NASA SBIR 2005 Solicitation


PROPOSAL NUMBER:05 X10.02-8043
SUBTOPIC TITLE:Critical Technologies for In-Space Application of Nuclear Thermal Propulsion
PROPOSAL TITLE:Development and Evaluation of Mixed Uranium-Refractory Carbide/Refractory Carbide Cer-Cer Fuels

SMALL BUSINESS CONCERN (Firm Name, Mail Address, City/State/Zip, Phone)
New Era Technology
3720 NW 43rd Street
Gainesville ,FL 32606 - 6190
(352) 380 - 9880

PRINCIPAL INVESTIGATOR/PROJECT MANAGER (Name, E-mail, Mail Address, City/State/Zip, Phone)
Travis W Knight
3720 NW 43rd Street
Gainesville, FL  32606 -6190
(352) 380 - 9880

A new carbon-based fuel is introduced with outstanding potential to eliminate the loss of uranium, minimize the loss of carbon, and retain fission products for many hours of operation in hydrogen environment at temperatures in excess of 3,200K. The proposed fuel is a Cer-Cer made of mixed uranium-refractory carbide particles such as (U, Zr)C or (U, Zr, Nb)C dispersed in a refractory carbide matrix such as ZrC. For efficient operation in NTR applications for Isp of 1000 sec. or more, a fuel temperature of 3000 K or greater is necessary. Various fuel materials have been tested for NTR applications with most based on carbide fuel technology because of their improved thermal properties enabling the design of very small, high power density cores. Fuel designs from dispersed microspheres in graphite, to composite mixed carbides with graphite, to solid solution mixed carbides have been tested. Fuels bearing graphite are not tenable because of the high reactivity of free carbon with the hot hydrogen propellant. Solid solution, mixed carbides are most often brittle but otherwise perform well under the high temperature flowing hot hydrogen environment. The life limiting phenomenon for their use in NTR applications is the loss of uranium due to vaporization from the fuel surface at temperatures in excess of 2800 K. Though the proposed Cer-Cer fuel is relatively at lower level of technology maturity, its unique potential for elimination of uranium loss and retention of fission fragments at very high operational temperatures would amply justify the proposed research program.

The success of the proposed research program will bring about a nuclear fuel with optimum performance characteristics for use in NTP and Bimodal Propulsion systems. Results of more than 50 years of research including more than 20 years of research by the group headed by Professor Samim Anghaie at University of Florida have culminated to the development of the uranium-carbide Cer-Cer fuel concept that is described in this proposal. The main idea behind the development of the proposed uranium-carbide Cer-Cer design is to come up with an NTP fuel that features the highest performance potential in the areas including operational temperature margin, stability in hot hydrogen, retention of fission products, and mechanical properties. The proposed Cer-Cer fuel possess fundamental physical and chemical properties comfortably above the best carbon based fuels such as (U, Zr, Nb)C and (U ,Zr, Ta)C, and the best cermet fuels such as (U, Zr)CN or stabilized UO2 coated with tungsten in W/Re matrix/clad. With the renewed interest in the development of the NTP and Bimodal propulsion systems, it is time to reevaluate the fundamental properties of materials with highest performance potential as we know them in 2005. Considering fundamental materials properties as we have known them, the proposed uranium-carbide Cer-Cer uniquely combines all the right properties to make the best and most robust fuel for the NTP and Bimodal Propulsion applications.

For terrestrial ultra-high temperature gas-cooled GEN IV and advanced light-water reactors, uranium-refractory carbide Cer-Cer fuels offer a revolutionary improvement in core safety performance, increased efficiency and reduced cost. The proposed Cer-Cer fuels with high enrichments can be used in space based reactors and in terrestrial reactors permitted to burn stockpiled highly enriched uranium (HEU) from as a means of HEU disposal.

Using uranium-refractory carbide Cer-Cer fuels in commercial nuclear power plant could potentially result in greater efficiency, reduced cost, and increased safety margin through:
? Higher burnup possible leading to fewer outages and associated costs for fuel replacement.
? Less thermal energy is stored in the core as a result of the higher fuel thermal conductivity.
? Reduced probability of fuel melt or fuel pellet and clad mechanical interaction in an accident scenario ? the higher thermal conductivity reduces the fuel centerline temperature and the higher fuel melting point both give an increased margin to fuel melting. Lower coefficient of thermal expansion reduces the probability of partial or full fuel pellet contact with clad.
? Eliminated or at least significantly reduced core melt probability that is identified as the potential maximum public health risk for light water reactors.

NASA's technology taxonomy has been developed by the SBIR-STTR program to disseminate awareness of proposed and awarded R/R&D in the agency. It is a listing of over 100 technologies, sorted into broad categories, of interest to NASA.

Nuclear (Adv Fission, Fusion, Anti-Matter, Exotic Nuclear)

Form Printed on 09-19-05 13:12