Various techniques are provided to detect the direction and location of one or more radiation sources. In one example, a system includes a plurality of radiation detectors configured to receive radiation from a radiation source. A first one of the radiation detectors is positioned to at least partially occlude a second one of the radiation detectors to attenuate the radiation received by the second radiation detector. The system also includes a processor configured to receive detection information provided by the first and second radiation detectors in response to the radiation, and determine a direction of the radiation source using the detection information. A modular system including gamma radiation detectors and neutron radiation detectors and related methods are also provided. In some cases, radiation source type may be determined in addition to or separate from radiation source direction.