SBIR-STTR Award

Uranium Dioxide (UO2) has long been the workhorse of the nuclear power industry. Manufacturing methods are well established and build upon well-known processing technologies such as metallurgy and powder sintering.As the Department of Energy, Office of Nuclear Energy, as well as industry, strive to achieve safer, higher efficiency fuels, new fuel formulations rise to prominence; for example Uranium Silicide (U3Si2) and Uranium Nitride (UN). Other, refractory fuels such as Uranium Carbide and intermetallic carbides, such as Uranium-Tungsten Carbide are also gaining interest for high-temperature nuclear applications. Advances in manufacturing and processing of such alternate fuel are regarded as important contributions towards improving fuel efficiency and accident tolerance while also extending the life of the fleet of extent nuclear power plants.Contrary to UO2, however, there are no well-established manufacturing processes for the proposed alternative nuclear fuel materials. This is where Free Form Fibers’ expertise in Material-Agnostic Additive Manufacturing can contribute significant advances. Rather than relying on ad-hoc metallurgy, Free Form Fibers’ unique approach is positioned to allow for low-cost synthesis of a wide range of refractory fuels directly from the gas phase. This direct conversion process eliminates onerous chemistry and powder metallurgy processes and can deliver material purities and compositions that rival with the microelectronics industry without the typical costs associated to chip fabrication.

The nuclear plant accident at Fukushima in Japan in 2011 has spurred a significant response in the United States, primarily through the Accident Tolerant Fuel program to devise new technologies and materials that will help avoid a similar situation in the U.S.As part of these efforts, Free Form Fibers has proposed deploying its rapid laser-driven chemical vapor deposition technology to produce alternative nuclear fuels from the traditionally used uranium dioxide, such an uranium disilicide and uranium nitride.These alternative fuels offer several important advantages over uranium dioxide, such as higher uranium loading and higher thermal conductivity, and have been aspirational in the nuclear power field (for both terrestrial and space travel applications) for many years.In fact, Free Form Fibers has performed an initial investigation into fabricating uranium disilicide through a partnership with Materials Characterization Laboratory, Inc.in Oak Ridge, Tennessee, as part of a Department of Energy Small Business Innovative Research phase I project.The rapid laser-driven chemical vapor deposition approach is an alternative to powder metallurgy techniques to forming alternative nuclear fuels, with simpler processing steps that primarily involve the delivery of a uraniumcontaining gas precursor source.In working with MCL, Inc., Free Form Fibers has a partner that is properly licensed to store and handle uranium hexafluoride.As part of the phase I project, Free Form Fibers designed and built a portable rapid laser-driven chemical vapor deposition rig that was delivered and installed at the MCL, Inc.facility.A brief initial round of experiments revealed only uranium tetrafluoride, a low temperature stable solid phase, deposited from the gas phase reaction.The proposed phase II work scope would include an expansion of the plan of experiments to cover a wider range of gas precursor mixtures and the implementation of a higher power laser to deliver more energy to the decomposition reaction, with the expectation of pushing the deposition temperature higher into a desired region on the uranium-silicon phase diagram.Examination of the gas mixture combinations will explore regions of high silicon to uranium ratios in order to drive excess silicon into the laser focal point of deposition, making it available to react with uranium atoms.This work would continue to be performed at MCL, Inc.as the deposition rig was left in place at the Tennessee facility in anticipation of future efforts.The overarching goal of the phase I and phase II projects is to demonstrate the feasibility of fabricating uranium disilicide from rapid laser-driven chemical vapor deposition, with the expected formed material to be of high chemical and phase purity as has been found in previous material studies with this technology.