Pictured: NASA Kilopower Reactor
Source: https://www.nasa.gov/sites/default/files/thumbnails/image/kilopower_experiment.jpg
United States
NASA plans to demonstrate its Kilopower reactor on the Moon by 2027. As noted in the Background section, Kilopower is not the first space reactor developed by the U.S. The U.S. created an orbital reactor to power its SNAP 10A experimental satellite in 1965. The reactor only operated a total of 43 days. The US explored the use of fission reactors again in 2005 to power a Jupiter Icy Moons Orbiter (JIMO). The project envisioned that the unmanned JIMO spacecraft would search for liquid water on Jupiter’s moons. The project was cancelled in the early planning stages though [1]. In 2012, Los Alamos National Laboratory announced that it had tested components of the potential first SNR system in the U.S. since 1965 [2]. The test used heat pipe technology and a Stirling engine to convert heat from a pre-existing critical assembly into 24 watts of electricity. The proposed reactor was designed to power installations on planetary surfaces. At that time, U.S. officials characterized the project as a “low-level development effort” [3]. These components were incorporated into the subsequent Kilopower reactor.
In 2017, Los Alamos National Laboratory published a White Paper that compared HEU and LEU options for planetary surface reactors, demonstrating more serious consideration of SNR deployment [4]. That same year, President Trump signed a directive meant to revive American space exploration. The document instructed NASA to “pursue human exploration of Mars” and to return astronauts to the Moon for “long-term exploration” [5]. As recently noted by NASA’s Chief Engineer Jeffrey Sheehy, the lack of “sustainable power” on the Moon or Mars poses a technical hurdle to achieving these goals [6].
The Trump Administration made clear though that NASA needed to surmount all hurdles quickly. By March 2019, the White House had expressly directed NASA to “land on the Moon’s South Pole by 2024, establish a sustainable human presence on the Moon by 2028, and chart a future path for Mars exploration” [7]. Accordingly, NASA has moved urgently to meet President Trump’s deadline by using HEU to test the Kilopower reactor in 2018. (Note: a LEU planetary surface reactor could not be ready for demonstration for several more years.) NASA also plans to ramp up spending. NASA officials presenting at the 2020 American Nuclear Society Annual Meeting revealed that NASA plans to increase annual spending on the nuclear surface power program from $60 million to $150 million in the next 5 years [8].
NASA also started developing a space reactor for nuclear thermal propulsion. In 2017, NASA awarded a contract to “initiate conceptual designs” for a propulsion reactor [9]. The reactor would replace traditional chemical rocket engines by using fission to heat hydrogen. Unlike the Kilopower reactor, though, NASA decided to fuel the propulsion reactor with LEU. In 2015, NASA and DOE project managers justified the decision to use LEU by pointing to the reduced cost of handling LEU and the political risks associated with HEU [10]. NASA has previously considered the higher costs for an HEU reactor, specifically in terms of the following factors: security; consequences of launch failure; research, design, and production; political opposition; and contravention of the HEU minimization norm (see Background section for further discussion of these costs). NASA decided that these disadvantages outweigh the potential benefits of HEU fuel, but so far only in the case of propulsion reactors.
The U.S. has more than enough HEU on hand to fuel an emergent SNR program. In 2005, DOE reserved 20 metric tons of civilian stocks of HEU specifically for research reactor and space reactor applications. The amount was set aside as fuel for space reactors in case “NASA reexamines its long-term mission needs” [11]. However, in 1992, the last domestic high-enrichment facility in the U.S. was shut down. This means that the long-term use of HEU by NASA could accelerate demand for construction of a new high enrichment facility.
The U.S. clearly meets the criteria of a Tier 1 state. The country has previously launched an HEU space reactor, and the 2018 Kilopower test suggests that its national space program plans to resume HEU reactor launches by 2027. However, the decision to use HEU is not yet final. While some NASA officials had suggested that the 2027 deadline is too soon to develop or deploy an LEU reactor, Congress has signaled that it may not accommodate President Trump’s ambitious timeline. This would allow NASA the flexibility needed to explore LEU options, so the U.S. could avoid becoming the first offender in an HEU space race.
[1] Blake Messer, “Space Reactors,” in Nuclear Terrorism and Global Security: The Challenge of Phasing out Highly Enriched Uranium, ed. Alan J. Kuperman (New York: Routledge, 2013): 217.
[2] Messer, “Space Reactors,” 217.
[3] Ibid., 218.
[4] Patrick Ray Mcclure et al., “White Paper - Comparison of LEU and HEU Fuel for the Kilopower Reactor,” Los Alamos National Laboratory, October 2018.
[5] “New Space Policy Directive Calls for Human Expansion Across Solar System,” NASA, December 11, 2017. https://www.nasa.gov/press-release/new-space-policy-directive-calls-for-human-expansion-across-solar-system
[6] Jeffrey Sheehy, “Fission Power for NASA Missions,” Panel presentation, Nuclear Energy in Space: Nonproliferation Risks and Solutions, Washington D.C., October 17, 2019.
[7] Sheehy, “Fission Power.”
[8] Lee Mason, “NASA STMD Nuclear Technology Portfolio,” Panel presentation, American Nuclear Society Annual Meeting, online virtual meeting, June 11, 2020.
[9] “BWXT Awarded $18.8 Million Nuclear Thermal Propulsion Reactor Design Contract by NASA,” BWX Technology Inc., August 03, 2017.
[10] Michael G. Houts et. al, “NASA’s Nuclear Thermal Propulsion Project,” American Institute of Aeronautics and Astronautics, 2015: 8. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150016484.pdf
[11] Wade Boese, “U.S. Trims Nuclear Material Stockpile,” Arms Control Association, December 2012, https://www.armscontrol.org/act/2005-12/us-trims-nuclear-material-stockpile.