Search

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.

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.

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 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.

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.

In today's society acts of terrorism must involve in some stages the illicit trafficking either of explosives, narcotics, chemical weapons, hazardous chemicals, radioactive materials and/or humans. Therefore the society must rely on the modern anti-trafficking infrastructure including adequate instrumental base. Old control measures slow down the traffic flow, they are time consuming and inefficient. Recently lots of efforts has be put into development of the concept of "the smart border", border management system that keeps pace with expanding trade while protecting from the threats of terrorist attack, illegal immigration, illegal drugs, and other contraband. Due to the size of container transport industry the shipping container control system must be an essential building block of the smart border concept. The world's total movement in containers is estimated to be 72m TEU ("20-foot equivalent units"). A single typical large container ship can carry up to 6, 000 TEU. Although the container has become indispensable to world commerce, it also turned out to be handy ways to smuggle drugs, contraband and illegal immigrants. Modern cargo inspection systems are non-invasive imaging techniques, the inspection systems using penetrating radiations (1.33 MeV gamma and 0.3 and 0.45 MeV x-rays) in the scanning geometry. Relative penetration of the commonly used radiation is 17.5, 10.0 and 4.43 cm-iron for 1.33, 0.45 and 0.3 MeV, respectively. The concept of the multisensor system is based on the integrated use of gamma or x-ray fast scanning of the interrogated object (i.e. the whole container) with subsequent detailed elemental analysis of suspicious volumes by using fast neutrons. The use of alpha particle tagged neutron beams is a unique feature of such device in that it can enhance by a large factor the signal/noise ratio of the system. In the work reported here the neutron beam was obtained by means of D+T reaction. The associated alpha particle detector was fixed in such a way that the associated neutron beam was in horizontal plane at 90º ; ; ; to the deutron beam. Slit in front of the scintlillator was used to define the geometrical dimensions of the beam on the interrogated object. The α -γ coincidence spectra were measured with the selection of α -γ coincidences performed by the 100 ns TAC range. The information on the position of the interrogated object was contained in the TAC spectrum, while object's composition gave rise to characteristic gamma ray spectrum. In addition, conceptual design of the system, and preliminary data, for the inspection of the shipping containers for radioactive materials in the small to medium size container ports are reported. The aim was to detect the presence of shielded or unshielded sources inside the shipping container. This could be accomplished during the movement of the container: (i) from the ship to the storage area by radiation detector mounted on the crane and (ii) from the storage area while leaving the container port by track or train by gate monitors or by using gamma inspection systems in the passive mode.