Design of a nanosecond beam bunching system

A nanosecond proton bunching system has been constructed at Korea Institute of Geoscience and Mineral Resources (KIGAM). This pulsed ion beam will be converted into corresponding duration of neutron pulse, which can reduce the scattered neutron background during neutron spectroscopy. The pulsed beam is obtained by deflection and double bunching by RF field. RF fields are applied to deflection and bunching electrodes as 2 kV p-p, 4 MHz and 2 kV p-p, 8 MHz, respectively. A push-pull RF amplifier has been designed and constructed with a maximum output power of 300 W continuous wave (CW) between 2 and 30 MHz. The main parameters of bunching beam were as follows: 8 MHz repetition rate, 2 ns FWHM, approximately 20% of duty factor and the maximum energy spread of 2 keV within a pulse.     

Multiple gamma-ray detection method and its application to nuclear chemistry

A new radionuclide quantification method is proposed on the basis of multiple gamma-ray detection, which is two or higher fold gamma-ray coincidence method. The coincidence method has so far been used for nuclear structure study. We apply this method for quantification of radioactive nuclei. The advantage of this method consists of high energy resolution and high sensitivity. It is successfully applied to nuclear waste analysis, neutron activation analysis and prompt gamma-ray analysis. The principle of the multiple gamma-ray detection method and future perspectives for an innovative pulsed neutron source and a new detector system will be presented.     

Application of multiple prompt gamma-ray analysis (MPGA) to geochemical and cosmochemical samples

A prompt gamma-ray analysis system using multiple detection method (MPGA system) was constructed at the neutron guide hall of the JRR-3M reactor of the Japan Atomic Energy Agency. We applied MPGA method to geochemical and cosmochemical samples to evaluate its analytical performance on signal to noise (S/N) ratio, sensitivity, and detection limit. The S/N ratio measured by MPGA system was larger than that by normal prompt gamma ray activation analysis (PGAA) at JRR-3M. For some elements, the S/N ratio was improved more than ten times. Several elements that are not detected by PGAA were detected by MPGA. At the present time, concentrations of major elements and trace elements with high neutron capture cross section in geochemical and cosmochemical samples were determined accurately by the MPGA system installed at JRR-3M. It is expected that it will determine a lot of trace elements after appropriate adjustments and modifications.     

Pulsed fast/thermal neutron analysis: a technique for explosives detection

Explosives, narcotics and other contraband material contain various chemical elements, such as hydrogen, carbon, nitrogen and oxygen, etc. in quantities and ratios that differentiate them from each other and from other innocuous substances. Neutrons and gamma-rays have the ability to penetrate through various materials to large depths. They are able to interrogate, in a non-intrusive manner, volumes ranging from suitcases to Sea-Land containers. Pulsed fast/thermal neutron analysis (PFTNA) is a neutron-based technique which utilizes the (n,n'gamma), (n,pgamma), and (n,gamma) reactions to identify and quantify a large number of elements. The elements emit characteristic gamma-rays that are the 'fingerprints' of each isotope. This technique is being employed in a variety of applications: bulk coal analysis, contraband detection and detection of explosives.     

Utilization of phoswich detectors for simultaneous,multiple radiation detection

Summary A phoswich radiation detector is comprised of a phosphor sandwich in which several different phosphors are viewed by a common photomultiplier. By selecting the appropriate phosphors, this system can be used to simultaneously measure multiple radiation types (alpha, beta, gamma and/or neutron) with a single detector. Differentiation between the signals from the different phosphors is accomplished using digital pulse shape discrimination techniques. This method has been shown to result in accurate discrimination with highly reliable and versatile digital systems. This system also requires minimal component count (i.e., only the detector and a computer for signal processing). A variety of detectors of this type have been built and tested including: (1) a triple phoswich system for alpha/beta/gamma swipe counting, (2) two well-type detectors for measuring low levels of low energy photons in the presence of a high energy background, (3) a large area detector for measuring beta contamination in the presence of a photon background, and (4) another large area detector for measuring low energy photons from radioactive elements such as uranium in the presence of a photon background. An annular geometry, triple phoswich system optimized for measuring alpha/beta/gamma radiation in liquid waste processing streams is currently being designed.     

Comparison of single- and dual-axis rotation techniques for total nitrogen in explosives by fast neutron activation analysis

Total nitrogen content in organic explosives and relate materials can be determined by fast neutron activation analysis (FNAA) to an absolute accuracy comparable to wet chemical or combustion analysis, i.e. to within less than 0.1% N. This is accomplished by dual-axis rotation of the sample and a carefully selected reference standard during neutron irradiation. The optimum reference standard is one of similar composition, density, weight and volume to the sample being analyzed. Rapid pneumatic transfer of organic explosives of low mechanical shock sensitivity poses no special safety problems. For large numbers of individual samples, a multiple sample irradiation system with single-axis rotation can be used for more rapid analysis. Precision and accuracy by this method are not as good as compared to a dual-axis rotation technique. Absolute accuracy for total nitrogen is in the order of 0.2%. This method is useful only for those reactions where the half-life of the product is long enough to allow for sequential counting of multiple samples for a single irradiation.     

Analysis of toxic elements by MPGA

In order to improve the sensitivity for the quantification of trace elements, we propose the combination of prompt gamma-ray analysis (PGA) and a multiple gamma-ray detection method. A new Ge detector system for multiple prompt gamma-ray analysis (MPGA) was constructed at the neutron guide-hall of the JRR-3M reactor of the Japan Atomic Energy Agency (JAEA). The first demonstration of this system was given with a plastic sample containing traces of cadmium. The quantification limit of cadmium in a plastic sample was found to be about 0.1 ppm.     

Characterization of a new external neutron beam facility at the Ohio State University

A thermal neutron beam facility has been designed and implemented at the Ohio State University Research Reactor. A project is underway to construct a large vacuum chamber such that the facility could have neutron depth profiling and neutron radiography capabilities as intended. The neutron beam is extracted from the reactor through a neutron collimator emplaced in Beam Port #2. The neutron spectrum entering the neutron collimator was unfolded from foil activation analysis results and also simulated with a full reactor core model in the MCNP Monte Carlo code. The neutron collimator uses polycrystalline bismuth as a gamma ray filter and single-crystal sapphire as a fast neutron filter. The beam is defined by multiple 3.0 cm diameter apertures made of borated aluminum. Characterization of the beam was performed using foil activation to find the flux and a low-budget neutron imaging apparatus to see the beam profile. The modulation transfer function was calculated to offer insight into the resolution of the imaging system and the collimation of the beam. The neutron collimator delivers the filtered thermal neutron beam with a ~4 cm diameter and a thermal equivalent flux of (1.27 ± 0.03) × 10⁷ n/(cm²s) at 450 kW power at the end of the collimator.     

Fast neutron activation analysis using short-lived radionuclides

Fast neutron activation analysis experiments were performed to investigate the analytical possibilities and prospective utilization of short-lived activation products. A rapid pneumatic transfer system for use with neutron generators has been installed and applied for detecting radionuclides with a half-life from 300 ms to 20 s. The transport time for samples of total mass of 1–4 g is between 130 and 160 ms for pressurized air of 0.1–0.4 MPa. The reproducibility of transport times is less than 2%. The employed method of correcting time-dependent counting losses is based on the virtual pulse generator principle. The measuring equipment consists of CAMAC modules and a special gating circuit. Typical time distributions of counting losses are presented. The same 14 elements were studied by the conventional activation method (single irradiation and single counting) by both a typical pneumatic transport system (run time 3 s) and the fast pneumatic transport facility. Furthermore, the influence of the cyclic activation technique on the elemental sensitivities was investigated.     

Development of a neutron beam line and detector system for multiple prompt gamma-ray analysis

A neutron beam line for multiple prompt gamma-ray analysis was constructed at the Japan Atomic Energy Agency. A detector system for the MPGA was constructed at the C2-3-2 beam line in January 2005. It comprised eight (upgraded in March 2007) clover Ge detectors with a BGO Compton suppressor. High efficiency detector system provides an advantage in terms of the detection limit of MPGA when compared to the result of PGA. The supermirror neutron bender was improved and a supermirror neutron guide was installed upstream of the sample position.     

Design and development of a neutron/X-ray combined computed tomography system at Missouri S&T

A new method for non-destructive analysis has been developed using a combined neutron/X-ray imaging system at the Missouri Science & Technology Reactor (MSTR). The interactions of neutrons and X-ray photons with matter produce differing characteristic information, resulting in distinctly different visual images. In order to obtain a more comprehensive picture of the structural and compositional data for a desired object, a prototype imaging system has been designed which utilizes neutron and X-ray imaging simultaneously without obstructing the beam geometry for each imaging mechanism. The current system is optimized for the imaging of small to medium sized objects of 0.5–50 mm. This new imaging capability in place at the MSTR promises great advances in the field of non-destructive testing, especially for nuclear engineering, nuclear medical science, and material science research. In an imaging object, a range of atomic number values and thermal cross-sections may be present. Where multiple materials having similar atomic number and differing thermal cross-section or vice versa may be present, exclusive neutron or X-ray analysis may exhibit shortcomings in distinguishing interfaces. However, fusing the neutron image and X-ray image into a combined image offers the strengths of both and may provide a superior method of analysis. In this paper, a novel combined X-ray and neutron imaging system will be introduced for superior analysis of certain imaging objects. Design details of experimental set-up and examples of preliminary imaging tests from individual modality will be detailed.     

Comparison Method for Neutron Activation Analysis with γ-γ Matrix

A comparison method, utilizing neutron activation analysis followed by multidimensional spectrum analysis was proven to provide accurate quantification of the multi-element samples. In this study, 23 elements were detected simultaneously in a sample containing standard elements for neutron activation analysis. The method presented here can be applied for about 50 elements.     

Contribution to 14 MeV neutron activation analysis using half-lives between 0.55 and 873 milliseconds

A study of the possibility of using half-lives between 0.55 and 873 msec in activation analysis with 14 MeV neutrons is presented here. The cyclic counting method is used: irradiation and detection are repeated several times and counts are memorised during all successive cycles until good final statistics are reached. The theoretical aspect of the cyclic counting method and the influence of neutron pulse shape on the activation results are discussed. The sample is activated and its activity measured in the same geometry: the sample and the scintillation detector are placed close to the target of the neutron generator. An electronic gating system is used to avoid photomultiplier gain fluctuations involved in neutron bombardment. Detection limits are measured for the following elements: Be, B, Al, Ca, As, Zr, In, Tl, Pb, Bi. Work carried out at: Centre d'Etudes Nucleaires de Grenoble, France.     

On the Use of Amperometry for Real Time Assessment of Drug‐Release Profile from Therapeutic Nanoparticles

A simple electrochemical method was used to directly assess the drug‐release profile. The method is based on the multiple pulse amperometric measurement of the oxidation and reduction of doxorubicin released from liposome at a MWCNTs‐modified glassy carbon electrode (MWCNT‐GCE). The released doxorubicin was detected at +0.60 and ?0.60 V by two different oxidation and reduction processes, respectively. The third potential pulse (?1.00 V) was applied for the regeneration of MWCNT‐GCE. The main advantage of this method is that there is no need for any operation for the quantitative analysis during the release of the drug from nanoparticles.     

Development of a method for high LET irradiation of liquid systems

A variety of processes, from material sterilization and cancer treatment to used nuclear fuel recycling, benefit from quantifying the sensitivity of the system to radiation. Determining the effects of alpha irradiation on a system may be of complementary interest to the effects of gamma irradiation, as alpha radiation has higher linear energy transfer (LET) and will likely result in different chemical damage effects. This becomes important in advanced nuclear fuel cycle processes where the radioactive materials to be handled in solutions contain significant amounts of alpha emitters. Here we describe a method for studying high LET radiation in a liquid system using a TRIGA^® reactor and the ¹⁰B(n,α)⁷Li reaction. By fitting a model based on neutron diffusion and absorption to experimentally obtained Fricke dosimetry data, the high LET dose to a sample was predictable over the full range of reactor power available and varying ¹⁰B concentration. This method may be applied to study the effects of high LET radiation on any liquid system as long as a suitable molecule containing boron is used and appropriate neutron diffusion coefficients are known. A wide range of high LET dose rates from <10 Gy/h to >1,000 kGy/h may be obtained with this method.     

Simultaneous flow injection analysis of cadmium and lead with differential pulse voltammetric detection

A flow injection (FI) method using multiple differential pulse voltammetric detection for the simultaneous determination of two metal ions was developed and applied to the resolution of Cd(II)-Pb(II) mixtures. The metals are detected by applying two sequential pulses to a three-electrode voltammetric system that uses a flow-through cell accommodating a static mercury-drop working electrode. The influence of the electrode area, flow-rate, pulse frequency, pulse width and sampling time was investigated. Under the experimental conditions used, the two metals were found to interfere with each other. The use of a neural network allows the simultaneous determination of both, in mixtures, with good accuracy. The proposed method is applicable to other complex systems involving different working electrodes and more than two electroactive species.     

Neutron activation determination of the uranium content of the primary coolant of water-water nuclear reactors

A neutron activation method for determination of uranium dissolved in the coolant of the first cycle of nuclear power stations is proposed. The method is based on preliminary concentration on activated carbon, irradiation with epithermal neutrons and gamma-spectrometry of²³⁹Np. The detection limit amounts to 1,3·10^–8 U/l. The method was sucessfully applied for the determination of uranium in the coolant of a nuclear power station.     

A pico-HPLC-LIF system for the amplification-free determination of multiple miRNAs in cells

MicroRNAs are a class of important biomarkers,and the simultaneous detection of multiple miRNAs can provide valuable information about many diseases and biological processes.Amplification-free determination has been developed for the analysis of multiple miRNAs because of its characteristic low cost and high fidelity.Herein,a method for the amplification-free analysis and simultaneous detection of multiple miRNAs based on a so-called pico-HPLC-LIF system is described.In this process,a bare open capilla ry with an inner diameter of 680 nm is used as a sepa ration column for a sample volume of several hundreds of femtoliters(300 fL),followed by separation and detection.The technique has a zeptomolar limit of detection.The method was applied to detect cellular miRNA from adenocarcinomic human alveolar basal epithelial(A549) cell extracts,and the simultaneous detection of the mir-182,miR-155,and let-7 a was achieved.The results showed that the expression of mir-182 and miR-155 was up-regulated and that of let-7 a was down-regulated in A549 cells.This method for multiple miRNAs detection is expected to have broad applications in miRNA-based disease diagnosis,prognosis,treatment,and monitoring.     

Determination of rhodium by thermal neutron activation analysis using g-ray spectrometry

Trace amounts of rhodium have been determined by thermal neutron activation analysis using both destructive and non-destructive methods. With a neutron flux of 10¹² n cm^-2 sec^-1 the lower limits of detection are about 0.1 μg and 0.01 μg, respectively. A rapid sodium-peroxide fusion followed by a pyridine extraction was used in the destructive method to separate the 4.4-mm ^104mRh from its matrix. The 44-sec¹⁰⁴Rh was used in the non-destructive method. Both radioactive isomers were measured by γ-ray spectrometry with a multichannel pulse height analyzer. The average time required per non-destructive analysis was 7 min while the chemical method averaged 20 min.     

Estimation of the volumetric water content in chrysanthemum tissues

Summary A method of estimating water in a neutron image was developed for cold neutron radiography, where the scanning method was applied to the plant sample at a beam port. The spectrum of the cold neutron beam as well as the effective cross section of water was determined to estimate the water thickness in chrysanthemum tissues. The resolution and contrast of the cold neutron radiography were sufficient for the estimation of the water thickness of fine veins in the chrysanthemum leaves. However, volumetric water content was overestimated when the sample shapes were cylindrical. This phenomenon can be explained by the reduction of the effect of neutron scattering from the sample when it is cylindrical.