From a homeland security point of view, it is important to detect the transportation of radioactive materials or potential radioactive contamination. The most commonly used devices are radiation portal monitors with plastic scintillation detectors. A signal from such detectors is processed by an amplitude analyser which can separate pulses into several mutually independent energy windows (representing energy intervals of gamma radiation). Therefore, the most appropriate method of evaluation is by the use of algorithms for multidimensional processing. This article describes a novel generalised approach designed with respect to the properties of radiation portal monitors. It includes a description of formulas and a whole algorithm as well as the procedure for determining the appropriate critical and detection limits. The predicted probability distribution for the proposed method of calculation was verified by simulations and experimental measurements. The algorithm was also compared with a commonly used gross counting algorithm.
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