A fledgling effort by the Department of Energy to revive domestic production of plutonium-238 (Pu-238) in order to fuel deep space missions by NASA shows promise but still faces challenges, according to a Government Accountability Office report released Oct. 4.
The Energy Department has demonstrated “a proof of concept” by producing 100 grams of Pu-238 since the inception of a joint NASA/DOE project in 2011. But DOE has work to do before it can meet the NASA target of 1.5 kilograms of Pu-238 annually by 2026.
Pu-238 would be used in the radioisotope power systems, or RPS, which one source likened to a “space battery. This power source is considered more reliable for deep space missions than solar panels. NASA plans to use an RPS in Mars 2020, a “flagship” mission expected to cost more than $2 billion.
But planned NASA missions could exhaust domestic supplies of Pu-238 within a decade. Large-scale U.S. production of the isotope ended in 1988 — and DOE has not bought Pu-238 from Russia since 2009.
As a result, NASA has provided the Energy Department an average of $50 million per year since 2014 to support the RPS fuel project. NASA has indicated it needs more information from DOE before it can fully calculate the cost of the supply program.
The Energy Department has not mastered the chemical processing needed to remove the Pu-238 from irradiated material to meet the production goal.
In addition, DOE will need to employ both the Advanced Test Reactor (ATR) at the Idaho National Laboratory and the High Flux Isotope Reactor at the Oak Ridge National Laboratory in Tennessee. Both units will irradiate neptunium targets for conversion to Pu-238. But only certain positions within these reactors are suitable for Pu-238 production, according to the GAO.
The ATR is also scheduled for a yearlong scheduled maintenance shutdown beginning in 2020.
