The Isotope Detection System (IDS), an automated gamma spectrometry system for the detection of fission products released from failed fuel rods has been installed at the Loss of Fluid Test Facility (LOFT) located at the Idaho National Engineering Laboratory. The IDS incorporates two germanium detectors monitoring four reactor sample streams -- the primary coolant from two locations, and the blowdown system liquid and vapor. The IDS is a dual processor system that operates in a master/slave mode. The slave processor is located in a plant area where personnel access is restricted. The system is interfaced to a variety of valves and pumps to control the sampling system and incorporates unique features to optimize the IDS for on-line reactor monitoring. The IDS will operate during an upcoming LOFT test during which the failure of several reactor fuel rods will occur.