NASA needs compact nuclear reactors to power future bases on the moon and Mars. These reactors require robust automatic control systems using low mass, rapid response, in-core reactor power monitoring sensors and radiation tolerant sensor interrogation systems that do not yet exist. Luna proposes to develop a new type of fiber optic miniature neutron flux and gamma flux sensor, which will have significantly faster response than recently developed fiber optic radiation sensors. The new sensors will maintain the advantages of current fiber optic reactor sensor technology, including small size for in-core sensor distributions, high temperature performance (above 600o
C), and immunity to electrical noise in the presence of ionizing radiation. During Phase I, Luna will demonstrate the feasibility of high-speed fiber optic gamma flux sensors in a nuclear reactor. Phase II will optimize the sensor design and the interrogation system for high temperature in-core monitoring of both gamma flux and neutron flux with internal thermal compensation and in-situ thermal calibration. At the end of Phase II, Luna will deliver a lightweight sensor interrogation system, utilizing experimentally verified radiation hardened components wherever possible, and including an analog output signal for interfacing with standard reactor control electronics.