Investigation of Uranium Molecular Species Formation Using Laser Ablation
Abstract
The chemical behavior of uranium in cooling nuclear fireballs presents a challenge for device assessments. In nuclear test debris, uranium is chemically fractionated from other refractory elements, but the mechanism is poorly understood. The ability to properly interpret uranium data is essential to post-detonation debris diagnostics. Fallout measurements require corrections for chemical fractionation effects before they can be properly interpreted. Empirical data correction methods have been developed, but they offer no insight into the physiochemical processes that control uranium volatility. In this project we will systematically investigate the formation of uranium molecular species during plasma condensation, as a function of gas species and concentrations, using a coupled experimental and modeling approach. The goal is to provide the technical nuclear forensics community with data that enables the development of advanced predictive capabilities. Uranium target materials will be volatilized using a pulsed laser to form a plasma. Ultrafast time-resolved infrared spectroscopy will be used to measure spatially- and temporally-resolved data for the molecular species that form in the cooling plasma. The spatiotemporal absorption data will be used to develop a kinetic physical model to describe the relative abundances of uranium molecular species as the plasma evolves. We will initially characterize uranium-oxygen (UOx) systems and add other chemical components later. The experimental measurements and the numerical simulations of the ablated plume will be compared together at each step of the project, with the aim to obtain a calibrated model that describes (1) uranium vapor speciation as a function of oxygen fugacity, and (2) the most important chemical pathways for uranium fractionation relative to other chemical constituents condensing from the plasma.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 13, 2016
- Source ID
- HDTRA11610020
Entities
People
- Shailendra Srivastava
Organizations
- Defense Threat Reduction Agency
- University of Illinois Urbana–Champaign