Los Alamos leading fast-paced reactor research to
power planned journey to Jupiter's icy moons
A proposed U.S. mission to
investigate three ice-covered moons of Jupiter will
demand fast-paced research, fabrication and realistic non-nuclear
testing of a prototype nuclear reactor within two years,
says a Los Alamos National Laboratory scientist.
The roots of this build and test effort have been under
way at Los Alamos since the mid-1990s, said David Poston,
leader of the Space Fission Power Team in Los Alamos'
Nuclear Design and Risk Analysis Group.
NASA proposes using use electrical ion propulsion powered
by a nuclear reactor for its Jupiter Icy Moons Orbiter,
an element of Project Prometheus, which is scheduled for
launch after 2011. However, the United States hasn't
flown a space fission system since 1965.
Poston discussed technical requirements for such a
fission reactor in two presentations Monday at the Space
Technology and Applications International Forum in
Albuquerque. Los Alamos is a co-sponsor of the forum.
Poston discussed "The Impact of Core Cooling
Technology Options on JIMO Reactor Designs" and
"The Impact of Power and Lifetime Requirements on
JIMO Reactor Designs."
Los Alamos is leading reactor design for the Jupiter Icy
Moons Orbiter mission, which would orbit Callisto,
Ganymede and Europa to study their makeup, possible vast
oceans beneath the ice, their history and potential for
sustaining life. Los Alamos is responsible for such key
reactor technologies as nuclear fuel, beryllium
components, heat pipes and diagnostic instruments, as
well as nuclear criticality testing of development and
"Nuclear power has long been recognized as an
enabling technology for exploring and expanding into
space, and fission reactors offer unprecedented power and
propulsion capabilities," Poston said.
The JIMO mission would demand a safe, low-mass, high-temperature
reactor that can be developed and qualified quickly, can
operate reliably in the harsh environment of space for
more than a decade, and can meet a wide range of mission
and spacecraft requirements, he said.
A science mission to explore the icy Jovian moons would
require kilowatts of electrical power for the scientific
payloads and up to 100 kilowatts of electricity for ion
propulsion to propel the spacecraft to Jupiter, maneuver
within the Jovian system and allow rendezvous with the
moons. The reactor also would power advanced science
experiments and systems to send data to Earth at high
Despite the lack of U.S. space reactor research in recent
decades, Los Alamos has continued to examine technologies
and concepts for a rapid and affordable development
program. Working with NASA's Marshall Space Flight
Center, Los Alamos has resolved many hardware issues at
the component and system level.
Los Alamos and NASA-Marshall researchers, working with
colleagues from NASA's Jet Propulsion Laboratory and
Sandia National Laboratories, have built successively
more powerful nuclear electric propulsion reactor
components, including a 30-kilowatt reactor core without
fuel, one-third of a 100-kilowatt system (core plus heat
exchanger) and a single module suitable for a 500-kilowatt
reactor core. Extensive non-nuclear testing of these and
other components continues.
Most researchers have agreed on the best fuels and
reactor construction materials for the proposed fast-spectrum,
externally controlled JIMO reactor. The major design
choice that remains is how best to transport power from
the reactor core to the power conversion system.
Los Alamos and NASA are examining three primary options
for core cooling: pumped liquid-metal sodium or lithium;
sodium or lithium liquid metal heat pipes; and inert
helium or helium-xenon gas. Many of these options have
been tested for decades for terrestrial reactors, but the
reactor for JIMO would be unique, Poston said.
"We believe the power and lifetime potential of
space fission reactors could easily accommodate the
requirements of future NASA missions," Poston said.
"However, it is clear that reactor performance and
technical risks are tightly coupled to power and lifetime
requirements, so we must thoroughly understand these
technical risks before developing the first system. For
example, there are fewer technical and development
challenges for a 500-kilowatt-thermal reactor than a 1,000-kilowatt-thermal
"The first step needs to be small enough to ensure
success and to put into place the experience, expertise
and infrastructure necessary for more advanced systems,"
Poston concluded. "After that, we can move on to the
systems needed for even more ambitious space exploration,
such as multi-megawatt nuclear electric propulsion or
nuclear thermal rockets. Our near-term efforts must be
focused on making the first mission succeed."
Los Alamos National Laboratory is operated by the
University of California for the National Nuclear
Security Administration (NNSA) of the U.S. Department of
Energy and works in partnership with NNSA's Sandia and
Lawrence Livermore national laboratories to support NNSA
in its mission.
Los Alamos develops and applies science and technology to
ensure the safety and reliability of the U.S. nuclear
deterrent; reduce the threat of weapons of mass
destruction, proliferation and terrorism; and solve
national problems in defense, energy, environment and
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