Nuclear Thermal Rocket - Risks

Risks

There is always an inherent possibility of atmospheric or orbital rocket failure which could result in a dispersal of radioactive material. Catastrophic failure, meaning the release of radioactive material into the environment, if it took place, would be the result of a containment breach. A containment breach could be the result of an impact with orbital debris, material failure due to uncontrolled fission, material imperfections or fatigue and human design flaws. A release of radioactive material while in flight could disperse radioactive debris over the Earth in a wide and unpredictable area. The zone of contamination and its concentration would be dependent on prevailing weather conditions and orbital parameters at the time of re-entry. The amount of contamination would depend on the size of the nuclear thermal rocket engine.

Fuel elements in solid-core nuclear thermal rockets are designed to withstand very high temperatures (up to 3500K) and high pressures (up to 200 atm); hence, it is highly unlikely that a reactor's fuel elements would be spread over a wide area. They are composed of very strong materials, either carbon composites or carbides, and normally coated with zirconium hydride. The solid core NTR fuel itself is conventionally a small percentage of U-235 buried well inside an extremely strong carbon or carbide mixture. Unless the physically small reactors have been run for an extended period, the radioactivity of these elements is quite low and would pose a minimal hazard.