下周一的午餐交流会，将由戴民汉老师邀请的，来自日本国立放射线医学综合研究所的郑建研究员主讲。详情如下：
主题：第二十八讲——New geochemical tracers for source identification and long-term environmental behavior studies of plutonium and radiocesium released from the Fukushima nuclear accident（新地球化学示踪方法研究福岛核事故释放的放射性钚和铯的源识别和长期环境行为）
主讲人：Prof. Jian Zheng, Research Center for Radiation Protection, National Institute of Radiological Sciences
时间：2014年1月19日（星期一）11:40-13:30（12:20开讲）
地点：周隆泉楼一楼多功能厅
郑建老师个人简历请见附件。
讲座摘要：The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released large amounts of radionuclides into the environment. In addition to the atmospheric releases, the release of highly contaminated water from the damaged reactor buildings resulted in the direct discharges of radionuclides into the sea. It has been estimated that the total amount of 137Cs released from the FDNPP accident to the atmosphere ranged from 15-35 PBq. For the refractory actinides, although in a tiny amount, the release of Pu isotopes has been detected in various environmental samples, such as soil, litter, aerosol, black substance and river sediment. The released radioactive materials posed radiation threat to human society. Thus, source identification of radioactive contamination and long-term environmental behavior of released radioactive materials are important issues of study after the FDNPP accident.
Since the FDNPP accident, intensive studies on the distribution of released fission products, in particular 134Cs and 137Cs, in the environment have been conducted, and the activity ratio of 134Cs/ 137Cs has been widely used as a tracer for contamination source identification. However, due to the short half-life of 134Cs (2.06 y), this tracer will become unavailable in the near future. Thus, for long-term environmental behavior studies of the released radionuclides, new tracers which can be used in a time scale of several tens-years or hundred years are highly required. In this work, we discuss new geochemical tracers, such as Pu isotope ratios (240Pu / 239Pu and 241Pu/239Pu) and radioactive Cs isotope ratios (135Cs/137Cs and 135Cs/ 133Cs) for contamination source identification and long-term environmental studies of Pu and Cs released from the FDNPP accident. To establish the feasibility of the proposed tracers, we identified the isotopic compositions of radioactive Cs and Pu isotopes released from the FDNPP accident, and estimated the released amounts of 135Cs and Pu isotopes. The potential applications of the obtained FDNPP-sourced Cs and Pu fingerprints in the study of long-term environmental behavior of the released radioactive materials will be discussed.
本次午餐会将为报名参加的师生提供午餐，所有午餐会的报名都通过网络进行。请老师同学们访问MEL网页（http:/lecture.asp?id=1），在本次午餐会的“报名”一栏填写并提交。
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1月16日（本周五）下午4点为截止报名时间，总报名人数限制在100名以内。如未及时报上名，可于12:20直接到场听报告。如已报名但因事不能参加，也请在周五下午4点前告知。
