Part 3 of 3 Parts (Please read Parts 1 and 2 first)
As NASA has proceeded with its propulsion and Kilopower projects, non-proliferation advocated have complained about NASA’s continued interest in using HEU. The American Nuclear Society hosted a debate on that topic at its annual meeting last June. The Society has generally supported the use of nuclear power for space propulsion in the past, it has decided to develop a position statement by spring of 2021 on whether or not to favor the use of LEU.
Among the attendees at the ANS meeting was U.S. Representative Bill Foster (D-IL) who is a former Fermilab physicist. He argued that proceeding with HEU would set a dangerous precedent. He added that, “If all of the spacefaring nations start using HEU reactors in space, then this would involve utilization of a significant amount of weapons grade material.” On the other hand, if the U.S. develops a LEU-based reactor design for space propulsion it could become a “de facto standard.” Foster also suggested that the high costs of security measures that would have to be implemented for handling HEU could outweigh any advantages of using HEU for propulsion.
Alan Kuperman is a policy scholar affiliated with the Nuclear Proliferation Prevention Project. He pointed to U.S. efforts since the 1970s to minimize the use of HEU in civilian applications. He argued that they are “based on the logic of no exceptions. If we say, ‘well, we're going to have exceptions,’ then other countries are going to say, ‘well, we want exceptions too,’ and then the whole thing falls apart.”
Among those attendees advocating in favor of HEU fuel, Kilopower chief reactor designer David Poston said that in his experience, regulators were most concerned about the possibility of a criticality accident resulting in a high-yield event. He said that HEU systems tend to mitigate such a concern.
Len Dudzinski is the NASA program executive for radioisotope power systems. He said that LEU reactors are just not powerful enough for certain potential missions such as drilling through thick ice sheets on the moons of Europa or Enceladus.
Bhavya Lal is a member of the National Academy study committee. She said that choosing between HEU and LEU is ultimately a political one and not a technical one. She mentioned that other countries might pursue HEU systems regardless of what the U.S. does. She advocated for not adopting a blanket ban on HEU. She said, “In my view, it would be prudent that we retain flexibility and allow the use of HEU in space systems only where the mission is not possible without HEU or where HEU is a significant enabler of mission scope or objective.”
The international Outer Space Treaty prohibits the placing of nuclear weapons in Earth orbit. If HEU is commonly used for space propulsion, some nations may launch radioactive materials into space with the claim that they will be used for space propulsion when they are actually intended to be used as weapons. This is a major area of concern.