中文摘要：

延迟符合法测量220 Rn和219 Rn是间接测量天然水中224 Ra和223 Ra的方法,能提供河口海洋混合区海底地下水流出情况及水与土壤相互作用的示踪信息。在实际测量计算中会用到Moore偶然符合修正方法,然而研究发现,Giffin和Moore方法还存在某些不完善之处。本文在Moore和Giffin方法的基础上,对Moore方法进行了改进（简称方法1）,同时提出了新的偶然符合修正公式（简称方法2）;构建实验装置分别测量低活度222 Rn、220 Rn、219 Rn源及220 Rn和219 Rn混合源,对偶然符合修正公式进行比对实验验证。结果表明,总计数率小于70min-1时,本工作提出的两种方法在准确度和误差方面均较Moore和Giffin方法有所改善。

英文摘要：

The delay coincidence measurement of 220 Rn and 219Rn has been proved to be a valid indirect method for measuring 224 Ra and 223Ra extracted from natural water, which can provide valuable information on estuarine/ocean mixing, submarine groundwater discharge, and water/soil interactions. In practical operation chance coincidence correc- tion must be considered, mostly Moore＇s correction method, but Moore＇s and Giffin＇s methods were incomplete in some ways. In this paper the modification （method 1） and a new chance coincidence correction formula （method 2） were provided. Experiments results are presented to demonstrate the conclusions. The results show that precision is improved while counting rate is less than 70 min-1.