Detection Of Radioactive Sources Research Articles

Design and development of a detector system and software tool installed on a mobile laboratory to provide both radiological characterisation of large areas and a simple tool for localising radioactive sources.

In emergency situations where an immediate response is required to make appropriate decisions by the competent authorities, it is essential to have measurement tools that provide results as accurate as possible in real-time. This paper presents the description of the upgrade of the mobile laboratory of the Radiological Alert Network of Extremadura, focusing on the characterisation of radioactive-contaminated land during emergency situations and the detection of radioactive sources. The detector system is based on two scintillation detectors and a car-borne dose rate monitor. Additionally, a software tool has been developed to collect information from the different devices involved (detectors, GPS, etc) and display it in an intuitive manner. This system has been tested in an area of a former phosphate facility where soils remain contaminated to varying degrees with radionuclides of TE-NORM origin.

Atmospheric effects on the laser-driven avalanche-based remote detection of radiation

The effect of realistic atmospheric conditions on mid-IR (λ = 3.9 µm) and long-wave-IR (λ = 10 µm) laser-induced avalanche breakdown for the remote detection of radioactive material is examined experimentally and with propagation simulations. Our short-range in-lab mid-IR laser experiments show a correlation between increasing turbulence level and a reduced number of breakdown sites associated with a reduction in the portion of the focal volume above the breakdown threshold. Simulations of propagation through turbulence are in excellent agreement with these measurements and provide code validation. We then simulate propagation through realistic atmospheric turbulence over a long range (0.1-1 km) in the long-wave-IR regime (λ = 10 µm). The avalanche threshold focal volume is found to be robust even in the presence of strong turbulence, only dropping by ∼50% over a propagation length of ∼0.6 km. We also experimentally assess the impact of aerosols on avalanche-based detection, finding that, while background counts increase, a useful signal is extractable even at aerosol concentrations 105 times greater than what is typically observed in atmospheric conditions. Our results show promise for the long-range detection of radioactive sources under realistic atmospheric conditions.

Rapid detection method of radioactive source based on low-count gamma spectra

This paper presented a mobile CsI gamma detector developed to solve the problem of radioactive source detection in a wide area. The performance of the detector was illustrated during the spectra collection investigation. 1-s spectrum collected by the detector was low-count signal, which is hard to distinguish whether it is a source contained signal or not. A rapid detection method of radioactive source based on the low-count gamma spectra was proposed. Principal component analysis (PCA) was the key technology which was able to extract the source information efficiently. The proposed method improved the detector sensitivity and accuracy.

Новый алгоритм для модернизации портальных радиационных мониторов с пластиковыми детекторами. Часть 4. Использование коллиматоров для повышения эффективности работы алгоритма

The way of improving of new algorithm by using additional lead collimators is discussed in the fourth part of the article. The results of calculations and direct measurements of collimators of different sizes for two variants of algorithm with four and six energy windows are presented in the paper. It is shown that using of lead collimators increases efficiency of algorithm and provides detection of radioactive sources less activity.

An IoT System for Radioactive Material Detection in Scrap Metal Recycling and Production Facilities

A radioactive source that is not under regulatory control because it is abandoned, lost, misplaced, stolen, or transferred without proper authorization is referred to as an orphan source. The melting of an orphan source, when mixed with scrap metal, has resulted in contaminated recycled metal and wastes and the consequences will be very serious for humans and the environment. In this paper, we propose and develop an Internet of Radiation Sensor System (IoRSS) to enhance the use of nuclear detection systems to detect nuclear and other radioactive materials out of regulatory control at points of entry/exit and other trade locations of scrap metal recycling and production facilities. The proposed IoRSS creates a robust and flexible network architecture along with advanced data fusion algorithms that combine information from many detectors. The test results show that the IoRSS system allows for accurate detection of radioactive sources and provides appropriate radiation incident response plans.

Enhancing the sensitivity for weak radioactive source detection

Considering the difficulties of the low signal-to-noise ratio in weak radioactive source detections, this study proposes an abandon Gaussian tails method based on the analysis of the characteristic information denoted by the full-energy peak of the gamma spectrum of a gamma-emitting radioactive source. Based on the study of the signal-to-background ratio and the statistical fluctuations in the signal of the weak radioactive source, a factor ζ, incorporating the statistical fluctuations of signal and background and the signal-to-background ratio, is suggested to characterize the sensitivity of a radioactive source detection. When ζ reaches its maximum value, the optimal counting window around the centroid of the full-energy peak can be obtained. To evaluate the effectiveness of the proposed approach, comparisons between the proposed abandon Gaussian tails, the conventional full-energy counting, and other experiential methods were performed. The results show that the sensitivity can be significantly improved. Further, experiments with different intensity of radiation sources and duplicated experiments were conducted to examine the stability of the proposed method.

Новый алгоритм для модернизации портальных радиационных мониторов с пластиковыми детекторами. Часть 2. Оптимизация величин порога срабатывания и сглаживания скорости счета монитора

The way of improving of traditional algorithm for portal radiation monitors with plastic detectors by optimization of values of alarming threshold and smoothing is discussed in the second part of the article. As the result of such optimization the probability of detection of radioactive sources may be significantly increased and probability of false alarms decreased as well.

Analysis of Source Detectability With Fast-Moving Sensors

We provide a comprehensive upper-bound analysis of radioactive source detection capabilities by characterizing performance of an idealistic system configuration. Specifically, we analyze scenarios where the sensors are moving relative to the source. We first present a simplified analytical model which allows us to compute a rough, yet comprehensive estimate of the minimum detectable amount (MDA) of source material for any given configuration. To our knowledge, this is the first analytical model to simultaneously account for and mutually relate sensor design parameters, physical properties of the environment, desired detection system performance, and application characteristics, all in one equation. For instance, for flyover applications, the model shows that if we reduce altitude of flight by half, we can increase the speed of the pass-by by a factor of approximately 8, while maintaining the same source detectability. We show the distributions of MDA that are feasible to attain across a variety of common sensor transport modalities and designs. By demonstrating what can possibly be attained in terms of detectability of sources of radiation when the ideal conditions are met, we can inform system design and perform comparative analysis of alternative designs, in particular. Our results are directly applicable to support system design, engineering, policy, and strategy decisions. They can mitigate risks and prevent time, resources, and funds from being directed toward attempts to achieve unrealistic goals in the broad range of applications of radiation detection technology.

Feasibility study of a lead-monoxide-based dosimeter for real-time radioactive source detection in HDR brachytherapy

Recently, cancer has been treated using high dose rates (HDRs), which requires highly reliable treatment plans. In current clinical practice, phosphors are widely used. However, these are of limited use for real-time verification of radiation during HDR brachytherapy; moreover, there is a possibility of electrical error via high-energy radiation because a photodiode is used to detect visible light. Therefore, it is necessary to develop a new dosimeter that can detect gamma rays effectively. This study aimed to investigate the feasibility of a lead monoxide- (PbO)-based dosimeter to detect the position of a radioactive source in HDR brachytherapy. It was confirmed that the fabricated PbO dosimeter has sufficient response coincidence, reproducibility, and dose linearity for gamma rays. Based on these results, it is demonstrated that the PbO dosimeter complies with the general requirements of HDR brachytherapy monitoring systems. Thus, the PbO dosimeter is expected to be used commercially in the future.

An Unmanned Aircraft System to Detect a Radiological Point Source Using RIMA Software Architecture

Unmanned Aircraft Systems (UASs), together with the miniaturisation of computers, sensors, and electronics, offer new remote sensing applications. However, there is a lack of hardware and software support to effectively develop the potential of UASs in different remote sensing applications, such as the detection of radioactive sources. This paper presents the design, development and validation of a UAS for the detection of an uncontrolled and point radioactive source. The article describes a flexible and reusable software architecture for detecting the radioactive source (NaTcO 4 , containing 99 m Tc) with a gamma-ray Cadmium Zinc Telluride (CZT) spectrometer as a proof of concept. The UAS is equipped with multichannel air-ground communications to perform missions beyond line of sight and onboard computation to process samples in real time and thus react to any anomaly detected during the mission. An ad hoc ground control station (GCS) has also been developed for the correct interpretation of the radioactive samples taken by the UAS. Radiological spectra plots, contour mapping and waterfall plots are some of the elements used in the ad hoc GCS. The article shows the results obtained in a flight campaign performing different flights at different altitudes and speeds over the radiological source, demonstrating the viability of the system.

A Methodology for Determining the Concentration of Naturally Occurring Radioactive Materials in an Urban Environment

The detection of radioactive sources in an urban setting is greatly complicated by natural background radiation, which emanates from various materials including roadways, sidewalks, soil, and building exteriors. The method presented and demonstrated here represents an effort to characterize the concentration of naturally occurring radioactive material (NORM) in these types of materials. The location surveyed in this work was the Fort Indiantown Gap Combined Arms Collective Training Facility in Lebanon County, Pennsylvania. Over 70 measurements with a high-purity germanium detector were performed to ascertain the NORM concentrations present in the soil, asphalt, gravel, concrete, and walls found throughout the site. Monte Carlo radiation transport calculations were used to obtain detector responses for these various geometries and materials to convert these measurements into NORM concentration estimates. Finally, synthetic spectra were simulated using the predicted source terms and compared to actual measurements, showing acceptable agreement.

Denial of Service Defence for Resource Availability in Wireless Sensor Networks

Wireless sensor networks (WSN) over the years have become one of the most promising networking solutions with exciting new applications for the near future. Its deployment has been enhanced by its small, inexpensive, and smart sensor nodes, which are easily deployed, depending on its application and coverage area. Common applications include its use for military operations, monitoring environmental conditions (such as volcano detection, agriculture, and management), distributed control systems, healthcare, and the detection of radioactive sources. Notwithstanding its promising attributes, security in WSN is a big challenge and remains an ongoing research trend. Deployed sensor nodes are vulnerable to various security attacks due to its architecture, hostile deployment location, and insecure routing protocol. Furthermore, the sensor nodes in WSNs are characterized by their resource constraints, such as, limited energy, low bandwidth, short communication range, limited processing, and storage capacity, which have made the sensor nodes an easy target. Therefore, in this paper, we present a review of denial of service attacks that affect resource availability in WSN and their countermeasure by presenting a taxonomy. Future research directions and open research issues are also discussed.

Commissioning and Field Tests of a Van-Mounted System for the Detection of Radioactive Sources and Special Nuclear Material

MODES_SNM project aimed at developing a mobile/portable modular detection system for radioactive sources and Special Nuclear Material (SNM). Its main goal was to deliver a tested prototype capable of passively detecting weak or shielded radioactive sources with accuracy higher than that of currently available systems. By the end of the project all the objectives have been successfully achieved. Results from the laboratory commissioning and the field tests are presented in this publication.

Detection of radioactive sources in urban scenes using Bayesian Aggregation of data from mobile spectrometers

Mobile radiation detector systems aim to help identify dangerous sources of radiation while minimizing frequency of false alarms caused by non-threatening nuisance sources prevalent in cluttered urban scenes. We develop methods for spatially aggregating evidence from multiple spectral observations to simultaneously detect and infer properties of threatening radiation sources.Our Bayesian Aggregation (BA) framework allows sensor fusion across multiple measurements to boost detection capability of a radioactive point source, providing several key innovations previously unexplored in the literature. Our method learns the expected Signal-to-Noise Ratio (SNR) trend as a function of source exposure using Bayesian nonparametrics to enable robust detection. The method scales well in spatial search by leveraging conditional independence and locality in Bayesian updates. The framework also allows modeling of source parameters such as intensity or type to enable property characterization of detected sources. Approaches for incorporating modeling information into BA are compared and benchmarked with respect to other data fusion techniques.

In situ clouds-powered 3-D radiation detection and localization using novel color-depth-radiation (CDR) mapping

The article presents an in situ clouds-powered radioactive source detection and localization approach, namely color-depth-radiation mapping, using 3-D land mapping within hazardous indoor environment and incorporating sensor fusion between a RGB-D camera and a portable radiation detector. In the approach, to achieve fast and robust image registration, color images detected by the camera are initially employed to extract crucial visual features and establish pairs of matched image features between successive scanned images. Following this, matched features are incorporated with the corresponding calibrated depth information to generate 3-D keypoint cloud pairs. To remove potential noises in the acquired data-sets, a novel geometric-based filtering algorithm is developed to reject incorrect keypoint pairs prior to iterative closest point-based image registration. Most importantly, an algorithm to determine the radioactive sources’ parameters including strength and 3-D position is developed for accurate radioactive source detection and localization. With this, the radioactive sources can be accurately pinpointed in the established 3-D map for efficient contamination control and safety management. Two radiation testing experiments were performed to verify the feasibility of the approach and its detection accuracy. The simulation results indicate that the proposed approach can reach up to 95% accuracy of radiation source localization incorporated in the 3-D map.

Benefits of Position-Sensitive Detectors for Radioactive Source Detection

There are many systems for counting photons such as gamma-rays emitted from radioactive sources. Many of these systems are also position-sensitive, which means that the system provides directional information about recorded events. This paper investigates whether or not the additional information provided by position-sensitive capability improves the performance of detecting a point-source in background. We analyze the asymptotic performance of the generalized likelihood ratio test (GLRT) and a test based on the maximum-likelihood (ML) estimate of the source intensity for systems with and without position-sensitive capability. When the background intensity is known and detector sensitivity is spatially uniform, we prove that position-sensitive capability increases the area under the receiver operating characteristic curve (AUC). For cases when detector sensitivity is nonuniform or background intensity is unknown, we provide numerical results to illustrate the effect of the parameters on detection performance.

Radioactive source detection by sensor networks

Detection limits of sensor networks for moving radioactive sources are characterized, using Bayesian methods in conjunction with computer simulation. These studies involve point sources moving at constant velocity, emulating vehicular conveyance on a straight road. For networks involving ten nodes, respective Bayesian methods are implementable in real time. We probe the increased computational requirements incurred by larger numbers of nodes and source trajectory parameters. The complexity appears quadratic in the number of nodes and, also, numerous trajectory parameters may be used. We investigate the consequences of different levels of background radiation. Simulations are shown to be useful for ranking candidate node layouts. We study the detection capabilities of individual sensors and the scalability of detection with sensor density; near the detection limit, increasing the number of sensors can accrue subproportional network sensitivity.

Nonparametric Statistical Tests for Radioactive Source Detection

This work describes a study carried out to assess the feasibility of using radiation sensors for real-time detection of radioactive sources within a facility. The source detection problem is formulated as a nonparametric hypothesis test using statistics computed from the radiation sensor signals. The purpose of this study is the development of tools that enhance the security and safety of nuclear material processing facilities by introducing new sensor modalities and developing remote monitoring capabilities. The results indicate that a source can be detected quite well using non parametric statistical tests in spite of poor signal to noise ratios, unknown background signals, and high measurement noise levels.

Evaluation of two rounds of testing of types of devices for monitoring radioactive sources in loaded vehicles

Tests of stationary devices for the detection of radioactive sources in moving trucks were performed by the Czech Metrological Institute – Inspectorate for Ionising Radiation, Prague in December 1996 and September 1997. The different systems were installed at a railway polygon. Each system contained two detection units placed symmetrically at the rail in a distance 2.3 m from the axes of each rail. The train comprising empty and scrap-filled trucks passed along the detection units at a speed of 5–30 km/h. The wide range of radioactive sources with 137Cs (activity ranging from 0.4 MBq to 5 GBq) were located at different positions in the truck. The purpose was to determine a detection limit under different conditions. Sources with 57Co, 60Co, 241Am were also used. The truck passed the polygon more than 1000 times. About 250 passes were free of source. All systems were also tested in a climatic chamber. The main parameters evaluated were the detection limit for an empty truck, detection limit for a truck filled with scrap (density 0.89 t/m 3), percentage of false alarms and stability of response at different temperatures. The other parameters like energy dependence, position dependence, linearity and overload, detection response time, etc., were also evaluated. The tested systems showing a positive result will be used in the field of steel recycling, metallurgy and the supervision of illegal transport.