Advancing Methods for Providing Attribution for the HEU Used in a Terrorist Nuclear Weapon

Abstract:

An algorithm was developed that uses measured isotopic ratios from fission product residue following the detonation of a nuclear weapon to compute the original attributes of the nuclear material used in the weapon. While more accurate (and more computationally intensive) methods are being explored by others, the method described here could serve as a preprocessing step to a more detailed methodology (potentially saving on computational time). This would, in turn, expedite the process of determining where the device came from, eventually leading to which terrorist group perpetrated the event. This work was restricted only to Highly Enriched Uranium (HEU) devices; however, future efforts will consider plutonium devices as well. The attributes determined include original material uranium isotopics (at present considering only 234U, 235U, and 238U) and the type of enrichment process used to create the material (e.g., gaseous diffusion, gas centrifuge, etc.). The approach to developing this algorithm involved a simulation of the fission products and actinides present following a nuclear explosion and a detailed evaluation to determine valid ratios that could be used to work backward and achieve the original material in the device. The algorithm used was purely analytical, derived directly from burnup and radioactive decay equations. Thus, this methodology provided solutions with essentially no computational time required.