Neutron and Gamma-Ray Detection System Coupled to a Multirotor for Screening of Shipping Container Cargo

Abstract

In order to detect special nuclear materials and other radioactive materials in Security and Defense scenarios, normally, a combination of neutron and gamma-ray detection systems is used. In particular, to avoid illicit traffic of special nuclear materials and radioactive sources/materials, radiation portal monitors are placed at seaports to inspect shipping-container cargo. Despite their large volume (high efficiency), these detection systems are expensive, and therefore only a fraction of these containers are inspected. In this work, a novel mobile radiation detection system is presented, based on an EJ-200 plastic scintillator for the detection of gamma rays and beta particles, and a neutron detector EJ-426HD plastic scintillator (with 6Li) embedded in a compact and modular moderator. The use of silicon photomultipliers in both detectors presented advantages such as lightweight, compactness, and low power consumption. The developed detection system was integrated in a highly maneuverable multirotor. Monte Carlo simulations were validated by laboratory measurements and field tests were performed using real gamma-ray and neutron sources. The detection and localization within one meter was achieved using a maximum likelihood estimation algorithm for 137Cs sources (4 MBq), as well as the detection of 241Am–beryllium (1.45 GBq) source placed inside the shipping container.

Radioactive Source Localization Using a Mobile Radiation Detection System Featuring Informed Path-Based Decisions

“…Moreover, compared to previous work [30], in which only predefined paths were considered (estimated-to-actual source distances up to 2.5 m), an increased source localization accuracy was obtained by considering an informed path and a three-dimensional MLE algorithm for the source position estimation. The experimental results validate the recently presented work [31].…”

“…In a previous study [30], the authors tested the use of plastic scintillators with SiPM readout for the detection and localization of gamma-ray and neutron sources within a maritime shipping container. However, only predefined paths around the container were considered and the MLE algorithm used for the source position estimation was constrained to only two dimensions (not accounting for the source's height), resulting in a gamma-ray source position accuracy better than 1.3 m and 2.5 m when using the detection system as a handheld equipment or integrated in a multirotor respectively.…”

A mobile radiation detection system for security inspection and monitoring

“…-The radiation detection system performs complete paths around the container at a horizontal speed of 0.2 m/s. This speed was also considered in [6], allowing sufficient radiation data points for the source position estimation according to the acquisition rate of 1 Hz. -A safety distance of 50 cm between the detection system and the container walls is kept constant during the container inspection.…”

“…Either a single path at one-third the container´s height and a double path at one-third and at two-thirds the container´s height was considered. The paths' heights were chosen according to previous work performed by the authors [6], however other heights could be considered (which would not change the conclusions of this work). -Informed paths: The detection system initially performs complete turns around the container based on a predefined path.…”

“…Therefore, the development of a low-cost and highly efficient mobile radiation detection system capable of detecting both gamma-rays and neutrons is of paramount importance. In this study, a novel radiation detection system combining two independent detectors was developed: a 110 mm diameter and 30 mm thick EJ-200 plastic scintillator (for gamma and beta detection) and a thermal neutron detector EJ-426HD plastic scintillator embedded on a modular and compact high-density polyethylene (HDPE) moderator [6] [7]. For this study, only the EJ-200 detection system will be considered.…”