| Reactor | Incidents involving research reactors, commercial power reactors, or military reactors |
| Weapons Facility | Accidents or intentional releases at weapons production, test, or storage facilities |
| Fuel Fabrication | Criticality accidents or other incidents in the course of fuel fabrication or reprocessing (a separate category because the amounts of material present in the factory environment heavily penalize carelessness) |
| Disposal Site | Leaks or other mishaps at waste disposal sites Includes intentional dumping at sea (as done by Russia in Arctic or by U.S. Navy in Pacific.) |
| Bomb Test | Fallout release or other damage due to nuclear bomb testing |
| Missile or Spacecraft | Aborted launches or other missile and spacecraft accidents involving unplanned release of radiation |
| Ship Loss | Radiation release or loss of nuclear weapons from submarines and surface ships. Includes any damage to the vessel that threatens immediate or eventual release, such as fire, collision, sinking or scuttling. |
| Airplane Loss | Crashes involving aircraft carrying nuclear weapons, or the loss of such weapons from the aircraft |
| Tosses & Losses | Unauthorized release or removal of radioactive material from or within the facility making or using it, whether intentional or not. Here, "release" includes exposure to radiation, and "facility" means any place involved with radiation for a purpose unrelated to production of power or nuclear weapons. |
| Research | Incidents or releases during basic research — especially the Manhattan Project |
| Transport | Incidents or releases during transport of radioactive material, whether bombs, missiles, RTGs, fuel rods, NBC training aids, medical & industrial sources, consumer products, or waste |