By Andrew Nusca
Posting in Energy
A shortage of the particular type of plutonium needed to power deep space probes may stall planned NASA space exploration.
Some scientists insist that the U. S. must urgently restart production of plutonium-238, but that effort depends on whether whether Congress will provide the $30 million requested by the administration earlier this year for the Department of Energy.
Plutonium-238 generates a considerable amount of heat, which can then be converted to electricity. (Nuclear weapons use plutonium-239.)
All that heat can be converted into electricity. "And this electricity is very, very useful, when you're in a remote or a hostile environment," says Johnson, "such as when you're in space and when you're too far away from sun to use solar power."
Famed space missions have been powered by plutonium-238, such as the Voyager probes in the 1970s, Galileo prove that orbited Jupiter and the Cassini spacecraft currently orbiting Saturn.
But reserves of plutonium-238, a man-made material left over from the Cold War and no longer in production, are running low.
So have Russia's reserves, from which the U.S. was buying for some time. Now those reserves are nearly depleted, too.
NASA says it has enough plutonium-238 for the next two missions -- a Mars rover named the Mars Science Laboratory and another major mission -- but the agency continues to face a sustainability issue.
The agency is experimenting with new, more efficient power conversion technology, but such technology would only slow use of a still-endangered material. (There is no alternate substitute for plutonium-238.)
That means NASA space exploration beyond the reaches of the sun -- where it can use solar power -- may get pushed to the back burner in the form of delays, limitations or outright cancellations.
The situation is so dire that even if production of plutonium-238 is restarted today, it would still take eight years to ramp up to making the roughly 11 pounds needed by NASA each year.
According to a NASA report issued in May, production would also cost in excess of $150 million.
Sep 28, 2009
The half-life of U-235 is 7 x 10^8 years and produces far less energy per gram than Pu-238 with a half-life of 88 years. Thus, you would need 10^6 times the mass U-235 than Pu-238 to generate the same amount of energy and in space vehicles getting the mass off the ground is everything. BTW - the author needs to change "proves" to probes!
The technology to miniaturise any sort of nuclear reactor to fit on a space probe does not exist. The point of P238 is that with it's 88 year half life, it's constantly generating a lot of energetic radiation, which can be easily captured as heat and used as a power source.
Please see http://www.ccnr.org/aecl_mox_plans.html I thought there was lots of U-238, though contaminated with lots of other stuff!
Uranium is used in power plants, to do the same thing: generate heat. Is uranium too unstable? You'd need too much of it? (a weight issue?) There must be some quality of P238 that I'm missing here. It'd be nice if the articles on this would have explained this a bit more.