Plutonium in space – another great idea from the pro nuclear lobby

despite precautions, scenarios exist in which plutonium-238 from spacecraft could contaminate Earth. If a nuclear-laden spacecraft performed a high-speed slingshot fly-by and a calculation mistake occurred, the craft could enter the Earth’s atmosphere, disintegrate, and spew plutonium throughout the planet.

The public will have to weigh the benefits [what benefits? – Christina Macpherson] of these pioneering space missions against the costs and risks of use

Nuclear Renaissance in Space, Miller-McCune, By Wendee Holtcamp, April 6, 2012 As the U.S. prepares to relaunch domestic production of plutonium-238, the space community wishes to assure the public of its safety. Are they right?

In this, the 50th year of using nuclear energy for space missions, the U.S. is preparing to restart domestic production of a plutonium isotope that fuels space vehicles — a topic that was front and center at the recent Nuclear and Emerging Technologies for Space conference, held in The Woodlands, Texas….
Plutonium-238 is used because its rate of radioactive decay generates
sufficient heat, and hence power generation, to finish missions that
span years or decades. (Its rate of decay, or half-life, is 87.7
years, compared to the 24,100 years of P-239, the stuff used in
nuclear power plants and weapons.) Also, P-238 only emits alpha
particles as it decays, rather than the more penetrating gamma or
X-rays emitted by other radioisotopes.
Ralph McNutt, space scientist at the Applied Physics Laboratory at
Johns Hopkins University and project scientist for the MESSENGER
Mercury space probe, described the technology’s history and current
use in an opening plenary session at the conference. “Radioisotope
power systems are an enabling technology that we use on space missions
to be able to go out in regions of the solar systems and do things we
simply could not do any other way,” he explained……

But supplies of plutonium-238 are just about spent. The U.S. stopped
producing the isotope in 1988, and subsequently bought it from Russia,
which recently reneged on its contract to supply the U.S. At the
conference, Wade Carroll, the Department of Energy’s deputy director
for space and defense power systems, announced that the federal budget
includes money to relaunch domestic production.
NASA was appropriated $3.5 million in the 2011 fiscal year and $10
million the next to relaunch domestic production of plutonium-238 at
Oak Ridge National Laboratory, but before that begins, it must undergo
a full National Environmental Policy Act review. If approved, the U.S.
would produce up to 2 kilograms per year. It will take five or six
years before new plutonium will be available.
Danger associated with plutonium-238 comes almost exclusively from
inhaling it; particles can lodge in the lungs, where they emit
damaging alpha particles into the body. Once in the lungs, it can
spread throughout the blood and get lodged in bone and the liver,
leading to cancer. On the other hand, if particles land on skin, the
layer of dead skin cells block radioactive alpha particles from moving
deeper and the radioisotope can be readily washed off. Even swallowing
the isotope is not a significant health risk; the digestive tract does
not readily absorb it.
Accidents associated with producing or maintaining the radioisotope
have occurred. In 2000, a faulty glovebox at Los Alamos National Lab
leaked, exposing several workers to radiation from the lab’s
plutonium-238 stockpiles.
And despite precautions, scenarios exist in which plutonium-238 from spacecraft could contaminate Earth. If a nuclear-laden spacecraft performed a high-speed slingshot fly-by and a calculation mistake occurred, the craft could enter the Earth’s atmosphere, disintegrate, and spew plutonium throughout the planet.

After the Cassini-Huygens probe launched in 1997, NASA guided it in
slingshot maneuvers by Venus, Earth, and Jupiter before heading out to
Saturn, and if an accident would have occurred during this maneuver,
it could have resulted in an estimated 2,300 cancer deaths worldwide.
No current or upcoming space mission plans to use a high-speed Earth
flyby.
Plutonium pellets are clad in iridium and then placed in carbon fiber
shells to protect them from extreme heat in the case of an accident.
Unlike in the case of a slingshot maneuver, if an accident occurred
during launch, the pellets would break into chunks too large to stay
airborne and be inhaled. Protestors attended the launch of the
Cassini-Huygens probe in 1997, but not the more dangerous flyby. Both
went off without a hitch. “The stresses that can occur in a launch
accident cannot destroy these things,” says Squyres, who chairs the
NASA Advisory Committee.
Later launches of the Mars Rovers and most recently, the Mars Science
Laboratory Curiosity, which lands August 5, have not met with any
protests. “People are starting to get that launching these things is
not risky,” said Leonard Dudzinski, NASA executive for radioisotope
power, at the plenary Q&A.
“Anybody involved in flying one of these things knows how much goes
into worrying about safety,” said McNutt. Analysis, an environmental
impact statement, and presidential approval are required anytime
nuclear material gets launched into space.
“Unless we maintain the ability to make plutonium-238, we will not
have these missions,” concluded McNutt. The public will have to weigh
the benefits of these pioneering space missions against the costs and
risks of use, including domestic production, and will get a chance as
NASA submits its plans for new domestic production and the National
Environmental Policy Act process unfolds.
http://www.miller-mccune.com/science/nuclear-renaissance-in-space-40882/