THE THREAT OF THEFT AND OTHER SUBVERSIVE ACTIVITIES HAS LONG BEEN A CONCERN OF UNION CARBIDE CORPORATION'S NUCLEAR DIVISION IN OAK RIDGE. VARIOUS TYPES OF INTERIOR VOLUMETRIC INTRUSION DETECTION DEVICES, SUCH AS INFRARED AND MICROWAVE TECHNIQUES, HAVE BEEN USED TO PROVIDE COMPLETE COVERAGE OF ALL AVENUES AN INTRUDER MIGHT USE. TO EXTEND THE VOLUME COVERAGE AND TO ADD TO THE PLANT'S REPERTOIRE OF VOLUMETRIC INTRUSION ALARM, A VIDEO MOTION DETECTION SYSTEM WAS DEVELOPED. THIS SYSTEM IS BASED ON THE USE OF A MICROCOMPUTER THAT LOOKS AT AN AREA VIA A NETWORK OF VIDEO CAMERAS. MOTION IN THE FIELD OF VIEW IS DETECTED BY COMPARING SUCCESSIVE VIDEO FRAMES AND MAKING A SOFTWARE-BASED ALARM DECISION. THE COVERAGE VOLUME AND SENSITIVITY TO OBJECT SIZE CAN BE CONTROLLED TO SOME EXTENT BY USING DIFFERENT LENSES. THE SOFTWARE-BASED NATURE OF THE MOTION DETECTOR, HOWEVER, LENDS THE GREATEST AMOUNT OF VERSATILITY AND ADAPTABILITY TO THE SYSTEM. ALARM DECISION VARIABLES THAT CAN BE EASILY ADJUSTED THROUGH SOFTWARE ARE THE PERCENT CHANGE IN GRAY LEVEL REQUIRED TO LABEL A PIXEL (PICTURE ELEMENT) AS SUSPECT, THE NUMBER OF SUSPECT PIXELS REQUIRED TO GENERATE AN ALARM, THE PIXEL PATTERN TO BE SAMPLED FROM THE IMAGE, AND THE RATE AT WHICH A NEW REFERENCE FRAME IS TAKEN. THE MOTION DETECTION SYSTEM IS BEING EVALUATED IN A WAREHOUSE FOR POTENTIAL APPLICATION TO SEVERAL AREAS OF THE NUCLEAR PLANT. HARDWARE AND SOFTWARE DESIGN DETAILS CONCERNING THE SYSTEM ARE PRESENTED. PROBLEMS ENCOUNTERED IN SYSTEM IMPLEMENTATION PERTAIN TO IMAGE RETENTION, EXTRANEOUS LIGHT SOURCES, PERSONNEL TRAFFIC CONTROL, CAMERA FIXTURING, TEMPERATURE EXTREMES, AND INTERFERENCE BY ANIMALS AND INSECTS. ILLUSTRATIONS AND PHOTOGRAPHS ARE PROVIDED. (DEP)