A radiation upset detector is provided. The radiation upset detector includes at least one radiation sensitive memory initialized with at least one respective known-signature word; and at least one radiation hardened logic circuitry communicatively coupled to the at radiation sensitive memory to check the known-signature word at at least a kHz rate to detects errors. Responsive to detecting an error in the known-signature word in the radiation sensitive memory, the radiation hardened logic circuitry sends an action command. At least one of: a memory size of the memory; a number of circuits in the logic circuitry; a clock rate for the checking the known-signature word; and at least one corruption threshold is selected based on system reliability requirements of the protected system including at least one of: an overall operational reliability requirement of the protected system; a probability of detection success; false alarm rates; and a required speed of detection.