Current and Prospective Radiation Detection Systems, Screening Infrastructure and Interpretive Algorithms for the Non-Intrusive Screening of Shipping Container Cargo:A Review

The non-intrusive screening of shipping containers at national borders serves as a prominent and vital component in deterring and detecting the illicit transportation of radioactive and/or nuclear materials which could be used for malicious and highly damaging purposes. Screening systems for this purpose must be designed to efficiently detect and identify material that could be used to fabricate radiological dispersal or improvised nuclear explosive devices, while having minimal impact on the flow of cargo and also being affordable for widespread implementation. As part of current screening systems, shipping containers, offloaded from increasingly large cargo ships, are driven through radiation portal monitors comprising plastic scintillators for gamma detection and separate, typically 3He-based, neutron detectors. Such polyvinyl-toluene plastic-based scintillators enable screening systems to meet detection sensitivity standards owing to their economical manufacturing in large sizes, producing high-geometric-efficiency detectors. However, their poor energy resolution fundamentally limits the screening system to making binary “source” or “no source” decisions. To surpass the current capabilities, future generations of shipping container screening systems should be capable of rapid radionuclide identification, activity estimation and source localisation, without inhibiting container transportation. This review considers the physical properties of screening systems (including detector materials, sizes and positions) as well as the data collection and processing algorithms they employ to identify illicit radioactive or nuclear materials. The future aim is to surpass the current capabilities by developing advanced screening systems capable of characterising radioactive or nuclear materials that may be concealed within shipping containers

A study of SPRT algorithm and New-Guard for radiation detection

A novel and efficient radiation detection algorithm combined with a measuring unit will produce an ideal detector to battle field radiation measurement problems. Studies of Sequential Probability Ratio Test (SPRT) for radiation detection are essential towards developing efficient and accurate radiation detection algorithms. In this study, the performance of the classical Single-Threshold-Test (STT) and the SPRT First-In-First-Out (FIFO) algorithms is considered. Next, improvements made by the Last-In-First-Elected-Last-Out (LIFELO) algorithm are analyzed. Further, enhancements to the LIFELO algorithm, using the Dynamic Background Updating and Maximum Likelihood Estimator (MLE), are performed; The thesis also provides detailed requirements for an innovative hand-held radiation detection system and underlines additional features available on a New Generation User Adaptable Radiation Detector (New-GUARD) to help the field survey processes. Currently available technologies are studied to rationalize the need for the New-GUARD prototype. The New-GUARD is compared to similar products that are already available in the market to show its completeness as a radiation detector incorporated with Global Positioning System (GPS), wireless communication, and a self-correcting system. Primary performance evaluations of the algorithms are executed using Mathematica and further analysis is carried out with Matlab and C

Time-Interval Analysis for Radiation Monitoring

On-line radiation monitoring is essential to the U.S. Department of Energy (DOE) Environmental Management Science Program for assessing the impact of contaminated media at DOE sites. The goal of on-line radiation monitoring is to quickly detect small or abrupt changes in activity levels in the presence of a significant ambient background. The focus of this research is on developing effective statistical algorithms to meet the goal of on-line monitoring based on time-interval (time-difference between two consecutive radiation pulses) data. Compared to the more commonly used count data which are registered in a fixed count time, time-interval data possess the potential to reduce the sampling time required to obtain statistically sufficient information to detect changes in radiation levels. This dissertation has been formulated into three sections based on three statistical methods: sequential probability ratio test (SPRT), Bayesian statistics, and cumulative sum (CUSUM) control chart. In each section, time-interval analysis based on one of the three statistical methods was investigated and compared to conventional analyses based on count data in terms of average run length (ARL or average time to detect a change in radiation levels) and detection probability with both experimental and simulated data. The experimental data were acquired with a DGF-4C (XIA, Inc) system in list mode. Simulated data were obtained by using Monte Carlo techniques to obtain a random sampling of a Poisson process. Statistical algorithms were developed using the statistical software package R and the programming function built in the data analysis environment IGOR Pro. 4.03. Overall, the results showed that the statistical analyses based on time-interval data provided similar or higher detection probabilities relative to other statistical analyses based on count data, but were able to make a quicker detection with fewer pulses at relatively higher radiation levels. To increase the detection probability and further reduce the time needed to detect a change in radiation levels for time-interval analyses, modifications or adjustments were proposed for each of the three chosen statistical methods. Parameter adjustment to the preset background level in the SPRT test could reduce the average time to detect a source by 50%. Enhanced reset modification and moving prior modification proposed for the Bayesian analysis of time-intervals resulted in a higher detection probability than the Bayesian analysis without modifications, and were independent of the amount of background data registered before a radioactive source was present. The robust CUSUM control chart coupled with a modified runs rule showed the ability to further reduce the ARL to respond to changes in radiation levels, and keep the false positive rate at a required level, e.g., about 40% shorter than the standard time-interval CUSUM control chart at 10.0cps relative to a background count rate of 2.0cps. The developed statistical algorithms for time-interval data analyses demonstrate the feasibility and versatility for on-line radiation monitoring. The special properties of time-interval information provide an alternative for low-level radiation monitoring. These findings establish an important base for future on-line monitoring applications when time-interval data are registered

A COMPARISON BETWEEN DATA-DRIVEN AND PHYSICS OF FAILURE PHM APPROACHES FOR SOLDER JOINT FATIGUE

Prognostics and systems health management technology is an enabling discipline of technologies and methods with the potential of solving reliability problems that have been manifested due to complexities in design, manufacturing, environmental and operational use conditions, and maintenance. Over the past decade, research has been conducted in PHM to provide benefits such as advance warning of failures, enable forecasted maintenance, improve system qualification, extend system life, and diagnose intermittent failures that can lead to field failure returns exhibiting no-fault-found symptoms. While there are various methods to perform prognostics, including model-based and data-driven methods, these methods have some key disadvantages. This thesis presents a fusion prognostics approach, which combines or ―fuses together‖ the model based and data-driven approaches, to enable increasingly better estimates of remaining useful life. A case study using an electronics system to illustrate a step by step implementation of the fusion approach is also presented. The various benefits of the fusion approach and suggestions for future work are included

TRACKING OF MOVING RADIOACTIVE SOURCES

A system for detecting unsecured nuclear materials. Whereas current portal monitors rely in part on physical prominence to deter materials from entering the country, their application at intra-modal transport points may actually serve to divert the movement of nuclear materials rather than aid in interception. A flexible and low-profile system has been developed for unobtrusive detection and tracking of radioactive sources in transit suited for deployment at traffic choke points such as rest stops, toll collection plazas, truck stops, and bridges. The system includes gamma radiation detectors, networking for linking these detectors, signal processing algorithms, and a central processing and control unit

Nevada Test Site-Directed Research and Development, FY 2007 Report

The Nevada Test Site-Directed Research and Development (SDRD) program completed a very successful year of research and development activities in FY 2007. Twenty-nine new projects were selected for funding this year, and eight projects started in FY 2006 were brought to conclusion. The total funds expended by the SDRD program were $5.67 million, for an average per-project cost of$153 thousand. An external audit conducted in September 2007 verified that appropriate accounting practices were applied to the SDRD program. Highlights for the year included: programmatic adoption of 8 SDRD-developed technologies; the filing of 9 invention disclosures for innovation evolving from SDRD projects; participation in the tri-Lab Laboratory Directed Research and Development (LDRD) and SDRD Symposium that was broadly attended by Nevada Test Site (NTS), National Nuclear Security Administration (NNSA), LDRD, U.S. Department of Homeland Security (DHS), and U.S. Department of Defense (DoD) representatives; peer reviews of all FY 2007 projects; and the successful completion of 37 R&D projects, as presented in this report. In response to a company-wide call, authors throughout the NTS complex submitted 182 proposals for FY 2007 SDRD projects. The SDRD program has seen a dramatic increase in the yearly total of submitted proposals--from 69 in FY 2002 to 182 this year--while the number of projects funded has actually decreased from a program high of 57 in FY 2004. The overall effect of this trend has helped ensure an increasingly competitive program that benefited from a broader set of innovative ideas, making project selection both challenging and rewarding. Proposals were evaluated for technical merit, including such factors as innovation, probability of success, potential benefit, and mission applicability. Authors and reviewers benefited from the use of a shortfalls list entitled the 'NTS Technology Needs Assessment' that was compiled from NTS, National Weapons Laboratory (NWL), and NNSA sources. This tool continues to be of considerable value in aligning the SDRD program with mission priorities, and was expanded in FY 2007 to include technology development needs from the DHS and other agencies with missions closely aligned to that of the NTS

Radiation source detection from mobile sensor networks using principal component analysis

Detecting the presence of possible illicit radioactive materials in large areas is challenging because of changing background radiation, shielding effects and short collection time, especially when the radioactive materials are moving. The concept of mobile sensor networks is put forward to solve this problem. In this thesis, a small mobile sensor network is established using commercially available radiation detectors and cell phones. A spectrum decomposition and reconstruction method based on Principal Component Analysis (PCA) is proposed to work with mobile sensor networks. Two experiments are designed to test this method's performance on real-world data. The PCA-based method's performance is analyzed using receiver operating characteristic, or ROC curves. Further study finds that although the PCA-based method doesn't work well on current mobile sensor networks, its performance can be improved by increasing the radiation spectral quality