Optimization of HANARO cold neutron induced prompt gamma activation analysis system by using Monte Carlo code

Prompt gamma activation analysis (PGAA) is a nuclear analytical technique for non-destructive determination of elemental and isotopic compositions. The principle of PGAA technique is based on detection of captured gamma-ray emitted from an analytical sample while being irradiated with neutrons. Use of a cold neutron beam guide greatly reduces the gamma-ray background at the analytical sample while maintaining a neutron capture rate is comparable to that of standard thermal neutron PGAA. A new cold neutron induced prompt gamma activation analysis (CN-PGAA) system has been under construction since April of 2009 at the HANARO Cold Neutron Building (KAERI, Republic of KOREA). In this study, the Compton suppression factor of the CN-PGAA system was estimated to be 5.5 using a ⁶⁰Co radioactive source in conjunction with the MCNPX simulations. Several parameters of the CN-PGAA system were studied to estimate and optimize the performance of the system: scintillation material in the guarded detector of a Compton suppression spectrometer (CSS); the relative positions of the HPGe detector and annular detector; and the distance between the HPGe detector and back catcher BGO detectors of the CSS. In addition, the neutron ray-trace simulation package, McStas, was adopted to predict the neutron flux and wavelength distribution at the end of the cold neutron beam guide. These results served as input for the MCNPX simulation of the CN-PGAA system.     

Prompt-gamma neutron activation analysis using an isotopic neutron source

This paper describes an experimental set up using an isotopic neutron source with graphite, preferably to a hydrogen-rich compound, as moderator. This low thermal flux source has been employed in PGNAA experiments. Only those elements having a high cross section can be quantitatively analyzed at low concentration levels, mainly, Gd, Cd, Sm, B and Hg; the other elements can only be probed at macroscopic levels. An application to the determination of boron content in collyria examplifies the possibilities of the technique.     

Combined application of Monte Carlo method and neural networks to simulate qualitative prompt gamma neutron activation analysis

Prompt gamma spectrum produced by thermal neutron absorption and fast neutron inelastic scattering is simulated using Monte Carlo code MCNP4C. The simulated spectrum is analyzed with artificial neural network techniques. The neural network in our study is trained based on back-propagation algorithm with 138 gamma ray spectra. Elements existing in the 20 different substances are specified. The ANN could identify elements correctly in 96% of input cases.     

Neutron self-shielding correction for prompt gamma neutron activation analysis of large samples

Summary Facilities and methods for INAA of large samples (up to 30 kg) have been developed and successfully tested at IRI, Delft. The methods encompass corrections for neutron self shielding in an isotropic neutron field and gamma self-absorption. The sample’s neutron absorption and scattering characteristics are determined by monitoring the neutron fluence rate around the sample and comparing the neutron densities measured with unperturbed fluence rates. We report on the possibility of developing similar methods for PGNAA. Relative self-shielding factors were measured as well as obtained from Monte Carlo computations. The agreement is good except for the most extreme case, with respect to absorption, attempted (CCl₄).     

Determination of boron in water samples by chemical prompt gamma neutron activation analysis

Boron concentration has been determined in groundwater samples, collected from Khuchch, Gujarat, India, by prompt gamma neutron activation analysis (PGNAA) after selective separation and pre-concentration by solvent extraction with 10% 2-ethyl hexane 1,3-diol in CHCl₃. Solvent extraction separation helped to eliminate the interfering elements in PGNAA determination of boron. The sensitivity of PGNAA is found to be 18.83 cps/mg B based on the slope of a calibration plot obtained by carrying out measurements on synthetic boric acid samples containing boron in the range of 30–150 μg. Detection limit of the method is 0.2 μg/g counted for 35,000 seconds at a sample size of 15 gram. The precision (relative standard deviation at 1σ level) and accuracy of the method is 5%. The analytical results of the present method agreed well with well-established spectrophotometric determination of boron as boron-curcumin complex and inductively coupled plasma atomic emission spectroscopy (ICP-AES).     

A neutron induced prompt gamma-ray spectroscopy system using a 252Cf neutron source for quantitative analysis of aqueous samples

A neutron induced prompt γ -ray spectrometry (NIPS) facility has been developed at the Nuclear Chemistry Research Division, of the Korea Atomic Energy Research Institute (KAERI) with the aim of analyzing the major components of various elements in aqueous samples. The facility is equipped with a ²⁵²Cf neutron source and a γ-γ coincidence setup with two n-type coaxial HPGe detectors based on NIM spectrometric modules in association with data acquisition and spectral analysis systems. The development of the system, its set-up and the calibration of detection efficiency up to 8 MeV using a set of radionuclides and the (n,γ) reactions of chlorine are described in the paper. This revised version was published online in July 2006 with corrections to the Cover Date.     

Intercomparison of inductively coupled plasma mass spectrometry, quantitative neutron capture radiography, and prompt gamma activation analysis for the determination of boron in biological samples

Boron determination in blood and tissue samples is a crucial task especially for treatment planning, preclinical research, and clinical application of boron neutron capture therapy (BNCT). Comparison of clinical findings remains difficult due to a variety of analytical methods, protocols, and standard reference materials in use. This paper addresses the comparability of inductively coupled plasma mass spectrometry, quantitative neutron capture radiography, and prompt gamma activation analysis for the determination of boron in biological samples. It was possible to demonstrate that three different methods relying on three different principles of sample preparation and boron detection can be validated against each other and yield consistent results for both blood and tissue samples. The samples were obtained during a clinical study for the application of BNCT for liver malignancies and therefore represent a realistic situation for boron analysis.     

基于可移动中子源的瞬发γ活化成像研究进展

瞬发γ活化成像技术基于瞬发γ射线中子活化分析,结合准直测量或者伴随粒子测量手段,以实现对样品内部中元素位置分布的测量。当前大多数相关研究都是基于大型中子源开展的,这限制了该技术的应用场景,可移动小型化中子源是该技术现场应用的必然要求。基于可移动中子源的瞬发伽马活化成像技术按照准直方式可分为基于单孔准直、编码孔准直及伴随粒子测量三类,本文对其技术原理、研究进展及仍存在的问题进行介绍与讨论。目前的技术在空间分辨率上还需要进一步提升,未来将进一步结合图像处理算法提高成像质量并降低测量时间。     

A program for complete quantitative neutron activation analysis using Ge(Li) detector gamma spectrometry and a small computer

It is shown that the large sophisticated programs designed for big computers can be efficiently used on medium scale machines for complete quantitative neutron activation analysis with Ge(Li) detectors.     

Neutron activation analysis applications at the Savannah River Site using an isotopic neutron source

NAA using ²⁵²Cf is used to address important areas of applied interest of the Savanah River Site (SRS). Sensitivity needs for many of the applications are not severe; analyses are accomplished using a 21 mg ²⁵²Cf NAA facility. Because NAA allows analysis of bulk samples, it offers strong advantages for samples in difficult-to-digest matrices when its sensitivity is sufficient. Following radiochemical separation with stable carrier addition, chemical yields for a number of methods are determined by neutron activation of the stable carrier. In some of the cases where no suitable stable carriers exist, the source has been used to generate radioactive tracers to yield separations.     

Characterization of a South-Levantine bronze sculpture using position-sensitive prompt gamma activation analysis and neutron imaging

Journal of Radioanalytical and Nuclear Chemistry - Complementary neutron-based elemental analytical and imaging methods, i.e. position sensitive prompt gamma activation analysis and neutron...     

Effects of hydration on elemental sensitivities in neutron activation analysis using prompt and delayed gamma rays

A 1.85×10¹¹ Bq (5Ci) Am/Be neutron source is being used to investigate the feasibility of applying the absolute method in the elemental analysis of bulk samples by instrumental neutron activation making use of prompt and delayed gamma rays. Among the different factors which might contribute to variations in sensitivity or in the uncertainly associated with the elemental concentration is the presence of hydrogen in the sample. It is the purpose of this study to examine whether the presence of water in bulk samples such as landfill waste produces significant variations in measured elemental concentrations and if so, requires samples to be dried, which can be a time consuming and expensive process. The effect of hydration of samples on the sensitivity of ten elements has there fore been investigated. Samples with different water concentrations in a fixed volume and shape were prepared and used in the analysis in order to obtain a measure and an understanding of the effects involved.     

Test of multielement analysis of bone samples using instrumental neutron activation analysis (INAA) and anti-Compton spectrometry

INAA and anti-Compton spectrometry has been employed in the analysis of test bone samples. Validity and accuracy of the method were checked by the use of two biological reference materials procured from the National Institute of Standards and Technology, USA (NIST) and the International Atomic Energy Agency, Austria (IAEA). NIST 1486 Bone Meal (ca. 200–800 mg) and A-11 Milk Powder (ca. 200–600 mg) samples were irradiated in the 100 kW TRIGA Mainz reactor. Concentrations of 13 elements in both biological reference materials have been determined and were found in good agreement with the certified and provisional values.     

Coincidence and anti-coincidence measurements in prompt gamma neutron activation analysis with pulsed cold neutron beams

A novel approach is implemented to alleviate some persistent problems in neutron capture prompt gamma activation analysis (PGAA). Detection sensitivities of PGAA are often restricted by the following factors: poor signal to noise ratios, interferences from background signals, and, in some cases, overlapping energy lines from different origins, namely ultra short-lived decay lines interfering with prompt decay. Timing the gamma-ray acquisition with the actual capture events using a pulsed beam of cold neutrons allows discrimination between prompt and delayed emissions from a sample source as well as against background events. Coincidence gating selects the prompt gamma-ray emissions. Contributions of background capture gamma-rays are suppressed because of different flight times of neutrons to the sources of background radiation, providing a reduction in direct gamma-ray interferences. Anti-coincidence gating allows measurement of only decay radiation that originates from short-lived activated states of the nuclides after capture. Spectra of decaying nuclides are free of interfering prompt activities, as well as have lower continuum background from Compton scattering of high-energy prompt gamma-rays in the detector. The measurements provide the opportunity to use ultra-short half-life nuclides for analytical purposes, no sample transfer times are lost, and repetitive activation and counting cycles are achieved with the use of pulsed neutron beams.     

Application of prompt gamma activation analysis and neutron activation analysis to the use of samarium as an intestinal marker

The use of prompt gamma activation analysis (PGAA) as a method for detection of the intestinal rare earth marker, samarium, has been evaluated by comparison with thermal neutron activation analysis (NAA). PGAA detection has significant advantages with respect to its higher reaction cross section and possible rapid experimental turnaround time. Serious disadvantages are lower neutron fluxes available to the target and nonavailability of numerous PGAA facilities. Results of the technique comparisons are generally very good. Pony fecal concentrations of samarium in samples obtained at various times after administration of a marked meal were measured by both techniques. In only one sample did results of the methods differ by more than the experimental errors involved.     

Multielement neutron activation analysis of biological materials using chemical group separation and Ge(Li) gamma spectrometry

Neutron activation analysis (NAA) for the determination of some trace elements in biological materials is described. The method presented permits the simple and rapid determination of Se, Ag, Au, Sb, Pt (via¹⁹⁹Au), Hg, Co, Ni (via⁵⁸Co), Fe, Zn, Mo, Sn, Cr, Cd, Cu and As after radiochemical separation from Na, K, Cs, Rb and partially Br. For this purpose, postirradiation separation by extraction with mercury or zinc amalgam was used. Separation of gold by extraction with ethyl acetate or by precipitation with dimethylglyoxime was applied for the determination of gold and platinum in biological materials.     

Determination of carbon, nitrogen, and phosphorus in cattail using thermal neutron prompt gamma activation analysis

A previous study on the determination of carbon, nitrogen, and phosphorus in cattail using cold neutron prompt gamma activation analysis (CNPGAA) demonstrates that the results of numerous cattail samples showed favorable comparison to results from an elemental analyzer (EA) for C and N. However, the results for P overestimated the results from a UV-VIS spectrophotometer because of the interference of chlorine existing in cattail collected from an estuarine environment. To compare to CNPGAA, a method for the determination of C, N, and P in cattail using thermal neutron prompt gamma activation analysis (TNPGAA) has been developed in the TNPGAA facility at the National Institute of Standards and Technology (NIST) and evaluated through the analysis of standard reference materials (SRMs).     

Application of prompt gamma neutron activation analysis in the aluminium industry of Egypt

Prompt gamma-ray energy spectrum following the capture of thermal neutrons by the atomic nuclei in an alumina ore sample was measured using a HPGe detector in a borehole environment. Based on the in formation obtained from the spectrum and nuclear data the nuclear ratio that compares the content of an unknown element with an estimate of aluminium in the ore can be determined. The work aimed to explore the applicability of this technique for quality control measurements in the aluminium industry of Egypt.     

A cyclic neutron activation system using an isotopic neutron source for the measurement of short-lived isotopes

The design and construction of an activation analysis system using an isotopic neutron source which allows the measurement of prompt and delay gamma-rays, in conventional activation and cyclic activation modes, is briefly described with emphasis laid on its flexibility, transportability and low cost. Photon spectra obtained from the irrdiation of large samples under prompt, delay and cyclic conditions using both NaI(Tl) and Ge(Li) detectors are presented and described with respect to ‘in-vivo’ neutron activation analysis and the measurement of N, O, Na, P, Cl and Cd. It is pointed out that, despite the attractive possiblity of measuring Se in liver, ‘in-vivo’, by cyclic activation analysis, the system may potentially prove a very useful tool for industrial and other non-medical applications.