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Particle therapy (PT) used for cancer treatment can spare healthy tissue and reduce treatment toxicity. However, full exploitation of the dosimetric advantages of PT is not yet possible due to range uncertainties, warranting development of range-monitoring techniques. This study proposes a novel range-monitoring technique introducing the yet unexplored concept of simultaneous detection and imaging of fast neutrons and prompt-gamma rays produced in beam-tissue interactions. A quasi-monolithic organic detector array is proposed, and its feasibility for detecting range shifts in the context of proton therapy is explored through Monte Carlo simulations of realistic patient models and detector resolution effects. The results indicate that range shifts of [Formula: see text] can be detected at relatively low proton intensities ([Formula: see text] protons/spot) when spatial information obtained through imaging of both particle species are used simultaneously. This study lays the foundation for multi-particle detection and imaging systems in the context of range verification in PT. ispartof: SCIENTIFIC REPORTS vol:13 issue:1 ispartof: location:England status: published

Purpose: Measurement of carbon in cores of undisturbed sediments may provide valuable information on historical trends in sea primary production and carbonate precipitation which can be related to climate changes. Since core sediments are usually subjected to a different analysis, it is important to preserve the sample. Anon-destructive technique for carbon measurement in sedimentsbased on Fast Neutron Activation Analysis (FNAA) has been developed, which might replace the Loss-on-Ignition (LOI) as a conventional method for carbon analysis. Materials and methods: Method was tested on sediment samples collected from the Western Black Sea at depths up to 22 m. A surface sample and a corecut in centimeter intervals were freeze-dried. Samples weighing between 60 and 300 g were irradiated with the portable neutron generator. Gamma rays from 12C(n, n'γ)12C nuclear reaction were collected between 2000 and 4000 s by LaBr3:Ce detector. Standards for direct comparison and construction of the calibration line were prepared as mixtures of different amounts of quartz sand and graphite powder. FNAA results for total carbon (TC) were verified by LOIat 1000°C.LOIat 450°C and treatment with 1 M HCl were used to separate inorganic carbon (IC) and organic carbon(OC), respectively, followed by the FNAA measurements. Results and discussion: Climate effects on physical and biological marine processes are evident as historical changes in carbon flux to sediments. Carbon in sediments is found in the form of the OC produced byphotosynthetic organisms and as IC produced by calcifying organismsand precipitated as calcite. The FNAA is usually applied to samples weighing more than 1 kg. The method was optimized to reduce the minimum weight of the sample to 60 g, after subsequent adaptation of the set-up geometry.Carbon content measured in cores and surface sediment was between 2.8 and 6.1 wt%. OC constituted up to 84% of TC measured in the core.FNAA measurements were in good agreement with LOI analysis. Conclusions: The results have shown that FNAA can be used for the non-destructive determination of carbon in sediments in samples weighing ≥ 60g.FNAA is non-destructive, robust and fast in comparison to conventional methods for carbon determination such as LOI.The disadvantage is a relatively high MDL of 1%.

Prompt gamma-ray neutron activation analysis (PGNAA) has been widely used for elemental analysis of bulk samples as it provides an on-line, rapid and non-destructive means of performing such analysis. The Monte Carlo Library Least-Squares (MCLLS) approach is one of the methods for quantitative analysis providing elemental weight fractions via an assumption that the total prompt gamma-ray spectrum is a linear combination of the contributions from the individual prompt gamma-ray spectra of the sample constituents. For the generation of prompt gamma-ray libraries of each constituent, a specific purpose Monte Carlo code system called Center for Engineering Applications of Radioisotopes Coincidence Prompt Gamma-Ray (CEARCPG) is utilized. In this work, the focus was on detecting and measuring chlorine impurity in crude oil samples, i.e. trace amounts of chlorine. A preliminary study investigating the feasibility of PGNAA method in conjunction with the MCLLS approach for measuring trace amounts of chlorine in oil samples was performed. For this purpose, an extended version of the MCLLS approach, the so-called MCLLSX approach, was proposed and applied for the quantitative analysis. The results presented in this paper prove the feasibility of the proposed approach.

Red mud (RM) contains large quantities of microscale particles < 1 micrometer and high concentrations of potentially toxic elements. In this research, we have used two types of RM of similar chemical properties but containing different quantities of micro-particles, to test whether their size plays a role in the uptake of chemical elements by earthworm Eisenia fetida. Earthworms were exposed for seven days to artificial soils (prepared in the laboratory following a protocol) amended with increasing quantities of RM. Mortality of 86% occurred when earthworms were exposed to amended soil containing 46% of particles below 1 µm. Surprisingly, tissue analyses have shown decreased concentrations of metals instead of the expected toxic effect. SEM analysis revealed that micro-particles strongly adhere to the earthworm epidermis putting them under the large stress. Micro-particles in RM clog their minute dermal pores of 90 nm to 735 nm in diameter, which size depends on whether the earthworm’s body is contracted or stretched. Strong adhesion of micro-particles to earthworms’ epidermis and blockage of their microsize pores prevented normal dermal respiration and absorption of chemical elements through their epithelium resulting in a decrease of most measured metals, especially essential elements potassium, calcium and iron, followed by the lethal outcomes.

Neutron inspection of sea-going cargo containers has been widely studied in the past 20 yr to non-intrusively detect terrorist threats, like explosives or Special Nuclear Materials (SNM), and illicit goods, like narcotics or smuggling materials. Fast 14 MeV neutrons are produced by a portable generator with the t(d, n)α fusion reaction, and tagged in both direction and time thanks to the alpha particle detection. This Associated Particle Technique (APT) allows focusing inspection on specific areas of interest in the containers, previously identified as containing suspicious items with X-ray radiographic scanners or radiation portal monitors. We describe the principle of APT for non-nuclear material identification, and for nuclear material detection, then we provide illustrations of the performances for 10 min inspections with significant quantities (kilograms) of explosives, illicit drugs, or SNM, in different cargo cover loads (e.g. metallic, organic, or ceramic matrices).

An important challenge in the petroleum industry is to reduce the salt content to acceptable levels in crude oil. Continuous monitoring of crude oil salinity is thus an important aspect. However, development of safe and reliable on-line and non-intrusive monitoring systems is still a challenging task. In this work, a method for non-intrusive, on-line monitoring of the chlorine impurity in crude oil based on prompt gamma-ray neutron activation analysis (PGNAA) in conjunction with a portable pulsed neutron generator producing 14 MeV neutrons in deuterium-tritium (DT) nuclear reactions is proposed and tested. Simulations with Monte Carlo N-Particle version 6 (MCNP6) transport code combined with Center for Engineering Applications of Radioisotopes Detector Response Function (CEARDRF) and a specific purpose Monte Carlo code called Center for Engineering Applications of Radioisotopes Coincidence Prompt Gamma-Ray (CEARCPG) were used for the design optimization of the experiments. Preliminary results indicate that a minimum detection limit for chlorine impurity of about 71 mg/L is achievable for an integration time of 30 min.

A proposal for an autonomous and flexible ship container inspection system is presented. This could be accomplished by the incorporation of an inspection system on various container transportation devices (straddle carriers, yard gentry cranes, automated guided vehicles, trailers). The configuration is terminal specific and it should be defined by the container terminal operator. This enables that no part of the port operational area is used for inspection. The inspection scenario includes container transfer from ship to transportation device with the inspection unit mounted on it. The inspection is performed during actual container movement to the container location. A neutron generator without associated alpha particle detection is used. This allows the use of higher neutron intensities ( $5\times {10^9} - {10^{10}} \ \text{n/s}$ in $4\pi $ ). The inspected container is stationary in the “inspection position” on the transportation device while the “inspection unit” moves along its side. The following analytical methods will be used simultaneously: neutron radiography, X-ray radiography, neutron activation analysis, (n, $\gamma $ ) and (n,n’ $\gamma $ ) reactions, neutron absorption. and scattering, X-ray backscattering. The neutron techniques will utilize “smart collimators” for neutrons and gamma rays, both emitted and detected. The inspected voxel is defined by the intersection of the neutron generator and the detectors solid angles. The container inspection protocol is based on identification of discrepancies between the cargo manifest, elemental “fingerprint” and radiography profiles. In addition, the information on container weight is obtained during the container transport and screening by measuring of density of material in the container.

The possibility of using fast 14 MeV neutrons and the associated alpha particle technique, together with a library least-squares fitting technique to detect the various CW agents as well as explosives and narcotics were investigated. The Quality Assurance/Quality Control (QA/QC) procedures for neutron sensors were established and further developed for CW agents, with the aim to reduce the false positive and false negative rates. Simulants of the various types of CW agents were prepared and measured as well as appropriate standards for measuring the ratios of chemical elements abundances: C/Cl, C/N, C/S, C/F, C/P, C/O. The influence of the measurement environment and material in which the targets were hidden was investigated.

Purpose: There is a growing understanding that methane hydrates (MHs) distributed globally in permafrost and deep sea sediments present an enormous unconventional reservoir of methane (CH4) ; however, there is also increasing concern about their role in the global climate change. The study focuses on the evaluation of the environmental conditions in the deep Adriatic Sea during the Last Glacial Maximum (LGM, 21.5–18.3 ka BP) and presently with respect to MHs potential occurrence. Materials and methods: The MHs phase stability diagram was calculated in order to evaluate the methane hydrate stability zone (MHSZ) by using the Croatian Legacy Data and the digital bathymetry map of the Adriatic Sea obtained from the Croatian Hydrocarbon Agency (CHA). Environmental data from different surveys published in the scientific literature were used to assess the environmental conditions in the deep Adriatic Sea during the LGM and present. The sea level rise of 100 m since the end of the LGM was taken into consideration. The volume of methane in place (MIP) as an estimation of the amount of CH4 stored in MHs deposits at standard conditions of pressure and temperature (SPT, T0 = 273.15 K, P0 = 0.101325 MPa) was calculated by using combined gas law VSPT = (P×V/T) × (TSPT/PSPT). Results and discussion: Evaluation of the MHs phase stability diagram for the Adriatic Sea in present environmental conditions has revealed that MHs are exactly at the boundary of stability. This has been calculated for the potential temperature of 13 °C, the salinity of 3.87% (data measured at the E2-M3A deep ocean observatory of the Southern Adriatic), and the average geothermal gradient of 17 °C km−1 reported in the literature and verified by the Croatian Legacy Data of CHA. According to the published literature, LGM deep sea temperature was 2–4 ° C lower and seawater was saltier. Consequently, the estimation of MHSZ during the LGM taking into consideration the temperature of 10 °C and salinity of 3.98% revealed a potential deposit of methane in place (MIP) of more than 415 × 109 m3, the majority of which probably dissociated in the sea/atmosphere system in the last 18 ka. Conclusions: The results have shown that MHs reservoir in the deep sea Adriatic basin shows boundary instability for MHs occurrence which might be of importance for studying the role of MHs in climate change. Further research is needed as follows: (1) thermodynamic modeling in order to understand if the MHs dissociation is concluded ; and (2) in the case of the transient condition, seismic data analysis in order to reveal the presence of a relic bottom simulating reflection.

The prospecting activities for finding new rare earth elements (REE) sources have increased greatly in recent years. One of the main discoveries was announced in 2011 by Japanese researchers who found large quantities of REE on the ocean seafloor at the sea depths greater than 4,000 m. The classic approach to investigate REE in deep sea sediments is to obtain sediment samples by drilling that is followed by laborious laboratory analysis. This is very expensive, time consuming and not appropriate for exploring vast areas. In order to efficiently explore the ocean floor for REE deposits, the further development of affordable sensors is needed. Here, we propose two nuclear techniques for exploring REE in surface deep sea sediments: i) Passive measurement of lutetium-176 radioactivity, appropriate if long-term in-situ measurements are possible, and ii) The use of the neutron sensor attached to a remotely operated vehicle for rapid in-situ measurement of gadolinium by thermal neutron-capture. Since concentrations of lutetium and gadolinium show strong linear correlation to the total REE concentrations in deep sea sediments, it is possible to deduce the total REE content by measuring Lu or Gd concentrations only.

A next generation system, as an upgrade of a robotic mobile system for anti-personnel landmine clearance, was considered. In contrast to the first generation system where the fast neutron activation method and the associated alpha particle imaging (API) was supposed to be used for finding the residual explosives and/or landmines, in the next generation system fast neutrons (FN) was considered to be used only for the confirmation of the explosive in the suspected object previously found by the ground penetrating radar (GPR), metal detector (MD) and infrared imaging (IR). Such system is expected to have the acceptable price and the optimal demining vehicle speed of 10 cm/s. In contrast to the previous system only one neutron generator (NG) is needed. In order to study the possibility of FN to confirm the presence of TNT explosive in the real environment the tests were made with the soil of different moisture contents. Comparative study was done by using the $7.62~hbox{; ; cm}; ; times 7.62~hbox{; ; cm}; ; $ BGO, $7.62~hbox{; ; cm}; ; times 7.62~hbox{; ; cm}; ; {; ; rm LaBr}; ; _{; ; 3}; ; :{; ; rm Ce}; ; $ and $7.62~hbox{; ; cm}; ; times 7.62~hbox{; ; cm}; ; $ NaI(Tl) gamma-ray detectors. Although nitrogen was easily detected in larger amount of TNT explosive, its signal was weak in detection of Anti-Personal (AP) mine like DLM2.4. The presences of soil additionally diminish the possibility of nitrogen detection even in the Anti-Tank mines (AT).

The maintenance and repair of reinforced concrete structures, especially those submerged in the sea-water require effective inspection and monitoring techniques for assessing the state of corrosion in the reinforcement material. An underwater inspection system was developed which is able to monitor the corrosion of the reinforcement. The system is composed of a remotely operating vehicle (ROV) equipped with the sealed tube neutron generator (NG). By rotating the NG and by using the associated alpha particle technique it is possible to measure the concrete cover thickness together with the reinforcing bar diameter. The possibility of estimating the carbon and chloride contents in the concrete was investigated. Iron plates of different thickness, covered by 6 cm thick concrete block, were successfully detected and the thickness of the concrete cover was estimated. In addition, reinforcing bar of one and 3 cm in diameter were identified and measured. All measurements could be performed without cleaning the concrete surface from fouling material.

International audience; A system using a neutron sensor installed within a Remotely Operated Vehicle (ROV) for underwater inspection has been developed. The system can inspect objects for the presence of threat materials, such as explosives and chemical agents, by using alpha particle tagged neutrons from a sealed tube d + t neutron generator to produce characteristic gamma rays within the interrogated object. Here we show that the measured gamma spectra for commonly found ammunition charged with TNT explosives are dominated by C, O and Fe peaks enabling the underwater determination of explosives inside an ammunition shell.

In order to perform Quality Assurance/Quality Control (QA/QC) procedures for a system dedicated to the neutron interrogation of objects for the presence of threat materials one needs to perform measurements of reference materials (RM) i.e. simulants having the same (or similar) atomic ratios as real materials. It is well known that explosives, drugs, and various other benign materials, contain chemical elements such as hydrogen, oxygen, carbon and nitrogen in distinctly different quantities. For example, a high carbon-to-oxygen ratio (C/O) is characteristic of drugs. Explosives can be differentiated by measurement of both (C/O) and nitrogen-to-oxygen (N/O) ratios. The C/N ratio of the chemical warfare agents, coupled with the measurement of elements such as fluorine and phosphorus, clearly differentiate them from the conventional explosives. Here we present the RM preparation, calibration procedure and correlations attained between theoretical values and experimentally obtained results in laboratory conditions for C/O and N/C ratios of prepared hexogen (RDX), TNT, DLM2, TATP, cocaine, heroin, yperite, tetranitromethane, peroxide methylethylketone, nitromethane and ethyleneglycol dinitrate simulants. We have shown that analyses of the gamma ray spectra by using simple unfolding model developed for this purpose gave a nice agreement with the chemical formula of created simulants, thus the calibration quality was successfully tested.

Red mud is a toxic waste left as a byproduct in aluminum production Bayer process. Since it contains significant concentrations of other chemical elements interesting for industry, including Rare Earths Elements (REEs), it is also potential secondary ore source. Recent events in some countries have shown that red mud presents a serious environmental hazard if not properly stored. The subject of our study is evaluation of the red mud elemental composition, especially yttrium, scandium, gallium and REEs, from an ex-aluminum plant in Obrovac, Croatia, left from the processing of bauxite mined during late 70's and early 80's at the eastern Adriatic coast and stored in open concrete basins for more than 30 years since then.

723 sediment samples collected along the eastern Adriatic coast have been analyzed using Energy Dispersive X-Ray Fluorescence. Factor Analysis and GIS have been used for the evaluation of the resulting data base containing information on K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Br, Rb, Sr, Y, and Pb concentration levels in order to find spatial relationships in distribution of measured elements. This study can be used to identify background values and to evaluate sediment quality standards.

A multi-sensor system was evaluated for the determination of barrel content with regard to eventual pollution hazards. The proposed system is able to investigate (in situ) the interior of a barrel filled with various unknown substances ranging from chemical and radioactive waste, raw sewage sludge, municipal incinerator ashes to common household trash. The crucial part of the system is a neutron sensor, which enables the identification of substance content without actually opening the barrel at all. A comparative laboratory test with the 3″×3″ and 5″×5″×10″ NaI(Tl) gamma ray detectors was made after which 3″×3″ detector was selected and incorporated in the submarine called “Surveyor”. A field test was made in the Croatian Adriatic coast on the island Losinj. Field tests show that the commercial system utilizing the described method could be constructed for barrel inspection regardless of the measurement environment (underwater, on land, dumping site, isolated location, etc.).

The EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) uses 14 MeV neutrons produced by the 3 H(d,n) 4 H fusion reaction to detect explosives and narcotics in cargo containers. Reactions induced by fast neutrons produce gamma rays, which are detected in coincidence with the associated alpha particle to determine the neutron direction. In addition, the neutron path length is obtained from a time-of-flight measurement, thus allowing the origin of the gamma rays inside the container to be determined. Information concerning the chemical composition of the target material is obtained from the analysis of the energy spectrum. The carbon, oxygen, and nitrogen relative count contributions must be converted to chemical proportions to distinguish illicit and benign organic materials. An extensive set of conversion factors based on Monte Carlo numerical simulations has been calculated, taking into account neutron slowing down and photon attenuation in the cargo materials. An experimental validation of the method is presented by comparing the measured chemical fractions of known materials, in the form of bare samples or hidden in a cargo container, to their real chemical composition. Examples of application to real cargo containers are also reported, as well as simulated data with explosives and illicit drugs.

Gamma-ray spectra produced in carbon, nitrogen, oxygen, sodium, aluminium, silicon, chlorine, calcium, chromium, iron, nickel, copper, zinc, and lead by 14. MeV tagged neutrons have been collected with NaI(Tl) detectors of the EURITRACK system, which low-energy threshold has been reduced to 0.6. MeV to detect gamma rays of major elements like iron. The spectra have been compared with Monte Carlo simulations to check the tabulated gamma-ray production data. A quantitative approach to subtract the scattered neutron background is also reported.

The EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) inspection system uses 14 MeV neutrons produced by the D(T,n α) reaction to detect explosives in cargo containers. Reactions induced by fast neutrons inside the container produce gamma rays, which are detected in coincidence with the associated alpha particle, the detection of which allows the neutron direction to be determined. The neutron path length is obtained from a neutron time-of-flight measurement, thus allowing the origin of the gamma rays inside the container to be determined, while the chemical composition of the target material is correlated with their energy spectrum. Gamma-ray spectra have been collected with the inspection portal equipped with large volume NaI (Tl) detectors, in order to build a database of signatures for various elements (C, O, N, Fe, Pb, Al, Na, Si, Cl, Cu, Zn) with a low energy threshold of 0.6 MeV. The spectra are compared with previous ones, which were acquired with a 1.35 MeV threshold. The new library is currently being tested to unfold the energy spectra of transported goods into elemental contributions. Results are compared with data processed with the old 1.35 MeV threshold database, thus illustrating the improvement for material identification.

The coastal sea floor is littered with many of man made objects and materials including a variety of ammunition. In addition, sediments in ports, harbors and marinas have increased concentrations of chemicals used as biocides in antifouling paints. In this report the locations in Adriatic Sea and whole Mediterranean for which there are evidences that are contaminated by different ammunition are presented. In order to be able to establish if an object on the sea floor contains some sort of threat material (explosives, chemical warfare) a system using neutron sensor installed within an unmanned underwater vessel has been developed and tested. When positioned above the object such a system can inspect the object for the presence of the threat material by using alpha particle tagged neutrons from the sealed tube d+t neutron generator. The same system can also be used to inspect ship hulls, either to detect potential anomalies attached to the hull, or to determine the nature of materials within hull, especially of sunken ships.

The Mediterranean coastal seafloor is littered with man-made objects and materials, including a variety of ammunition in many areas. In addition, sediments in ports, harbors and marinas are contaminated with elevated concentrations of chemicals used as biocides in antifouling paints. In order to reach a satisfactory level of environmental security of the coastal sea areas, fast neutron activation analysis with detection of associated alpha particles and energy dispersive X-ray fluorescence, both in laboratory and inside an autonomous underwater vehicle for in-situ measurements, has been used for the characterization of the objects on the seafloor. Measurements have shown that gamma ray spectra are able to distinguish threat material from the surrounding material. Analysis of more than 700 coastal sea sediment samples has resulted in concentration distribution maps indicating the locations of “hot spots”, which might interfere with threat material identification.

The container scanning system based on the elemental analysis of suspect cargo by use of fast 14 MeV neutrons with detection of associated alpha particle has been recently developed under the EU-FP6 “EURITRACK” project. The system is currently set-up in port of Rijeka, Croatia, to be tested and upgraded under the EU-JLS ERITR@C project. Here we present results of analysis performed on 152 screened containers selected by the Croatian Custom and detail descriptive statistical analysis of their shipping manifests. Statistics such as distribution functions of container types, type of packages, type of cargos and average cargo densities were obtained in order to establish the properties of standard cargo traffic. The analyses by using multivariate statistical approach that included principal component analysis (PCA) and between group analysis (BGA) have shown that cargo matrices can be classified as metallic (Fe, Al, Cu, Zn, Ni…), ceramic–glass (Si, O) and organic (C, O, N). In this paper the organic matrices have been analysed in more detail since they are identified as most difficult because of their potential interference with main elements contained in threat materials such as explosives or drugs. Density as a discriminating factor has been included for better recognition of different types of goods.

It was demonstrated in the previous work that various threat materials could be detected inside the sea going cargo container by measuring the three variables, carbon and oxygen concentration and density of investigated material. Density was determined by measuring transmitted neutrons, which is not always practical in terms of setting up the instrument geometry. In order to enable more geometry flexibility, we have investigated the possibility of using the scattered neutrons in cargo material identification. For that purpose, the densities of different materials were measured depending on the position of neutron detectors and neutron generator with respect to the target position. One neutron detector was put above the target, one behind and one in front of the target, above the neutron generator. It was shown that all three positions of neutron detectors can be successfully used to measure the target density, but only if the detected neutrons are successfully discriminated from the gamma rays.

The EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) inspection system uses 14 MeV neutrons produced by the D(T,n α) reaction to detect explosives in cargo containers. Fast-neutron-induced reactions inside the container produce gamma rays, which are detected in coincidence with the associated alpha particle. The definition of the neutron path and the time-of-flight measurement allow positioning the source of the gamma ray inside the container, while the chemical composition of the target material is correlated with the energy spectrum of the coincident gamma rays. However, in case of dense cargo, neutron moderation and photon attenuation inside the container make difficult the reconstruction of the material composition from the measured gamma-ray energy spectrum. An analytical method has been developed and validated against experimental data, which allows obtaining the chemical carbon-to-oxygen and carbon-to-nitrogen ratios of the inspected items from the gamma-ray energy spectra. The principle of the method is presented along with validation tests.

The possibility of the detection of “dirty bomb” presence inside sea containers is evaluated. The method proposed for explosive and fissile material detection makes use of two sensors (X-rays and neutrons). A commercial imaging device based on the X-ray radiography performs a fast scan of the container, identifies a “suspect” region and provides its coordinates to the neutron based device for the final “confirmatory” inspection. In this two sensor system a 14 MeV neutron beam defined by the detection of associated alpha particles is used for interrogation of only volume elements marked by X-ray sensor. The object’s nature is determined from passive and neutron induced, gamma energy spectra measurements. Experimental results (time-of-flight and gamma energy spectra) obtained for the irradiation 30 kg of TNT, depleted uranium and other materials hidden inside the container are presented.

The EURopean Illicit TRAfficing Countermeasures Kit (EURITRACK) project is part of the 6th European Union Framework Program. It aims at developing a Tagged Neutron Inspection System (TNIS) to detect illicit materials, such as explosives and narcotics, in cargo containers. Fast neutron induced reactions produce specific gamma-rays used to determine the chemical composition of the inspected material. The associated particle technique is employed to precisely locate the interaction points of the neutrons. A new deuterium– tritium neutron generator has been developed, including a pixelized alpha particle detector. The TNIS also comprises high-efficiency fast neutron and gamma-ray detectors, a dedicated front-end electronics and an integrated software to entirely drive the system and automatically process the data. Most components have been integrated during last months at Institute Ruder Boskovic, in Zagreb, Croatia. An overview of the TNIS and of its preliminary performances is presented.

Once the presence of the anomaly on the bottom of the coastal sea water is confirmed it is necessary to establish if it contains explosive charge. This could be performed by using neutron sensor installed within an underwater vessel. When positioned above the object the system inspects the object for the presence of the threat materials by using neutrons from the sealed tube d+t neutron generator with detection of associated alpha particles. The detection of alpha particles defines the neutron beam which helps the reduction of the background. Whole spectrum signature could be used for the identification of threat materials investigated.

The aim of the research reported here is the development of a methodology for the measurement of small scale variations in chemical elements concentrations, in particular of carbon to oxygen ratio. Knowledge of the C/O ratio is of importance to many problems in various fields. Here we single out the application in obtaining important information about the oilfields. The most fundamental reservoir parameters-oil, gas and water content-are critical factors in determining how each oilfield should be developed. It is well established that carbon to oxygen ratio log yields accurate and repeatable data that can be used to identify and monitor reserves depletion. Recent improvements in neutron generator and gamma detector technologies resulted in small devices which allowed through-tubing measurements. Although the ratio of carbon and oxygen yields is a measure of the amount of oil around the tool it should be realized that a carbon signal can originate from several sources including the borehole, the cement behind the casing, the formation rock and the formation fluid. In order to evaluate these contributions individually we are proposing the modification of the neutron generator by insertion of segmented associated alpha particle detector. From the measurement of neutron time of flight spectra (alpha particle detector-start signal ; gamma ray detector-stop signal) it would be possible to determine the location of gamma-ray production voxel and in such a way to determine radial variations in chemical elements concentrations, in particular of C/O ratio.

Gamma rays produced by scattering of 14 MeV neutrons with detection of associated alpha particles were used for determination of object location in a shipping container. It is shown that is possible to locate an object’s position inside the container and, in some cases, also obtain some compositional information (at least carbon and oxygen in TNT). The movement of the peak in the time spectrum corresponds to the change of the object location in the container. Carbon was successfully identified together with its position in the container, even behind 5.1 cm thick iron slabs which is impossible to be seen by an industrial 300 keV X-ray radiographic system. Also, 7.5 kg of TNT was successfully identified inside containers filled with soil.

A prototype of portable sealed neutron generator has been recently built to deliver 14 MeV neutron beams tagged by a YAP:Ce α -particle detector. In order to produce simultaneously multiple neutron beams to irradiate complex samples, a study of the position sensitivity of the α -particle detector has been performed. Possible applications in non-destructive analysis and future developments of the tagged neutron inspection system (TNIS) concept are discussed.

Non-destructive inspection of luggage has been simulated in laboratory conditions by using a 14 MeV tagged neutron beam and BaF 2 scintillation detectors (Tagged Neutron Inspection System, TNIS). The tagged neutron beam is produced by detecting the associated alpha particle emitted in the D+T reaction by means of a YAP:Ce scintillator. The TNIS intrinsic time resolution has been measured to be δ t =0.9 ns [FWHM], which allows inspection of a minimum voxel of 5 cm depth along the neutron flight path. This characteristic is demonstrated by identifying graphite and water samples hidden inside a hard plastic suitcase filled with background material. Finally, explosive devices such as small anti-personnel or anti-tank landmines have been inspected when placed inside the suitcase. In the case of relatively large explosive objects such as an anti-tank landmine, the system is capable of testing directly the TNT charge inside the device, separating this material from the external plastic case. Further developments of the TNIS concept are discussed.

The detection of landmines by using available technologies is a time consuming, expensive and extremely dangerous job, so that there is a need for a technological breakthrough in this field. Atomic and nuclear physics based sensors might offer new possibilities in de-mining. Among the available nuclear techniques, the neutron backscattering technique (NBT), based on the detection of the produced thermal neutrons, is thought to be the most promising for field applications. We discuss here two limitations of NBT, being related to the soil moisture. First, the critical value of the soil moisture, reached when the density of the hydrogen atoms in the landmine is equal to that in the background soil, defines a condition for which the detection is not possible. Critical values are small for some of the landmine types, thus suggesting the application of the method to arid countries, where the soil moisture is lower than 10%. Furthermore, small-scale variations of the soil moisture content, experimentally determined for different soil types, are found to be capable of generating false positive readings. To avoid this problem, the integration of the NBT with a second sensor, as the metal detector, is proposed.

Measurements have been made of characteristic gamma rays spectra from A(n,n ′ γ)A reactions induced by 14.1 MeV neutrons on bulk samples of different substances: C, H 2 O, SiO 2 , C 3 H 6 N 6 and samples of soil. Background radiation was reduced by the associated alpha particle technique.

Relatively recently, in the last 20 years, it was discovered that methane hydrate (MH) deposits are globally distributed in the permafrost and oceans. Before 1965 when first deposits were discovered in nature, it was believed that MH can occur only in laboratory conditions or in vast parts of the Universe. Presently it is presumed that this solid crystalline compounds in which CH4 molecules occupies the water ice lattices (nominal chemical formula of MH is C4H62O23) can serve as an energy source favorably to the all of the world remaining conventional hydrocarbon sources. The worldwide estimates of MH deposits range from 2x1014 m3 to 3.053x1018 cubic meters. This uncertainty partly results from our limitations in geological understanding of the MH deposits, which is due to the relatively bad quality of data obtained by presently available seismic and electromagnetic techniques. Moreover, MH deposits can become vulnerable to climate changes, which were already occurring in geological past whit tremendous consequences for the global life on Earth. Thus, further development of advanced techniques is needed to enhance our abilities to better characterize, quantify and monitor the MH deposits. In the work presented 14 MeV neutrons and associated alpha particle imaging (API) where used to quantify the amount of MH in the sample. Samples were prepared from sea sediment, quartz sand and MH simulant. MH simulant with chemical formula C4H46O23 was made from sucrose (25 % by mass) and water. MH quantity was measured by measuring the carbon content in the sample [1-8].

The reported loss of α-particles in the 14 MeV tagged neutron generators has been investigated using two neutron generators equipped with α-particle counters and two neutron detectors. One neutron detector was put right in the middle of the tagged neutron cone and another one was put outside the cone. By measuring the difference between double (neutron–neutron) and triple (α-neutron-neutron) coincidences it is possible to deduce the α-particle loss since the number of triple coincidences should be equal to the number of double coincidences. In all measurements performed a deficit of triple with respect to double coincidences has been observed. This deficit was smallest for the threshold of α-particle Constant Fraction Discriminator (αCFD) being 0 and maximum allowed voltage of α-particle detector being −1.7 kV. The smallest measured deficit value was equal to 13±1%. From the observed results it was concluded that the deficit was due to a number of non-detected α-particles that loose sufficient quantity of energy while traveling to the detector because of collisions with particles present in the neutron tube and/or in the tritium target. These α-particles will not be detected as they fall under the threshold of αCFD discriminator. Magnetic fields present in the system worsen the situation since they are forcing α-particles to travel larger distances because of toroidal movement and undergoing additional collisions. Tagged neutron technique has many kind of applications and it is particularly important for high accuracy nuclear cross-sections measurements when α-particles losses must be carefully assessed.

The aim of the research reported here is the development of a methodology for the measurement of small scale variations in chemical elements concentrations, in particular of carbon - oxygen ratio. Knowledge of the C/O ratio is of importance to many problems in various fields. Here we single out the application in obtaining important information about the oilfields. The most fundamental reservoir parameters - oil, gas and water content - are critical factors in determining how each oilfield should be developed. It is well established that carbon to oxygen ratio log yields accurate and repeatable data that can be used to identify and monitor reserves depletion. Recent improvements in neutron generator and gamma detector technologies resulted in small devices which allowed through-tubing measurements. Although the ratio of carbon and oxygen yields is a measure of the ammount of oil arround the tool it should be realized that a carbon signal can originate from several sources including the borehole, the cement behind the casing, the formation rock and the formation fluid. In order to evaluate these contributions individualy we are proposing the modification of the neutron generator by insertion of segmented associated alpha particle detector. From the measurement of time of flight spectra (alpha particle detector - start signal; gamma ray detector - stop signal) it would be possible to determine the location of gamma ray producing voxel and in such a way to determine radial variations in several chemical elements concentrations, in particular of carbon to oxygen ratio.

Here we describe a prototype for non-destructive, in-situ, accurate and cost-effectively measurement procedure of carbon in soil based on neutron activation analysis using 14 MeV tagged neutron beam. This technology can be used for carbon baseline assessment on regional scale and for monitoring of its surface and depth storage due to the changes in agricultural practices undertaken in order to mitigate global climate change. © 2012 SPIE.

The maintenance and repair of reinforced concrete structures, especially those submerged in the sea-water, require effective inspection and monitoring techniques for assessing the state of corrosion in reinforcement material. An underwater inspection system was developed which is able to monitor the reinforcement corrosion. The system is ROV equipped with the sealed tube neutron generator (NG). By rotating the NG and by using the associated alpha particle technique it is possible to measure the concrete cover depth together with the reinforcing bar diameter. The possibility to estimate the carbon and chloride content in the concrete was investigated. Iron plates of different thickness, covered by 6 cm thick concrete block, were successfully detected and the thickness of the concrete cover was estimated. In addition, reinforced bar of one and three centimeters in diameter was identified and measured.

Red mud is a toxic waste left as a byproduct in aluminum production Bayer process. Since it contains significant concentrations of other chemical elements interesting for industry, including REE, it is also potential secondary ore source. Recent events in some countries have shown that red mud presents a serious environmental hazard if not properly stored. The subject of our study is the red mud from an ex-aluminum plant in Obrovac, Croatia, left from processing of bauxite mined during late 70's and early 80's at the eastern Adriatic coast and since than stored in open concrete basins for more than 30 years. We have used energy dispersive x-ray fluorescence analysis (both tube and radioactive source excitation), fast neutron activation analysis and passive gamma spectrometry to identify a number of elements present in the red mud, their concentration levels and radioactivity in the red mud. The high concentrations of Al, Si, Ca, Ti and Fe have been measured. Chemical elements Sc, Cr, Mn, Co, Ni, Cu, Zn, Ga, As, Se, Br, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Pb, Th and U were found in lower concentrations. No significant levels of radioactivity have been measured.

Fast neutron interrogation with the associated particle technique can be used to identify explosives in cargo containers (EURITRACK FP6 project) and unexploded ordnance on the seabed (UNCOSS FP7 project), by detecting gamma radiations induced by 14 MeV neutrons produced in the 2H(3H,α)n reaction. The origin of the gamma rays can be determined in 3D by the detection of the alpha particle, which provides the direction of the opposite neutron and its time-of-flight. Gamma spectroscopy provides the relative counts of carbon, nitrogen, and oxygen, which are converted to chemical fractions to differentiate explosives from other organic substances. To this aim, Monte Carlo calculations are used to take into account neutron moderation and gamma attenuation in cargo materials or seawater. This paper presents an experimental verification that C, N, and O counts are correctly reproduced by numerical simulation. A quantitative comparison is also reported for silicon, iron, lead, and aluminium.

Tagged neutron inspection system was used for the underwater detection of explosives. Neutrons were produced in the d + t nuclear reaction with API 120 sealed tube neutron generator. Five kilograms of TNT explosive were measured in a pool filled with water. Measurements were done in target in, target out configuration. Also, a sandwich made of 6 mm thick iron plates with explosive placed between two layers of sea sediments was measured under the same conditions. Sediments were collected in the Adriatic Sea. Measurements were repeated with TNT explosive replaced by rocks of similar size and shape. Neutron tube was rotated in order to find the position of explosive (rocks) in the sandwich. It was found that TNT can be detected underwater and that is possible to distinguish TNT from the sea rocks placed between 6 mm thick iron plates or between layers of sediments by their ratios of carbon and oxygen.

In the frame of the FP7 UNCOSS project (Underwater Coastal Sea Surveyor), whose aim is to develop a neutron-based explosive detection system to identify unexploded ordnance (UXO) lying on the sea bottom, the choice of the gamma-ray detector is essential to reach the optimal performances. This paper presents comparative tests between the two candidates: NaI(Tl) and LaBr 3 (Ce) detectors, in favour to the 3 in.×3 in. LaBr 3 (Ce); thus, confirming the choice previously performed by numerical simulation because of its higher fast timing properties, spectral resolution, and efficiency per volume unit. The gamma-ray spectra produced by 14 MeV tagged neutron beams on the elements of interest (C, O, N, Al, Fe, Si, and Ca) have also been recorded with this detector in order to unfold the spectrum of the interrogated object into elementary contributions. A qualitative comparison with the gamma-ray spectra simulated with the MCNPX computer code and the ENDFB/VII.0 nuclear library has also been performed to validate the numerical model. An additional quantitative validation has been performed with an explosive-like material (ammonium acetate).

A tagged neutron inspection system has been used for the detection of explosive and illicite drugs. Simulant of the RDX explosive was measured in different environments and its gamma ray spectra were compared with the gamma ray spectra of benign materials like paper, sugar and rise. "Fingerprint" of the RDX simulant was found by detecting the nitrogen as well as by making the triangle plot which coordinates show the carbon and oxygen content and density. Density was obtained by measuring the intensity of the transmited tagged neutrons. Hence, the presence of the simulant can be confirmed by using two different methods. The possibility of using the triangle plot for detection of illicit drugs like heroin, cocain and marihuana is also discused.

In order to demonstrate the possibility of identifying the material within the objects on the sea floor we have performed tests with the 14 MeV sealed tube neutron generator incorporated inside a small submarine, SURVEYOR, submerged in the test basin filled with sea water. The materials inside the investigated objects were identified by measuring the gamma ray spectra and by using the window on the measured alpha- gamma time spectrum. In addition, we describe our field test facility and measurements done at this location in the framework of the EU FP7 project UNCOSS. The existence of a data base of potentially explosive devices on the floor of coastal sea, especially ports and waterways, is of paramount importance. However, the sea floor is littered by number of different objects and the water is not very transparent on such locations. This makes the identification of objects extremely difficult even on known locations. We discuss how to position the SURVEYOR when the object investigated for the presence of explosive has been identified by other sensors (camera, sonar, magnetometer, etc.).