Radiation, even shielded, gives off heat (detectable from satellites and aerial drones) and causes various types of shielding to emit detectable chemical fumes...which can be picked up by aerial drones and filters.
How does the arial radiation monitoring work?
Radiation, even shielded, gives off heat (detectable from satellites and aerial drones) and causes various types of shielding to emit detectable chemical fumes...which can be picked up by aerial drones and filters.