| Project/Area Number |
15310035
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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 |
Risk sciences of radiation/Chemicals
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| Research Institution | Kanazawa University |
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Principal Investigator |
NAKANISHI Takashi Graduate School of Natural Science and Technology, Professor, 自然科学研究科, 教授 (00019499)
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| Co-Investigator(Kenkyū-buntansha) |
YOKOYAMA Akihiko Graduate School of Natural Science and Technology, Associate Professor, 自然科学研究科, 助教授 (80230655)
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| Project Period (FY) |
2003 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥10,400,000 (Direct Cost: ¥10,400,000)
Fiscal Year 2006: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2005: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2004: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2003: ¥6,800,000 (Direct Cost: ¥6,800,000)
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| Keywords | samples exposed to atom-bombing / atomic-bomb neutrons / neutron-induced radioactivity / Eu-152 / Ac-227 / fluorescent X-ray of Sm / Euの化学分離精製 |
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| Research Abstract |
The current dosimetry system (DS) to calculate neutron dose received by the survivor of atom-bombing in Hiroshima and Nagasaki must be proved its validity by reproducing specific radioactivity of neutron-induced radionuclides in samples exposed to atomic bomb in Hiroshima or Nagasaki. But, for the samples exposed to atomic-bomb neutrons at positions beyond 1170 m from the explosion point of Nagasaki atomic bomb, no data have been obtained for specific radioactivity of radionuclides induced with atomic-bomb neutrons.
In the present research started in 2003, highly accurate value of specific radioactivity of europium (Eu)-152 (half-life 13.542 y) was aimed to obtain for a sample exposed to atomic-bomb explosion at position 1595 m from the explosion point of Nagasaki atomic bomb.
About 19 kg of the exposed sample was subjected for the chemical separation of Eu, and crude specimen enriched in Eu thus obtained was measured with a gamma-ray spectrometer. As a result of the measurement, it beca
… More
me clear that the measurement of ultra-low-level radioactivity of residual Eu-152 was seriously interfered with daughter nuclides of actinium (Ac)-227. Hence, chemical procedure to remove Ac from Eu was developed in the present research, and purification of the crude specimen enriched in Eu was carried out. The refined Eu-fraction was counted by low-energy photon spectrometer (LEPS) by which samarium (Sm) K-X ray emitted after electron-capture decay of Eu-152 was measured. The result of LEPS measurement showed that measured specific radioactivity of Eu-152 was about ten times higher than the calculated one by DS methodology.
For the reason of high measured/calculated ratio, incremental fluorescent X-ray was suspected, i.e. Sm in the counting specimen are excited with alpha-and beta-rays from the specimen to generate Sm-K-X ray, and a systematic study on the yield of fluorescent X-ray was carried out. The measured value by LEPS was then corrected for fluorescent X-ray, but it was found that the correction was not effective to lower the measured/calculated ratio. The refined Eu-fraction was then measured with ultra-low-level gamma spectrometer at Ogoya Underground Laboratory (OUL) of Kanazawa University. It was found that LEPS result and OUL result agreed well with each other. Hence, the reason of the disagreement between measured value and calculated value is still an open question. Less
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