缓发中子标准衰减曲线法用于铀的定量研究

Study on standard decay curve method in uranium determination by delayed neutron counting

缓发中子铀分析技术以其快速、准确的特点在地质、生物、材料、核查等领域得到广泛的应用。针对传统缓发中子铀定量分析中固定照射时间、冷却时间和测量时间所带来的弊端,如样品中铀含量很高导致缓发中子计数率过高而造成计数丢失,或者铀含量较低导致计数统计不足而带来结果偏差较大的问题,提出利用"标准样品"得到的无计数率丢失且有足够好计数统计的标准衰减曲线对未知样品中铀元素的含量进行快速、准确定量。在微堆上的实验表明,缓发中子标准曲线法适用于较宽范围铀含量样品中铀的定量测定。

Background： Delayed neutron counting （DNC） is a rapid and accurate uranium determination method applied in many fields, such as geology, materials, and nuclear safeguards. Purpose： Usually the method is done as following, one sample is irradiated by reactor neutrons for 60 s, then transferred to a position waiting for delayed neutron counting, which starts after 30 s from the end of irradiation for a counting time of 60 s. The routine of DNC may lead to some problems. For example, when the uranium concentration of a sample is very high, some delayed neutron counts would be lost. On the contrary, when the uranium concentration of a sample is too low, the counting statistics would be very poor. Methods： A standard curve method was proposed to solve the problem. Results ＆ Conclusion： Preliminary experiments show that this method is suitable for the determinations of uranium in samples with a wide range of uranium concentrations.