Source: http://www.scientificamerican.com/articl...

But outside experts familiar with the situation say this explanation is a classic example of circular reasoning. “There are tons of things NASA could use the new plutonium for, but there’s nothing on the books,” says Casey Dreier, director of advocacy at the Planetary Society. “Why is that? Because NASA isn’t sure when or if it will have the plutonium it needs!”

Part of the problem is that plutonium is very expensive to make, and no one is particularly eager to pay for it: The production pipeline is scattered between national labs in Idaho, Tennessee and New Mexico, and maintaining it all costs upwards of $50 million per year. Historically, the DOE covered those costs, but that all changed when production restarted in 2013, because Congress and the White House shifted the financial burden of restarting and maintaining production solely to NASA.

NASA’s leadership passed the buck to the agency’s Planetary Science division, because interplanetary missions are NASA’s primary plutonium consumers. Perversely, because the funding for plutonium production comes from the division’s technology development budget, this channels money away from projects exploring how to sustainably use the scarce plutonium supply.