Group Title: Innovative Nuclear Space Power and Propulsion Institute informational brochures
Title: Square lattice honeycomb reactor
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Permanent Link: http://ufdc.ufl.edu/UF00091281/00003
 Material Information
Title: Square lattice honeycomb reactor
Series Title: Innovative Nuclear Space Power and Propulsion Institute informational brochures
Physical Description: Archival
Language: English
Creator: Innovative Nuclear Space Power and Propulsion Institute, University of Florida
Publisher: Innovative Nuclear Space Power and Propulsion Institute, University of Florida
Place of Publication: Gainesville, Fla.
 Record Information
Bibliographic ID: UF00091281
Volume ID: VID00003
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

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"Space Exploration is the ultimate
investment in America's Future"
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FPI


An International Leader
in Space Applications


Contact Information
General: Ms. Lynne Schreiber, lynne@inspi.ufl.edu
Research: Dr. Travis Knight, knight@inspi.ufl.edu
Academic: Ms. Ines Aviles-Spadoni, iaviles@ufl.edu
INSPI
P.O. Box 116502
Gainesville, FL 32611-6502
Phone: (352) 392-1427
FAX: (352) 392-8656
www.inspi.ufl.edu


Tri-Carbide Square
(SLHC) Reactor


Lattice Honeycomb


The Innovative Nuclear Space Power and
Propulsion Institute (INSPI) at the University of
Florida has developed the Square Lattice
Honeycomb (SLHC) core reactor design to
overcome the manufacturing difficulties
imposed by the high performance tri-carbide
fuels. This innovative space reactor builds on
previous Rover/NERVA reactor configurations.
Currently, two new design options are being
considered: the SLHC and the Moderated SLHC.
Due to stringent size and weight requirements
and ultra-high operating temperatures of
multimegawatt space reactors, fuel plays a
pivotal role in all design considerations of these
systems. At 3000K factors such as fuel chemical
stability, thermal and mechanical performance,
and nuclear criticality guide the design
optimization process.

SLHC Features


UNIVERSITY OF
FLORIDA


* High Temperature Performance
* Innovative Fuel Element Design
* Core Power Shaping
* Manufacturing Simplicity
* Cost Effective Core Configuration
* Power and Thrust Scalability


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Tri-Carbide
Wafer


High Temperature Performance
Recent experiments have proven the high
temperature performance of tri-carbide solid
solution fuels of either (U,Zr,Nb)C or (U,Zr,Ta)C.
The melting point and thermal conductivity of
these compounds exceed those of all previous
nuclear fuels. Due to their hardness, these tri-
carbide fuels make previous Rover/NERVA core
designs very expensive and difficult to produce.

Innovative Fuel Element Design (SLHC)
Similar to Rover/NERVA reactors, the core is
fueled with 93% enriched uranium. However, this
solid solution tri-carbide fuel is fabricated in the
form of 1 to 2 mm thick grooved wafers and
assembled to form "hockey puck" type fuel sub-
assemblies with equal diameter and length of 5
cm and a 30% cross-sectional void area for
flowing hydrogen propellant. The honeycomb
configuration of the wafers is lightweight and
provides strength to the core.
The square channels formed within these
interlocking wafers substitutes for the coolant
channels in previous fuel element designs. This
circular grid is then fitted into the graphite
shroud. Tabs on both sides of each fuel wafer
slide into matching grooves on the shroud. This
combination serves as a support mechanism
against axial forces. Six of these shroud and fuel
sub-assemblies are stacked on top of each other
to form the complete length of the core.

Core Power Shaping
The use of stacked shroud-grid fuel modules
provides added fuel temperature control by
allowing the manipulation of the power shape.
Loading each module with different
concentrations of uranium can alter the power
shape or power distribution within the core. For
example, placing high enrichment modules on
the top and bottom of the stack can flatten the
core's power shape. Since the power distribution
is directly related to the heat flux, a flattened
power shape insures that the whole length of the
core is operating at its highest and most efficient
temperature.


Manufacturing Simplicity
The primary driver for the innovative SLHC design
is the manufacturing simplicity of thin fuel wafers
that lends itself to net-shape fabrication, essential
to processing of super hard tri-carbide fuels. The
most improved design feature of tri-carbide fuels
for NTP applications is the elimination of a
protective carbide coating that that was required
in graphite matrix Rover/NERVA reactor fuels.

Cost Effective Core Configuration
By hot pressing the powder into the desired wafer
dimensions, the slits can be incorporated within
the die, which would eliminate the need for any
significant finishing operations (compared to the
difficulty in extruding and machining required for
the Rover/NERVA elements that incorporated
tubular coolant channels). This means large
savings in the overall manufacturing cost of the
fuel.

Power and Thrust Scalability
An important feature of the SLHC fuel is the power
scaling by adjusting the thickness of the fuel
wafers. The same core that is used to provide
150kN thrust with 2 mm thick fuel wafers could be
loaded with the same volume of 1 mm thick fuel
wafers for larger thrust and power operations.
This allows the same processing and fabrication
technology to be applied to the development of an
entire class of propulsion systems with different
capabilities.

Moderated SLHC Reactor Core (M-SLHC)
A moderated SLHC reactor core has been designed
with 18 smaller fuel assemblies arranged in two
concentric rings. A smaller (inner) ring contains 6
fuel assemblies, while the outer ring contains 12.
Six to 10 fuel sub-assemblies are stacked inside a
laminar graphite-zirconia tube to form a single
fuel assembly for the SLHC reactor. The region
between assemblies is designed with narrow flow
channels for cooling the ZrH2 moderator and pre-
heating the hydrogen propellant. The M-SLHC
utilizes ZrH2 to thermalize the spectrum to
significantly reduce the amount of 235U required.


Fuel
Assembly


Moderated
SLHC
Reactor Core


Fuel Sub-
Assembly


Fuel
Element


Shroud &
Fuel Sub-
Assembly


Fuel
Assembly




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