An Application of Control Charts to Radiation Portal Monitoring

Radiation detection systems are deployed at U.S. borders to guard against entry of illicit radioactive material. This paper compares six control chart methods in analyzing neutron count data collected as a vehicle passes through a radiation portal monitor. The six methods are based on cumulative counts, maximum count, sequential probability ratio test (SPRT), sequential cumulative sum (CUSUM), exponentially weighted moving average (EWMA) and a matched filter, under different vehicle and illicit material scenarios through a simulation study. Also, an algorithm to determine thresholds for the SPRT method is described.