Novel Methods for International Safeguard Sensing: Nonlinear Chemical Waves and In Situ Logic-Tree Analysis.

Abstract

Chemical waves are self-sustaining fluctuations in chemical concentrations that arise from nonlinear coupling of transport and chemical reaction in a fluid medium. Chemical waves respond to and retain a history of encountered stimuli, and the waves propagate spatially even in the absence of advection. We investigate use of gas-aerosol and aqueous phase chemical wave systems as a basis for novel methods of Safeguards sensing. Amplitude and frequency of chemical waves can be tuned in sensitivity to indicate presence of targeted products or signatures, and the waves can be triggered by the trace presence of solid, gaseous, or liquid chemical trace compounds, physico-acoustic perturbations, magnetic fields, and optical stimulation. We use computational fluid dynamics modeling to demonstrate scenarios of detection; these include using an ozone-aerosol autocatalysis in detection of breaches in dry cask storage of spent fuel, and intrusion detection in a subsurface geologic repository for nuclear waste storage. Fault tree or event tree analysis involves representation of events or features of system as an interconnected series of Boolean operations or logic gates. The logic tree allows assessment of the root cause of a particular event, or an analysis of the cascading events that arise from a given event. We create a chemical-based tree analysis within the system of interest itself, using chemical waves as the “telegraph line” to transmit information and molecular logic gates as the Boolean logic gates of a tree analysis. that develop chemical waves. We show that the nature of chemical waves is sensitive to environmental conditions including geometry, radiation conditions, aerosol concentrations, pH, organic substrates, and other examples. We apply these concepts to Safeguards sensing in a subsurface nuclear waste repository; we also examine breaching of dry cask spent fuel storage and discuss the use of chemical wave sensing in other International Safeguards contexts.