Falling Space Reactors: Assessing the Risk

A new NASA report examines various scenarios in which nuclear reactors that are used to power spacecraft could accidentally reenter the Earth’s atmosphere.

“There are a number of types of reentry events that can potentially occur with missions containing fission reactors. Each type of reentry event can produce a variety of possible adverse environments for the fission reactor,” the report said.

The postulated scenarios include accidental reentry upon launch, reentry from orbit, and reentry during Earth flyby.

“There are three potential outcomes for a fission reactor in a reentry scenario,” the report explains. “First, the fission reactor can burn up in the atmosphere due to the aerothermal loads imparted to it during reentry. Second, it can survive the reentry and impact the Earth’s surface with or without additional spacecraft components. Finally, it can break apart during reentry, but its various components survive reentry and impact the Earth’s surface (a scattered reentry).”

See Fission Reactor Inadvertent Reentry: A Report to the Nuclear Power & Propulsion Technical Discipline Team, by Allen Camp et al, NASA/CR−2019-220397, August 2019.

A conference on “Nuclear Energy in Space: Nonproliferation Risks and Solutions” will be held in Washington DC on October 17 that will focus on the anticipated use of highly enriched uranium in space nuclear reactors, and the feasibility of using low enriched uranium instead. The conference is sponsored by the Nuclear Proliferation Prevention Project (NPPP) at the University of Texas at Austin.

Several previous technical analyses have concluded that use of low enriched uranium in space reactors is in fact feasible, but that it would probably require a reactor of significantly larger mass.

See “White Paper – Use of LEU for a Space Reactor,” August 2017 and “Consideration of Low Enriched Uranium Space Reactors” by David Lee Black, July 2018.

Luncheon Briefing on Advanced Nuclear Reactors

Luncheon Briefing: Making the Next Step Forward with Advanced Nuclear Reactors: Assessing Progress and Overcoming Roadblocks on Safety, Technology and Policy


Thursday, July 24, 2014

11:30 a.m. – 1:30 p.m.

Rayburn House Office Building, Room B-318

Washington, DC


The Federation of American Scientists (FAS) and the American Nuclear Society (ANS) hosted a workshop that addressed the state of the safety, science, and technology for advanced nuclear reactors and discussed policy considerations to overcome roadblocks to their development and adoption.

Briefing Materials for the event can be found below.


Presentation Slides: Past, Present and Future of Nuclear Power in U.S., Dr. Peter B. Lyons, Assistant Secretary for Nuclear Energy, Department of Energy

Fast Reactor Technology: A Path to Long-Term Energy Sustainability, American Nuclear Society

Enabling a Sustainable Nuclear Energy Future, Argonne National Laboratory

PROTEUS: Simulation Toolset for Reactor Physics and Fuel Cycle Analysis, Argonne National Laboratory

SHARP: Reactor Performance and Safety Simulation Suite, Argonne National Laboratory

Consortium for Advanced Simulation of Light Water Reactors (CASL), U.S. Department of Energy

A Look Inside America’s Source of Energy and Security Solutions, Idaho National Laboratory

Solving Big Problems: Science and Technology at Oak Ridge, Oak Ridge National Laboratory



11:20 a.m. – Luncheon and Registration

11:30 a.m. – Opening Address by Dr. Charles D. Ferguson, President, Federation of American Scientists

  • Keynote Speaker: Dr. Peter B. Lyons, Assistant Secretary for Nuclear Energy, Department of Energy

11:45 a.m. – Panel Session One: What is the current state of U.S. science and technology for advanced nuclear reactors?

Moderator: Dr. Mark Peters, Argonne National Laboratory


  • Dr. Leslie Dewan, Transatomic Power
  • Dr. Dan Ingersoll, NuScale
  • Dr. Hussein Khalil, Argonne National Laboratory
  • Dr. Doug Kothe, Oak Ridge National Laboratory
  • Dr. John Parmentola, General Atomics

12:30 p.m. – Panel Session Two: What policies and partnerships might increase the NRC’s consideration of and funding for new nuclear technologies?

Moderator: Dr. Kennette Benedict, Executive Director and Publisher of the Bulletin of the Atomic Scientists


  • Dr. George Apostolakis, former NRC Commissioner
  • Mr. David Blee, Nuclear Infrastructure Council
  • Mr. Phil Hildebrandt, Idaho National Laboratory
  • Mr. Craig Piercy, American Nuclear Society
  • Mr. Daniel Stout, Tennessee Valley Authority