Safeguards Applications Research Articles

Dual-particle imaging system based on simultaneous detection of photon and neutron collision events

A dual-particle imaging (DPI) system capable of simultaneously detecting and imaging fast neutrons and photons has been designed and built. Imaging fast neutrons and photons simultaneously is particularly desirable for nuclear nonproliferation and/or safeguards applications because typical sources of interest (special nuclear material) emit both particle types. The DPI system consists of three detection planes: the first two planes consist of organic-liquid scintillators and the third plane consists of NaI(Tl) inorganic scintillators. Pulse shape discrimination technique(s) may be used for the liquid scintillators to differentiate neutron and photon pulses whereas the NaI(Tl) scintillators are highly insensitive to neutrons. A prototype DPI system was set up using a digital data acquisition system as a proof of concept. Initial measurements showed potential for use of the DPI system with special nuclear material. The DPI system has efficiencies of the order of 10−4 correlated counts per incident particles for both neutron and photon correlated counts, with simple-backprojection images displaying peaks within a few degrees of the source location. This uncertainty is expected to decrease with more extensive data interpretation.

Assessment of Fuzzy Logic Radioisotopic Pattern Identifier on Gamma-Ray Signals with Application to Security

Analysis of acquired nuclear detector gamma-ray signals for recognition of present radioisotopic signatures is crucial to national security and security applications. Identification algorithms must be accurate and rapid. Artificial intelligence is a scientific field with a variety of tools suitable to implement automated processing of nuclear signals. The use of low resolution portable detectors to measure gamma-ray signals has found a wide use in security and safeguards applications. In this paper, the fuzzy logic based analysis methodology that has been previously developed is applied and assessed on a variety of nuclear signals obtained with a low resolution scintillation detector, and more particularly a sodium iodide (NaI) detector. Various types of fuzzy membership functions are employed and their performance is assessed with regard to the number of positive detections, misses, and false alarms. Furthermore, recorded results from the set of low resolution gamma ray signals are used to estimate the detection sensitivity for each membership function. Results demonstrate the overall effectiveness of the fuzzy logic based identifier, and consist of the main course for the assessment of each membership function. Furthermore, comparison of results designates the triangular membership function as the best membership shape for this type of detector signals.

A study of possibility to design a fast neutron spectrometer based on the organic scintillator with surrounding materials

This paper deals with the design of a novel spectrometer of fast neutrons in nuclear safeguards applications based on the liquid organic scintillator EJ-309 with materials of different thickness surrounding the detector. The investigation was performed on the simulated data obtained by the MCNPX-PoliMi numerical code based on the Monte Carlo method. Among the various materials (polyethylene, iron, aluminum, and graphite) investigated as layers around the scintillator, polyethylene and iron have shown the most promising characteristics for evaluation of fast neutron energy spectra. The simulated pulse height distributions were summed up for each energy bin in the neutron energy range between 1 MeV and 15 MeV in order to obtain better counting statistics. The unfolded results for monoenergetic neutron sources obtained by a first order of Tikhonov regularization and non-linear neural network show very good agreement with the reference data while the evaluated spectra of neutron sources continuous in energy follow the trend of the reference spectra. The possible advantages of a novel spectrometer include a less number of input data for processing and a less sensitivity to the noise compared to the scintillation detector without surrounding materials.

Synthesis of a New Amberlite 7HP Sorbent Impregnated by Nano Manganese Dioxide and Its Applications for Uranium Separation

ABSTRACT In this work, a commercially available Amberlite 7HP has been modified using nano-flakes MnO2 prepared by a simple reduction method. The characterization of the new sorbent impregnated by nano manganese dioxide was performed by scanning electron microscope, transmission electron microscope, energy-dispersive X-ray, X-ray diffraction, and Fourier transformation infrared spectrometric analyses. The performance of the new sorbent for ion separation in aqueous medium was studied in detail by varying the pH, contact time, initial concentration, bed height, and flow rate. The maximum sorption has been achieved at a solution of pH 3.1. Sorbed ions were desorbed with 10 mL of 1.5 M HCl solution. The kinetics and isothermal parameters of the sorption of ions onto the new sorbent have been studied. The kinetic experimental data properly correlate with the second-order kinetic model and the time required to reach sorption equilibrium is 240 min. The sorption data could be well interpreted by the Langmuir sorption isotherm and the monolayer sorption capacity was found to be 56.3 mg · g−1. The sorption data were fitted to two well-established fixed-bed sorption models, namely, Thomas and Yoon–Nelson models, with a correlation coefficient, R2, ≥0.993. The separation performance of the new sorbent was demonstrated by using different real samples. Consequently, the developed sorbent resin was successfully utilized for the separation of uranyl ions in safeguard applications.

Offsetability is highest for common and widespread biodiversity: response to Regneryet al.

We welcome the attempts of Regnery et al. (2013) to apply our global offsetability process (Pilgrim et al. 2012) to the French context: national adaptation is essential for testing and improving this process. We wholeheartedly agree that conserving common biodiversity is crucial for ecosystem functioning. Unfortunately, the authors misinterpret the purpose of our process. Far from recommending that offsets only be undertaken for impacts on rare biodiversity, our process is specifically intended to highlight the risks of offsetting impacts on biodiversity that is particularly vulnerable or irreplaceable, and/or where management opportunities are limited. Our approach thus emphasizes that offsets have a much higher chance of success for more common and widespread biodiversity. Beyond this general misunderstanding, the assessment of Regnery et al. that 99% of areas developed in France in 2010 would not be subject to our offsetability process is flawed in at least four ways. First, they suggest that our process only applies to species, when we explicitly state that it relates to both species and ecosystems (and suggest that ecological processes be integrated when data permit). Second, they suggest that impacts on LC or NT biodiversity are only considered greater than “Low” if ≥10% of their population is impacted, when in fact this threshold relates to the area of analysis, which we note will “almost always be larger than the predicted project impact area.” Third, Regnery et al. seem not to have assessed which development sites in France in 2010 held ≥10% of Least Concern (LC) or Near Threatened (NT) biodiversity, instead incorrectly assuming that a “Low” categorization applies to any site holding solely LC or NT biodiversity. Last, and most importantly, they directly replace global with national threat categories, despite our advice that there should be “development of national or subnational quantitative thresholds for each issue, via a stakeholder consultation process.” In summary, far more than 1% of areas developed in France in 2010 would likely be subject to our offsetability process if applied correctly. We suggest that biodiversity of Low Conservation Concern might “be viewed as the lower threshold for offsetting, at which offsets might not be required if cumulative loss is not a significant issue.” Offsetting 100% of impacts to achieve No Net Loss across landscapes would be ideal, but transaction costs would render such a system impractical. Offsetting all small-scale impacts on biodiversity of least conservation concern would only be practicable if a simple compensation system—such as a system of developer contributions or “in-lieu” fees (Treweek et al. 2009)—were established, though this would likely not reach the high bar of No Net Loss offsetting (e.g., BBOP 2012). We encourage further development of our offsetability process for France, given its high global responsibility for biodiversity (Mittermeier et al. 2008). Regnery et al. note that “policy frameworks for the conservation of threatened species and habitats” exist in France, but development in overseas departments and territories has often proceeded without appropriate application of such safeguards (e.g., Bouchet et al. 1995).

Experimental parameters for a reactor antineutrino experiment at very short baselines

Reactor antineutrinos are used to study neutrino oscillation, search for signatures of non-standard neutrino interactions, and to monitor reactor operation for safeguard applications. The flux and energy spectrum of reactor antineutrinos can be predicted from the decays of the nuclear fission products. A comparison of recent reactor calculations with past measurements at baselines of 10-100m suggests a 5.7% deficit. Precision measurements of reactor antineutrinos at very short baselines O(1-10 m) can be used to probe this anomaly and search for possible oscillations into sterile neutrino species. This paper studies the experimental requirements for a new reactor antineutrino measurement at very short baselines and calculates the sensitivity of various scenarios. We conclude that an experiment at a typical research reactor provides 5{\sigma} discovery potential for the favored oscillation parameter space with 3 years of data collection.

Alternatives for Helium-3 in Multiplicity Counters

Alternatives to helium-3 are being actively pursued due to the shortage and rising costs of helium-3. For safeguards applications, there are a number of ongoing investigations to find alternatives that provide the same capability in a cost-effective manner. One of the greatest challenges is to find a comparable alternative for multiplicity counters, since they require high efficiency and short collection or die-away times. Work has been progressing on investigating three commercially available alternatives for high efficiency multiplicity counters: boron trifluoride (BF3) filled proportional tubes, boron-lined proportional tubes, and lithium fluoride with zinc sulfide coated light guides. The baseline multiplicity counter used for the investigation is the Epithermal Neutron Multiplicity Counter with 121 helium-3 filled tubes at 10 atmosphere pressure, which is a significant capability to match. The primary tool for the investigation has been modeling and simulation using the Monte Carlo N-Particle eXtended (MCNPX) radiation transport program, with experiments to validate the models. To directly calculate the coincidence rates in boron-lined (and possibly other) detectors, the MCNPX code has been enhanced to allow the existing coincidence tally to be used with energy deposition rather than neutron capture reactions. This allows boron-lined detectors to be modeled more accurately. Variations of tube number and diameter along with variations in the amount of inter-tube moderator have been conducted for the BF3 and boron-lined cases. Tube pressure was investigated for BF3 , up to two atmospheres, as well as optimal boron thickness in the boron-lined tubes. The lithium fluoride was modeled as sheets of material with light guides in between, and the number and thickness of the sheets investigated. The amount of light guide, which in this case doubles as a moderator, was also optimized. The results of these modeling and simulation optimization investigations are described and results presented.

A Novel Neutral Carrier for Uranyl Ion Based on a Commercially Available Aminophosphate Derivative: Evaluation in Membrane Electrodes and Nuclear Safeguards Applications

AbstractThe construction and performance characteristics of uranyl membrane electrodes based on cheap and commercially available amino(trimethyl)phosphate are described. The influence of various membrane constituents on the potentiometric responses of the prepared membrane electrodes has been studied. Optimized membrane electrodes exhibited performance characteristics comparable with those based on high cost and commercially available ionophores. Selectivity studies indicated that the developed membrane electrodes are selective towards uranyl ion over a large number of cations including the well‐known uranyl ion interferents (e.g., Fe3+, Th+4). The analytical utility of the proposed membrane electrode has been demonstrated through its application in nuclear safeguards verification purposes.

Comparison of active and passive environmental sampling for safeguards applications

Environmental sampling (ES) of surfaces using cotton swipes at nuclear facilities is one of the standard sampling protocols used by International Atomic Energy Agency (IAEA) inspectors to verify treaty compliance. Described herein is a series of studies undertaken to (1) survey a variety of low latent uranium content sampling media for efficacy of collecting nuclear materials and (2) compare active collection of particulates to swipe sampling. Findings from the evaluation of 40 natural and synthetic woven swipes will be presented. Results from a joint Oak Ridge National Laboratory (ORNL) and Savannah River National Laboratory (SRNL) project wherein a variety of passive deposition surfaces and active collections were examined for efficacy of sampling uranium processing effluents will also be detailed. For the swipe material evaluation portion of this work, uranium (U) particulate collection efficiency was evaluated on woven materials as-received and coated with complexants/solvents. The relative merits of each sampling matrix were reviewed on the basis of: (1) latent U background, (2) ease of separating the swipe material from the nuclear components, (3) presence of isobaric interferences from the swipe, and (4) efficiency in collecting uranium from contaminated surfaces. The second series of experiments evaluated the collection characteristics of active aerosol collection versus swipe sampling. ORNL and SRNL are collaborating on the development of the next generation of ES equipment for air grab and constant samples that could become an important addition to the international nuclear safeguards inspector’s toolkit. Described herein are findings from the evaluation of collection efficiency of swipe sampling and active collection using an aerosol contaminant extractor (ACE) developed by SRNL.

Experimental evaluation of a boron-lined parallel plate proportional counter for use in nuclear safeguards coincidence counting

Boron-lined proportional technologies are increasingly being considered as a viable option for the near-term replacement of 3He-based technologies for use in international nuclear safeguards neutron detection and coincidence counting applications. In order to determine the applicability and feasibility of any replacement technology for international safeguards, it must be evaluated against performance parameters specific to nuclear safeguards applications. In this paper, we present an experimental evaluation of a boron-lined parallel plate proportional counter developed by Precision Data Technology, Inc. (PDT). The counter performance was evaluated using a high-rate 252Cf spontaneous fission neutron source and a set of 137Cs gamma-ray sources with a dose rate of 450mR/h at the detector face. The performance data were subsequently compared with an equivalent 3He-based system defined using the Monte Carlo N-particle eXtended (MCNPX) radiation transport code.

Nuclear safeguards applications using LG‐SIMS with automated screening capabilities

A primary tool for detecting undeclared nuclear activities is the analysis of uranium‐bearing particles collected on cotton swipes. For many years, secondary ion mass spectrometry (SIMS) has been used as one of the mainstay techniques for particle analysis of nuclear safeguards samples. SIMS is unique in that it is the only technique that can both localize the particles of interest and also provide the isotopic composition of single particles. This paper presents data obtained on standard uranium particle samples using large geometry (LG)‐SIMS instruments equipped with the newly developed, automated particle measurement screening software. Both sample screening measurements and microbeam analyses on individual particles are presented. The enhanced performance of the SIMS method for nuclear safeguards applications using LG‐SIMS instruments equipped with automated screening capabilities is also discussed. Copyright © 2012 John Wiley & Sons, Ltd. and Crown copyright

Resonance Region Nuclear Data Analysis to Support Advanced Fuel Cycle Development

The Oak Ridge National Laboratory (ORNL) and the Korean Atomic Energy Research Institute (KAERI) are performing collaborative research as part of a three-year United States (U.S.)–Republic of Korea (ROK) International Nuclear Energy Research Initiative (I-NERI) project to provide improved neutron cross-section data with uncertainty or covariance data important for advanced fuel cycle and nuclear safeguards applications. ORNL and KAERI have initiated efforts to prepare new cross-section evaluations for Pu, Np, and the stable Cm isotopes. At the current stage of the I-NERI project, ORNL has recently completed a preliminary resonance-region cross-section evaluation with covariance data for Pu and has initiated resonance evaluation efforts for Np and Cm. Likewise, KAERI is performing corresponding high-energy cross-section analyses (i.e., above the resonance region) for the noted isotopes. The paper provides results pertaining to the new resonance region evaluation efforts with emphasis on the new Pu evaluation.

Neutron detection gamma ray sensitivity criteria

The shortage of 3He has triggered the search for effective alternative neutron detection technologies for national security and safeguards applications. Any new detection technology must satisfy two basic criteria: (1) it must meet a neutron detection efficiency requirement, and (2) it must be insensitive to gamma-ray interference at a prescribed level, while still meeting the neutron detection requirement. It is the purpose of this paper to define measureable gamma ray sensitivity criteria for neutron detectors. Quantitative requirements are specified for: intrinsic gamma ray detection efficiency and gamma ray absolute rejection. The ratio GARRn is defined, and it is proposed that the requirement for neutron detection be 0.9 < GARRn < 1.1 at a 10 mR/h exposure rate. An example of results from a 3He based neutron detector are provided showing that this technology can meet the stated requirements. Results from tests of some alternative technologies are also reported.

Detection of anomalous reactor activity using antineutrino count evolution over the course of a reactor cycle

Abstract

Digital filter and clustering algorithms for improving energy resolution of CdZnTe detectors

CdZnTe (CZT) detectors are promising detectors especially for portable gamma spectroscopy and safeguards applications. However, energy resolution of CZT is suffering from poor mobilities of charge carriers, which result in a large signal shape variations depending on the interaction position inside the detector. Clustering technique was used to classify and independently treat these shape variations. Before the classification process, a digital filter was used to remove noises from CZT signals. The filtered signals were classified using Maxi-Mini Distance algorithm. Much improvement was obtained in the energy resolution of the CZT after the classification of the filtered signals than the unfiltered signal.

Nuclear resonance fluorescence ofNp237

Identification and characterization of fissile material is of international concern because of the possibility of proliferation. For safeguards applications, techniques providing isotopic information are necessary [1]. However, few techniques can distinguish between fissile isotopes. Nuclear resonance fluorescence is one technique that can be used in applications to identify and quantify isotopic content. NRF has also been proposed in several detector systems as a viable way to identify fissile material in cargo containers [2, 3]. It is necessary to measure the characteristic resonances of each isotope that is to be distinguished in identification and assay applications.

Neutron spectroscopy of plutonium oxide using matrix unfolding approach

The knowledge of a neutron energy spectrum is extremely valuable in nuclear non-proliferation and safeguards applications. Unfortunately, conventional gas and fission-type detectors are not adapted to determine incident neutron energy. As a result, a matrix inversion technique was implemented to generate desirable and consistent neutron energy spectra from an EJ-309 liquid scintillator. To overcome the ill-posed unfolded solutions, the method of sequential least squares is reviewed briefly, and the conditions under which it is used are stated. From the analysis, unfolded energy spectra solutions of five distinct PuO2 fuel samples and a 252Cf source are presented and compared to the simulated unfolded and reference energy distributions.

Application of Safeguards and Anti-Dumping Duties in Colombia

Colombia's experience in the use of safeguards and antidumping duties differs from international trends. On the one hand, the number of investigations conducted is substantially lower than that recorded in most of the hemisphere's large and medium-size countries. On the other hand, while there is a growing international trend of more frequent use of antidumping as opposed to safeguards, in Colombia the safeguard process has been the more used policy instrument. Although several large and medium-size firms are familiar with the application of safeguards and antidumping duties, there is still a relative unfamiliarity regarding the instruments in most of the private sector. The institutional arrangements related to the investigations and the decisionmaking processes have proven to be stable and sound. The trade liberalization process in the country has created awareness of the importance of preserving the competitiveness of production chains to strengthen their insertion in international markets, which has restrained the authorities from restricting access to intermediate goods and raw materials. The evaluation of the Colombian experience also raises concerns about the potential discretional use of these instruments. The relatively intense use of safeguards and antidumping measures in some specific periods and sectors, especially in the agricultural sector, shows that the institutional framework is not always enough to guarantee a disciplined use of the instruments.

I can see you: harassment and stalking on the Internet

It is an inevitable consequence of plausible anonymity and deliberately lax regulation that the potential for ‘virtual’ harassment or ‘cyber-’stalking, with the attendant possibility of threats, alarm, distress, slander and physical danger that go hand in hand with real world harassment, will increase the more widely available access to the Internet. The (relatively) recent explosion in casual exchange of personal information following the growth of sophisticated social networking platforms, the logical successors to more basic Internet chat-rooms, opens further the possibility of acquiring an unwanted connection with an obsessive party. The authors consider the application of current UK legislative safeguards to the Internet, looking at the suitability of the Protection from Harassment Act 1997, data protection, unauthorised modification of computer software, libel law, external Internet regulation, Convention and Codes, and the potential for vicarious liability of employers where harassment is carried out by an employee, amongst other issues and conclude that there is a pressing need for primary legislation to counter the inadequacy and lacunae found in current domestic law. The authors go on to consider the extraterritorial application of such legislation and postulate the need for a re-balancing of the competing rights of freedom of speech and personal safety and wellbeing. The authors further consider the potential liabilities of Internet Service Providers (ISPs), webhosts and Social Networking and chat-room forum sites, concluding that a shift in liability for Internet harassment from progenitor to facilitator is inevitable.

Isotope ratio analysis of actinides, fission products, and geolocators by high-efficiency multi-collector thermal ionization mass spectrometry

A ThermoFisher “Triton” multi-collector thermal ionization mass spectrometer (MC-TIMS) was evaluated for trace and ultra-trace level isotope ratio analysis of actinides (uranium, plutonium, and americium), fission products and geolocators (strontium, cesium, and neodymium). Total efficiencies (atoms loaded to ions detected) of up to 0.5–2% for U, Pu, and Am, and 1–30% for Sr, Cs, and Nd can be reported employing resin bead load techniques onto flat ribbon Re filaments or resin beads loaded into a millimeter-sized cavity drilled into a Re rod. This results in detection limits of <0.1 fg (10 4 atoms to 10 5 atoms) for 239–242+244Pu, 233+236U, 241–243Am, 89,90Sr, and 134,135,137Cs, and ≤1 pg for natural Nd isotopes (limited by the chemical processing blank) using a secondary electron multiplier (SEM) or multiple-ion counters (MICs). Relative standard deviations (RSD) as small as 0.1% and abundance sensitivities of 1 × 10 6 or better using a SEM are reported here. Precisions of RSD ≈0.01–0.001% using a multi-collector Faraday cup array can be achieved at sub-nanogram concentrations for strontium and neodymium and are suitable to gain crucial geolocation information. The analytical protocols reported herein are of particular value for nuclear forensic and nuclear safeguard applications.