Generating Fallout-Like Particles by Improving an Existing Setup

Project Overview

Fallout analysis remains a crucial field of study, as it provides insight into the structural interactions that occur between radiological components and their surroundings following a nuclear event. Due to the complexity of actual nuclear-fallout samples, setups like our plasma-flow reactor have been developed to synthesize fallout in a controlled environment. While the flow reactor can achieve sufficient temperatures to generate fallout-like particles from a variety of starting materials, we are currently limited to analyzing cooling timescales on the order of 20ms, much shorter than the timescales observed in real nuclear fireballs. Our goal with this study was to determine if the flow-reactor setup can be modified to sustain higher temperatures along the flow tube to achieve longer cooling times that better reflect what is observed in actual nuclear events. To that end, we tested the feasibility of two different approaches for lengthening cooling time scales: (1) lowering the gas flow rates within the system and (2) minimizing heat loss between the setup and its surroundings. Under the first method, we found that flow rate significantly affects both the temperature within the system and the size of the resulting fallout-like particles. For method two, we incorporated a commercial tube furnace into the existing setup and demonstrated that it allows for fine-tuned control of the internal temperature of the system. With these added capabilities in place, the improved plasma-flow reactor will now be used to provide data for an ongoing project to explore the effect of different cooling time scales on chemical speciation and particle-size distribution of actinides.

Mission Impact

This research has served to significantly expand the capabilities of the existing plasma-flow-reactor setup, which has been used in a range of projects funded both internally (e.g., LDRD) and externally (e.g., DHS, DTRA, and NA22). In addition to lending support for these ongoing projects, the new capabilities also help make the flow reactor well-suited for new research directions, including investigations into complex phase separation (only possible at the newer, higher temperatures now achievable) and studies into the decomposition and evolution of water. As such, this work also directly addresses areas of mission relevance, including the development of science and technology tools and capabilities to meet future national-security challenges, as well as the DOE's energy- and environmental-security missions.