NASA will have to pay for the entire cost of plutonium-238 production, which was resumed a few months ago by the U.S. Department of Energy (DOE) after almost 25 years.

“Since the [Obama] Administration has a ‘user pays’ philosophy, we are now in a position to pay for basically the entire enterprise, including the base infrastructure at the DOE,” NASA chief financial officer Beth Robinson said in an April 10 press conference. “We’ll be partnering with DOE in the next couple of months to figure out how to best do this, and how to streamline the program to produce plutonium-238.”

According to the previous agreement, NASA would have split the program reboot cost with the DOE. However, since NASA is the only user of the radioactive material, the arrangement changed, as showed in the agency’s federal budget request for 2014. NASA has requested $50 million to support the radioisotope power system development infrastructure through full-cost recovery mechanisms at the Department of Energy. In the meantime, as outlined by The Planetary Society blog, NASA also received from the U.S. Senate additional funding for the remainder 2013, including an additional $14.5 million for Pu-238 production.

Pu-238 is a radioactive isotope used as a power source for deep space exploration spacecraft, where solar power may be inadequate. It generates heat via radioactive decay in radioisotope thermoelectric generators (RTGs). Pu-238, although highly toxic, is not used in nuclear bombs as is Plutonium-239. RTGs have powered NASA spacecraft for many decades, among them two Voyager probes, the Cassini spacecraft, and Curiosity rover.

The last time the U.S. produced plutonium-238 was in 1988. NASA had bought the precious isotope from Russia in the intervening years until the contract was cancelled in 2009. NASA and DOE have estimated the rebooting will cost between $75 million and $90 million over five years. According to NASA officials, the agency expects to have 1.5 to 2 kilograms produced per year, starting 2018.