Patent ID: 6891470

Claim:
A method of detecting radioactive material within a plurality of cargo receptacles using a master unit/master module and a plurality of radioactive material detection apparatuses, each apparatus having a transmitter, a detection controller and a radiation sensor configured to detect radiation over a predetermined or commanded period of time, the method comprising: (a) mounting the plurality of radioactive material detection apparatuses to the plurality of cargo receptacles, the total set of detection apparatuses comprising an array of detector and cargo receptacle locations; (b) sensing at least one of gamma radiation and neutrons in totality and/or by spectral distribution at each radioactive material detection apparatus and transmitting; initially sensed signals to the master unit/master module; (c) sensing at least one of gamma radiation and neutrons in totality and/or by spectral distribution over the predetermined or commanded period of time at each radioactive material detection apparatus and transmitting currently sensed signals to the master unit/master module; (d) calculating the difference between the initially sensed and currently sensed signals, the difference representing the radiation measured at each radioactive material detection apparatus location throughout the array of radioactive material detection apparatuses over a sensing period of time; (e) calculating an average measured radiation level at each radioactive material detection apparatus location throughout the entire array of radioactive material detection apparatuses by averaging the radiation sensed at radioactive material detection apparatuses proximate to each radioactive material detection apparatus, the set of average values for the plurality of radioactive material detection apparatuses forming a varying set of calculated estimates of background radiation space for the plurality of radioactive material detection apparatuses and corresponding cargo receptacles; and (f) comparing the measured radiation at each radioactive material detection apparatus location to the calculated estimate of background radiation space at each location in order to identify an anomaly amongst the plurality of cargo receptacles.