2002 Fiscal Year Final Research Report Summary
Study on the Variation of Environmental Neutron Dose During a Solar Maximum Period and its Effect
| Project/Area Number |
12480133
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Nuclear engineering
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
NAKAMURA Takashi Tohoku University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (70026029)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAGI Shunji Mitsubishi Research Institute Co.Ltd., Researcher, 総合安全研究センター・原子力システム研究部, 研究員(研究職)
IWASAKI Tomohiko Tohoku University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (70184869)
BABA Mamoru Tohoku University, Cyclotron and Radioisotope Center, Professor, サイクロトロン・ラジオアイソトープセンター, 教授 (20005466)
NUNOMIYA Tomoya Tohoku University, Graduate School of Engineering, Japan Society for promotion of Science Researcher, 大学院・工学研究科, 日本学術振興会特別研究員
TAKADA Masashi National Institute of Radiological Sciences, Researcher, 国際宇宙医学研究センター, 研究員(研究職) (50291109)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Cosmic-Ray Neutrons / Solar Flare / Solar Activity / Dose / Energy Spectrum / Rem Counter / Liquid Organic Scintillator / Multi-Moderator Spectrometer |
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| Research Abstract |
The Cosmic-ray neutron spectrum and dose rate have been measured with three neutron detectors. Bonner sphere(Multi-moderator), high-sensitivity rem counter and NE213 organic liquid scintillator sequentially from October 2000 to March 2003, where the solar activity reaches a maximum. The neutron spectra have three distinct peaks, thermal energy peak, evaporation peak around a few MeV and cascade peak around 100 MeV. There can be seen a tendency that a cascade peak relatively increases on the day of higher neutron flux compared with other two peaks. The neutron flux and dose rate show a clear negative correlation with the atmospheric pressure according to the exponential attenuation during the observation period, and also a Forbush decrease in some cases just after big solar flares. The neutron fluxes above 20 MeV Measured with the Bonner sphere and the NE213 gave almost the same values during the observation period to be about 2 x 10^<-3> n cm^<-2>s^<-1>.
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