The invention discloses a device and method for producing medical isotopes. A hybrid nuclear reactor that is operable to produce a medical isotope includes an ion source operable to produce an ion beam from a gas, a target chamber including a target that interacts with the ion beam to produce neutrons, and an activation cell positioned proximate the target chamber and including a parent material that interacts with the neutrons to produce the medical isotope via a fission reaction. An attenuator is positioned proximate the activation cell and selected to maintain the fission reaction at a subcritical level, a reflector is positioned proximate the target chamber and selected to reflect neutrons toward the activation cell, and a moderator substantially surrounds the activation cell, the attenuator, and the reflector.