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Journal Articles

Simultaneous determination of neutron-induced fission and radiative capture cross sections from decay probabilities obtained with a surrogate reaction

P$'e$rez S$'a$nchez, R.*; Jurado, B.*; M$'e$ot, V.*; Roig, O.*; Dupuis, M.*; Bouland, O.*; Denis-Petit, D.*; Marini, P.*; Mathieu, L.*; Tsekhanovich, I.*; et al.

Physical Review Letters, 125(12), p.122502_1 - 122502_5, 2020/09

 Times Cited Count:1 Percentile:41.09(Physics, Multidisciplinary)

Journal Articles

Intercomparison of numerical atmospheric dispersion prediction models for emergency response to emissions of radionuclides with limited source information in the Fukushima Dai-ichi Nuclear Power Plant accident

Iwasaki, Toshiki*; Sekiyama, Tsuyoshi*; Nakajima, Teruyuki*; Watanabe, Akira*; Suzuki, Yasushi*; Kondo, Hiroaki*; Morino, Yu*; Terada, Hiroaki; Nagai, Haruyasu; Takigawa, Masayuki*; et al.

Atmospheric Environment, 214, p.116830_1 - 116830_11, 2019/10

 Times Cited Count:1 Percentile:82.72(Environmental Sciences)

The utilization of numerical atmospheric dispersion prediction (NDP) models for accidental discharge of radioactive substances was recommended by a working group of the Meteorological Society of Japan. This paper is to validate the recommendation through NDP model intercomparison in the accidental release from the Fukushima Dai-ichi Nuclear Power Plant in 2011. Emission intensity is assumed to be constant during the whole forecast period for the worst-case scenario unless time sequence of emission is available. We expect to utilize forecasts of surface air contaminations for preventions of inhalations of radioactive substances, and column-integrated amounts for mitigation of radiation exposure associated with wet deposition. Although NDP forecasts have ensemble spread, they commonly figure out relative risk in space and time. They are of great benefit to disseminating effective warnings to public without failure. The multi-model ensemble technique may be effective to improve the reliability.

Journal Articles

Effects of the nuclear structure of fission fragments on the high-energy prompt fission $$gamma$$-ray spectrum in $$^{235}$$U($$n_{rm th},f$$)

Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, R.; L$'e$guillon, R.; Ogawa, Tatsuhiko; Soldner, T.*; K$"o$ster, U.*; Pollitt, A.*; Hambsch, F.-J.*; et al.

Physical Review C, 100(4), p.044610_1 - 044610_7, 2019/10

 Times Cited Count:3 Percentile:50.15(Physics, Nuclear)

Journal Articles

International challenge to model the long-range transport of radioxenon released from medical isotope production to six Comprehensive Nuclear-Test-Ban Treaty monitoring stations

Maurer, C.*; Bar$'e$, J.*; Kusmierczyk-Michulec, J.*; Crawford, A.*; Eslinger, P. W.*; Seibert, P.*; Orr, B.*; Philipp, A.*; Ross, O.*; Generoso, S.*; et al.

Journal of Environmental Radioactivity, 192, p.667 - 686, 2018/12

 Times Cited Count:4 Percentile:66.2(Environmental Sciences)

It is very important to understand the impact for CTBT stations caused by radioxenon emitted from medical isotope production facilities for detection of underground nuclear tests. Predictions of the impact on six CTBT radionuclide stations in the Southern Hemisphere of radioxenon emitted from the medical isotope production facility in Australia were carried out by participants from ten nations using ATM (Atmospheric Transport Modeling) based on the emission data of radioxenon from this facility, as part of study on impact of radioxenon emitted from medical isotope production facilities on CTBT radionuclide stations.

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:11 Percentile:29.77(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

A New detector system for the measurement of high-energy prompt $$gamma$$-rays for low-energy neutron induced fission

Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, R.; L$'e$guillon, R.*; Ogawa, Tatsuhiko; Soldner, T.*; Hambsch, F.-J.*; A$"i$che, M.*; Astier, A.*; et al.

Nuclear Instruments and Methods in Physics Research A, 906, p.88 - 96, 2018/10

 Times Cited Count:3 Percentile:45.23(Instruments & Instrumentation)

We have developed a new setup to measure prompt fission $$gamma$$-ray spectra in neutron induced fission up to energies sufficient to reveal the structure associated with giant dipole resonances of fission fragments. The setup consists of multi-wire proportional counters, to detect both fission fragments in coincidence, and two large volume (101.6 mm in diameter and 127.0 mm in length) LaBr$$_{3}$$(Ce) scintillators, to measure the $$gamma$$-rays. The setup was used to obtain the prompt fission $$gamma$$-ray spectrum for thermal neutron induced fission of $$^{235}$$U at the PF1B cold-neutron beam facility of the Institut Laue-Langevin, Grenoble, France. We have successfully measured the $$gamma$$-ray spectrum up to energies of about 20 MeV, what extends the currently known $$gamma$$-ray spectrum limit to higher energies by approximately a factor of two.

Journal Articles

Atmospheric modeling of $$^{137}$$Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of Japan

Kitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.

Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07

 Times Cited Count:12 Percentile:26.05(Meteorology & Atmospheric Sciences)

We compared seven atmospheric transport model results for $$^{137}$$Cs released during the Fukushima Daiichi Nuclear Power Plant accident. All the results had been submitted for a model intercomparison project of the Science Council of Japan in 2014. We assessed model performance by comparing model results with observed hourly atmospheric concentrations of $$^{137}$$Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for $$^{137}$$Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated $$^{137}$$Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated $$^{137}$$Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced $$^{137}$$Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.

Journal Articles

Measurement of high-energy prompt $$gamma$$-rays from neutron induced fission of U-235

Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, R.; L$'e$guillon, R.; Ogawa, Tatsuhiko; Soldner, T.*; Hambsch, F.-J.*; Astier, A.*; Pollitt, A.*; et al.

EPJ Web of Conferences, 146, p.04036_1 - 04036_4, 2017/09

 Times Cited Count:3 Percentile:5.65

The measurement of the prompt fission $$gamma$$-ray spectrum (PFGS) is quite important to study the de-excitation process of neutron-rich fission fragments as well as to generate data required to design a generation-IV reactors. The PFGS measured for spontaneous fission of $$^{252}$$Cf shows a broad hump at energies more than 8 MeV. This is interpreted as a giant dipole resonance (GDR) of the fragments centered around 15 MeV. To understand how the GDR is populated in the fission process, one needs to measure the PFGS for the reactions with the mass yields different from the spontaneous fission of $$^{252}$$Cf, such as (n,f). The measurements of the PFGS for (n,f), however, are limited less than 9 MeV even in the recent experiment. This prompts us to make a new measurement to extend the know PFGS up to 20 MeV. The measurement has been carried out at the PF1B beam line of Institut Laue-Langevin. In this contribution we will present the results obtained the measurement.

Oral presentation

Environmental dynamics analysis of $$^{137}$$Cs due to the Fukushima Daiichi Nuclear Power Station accident based on the intercomparison of atmospheric dispersion models

Morino, Yu*; Kitayama, Kyo*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.

no journal, , 

For the evaluation of the validity and variability of atmospheric transport model results, we compared results of seven models submitted for the model inter-comparison project of Science Council of Japan to simulate $$^{137}$$Cs released from the Fukushima Daiichi Nuclear Power Plant. Model reproducibility was assessed with the observed hourly atmospheric concentrations of $$^{137}$$Cs in Tohoku and Kanto regions. Among nine plumes from 12 to 21 in March 2011, performance of the models was the best for the plume which dispersed over the Kanto region in 15 March. The models generally reproduced the observed $$^{137}$$Cs concentrations in plumes which widely spread inland of Tohoku or Kanto regions. By contrast, the models largely underestimated the observed $$^{137}$$Cs concentrations for the case which passed coastal areas of Japan. Ensemble average of seven models showed reasonable performance for most of plumes, and no individual models reproduced better than the ensemble average.

Oral presentation

Model inter-comparison of atmospheric Cs-137 from the Fukushima Daiichi Nuclear Power Plant accident

Kitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.

no journal, , 

For the evaluation of the validity and variability of atmospheric transport model results, we compared results of seven models submitted for the model inter-comparison project of Science Council of Japan to simulate $$^{137}$$Cs released from the Fukushima Daiichi Nuclear Power Plant. Model reproducibility was assessed with the observed hourly atmospheric concentrations of $$^{137}$$Cs in Tohoku and Kanto regions. Among nine plumes from 12 to 21 in March 2011, performance of the models was the best for the plume which dispersed over the Kanto region in 15 March. The models generally reproduced the observed $$^{137}$$Cs concentrations in plumes which widely spread inland of Tohoku or Kanto regions. By contrast, the models largely underestimated the observed $$^{137}$$Cs concentrations for the case which passed coastal areas of Japan. Ensemble average of seven models showed reasonable performance for most of plumes, and no individual models reproduced better than the ensemble average.

Oral presentation

2nd atmospheric model intercomparison project for Fukushima Daiichi Nuclear Power Plant Accident on March 2011; 2nd FDNPP-MIP

Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Grahn, H.*; Br$"a$nnstr$"o$m, N.*; von Schoenberg, P.*; Kondo, Hiroaki*; Terada, Hiroaki; Nagai, Haruyasu; et al.

no journal, , 

The second intercomparison of atmospheric model targeting on the radionuclide (i.e. $$^{137}$$Cs) released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) on March 2011 is conducted. Thirteen atmospheric models, which include both the Lagrangian- and Eulerian-based dispersion models, participate in this model intercomparison project (MIP). The purposes of this MIP are to (1) understand the transport process of the radionuclide in atmosphere, (2) estimate the uncertainties in wet and dry deposition process among the models, (3) reveal the essential key processes to reproduce the plume of $$^{137}$$Cs, (4) assess the multi-model ensemble mean, and (5) obtain the knowledge for improving the physical processes of the models. To exclude the uncertainties of the model results originated from the emission inventory, all models used the same emission inventory. The meteorological data with fine spatiotemporal resolution, which was calculated by the Japanese operational weather forecast model coupled with the local ensemble transform Kalman Filter data assimilation system, was applied for all models to reduce the uncertainties originated from the difference in the meteorological field. As well as the comparison among the models, the comparison between the models and in-situ measurement from the national suspended particle matter (SPM) sampling network are conducted. The comparisons between the model results and the SPM data indicate that the $$^{137}$$Cs concentration near the FDNPP transported without precipitation process was relatively well reproduced by using the meteorological data with fine spatiotemporal resolution. On the contrary, $$^{137}$$Cs concentration accompanied with precipitation has large inter-model spread. In the presentation, we will discuss the more detailed analyses about the physical process to determine the $$^{137}$$Cs concentration.

Oral presentation

Model intercomparison study for atmospheric $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Plant Accident using 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.

no journal, , 

An intercomparison of atmospheric dispersion model targeting on the physical process of $$^{137}$$Cs released from the Fukushima Daiichi Nuclear Power Plant was conducted. Twelve atmospheric models participated in this project. To exclude the uncertainties of the model result due to the emission inventory and meteorological data, all models used the same emission and meteorological data. Concentration of $$^{137}$$Cs from the national suspended particle matter monitoring network and the deposition density by the aircraft were used for the comparison between results of the model and observation. Our analyses elucidated the figure of merit in space (FMS) of the model ensemble mean was improved from a previous model intercomparson about the accumulated deposition. The model ensemble mean captured approximately 36% of the observed high concentration. The inter-model spread of the capture rate was from 8% to 38%. It was originated from the difference in deposition and diffusion processes among the models.

Oral presentation

Model intercomparison project for $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Station Accident using identical meteorological data and source term

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

no journal, , 

no abstracts in English

Oral presentation

Model intercomparison project for cesium ($$^{137}$$Cs) from the Fukushima Daiichi Nuclear Power Station Accident using identical meteorological data and source term

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

no journal, , 

no abstracts in English

Oral presentation

Measurement of high-energy prompt fission $$gamma$$-rays from neutron induced fission of $$^{235}$$U

Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, R.; L$'e$guillon, R.; Ogawa, Tatsuhiko; Soldner, T.*; Hambsch, F.-J.*; A$"i$che, M.*; Astier, A.*; et al.

no journal, , 

The Japanese government has a plan to remove the fuel debirs for the full deconstruction of Fukushima I Nuclear Power Plants. The fuel debris must be removed without reaching criticality. However, it is difficult to monitor the fission rate due to the background $$gamma$$ rays coming from long-lived fission products. We are proposing to develop a system based on the use of the high-energy prompt fission $$gamma$$ rays, whose energies are high enough to be separated from the background. To design the system, it is essential to know the spectrum of prompt fission $$gamma$$ rays up to more than 7 MeV for $$^{235}$$U($$n, f$$). So far, no data are available in the $$gamma$$-ray energy range larger than 7 MeV. This prompted us to make a new measurement to extend the $$gamma$$-ray spectrum limit to higher energies. The measurement has been carried out at the PF1b cold-neutron beam facility of the Institut Laue-Langevin. In this contribution we will present the results obtained the measurement.

Oral presentation

Measurement of high-energy prompt fission $$gamma$$ rays in $$^{235}$$U(n$$_{th}$$,f)

Ogawa, Tatsuhiko; Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, R.; L$'e$guillon, R.*; Soldner, T.*; Hambsch, F.-J.*; A$"i$che, M.*; Astier, A.*; et al.

no journal, , 

Measurement of $$gamma$$-rays emitted from fission of actinide has been conducted for radiation transport analysis in reactors, safety of spent fuel, and fundamental nuclear physics. In earlier studies, $$gamma$$-rays up to 8 MeV were measured because they are those emitted by fission fragments at excited states. According to some theoretical studies, however, some fission fragments have excitation energy up to 20 MeV and they emit $$gamma$$-rays above 8 MeV. In this study, the $$gamma$$-rays produced by fission of $$^{235}$$U induced by thermal neutrons were measured with LaBr scintillators at the high-flux reactor in the Institut Laue Langevin. The obtained $$gamma$$-ray spectrum agreed with the earlier measurement below 8 MeV, forms a bump above 10 MeV, and smoothly continued up to 20 MeV. The measurement in this study clarified the $$gamma$$-ray energy spectrum attributed to fission reactions up to 20 MeV in case of $$^{235}$$U(n$$_{th}$$,f).

Oral presentation

Measurement of high-energy prompt fission $$gamma$$ rays in $$^{235}$$U(n$$_{th}$$,f)

Ogawa, Tatsuhiko; Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, R.; L$'e$guillon, R.*; Soldner, T.*; Hambsch, F.-J.*; A$"i$che, M.*; Astier, A.*; et al.

no journal, , 

Measurement of $$gamma$$-rays emitted from fission of actinide has been conducted for radiation transport analysis in reactors, safety of spent fuel, and fundamental nuclear physics. In earlier studies, $$gamma$$-rays up to 8 MeV were measured because they are those emitted by fission fragments at excited states. According to some theoretical studies, however, some fission fragments have excitation energy up to 20 MeV and they emit $$gamma$$-rays above 8 MeV. In this study, the $$gamma$$-rays produced by fission of $$^{235}$$U induced by thermal neutrons were measured with LaBr scintillators at the high-flux reactor in the Institut Laue Langevin. The obtained $$gamma$$-ray spectrum agreed with the earlier measurement below 8 MeV, forms a bump above 10 MeV, and smoothly continued up to 20 MeV. The measurement in this study clarified the $$gamma$$-ray energy spectrum attributed to fission reactions up to 20 MeV in case of $$^{235}$$U(n$$_{th}$$,f).

Oral presentation

Measurement of high-energy prompt fission $$gamma$$-ray emission in $$^{235}$$U ($$n_{rm th},f$$)

Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, R.; L$'e$guillon, R.*; Ogawa, Tatsuhiko; Soldner, T.*; K$"o$ster, U.*; Hambsch, F.-J.*; Kawano, Toshihiko*; et al.

no journal, , 

Oral presentation

Measurement of high-energy prompt fission gamma-rays for $$^{235}$$U(n$$_{rm th}$$,f)

Nishio, Katsuhisa; Makii, Hiroyuki; Hirose, Kentaro; Orlandi, R.; L$'e$guillon, R.*; Ogawa, Tatsuhiko; Soldner, T.*; K$"o$ster, U.*; Pollitt, A.*; Hambsch, F.-J.*; et al.

no journal, , 

no abstracts in English

Oral presentation

Review of model intercomparison projects (MIPs) of atmospheric dispersion model for $$^{137}$$Cs emitted from Fukushima Daiichi Nuclear Power Plant; MIPs with identical source term and meteorological data

Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kadowaki, Masanao; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; et al.

no journal, , 

Two Model Intercomparison of Projects (MIPs) of atmospheric dispersion model targeting on $$^{137}$$Cs released from Fukushima Daiichi Nuclear Power Plant (FDNPP) on March 2011 were conducted. Both MIPs were conducted using an identical source term of $$^{137}$$Cs, identical meteorological data, and the same horizontal grid resolution (3 km and 1 km) to exclude the uncertainties of the model originated from them. Our analyses indicated that most of the model well simulated the atmospheric $$^{137}$$Cs obtained from the operational aerosol sampling of the national suspended particle matter network. Our analyses also indicated that meteorological data were most critical for reproducing the atmospheric $$^{137}$$Cs events, and the extent of the horizontal diffusion and the deposition were critical if the meteorological field was reasonably simulated. The comparison of the results between the two MIPs elucidated that the fine grid resolution is required to simulate atmospheric $$^{137}$$Cs in the vicinity of FDNPP, but the use of the fine grid resolution does not always improve the performance of the models especially for areas distant from the FDNPP. The results of both MIPs elucidated that the good performance of some models improved the performance of the multimodel, highlighting the advantage of using a multimodel ensemble.

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