A multichannel coincidence nuclear detector system for spectral charactertion of nuclear radiation sources at a remote location. The system is designed to detect and classify the radiation source in unfriendly territory and to provide a radio link back to a friendly receiver user station. The sensing elements are comprised of a plurality of plastic scintillator fiber sensors which may be several meters long and with each fiber having a different spectral sensitivity to gamma and neutron sources. Each of the scintillator fibers is connected to a transmitting optical fiber which may be 1 kilometer or more in length. The plurality of optical fibers transmit the optical signal generated by the radiation from a nuclear source impinging on the scintillator fibers to an electronic system. The electronic system is a sealed self contained battery operated device which is comprised of a photomuliplier detector and microprocessor based signal processing and data storage. The microprocessor compares the input signals from each scintillator fiber and determines the energy source. The data is stored in the microprocessor and may be interrogated by a radio frequency link to at a receiver station many kilometers away. The fiber sensors, optical fibers, and the electronics system including a transmitting antenna are all covertly positioned to prevent being observed by an unauthorized person.