Reevaluation of atomic-bomb neutron fluence through purification of europium separated from samples exposed to atom-bombing

通过纯化从原子弹爆炸样品中分离出的铕来重新评估原子弹中子注量

• 批准号: 15310035
• 负责人: NAKANISHI Takashi
• 金额: $ 6.66万
• 依托单位: Kanazawa University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-15310035/
• 关键词: 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

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

目前用于计算广岛和长崎原子弹爆炸幸存者所受中子剂量的剂量学系统（DS），必须通过再现广岛和长崎原子弹爆炸后样品中中子感生放射性核素的比放射性来验证其有效性。但是，对于在距离长崎原子弹爆炸点1170 m以外的位置暴露于原子弹中子的样品，没有获得原子弹中子感生的放射性核素的比放射性数据。铕（Eu）-152比放射性高精度测定（半衰期13.542 y）的目的是获得暴露于原子-在距离长崎原子弹爆炸点1595米处爆炸。对约19公斤暴露样品进行Eu的化学分离，用γ射线光谱仪测量由此获得的富集Eu的粗样品。测量的结果是， ...更多信息 结果表明，锕（Ac）-227子体核素对Eu-152的超低放射性测量产生了严重干扰。因此，在本研究中开发的化学程序，以消除Ac从铕，富集铕的粗样品的纯化进行。用低能光子谱仪（LEPS）对Eu-152的提纯组分进行计数，测量Eu-152电子俘获衰变后的Sm K-X射线。LEPS测量结果表明，Eu-152的比放射性测量值比DS法计算值高10倍左右，由于测量值与计算值的比值较高，因此怀疑存在增量荧光X射线，即计数样品中的Sm被样品中的α和β射线激发，产生Sm-K-X射线，并对荧光X射线产额进行了系统的研究。然后，对LEPS的测量值进行荧光X射线校正，但发现校正对降低测量/计算比无效。然后在金泽大学的小谷地下实验室（OUL）用超低水平伽马能谱仪测量了精制的Eu-部分。结果表明，LEPS结果与OUL结果吻合较好。因此，测量值和计算值之间不一致的原因仍然是一个悬而未决的问题。少

项目成果

放射化学用語辞典

放射化学术语词典

• 发表时间: 2006
• 作者: 五十嵐香織;榎本秀一;榎本秀一
• 通讯作者: 榎本秀一

^<152>Eu measurements in Japan

^<152>日本的欧盟测量

• 发表时间: 2005
• 期刊: In : Reassessment of the Atomic Bomb Radiation Dosimetry for Hiroshima and Nagasaki - Dosimetry System 2002 - Radiation Effects Research Foundation, Hiroshima, Japan(Eds : R.W. Young and G.D. Kerr) Vo1.2
• 作者: K.Shizuma;T.Nakanishi
• 通讯作者: T.Nakanishi

An upper limit to interstellar ^<244>Pu abundance as deduced from radiochemical search in deep-sea sediment : An account

根据深海沉积物放射化学搜索推断出的星际 ^<244>Pu 丰度上限：一项说明

• 发表时间: 2007
• 期刊: Journal of Radioanalytical and Nuclear Chemistry 272(2)
• 作者: M.Paul;T;Nakanishi;他9名
• 通讯作者: 他9名

細谷梨沙, 和泉宏謙, 能村哲平, 横山明彦, 中西 孝: "Euの化学分離と高純度化による原爆被曝試料の極微弱Eu-152残留放射能の測定"第5回「環境放射能」研究会要旨論文集. 5. 10-10 (2004)

Risa Hosoya、Hiroken Izumi、Teppei Nomura、Akihiko Yokoyama、Takashi Nakanishi：“通过化学分离和纯化 Eu 来测量原子弹暴露样品中极弱的 Eu-152 残留放射性”第 5 届“环境放射性”研究摘要集5. 10-10 (2004)

Search for α-decay of 229mTh produced from 229Ac β-decay following 232Th(γ, p2n) reaction

搜索 232Th(γ, p2n) 反应后 229Ac β 衰变产生的 229mTh 的 α 衰变

• DOI: 10.1524/ract.2005.93.9-10.507
• 发表时间: 2005
• 作者: H. Kikunaga;Y. Kasamatsu;K. Takamiya;T. Mitsugashira;M. Hara;T. Ohtsuki;H. Yuki;A. Shinohara;S. Shibata;N. Kinoshita;A. Yokoyama;T. Nakanishi
• 通讯作者: T. Nakanishi