基于TOA萃取色层的土壤中238Pu/239,240Pu活度比的分析方法

核设施周边环境土壤样品中²³⁸Pu/^239,240Pu活度比的信息特征可用于评估核活动，为了获得准确的核素比，需要建立²³⁸Pu/^239,240Pu活度比的分析方法。在三正辛胺（TOA）萃取法分析Pu含量的基础上，考察了盐酸和硝酸洗涤以及洗涤用量对U、Th、Am等杂质元素的去除情况，并引入共沉淀步骤进行前处理流程的优化，建立起一个基于TOA萃取色层的土壤样品中²³⁸Pu/^239,240Pu活度比的分析方法。当土壤样品量为25 g时，该方法Pu的化学回收率大于70%，U、Th的去污因子大于10⁴，Am的去污因子大于10³，²³⁸Pu的最低检测比活度为（6.0±1.6）×10^-6 Bq/g，^239,240Pu的最低检测比活度为（6.4±0.4）×10^-6 Bq/g(n=3)。该方法可应用于环境土壤样品中²³⁸Pu/^239,240Pu活度比的分析，为军控核查和环境监测提供技术支持。

Analytical Method for 238 Pu/239 ,240 Pu Activity Ratio Using TOA Extraction Chromatography

Institute of Materials, China Academy of Engineering Physics, Jiangyou 621907, ChinaAbstract:The characteristic of the²³⁸Pu/^239,240Pu activity ratio in the soil samples around nuclear facilities can be used to assess the nuclear activities. In order to obtain an accurate isotope ratio, an analytical method for²³⁸Pu/^239,240Pu activity ratio needs to be established. Based on the analysis procedure of plutonium activity concentration with TOA extraction, this paper was focused on the removal of impure elements such as U, Th and Am by scrubbing with proper amount of nitric acid and hydrochloric acid solutions. A co-precipitation step was introduced to optimize the pretreatment process, and a new procedure for determination of²³⁸Pu/^239,240Pu activity ratio in soils was developed. For 25 g soil sample, the chemical recovery of Pu of the procedure is greater than 70%, and the decontamination factors of U, Th and Am are greater than 10⁴, 10⁴ and 10³, respectively. The minimum detection activity concentrations are found to be (6.0±1.6)×10^-6 Bq/g for ²³⁸Pu and (6.4±0.4)×10^-6 Bq/g(n=3) for ^239,240Pu. This method can be widely applied to the analysis of²³⁸Pu/^239,240Pu activity ratio in environmental soil samples and thus provide technical support for arms control verification and environmental monitoring.