核裂变产物对地表环境Ba同位素体系的影响

Effect of Nuclear Fission Products on Ba Isotope System in the Earth Surface Environment

近年来,钡(Ba)同位素研究在地表生态环境领域的应用越来越广泛。然而,上世纪的核试验和核事故泄露在地表环境中释放了大量含有人工核素Ba的裂变产物,它们可能会改变地表自然样品的Ba同位素特征,从而不利于Ba同位素研究在该领域的发展和应用,因此需要评估其影响程度。本文根据Ba同位素最新研究进展和国际上已发表的数据,总结不同地表储库中Ba同位素的分布特征,利用核裂变理论计算核试验裂变产物的Ba同位素组成及裂变成因Ba的加入对环境样品Ba同位素组成的改变程度。结果显示,自然样品加入占其Ba含量0.01%的裂变成因Ba,能显著改变它的Ba同位素组成,因此需要引起重视。此外,基于计算结果发现,同时测量样品δ137/134 Ba和δ138/134 Ba值,根据其异常特征可以有效地排除受到沾染的样品。

In the recent years,the application of Ba isotope researches in the ecological and environmental fields on earth surface has become more and more extensive.However,a large amount of fission materials,which include fissiogenic Ba decayed from radioactive fission products,have been released to the environment through nuclear weapons testing in the last century,nuclear accidents,nuclear power plant operations as well as discharge from the reprocessing plants of spent nuclear fuel.These fissiogenic Ba could contaminate the natural samples on the surface and modify their Ba isotope characteristics,which is not conductive to development and application of Ba isotope research in this field.However,few studies have been focused on the influence of fissiogenic Ba to the environment.According to the previous and new data available,the Ba isotope distribution in different earth surface reservoirs was reviewed in this paper.Meanwhile,on the basis of nuclear fission theory,Ba isotope compositions of the fission products and their effect on the natural Ba compositions were calculated.The result shows that the natural Ba compositions can be obviously modified by fissiogenic Ba contamination,thus need to be payed attention.In addition,based on the calculation results,it was found that the simultaneous measurement ofδ137/134 Ba andδ138/134 Ba values could effectively exclude the contaminated samples,according to their abnormal characteristics.