Abstract: An apparatus and method are disclosed to remotely determine the location of an unknown nuclear radiation source or locations of unknown nuclear radiation sources which may even be shielded from the detection apparatus by known obstructions. The apparatus uses fixed position omnidirectional radiation intensity responsive detectors arranged in known geometry. Signals are provided from the detectors to a signal acquisition and computer system which monitors the detector outputs. The method is based on finding the ratios of the field intensities between the detectors due to each radiation source. A set of equations based on these ratios is used to locate and size a source or a set of algorithms is used to separate the signals into the component parts for each source and to determine the source locations and source sizes.