Publications

As part of the US DOE Nuclear Hydrogen Initiative, Sandia National Laboratories is designing and constructing a process for the conversion of sulfuric acid to produce sulfur dioxide. This process is part of the thermochemical Sulfur-Iodine (S-I) cycle that produces hydrogen from water. The Sandia process will be integrated with other sections of the S-I cycle in the near future to complete a demonstration-scale S-I process. In the Sandia process, sulfuric acid is concentrated by vacuum distillation and then catalytically decomposed at high temperature (850°C) to produce sulfur dioxide, oxygen and water. Major problems in the process, corrosion, and failure of high-temperature connections of process equipment, have been eliminated through the development of an integrated acid decomposer constructed of silicon carbide. The unit integrates acid boiling, superheating and decomposition into a single unit operation and provides for exceptional heat recuperation. The design of acid decomposition process, the new acid decomposer, other process units, and materials of construction for the process are described and discussed.

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Under an NASA STTR project funded through Marshall Space Flight Center, a team from Ultramet Inc., Sandia National Laboratories and the University of Florida has been developing a new high temperature, tricarbide fuel matrix consisting of ZrC, NbC and UC using an open-cell reticulated foam skeleton. The new fuel is envisioned for use in nuclear thermal propulsion systems, bi-modal reactors and terrestrial high temperature gas reactors and builds on the tricarbide fuel research in the former Soviet Union. This paper deals with conceptual mechanical and neutronics design of a NTR reactor core and pressure vessel by the team. The details of fuel form fabrication and foam layout is the subject of a companion paper. It is highly desirable for a nuclear thermal rocket reactor to provide low ΔTs between the fuel and the hydrogen propellant; this bespeaks a minimal fuel-propellant temperature gap. However, NTRs, in order to exhibit a significant power density, possess high thermal gradients. Historically, this has resulted in NTR core designs that were neutronically acceptable but either heavy (due to prismatic element design) or insufficiently mechanically robust. The new fuel is both mechanically robust and thermally efficient given its extremely high surface area, higher melting point, minimal thermal stresses, and much reduced pressure drop compared to conventional fuel types. The matrix is anticipated to operate at temperatures as high as 3000K with minimal hydrogen erosion. The foam is an engineered material in which the porosity, size and thermal conductivity of the ligaments can be controlled independently to meet specific requirements. In this article we review the design process of the foam fuel based NTR, a procedure that has resulted in a quite compact, epi-thermal spectrum reactor core that can produce high power densities A credible reactor design is described herein that will allow us to couple these results with a new MP-CFD modeling capability using detailed simulation of the porous media. Our near-term plans for infiltration of the matrix with UC, integration of the test article and hydrogen testing at the University of Florida and Marshall Space Flight Center Future possibilities for continued development and testing are summarized.

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A preliminary set of requirements for a robotic rover mission to the lunar polar region are described and assessed. Tasks to be performed by the rover include core drill sample acquisition, mineral and volatile soil content assay, and significant wide area traversals. Assessment of the postulated requirements is performed using first order estimates of energy, power, and communications throughput issues. Two potential rover system configurations are considered, a smaller rover envisioned as part of a group of multiple rovers, and a larger single rover envisioned along more traditional planetary surface rover concept lines.