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The neutron moderator structure of a prompt gamma-ray neutron activation analysis (PGNAA) system based on a deuterium–tritium (DT) neutron generator was re-optimized. In this study, a 1 cm lead combined with a 2 cm high-density polyethylene (HDPE) was set as a new moderator. The thermal neutron flux, fast neutron flux of more than 6 MeV and total neutron flux in the samples increased by 22%, 41% and 41%, respectively. The signal-to-interference ratio (SIR) increased from 15 to 19%. The measurement results with samples containing different element contents indicated that the detection sensitivity of the analyzer with the new moderator structure was significantly improved. [ABSTRACT FROM AUTHOR]

In this paper, an inelastic neutron scattering system was used for the analysis of metallic materials. Iron and chromium measurements were conducted with the system, and the copper foil activation was used for determining fast neutron flux. A Monte Carlo model was proposed for comparing with experimental measurements. The performance parameters including the signal-to-background ratio, sensitivity and mass detection limit, as well as ratio of fast neutron flux were compared. Comparisons show the simulation results agree well with experimental measurements. The results demonstrate that the proposed Monte Carlo model can well represent the system and be used for improving system performance in the further application. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • A measurement system for continuous monitoring of chlorine impurity in crude oil was built. • The MCLLSX approach for quantitative analysis of targeted elements with low-weight-fraction in the sample has been proposed. • The feasibility of determining low chlorine concentrations by using the MCLLSX approach in conjunction with PGNAA was shown. • The chlorine content could be estimated at a few hundred mg/L level. [ABSTRACT FROM AUTHOR]

A new Monte Carlo-Library Least Squares (MCLLS) method was developed for the neutron inelastic-scattering and thermal-capture analysis (NITA) techniques in real-time online analysis systems to determine boron content in Tinkal ore samples. The Geant4 toolkit was used to simulate the Prompt Gamma-ray Neutron Activation Analysis (PGNAA) system for the NITA technique. Tinkal ore samples were bombarded with 14 MeV neutron beams in order to represent neutrons released from the Deuterium-Tritium (DT) neutron generator. After the simulation of shooting Tinkal ore samples with 14 MeV neutron beams was completed, histograms were obtained from Geant4. Once the histograms are broadened according to the shape calibration of the BGO scintillation detector, the spectrum (broadened histograms) are ready to be used in the MCLLS process. A single element library was created by broadened histograms of the nine Tinkal ore samples. In addition, set #10 was selected to be an unknown sample and was used for validating MCLLS. After analysing the unknown sample spectrum, boron content was estimated by the single element library created by the MCLLS method. The estimated value of the boron content by MCLLS was consistent with the laboratory result. • New MCLLS method for PGNAA to determine boron in Tinkal ore. • The method was validated by comparing the obtained results with laboratory values. • MCLLS shows promise for boron in Tinkal ore with good accuracy, consistency. • Geant4 can be used to generate histograms for MCLLS calculations. • The use of updated libraries in Geant4 enhances simulation accuracy. [ABSTRACT FROM AUTHOR]

Abstract Design of deuterium–tritium (DT) neutron generator facilities requires a careful assessment of radiation shielding. In the models of such facilities an isotropic distribution of neutron flux produced by the neutron generator is usually assumed. However, prior studies have shown that neutron flux surrounding the neutron generator can be anisotropic. This anisotropy results mostly from the design of the generator tube, as well as the angular dependence of DT fusion reaction cross section. In this work, the angular neutron flux was measured for a standard commercially available DT generator (Thermo Fisher Scientific, Model P211) using an organic scintillator and a significant degree of anisotropy was confirmed to exist. The experimentally determined flux was then used in Monte Carlo simulations to examine the impact of anisotropy on the effectiveness of radiation shielding. Although the shielding effectiveness is not considerably affected by the anisotropy, the dose rates in air around the unshielded generator can be significantly different from those predicted when an assumption of isotropic flux is made. These considerations need to be included in modeling of the dose rate around the generator in neutron generator facilities that employ typical neutron generators, which exhibit some degree of anisotropy in neutron flux. [ABSTRACT FROM AUTHOR]

Highlights • Two D-T generators were fully characterised at NPL. • Detailed neutronics models were created. Neutron spectra and intensity calculated. • The neutron emission rate has been measured as a function of angle. • The anisotropy profile is shown to be reproducible with a detailed MCNP model. • Generator and model ready for in-vessel calibration of JET. Abstract A calibration of the JET neutron detectors was carried out prior to the upcoming deuterium-tritium experimental campaign. Two Compact DT neutron generators (NGs) were purchased for this purpose from VNIIA, Russia. These generators are capable of producing approximately 2 × 108 neutrons/s with a DT fusion energy spectrum. Preceding the in-vessel calibration measurements, these compact generators were tested and fully characterised at the UK's National Physical Laboratory (NPL). In order to support the characterisation measurements, detailed neutronics models were developed of the NGs, monitoring detectors and remote handling (RH) apparatus. Neutron spectra calculated from these models have been used to help determine NPL long counter efficiencies and effective centres, as well as NPL reference iron and aluminium activation foil reaction rates. The neutron emission rate has been measured for both generators as a function of angle using absolutely calibrated long counters and the relative emission rate by monitoring single crystal diamond detectors. The measured anisotropy profile is shown to be reproducible with a detailed NG MCNP model. Consequently, the neutron source routine and the MCNP model of the NGs can be reliably used for the analysis of the in-vessel calibration at JET. [ABSTRACT FROM AUTHOR]

A compact DT neutron generator (NG) based on the mixed-beam operation was used as a calibration neutron source in the latest in-situ calibration of neutron detectors at the Joint European Torus (JET). In order to meet the requirement for the total uncertainty of the neutron detector calibration below ±10 %, the neutron emission properties had to be experimentally characterized and reproduced through detailed modelling of the neutron source characteristics and geometry of the neutron generator. The detailed neutronics simulations were an essential part of both NG characterization and JET neutron detector calibration. The complex neutron emission properties of the NG were reproduced through a combination of simulations and highresolution neutron spectroscopy measurements. This meant that six different DT neutron source components resulting from NG's mixed beam operation were explicitly simulated and their relative intensities scaled based on experimentally obtained neutron spectrum measurements. Furthermore, the detailed model of the NG's geometry was produced based on information from the supplier of the NG and images from a computer tomography (CT) scan. Finally, the positioning of the neutron source inside the JET tokamak during in-situ calibration was reproduced based on the information from the remote handling system (RHS) at JET, the system responsible for the positioning of the source during the calibration experiment. The extensive effort presented in the paper significantly contributed to the total uncertainties of the calibration factors well within the target value of ±10 %.

The spectrum weighted responses of various detectors were calculated to provide guidance on the proper selection and use of survey instruments on the basis of their energy response characteristics on the neutron fields. To yield the spectrum weighted response, the detector response functions of 17 neutron-measuring devices were numerically folded with each of the produced calibration neutron spectra through the in-house developed software ‘K-SWR’. The detectors’ response functions were taken from the IAEA Technical Reports Series No. 403 (TRS-403). The reference neutron fields of 21 kinds with 2 spectra groups with different proportions of thermal and fast neutrons have been produced using neutrons from the 241Am-Be sources held in a graphite pile, a bare 241Am-Be source, and a DT neutron generator. Fluence-average energy (Eave) varied from 3.8 MeV to 16.9 MeV, and the ambient-dose-equivalent rate [H*(10)/h] varied from 0.99 to 16.5 mSv/h.

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. [ABSTRACT FROM AUTHOR]

TU Dresden operates an accelerator-based intensive DT neutron generator. Experimental activities comprise investigation into material activation and decay, neutron and photon transport in matter and R&D work on radiation detectors for harsh environments. The intense DT neutron generator is capable to produce a maximum of 1012 n/s. The neutron source is a solid-type water-cooled tritium target based on a titanium matrix on a copper carrier. The neutron yield at a typical deuteron beam current of 1 mA is of the order of 1011 n/s in 4Π. A pneumatic sample transport system is available for short-time irradiations and connected to wo high-purity germanium detector spectrometers for the measurement of induced activities. The overall design of the experimental hall with the neutron generator allows a flexible setup of experiments including the possibility of investigating larger structures and cooled samples or samples at high temperatures.

• The method of neutron spectrum determination of the DT NG is described. • The Gravel and MAXED unfolding codes have been applied in our study. • The impact of different values of deconvolution parameters has been examined. • The impact of the default neutron spectrum shape on results has been checked. Neutron generators (NGs) are available worldwide as powerful sources of neutrons suitable for a variety of applications. However, information concerning precise knowledge of the total neutron emission Y n and its energy distribution is not always provided by the manufacturer. Measurements using energy threshold diagnostics and numerical simulations may be used to determine such quantities. Here we describe our approach for neutron spectra determination of a SODERN DT NG based on combination of activation measurements, unfolding processes and numerical simulations using the FISPACT-II code. We have used these to estimate a priori neutron spectra, which have been applied as an input to unfolding codes, Gravel and MAXED. Various input values of deconvolution parameters have been investigated in this paper and results are discussed. The final reconstructed neutron spectrum of the DT NG has been derived from a combination of spectra obtained from these codes, with agreement with experimental data to within 10 %. [ABSTRACT FROM AUTHOR]