Algorithms Performance Investigation of a Generalized Spreader-Bar Detection System

Robinson, Sean M. ; Ashbaker, Eric D. ; Hensley, Walter K. ; Schweppe, John E. ; Sandness, Gerald A. ; Erikson, Luke E. ; Ely, James H.

Pacific Northwest National Laboratory (U.S.)

关键词: Radiation Detection;    Isotope Identification;    Gantry Crane;    Nonproliferation;    Spreader Bar;   

DOI  :  10.2172/1122335
RP-ID  :  PNNL-19921
RP-ID  :  AC05-76RL01830
RP-ID  :  1122335

美国|英语

来源: UNT Digital Library

【 摘 要 】

A “generic” gantry-crane-mounted spreader bar detector has been simulated in the Monte-Carlo radiation transport code MCNP [1]. This model is intended to represent the largest realistically feasible number of detector crystals in a single gantry-crane model intended to sit atop an InterModal Cargo Container (IMCC). Detectors were chosen from among large commonly-available sodium iodide (NaI) crystal scintillators and spaced as evenly as is thought possible with a detector apparatus attached to a gantry crane. Several scenarios were simulated with this model, based on a single IMCC being moved between a ship’s deck or cargo hold and the dock. During measurement, the gantry crane will carry that IMCC through the air and lower it onto a receiving vehicle (e.g. a chassis or a bomb cart). The case of an IMCC being moved through the air from an unknown radiological environment to the ground is somewhat complex; for this initial study a single location was picked at which to simulate background. An HEU source based on earlier validated models was used, and placed at varying depths in a wood cargo. Many statistical realizations of these scenarios are constructed from simulations of the component spectra, simulated to have high statistics. The resultant data are analyzed with several different algorithms. The simulated data were evaluated by each algorithm, with a threshold set to a statistical-only false alarm probability of 0.001 and the resultant Minimum Detectable Amounts were generated for each Cargo depth possible within the IMCC. Using GADRAS as an anomaly detector provided the greatest detection sensitivity, and it is expected that an algorithm similar to this will be of great use to the detection of highly shielded sources.