An Experimental Breeder Reactor II (EBR-II) anomalous reactivity meter was examined to verify its feasibility as a useful device in a fast reactor system. Anomalous reactivity is calculated by comparing “measured” reactivity with that predicted by system parameters; this provides useful diagnostic, alarm, and possible plant protective functions. Examples include application during an arbitrary rise-to-power for EBR-II as well as effectiveness during an EBR-II loss-of-primary -pumping-power event. Single subassembly flow loss events may be questionable for the crude anomalous reactivity meter described here, but flow disturbances of the magnitude required for this event have been observed with a reactivity meter.