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.