface $$^{137}$$Cs deposition around Chernobyl which was impossible to calculate in CASE-1 is predicted with high accuracy.

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