Environmental Compliance and Laboratory Services Division, Canadian Nuclear Safety Commission, 3484 Limebank Road, Ottawa, Ontario, Canada K1V 1E1.
J Environ Radioact. 2012 Apr;106:65-72. doi: 10.1016/j.jenvrad.2011.11.009. Epub 2011 Dec 7.
It is important to know the initial time, or zero-time, of a nuclear event such as a nuclear weapon's test, a nuclear power plant accident or a nuclear terrorist attack (e.g. with an improvised nuclear device, IND). Together with relevant meteorological information, the calculated zero-time is used to help locate the origin of a nuclear event. The zero-time of a nuclear event can be derived from measured activity ratios of two nuclides. The calculated zero-time of a nuclear event would not be complete without an appropriately evaluated uncertainty term. In this paper, analytical equations for zero-time and the associated uncertainty calculations are derived using a measured activity ratio of two nuclides. Application of the derived equations is illustrated in a realistic example using data from the last Chinese thermonuclear test in 1980.
知道核事件（如核武器试验、核电厂事故或核恐怖袭击（例如，使用简易核装置，IND）的初始时间或零时很重要。结合相关气象信息，计算出的零时用于帮助确定核事件的起源。核事件的零时可以从两种核素的测量活度比中得出。如果没有适当评估的不确定度项，核事件的零时计算将不完整。在本文中，使用两种核素的测量活度比推导出了零时和相关不确定度计算的分析方程。使用 1980 年中国最后一次热核试验的数据，通过一个实际示例说明了所推导方程的应用。
