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Using Nuclear Fuel for Future NASA Missions Gets Boost

The Obama Administration's plan to resume domestic production of the nuclear material needed to power future space missions has won its first, partial victory in Congress.

Last week, the Appropriations Committee of the House of Representatives voted to give NASA $10 million next year to restart production of plutonium-238, a radioisotope whose heat is converted to electricity to power inner and outer planetary missions in the 2020s and beyond. It's a belated endorsement of a plan that would use Department of Energy (DOE) facilities to produce the material that NASA needs. However, also last week, in a separate vote, the full House rejected the other half of the strategy—DOE's request for $10 million to begin the work needed to generate the radioisotope. The spending panel overseeing DOE's budget said that NASA should pay the full cost since DOE derives no direct benefit.

Pu-238 is produced by irradiating neptunium-237 in a nuclear reactor, and over the years it has powered 26 NASA space missions. The United States stopped production in 1988 at DOE's Savannah River site in South Carolina, but maintained an inventory of the material that was supplemented by purchases from Russia. Russia ended that arrangement in 2009, however, and in June 2010 the Obama Administration outlined a plan to Congress that involved using DOE's National Laboratories in Idaho and Oak Ridge, Tennessee.

DOE's request for $30 million in the 2010 fiscal year was shot down by legislators, and last year a Senate panel rejected DOE's request for $15 million in FY2011. A similar request from NASA was never put to a vote in the House. But this month, the House panel that controls NASA's budget embraced the idea. And its chair, Representative Frank Wolf (R-VA), has vowed to fight any attempt to remove the money from NASA's 2012 budget as it moves through Congress.

"It is something that Mr. Wolf is going to defend," says a Republican legislative aide. "If there is an effort to try to take it out, Mr. Wolf is going to try to defend it." The aide characterized its chances of remaining in NASA's 2012 budget as "very strong." In language accompanying the spending bill, legislators also urged NASA to continue working with DOE on improvements in its radioisotope propulsion system, in particular, the Advanced Stirling Radioisotope Generator, "that will allow NASA to make better, more efficient use of available Pu-238 stocks."

The panel's support is good news for the planetary science community, whose research turns on NASA's ability to send missions throughout the solar system. "The supply of plutonium in the United States is diminished, or still in use, so the authorization or appropriation of funds to enable production of more plutonium is very important," explains Ronald Greeley, chair of NASA's planetary science advisory committee and regents professor at Arizona State University. "It's not only outer planet missions that are dependent on radioactive sources for power, but also more ambitious missions in the inner solar system" such as the dark side of the moon and Mars.

A coalition of scientific societies, including the American Astronomical Society (AAS), the American Institute of Physics, the American Geophysical Union, and the American Physical Society, have been educating legislators on the issue, armed with a 2009 National Academies' report that said that resuming Pu-238 production should be a "high priority" for the White House and Congress. They see the House vote as an important step forward. "It doesn't matter whether [the funding ultimately] goes to NASA or DoE ... at this point our members just need the funding available for the program," says AAS's Bethany Johns.

DOE estimates that the total cost of resuming production at between $75 million and $90 million, and that it would take 5 or 6 years to produce any new material. Its plan calls for an average production rate of 1.5 kg per year, which NASA says will satisfy its projected mission needs for missions starting in 2015.