Instrumental charged-particle activation analysis of several selected elements in biological materials using the internal standard method

In order to study instrumental charged-particle activation analysis using the internal standard method, simultaneous determination of several selected elements, such as Ca, Ti, V, Fe, Zn, As, Sr, Zr and Mo, in oyster tissue, brewer's yeast and mussel has been examined by using the respective (p, n) reactions and a personal computer-based gamma-ray spectrometer equipped with a micro-robot for sample changing. In the above determination, constant amounts of Y and La were added to the sample and comparative standard as exotic internal standards. As a result, it was demonstrated that concentrations of the above elements can be determined accurately and precisely.     

Instrumental photon activation analysis of environmental materials using the internal standard method

In order to study effective applications of the photon activation analysis using the internal standard method, determinations of Cr, Co, Ni, Zn, As, Rb, Sr, Y, Zr, Nb, Sb, Cs, Ba, Ce and Pb in two marine sediments as environmental materials have been examined by the use of a personal computer-based gamma-ray spectrometer equipped with a micro-robot for sample changing. In these determinations, some major and minor constituent elements in the samples were properly used as effective internal standards to check the roles with each other. As a result, it was demonstrated that accurate and precise determinations of the above 15 elements were achieved efficiently and favourably.     

Electrochemical and spectroelectrochemical properties of neptunium(VI) ions in nitric acid solution

A benchmark study was carried out to verify whether MCNP is useful in the design stage of a PGNAA facility for large samples up to 1 m length and 0.15 m diameter, using a 2.54 cm diameter thermal neutron beam. For this facility neutron self-shielding and gamma-attenuation correction methods have to be developed. The relative spatial neutron-density distributions within three samples with different macroscopic scattering and absorption cross sections were studied in a comparison between an MCNP simulation and an irradiation experiment using copper wires as neutron monitors. The neutron density in the sample was within statistical agreement between experiment and simulation. Typically the relative spatial neutron-density distributions agreed to within 1%. Therefore, MCNP can be used in design studies for the development of a large sample PGNAA facility as specified. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of the hydrogen content in Nigeria palm oil by the neutron moderation method

The thermal neutron moderation analysis facility at the Institute of Experimental Physics, Debrecen, Hungary has been used to determine the weight percent of total hydrogen content in Nigerian palm oil. The facility utilizes the fast neutron moderation technique in which the intensity of reflected thermalized neutrons is proportional to the hydrogen content of the sample exposed to fast neutrons. Using a 100 cm³ sample the total hydrogen content in the oven-dry palm oil sample was found to be 12.0±0.1% within a measuring time of 5 minutes. The method is fast and can be used in plant quality control where the hydrogen content must be determined within specific limits.     

Pyroelectric Adaptive Nanodispenser (PYRANA) microrobot for liquid delivery on a target

Manipulation of micro-sized objects in lab-on-a-chip and microfluidic environments is essential for different experiments and procedures ranging from chemical to biological applications and for experimental biotechnologies. For example polymeric particles, useful as targets for encapsulating or for being covered by drug vaccines, can be manipulated and controlled with the aim of releasing them to specific sites. Here we show a novel ElectroHydroDynamic tool able to control and manipulate dielectric micro-targets by a touch-less approach. This approach allows one to manipulate liquids and nano-particles simultaneously for specific delivery applications (i.e. decoration and coating). Thus a sort of EHD micro-robot is proposed. This flexible tool provides a new and powerful way to operate various tasks as demonstrated by the experiments reported here.     

Ex situ transmission electron microscopy: a fixed-bed reactor approach.

A fixed-bed reactor has been designed and constructed for ex situ transmission electron microscopy (TEM) studies of heterogeneous catalysts. The ex situ facility exposes a fully prepared TEM sample on a grid to actual process conditions (e.g., temperature, pressure, gas composition, etc.) by placing the grid at the exit section of a conventional fixed-bed reactor. A unique reactor design allows grid transfer into the electron microscope and back into the reactor again under a controlled (inert) environment, thus allowing time-resolved monitoring of catalyst morphology changes under realistic, well-controlled conditions. This facility stands completely independent of the TEM. Thus, no special TEM modifications are required and long-term ex situ studies do not impact microscope utilization. The utility of the facility is demonstrated via the oxidation of intermediate size ( approximately 20- approximately 80 nm) supported copper particles.     

Trace-element determinations in very large samples: A new challenge for neutron activation analysis

At the Interfaculty Reactor Institute the development of large sample INAA has been started. A facility is being installed in the reactor's thermal column for irradiation of samples with, sizes up to 100 cm in length, and 15 cm in diameter and weights up to 50 kg. A gamma-ray spectrometer with a very large semiconductor detector and sample scanning options will be used for measurement of the induced radioactivity. Algorithms are being developed to correct for the neutron self-shielding and gamma-ray attenuation problems.     

The radiological services laboratory: Designed for the future

A new state of the art radiochemistry laboratory incorporating advanced design and environmental control elements has been constructed in Atlanta, Georgia. The design of the facility is oriented to the efficient production of analytical sample results which meet regulatory requirements while at the same time provides an atmosphere that is pleasurable for analysts and visitors alike. The laboratory building contains two separate and distinct laboratories under one roof. This allows the facility to handle samples with low levels of radioactivity on one side of the lab without fear of contamination of environmental work on the other side. Unlike most laboratories, this facility utilizes a scrubber system and liquid waste holdup system to prevent accidental releases to the environment. The potential spread of radioactive contamination is controlled through the use of negative pressure ventillation zones. Construction techniques, laboratory systems, instrumentation and ergonomic considerations will also be discussed.     

Improving the detection limit of silicon, magnesium and aluminum in neutron activation analysis of polymers using a TRIGA? reactor

The measurement of impurities, specifically; the combination of magnesium, silicon and aluminum, in polymers and in mixed additives is a common problem for industrial application of neutron activation analysis (NAA). Typically this problem can be addressed using XRF and ICP. However, in some cases, the available sample size, desired detection limit and the desired accuracy prohibit the use of XRF or ICP. Therefore under these requirements, as in the measurement of talc in milligram size polymer fibers, using NAA has become a niche for nuclear analytical applications. Other important advantages, apart from high precision and lower detection limit, are the non-destructive nature of the analysis and the minimal sample preparation necessary to carry out the measurement. Therefore, polymers such as polyethylene, polystyrene or poly-carbonate can be analyzed for these metals as organic solutions, beads, films, pellets or powders. This paper highlights some of the recent improvements made to the Dow NAA measurement facility to accomplish this task.     

Automation and Quality Assurance in the NAA Facilities in Delft

The facilities for instrumental neutron activation analysis in Delft are described. Technical details of the fast rabbit systems, the normal pneumatic rabbit system, the large sample facility and the various coaxial and well-type Ge-detector spectrometers and sample changers are given. The capacity of the facilities is in the order of 15,000 samples per annum for full multi-element analysis. The capacity of the fast rabbit systems for INAA for use with short half-life radionuclides is even larger. The facilities are accessible for use by scientists from other establishments and countries as well.     

Photometric cyclic-injection determination of phosphate ions in aqueous media using extraction preconcentration

A procedure for the automated extraction photometric determination of phosphate ions in aqueous media was proposed based on the formation of colored phosphomolybdic heteropoly acid followed by its extraction from the aqueous phase to 1-butanol in the units of a hydraulic facility for cyclic-injection analysis. The procedure ensures a lower limit of the analytical range at a level of 80 μg/L at a sample volume of 10 mL.     

Recent measurements of 36Cl in Yucca Mountain rock, soil and seepage

Samples of rock, soil and seepage were collected from Yucca Mountain, USA, and analyzed for ³⁶Cl/Cl ratios by accelerator mass spectrometry (AMS). Rock excavated from the Drill Hole Wash fault at repository horizon depths produced a ratio suggesting that small amounts of water with “bomb-pulse” ³⁶Cl had percolated to that site over the past 50 years. Rock from four other sites within the exploratory studies facility did not yield bomb-pulse ratios. Ratios in the soil varied depending on depth and location, with some samples producing bomb-pulse signatures. Ratios for seep water were slightly elevated above the present cosmogenic background value. This paper also discusses results from a column study mimicking the passage of ³⁶Cl through volcanic rock and from an experiment using bromide instead of chloride as a carrier in sample preparation for AMS.     

Activation analysis of rocks and ores using gamma-ray inelastic scattering reactions

A cycle of the theoretical and experimental works has been carried out for determination of the activation analysis of mineral products using gamma-ray inelastic scattering reaction. The interference factor effect was studied. High-intensity waveguide linac LUE-8-5A type is used for the sample activation. The determination limit of elements using the isomeric states is 10⁻⁴ to 10⁻⁵ wt.% at the energy of the upper boundary of the bremsstrahlung (8 MeV). For the automatic search of the optimal analysis conditions an algorithm and computer program is developed. A geometry of the sample irradiation and measurement of its induced activity is proposed which ensures the uniform activation of a material of 500 g weight and effective measurement of the gamma-radiation of the induced activity with two NaI(Tl) crystals. The results of the above studies were used to construct a completely automatic inductrial facility for the photon-activation analysis of the geological materials. The output of the facility in the regime of the gold determination exceeds 300 000 analyses per year at the capability of analyzing up to 3000 samples per twenty four hours.     

Design,construction and characterization of a prompt gamma activation analysis facility at the Oregon State University TRIGA<Superscript>®</Superscript> reactor

A prompt gamma neutron activation analysis facility has been designed, built, and characterized at the Oregon State University TRIGA^® reactor. This facility was designed for versatile multi-elemental analyses. The facility utilizes the leakage neutrons originating from beam port #4 of the Oregon State University TRIGA^® reactor. The neutrons are collimated through a series of lead and Boral^® collimators, and filtered through both a bismuth filter and single-crystal sapphire. Samples are irradiated in a sample chamber outside the biological shielding of the reactor, and the resulting gamma radiation produced from neutron interactions within the sample is monitored using a high-purity germanium detector (HPGe). The thermal and epithermal neutron fluxes were measured using gold-foil irradiations and found to be 2.81 × 10⁷ and 1.70 × 10⁴ cm^?2 s^?1, respectively. The resulting cadmium ratio was 106. Measured detection limits for boron, chlorine, and potassium in a NIST SRM 1571 orchard leaf were 5.6 × 10^?4 mg/g, 8.2 × 10^?2 mg/g, and 1.0 mg/g, respectively. Detection limits for additional elements and samples are presented.     

Flow injection analysis with inductively coupled plasma-atomic emission spectroscopy: critical comparison of conventional pneumatic, ultrasonic and direct injection nebulization

The analytical figures of merit observed under flow injection analysis (FIA) conditions of a direct injection nebulizer (DIN) interfaced to an inductively coupled plasma-atomic emission spectroscopy (ICP-AES) facility were found to be comparable to or better than conventional pneumatic nebulization in terms of limits of detection, reproducibility and interelement effects. The DIN offered clog-free operation and part per billion limits of detection for 30μl sample injection volumes and carrier stream consumption rates in the range of 100–200μl min ⁻¹. The relative detection limits observed were generally comparable to those obtained for: (a) FIA introduction of 200μl or continuous sample introduction into a conventional cross flow nebulizer; and (b) FIA introduction of 500μl or continuous sample introduction into an ultrasonic nebulizer. Absolute and relative detection limits were comparable to or within the range of values reported for electrothermal vaporization-ICP-AES and comparable or superior to those reported for the graphite cup, direct insertion-ICP-AES. The reported absolute detection limits for the graphite-rod direct insertion approach ranged from comparable values to superior by a factor of 30. At the normal compromise observation height (20 mm), the interelement effects, to the extent they were observable, were comparable in magnitude for both the DIN and conventional cross-flow pneumatic nebulizer.     

Fabrication and characterization of an irradiation facility for large-sample geometry

An irradiation facility consisting of a modified beam port shielding plug has been designed, fabricated built and characterized for use in irradiating non-standard sample geometries. The shielding plug features a graphite moderator at the core end with a hole, or “well” drilled of sufficient diameter and depth to accommodate an eight ounce (227 gram) sample bottle. Added shielding behind the graphite consists of castable neutron- and -gamma-ray shielding. The modified shielding plug can be removed relatively quickly from its irradiation position to minimize personnel exposures. It is mounted in close proximity to the Ohio State University Research Reactor reactor core to allow performance of high-sensitivity neutron activation analysis studies. Using the SAND-II unfolding code, the energy-dependent neutron flux has been measured in the sample irradiation position. When operating at 100 % power, the total flux is 3.9 × 10¹² n/cm²/s. Of this, 55 % is thermal (<0.5 eV), 23 % is epithermal (>0.5 eV, <0.5 MeV), and 22 % is “fast” (>0.5 MeV). This makes the facility suitable for neutron activation studies. Recently it has been used for irradiation of filter papers collected in a study of particulate air pollution in the form of atmospheric particulate matter in an urban environment.     

Determination of Si,Al, Ti,Fe and Zr in glass sand samples by 14 MeV neutron activation analysis

Fast neutron activation analysis technique was applied for the determination of Si, Al, Ti, Fe and Zr in glass sand rock samples. The samples and standards were irradiated with a mono-energetic neutron flux of 10⁸n · cm^– · s^–1. Pneumatic facility was used. The gamma activities from samples and standards were counted using a 30 cm³ Ge(Li) detector, with FWHM of 2.9 keV at 1.332 MeV, coupled to an on-line computer facility.     

Organization, management and operation of contemporary academic mass spectrometry service facilities

The rapid evolution of mass spectrometry in the past 15 years has moved mass spectrometry facilities from the traditional model in which instruments were located in and used for a single department's samples to a distributed model servicing entire universities. In this paper we describe two such shared instrument facilities that have evolved from a base in a single department to facilities that service a broad clientele. The Purdue University Campus-wide Mass Spectrometry Center (CWMSC) is a decentralized facility with multiple sites on campus. The CWMSC is a limited-access facility in which samples are run by service facility personnel in close cooperation with investigators. The Vanderbilt University Mass Spectrometry Research Center (VU-MSRC) is a centralized facility in the medical school that provides services to the university at large. The VU-MSRC is an open-access facility in which users are expected to prepare and analyze their own samples under the guidance of a trained operator. Perhaps the most significant benefit achieved by these models has been the minimization of academic barriers and the resultant intellectual cross-fertilization that has greatly enriched research at institutions where this approach has been adopted. The advantages and limitations of both models are discussed in terms of the traditional academic paradigm of service, research and education.     

Investigation,design and analysis of a fast neutron facility on beam port 4 at the University of Texas MARK II TRIGA Reactor

Graduate students in the Mechanical Engineering department at the University of Texas at Austin have designed and modeled a fast neutron prompt-gamma activation analysis facility as part of a new course introduced in the graduate program titled “The Design of Nuclear Systems.” The students were responsible for creating a design concept as well as implementing and modeling the concept to ensure its safety and functionality. The purpose of the class was to give graduate students the independence to create a project of their own vision, but to do so in a collaborative and formal manner as will be necessary in their future work. The fast neutron PGAA facility was successfully designed and computational models have been analyzed to display benefits of the fast neutron facility compared to the thermal neutron PGAA facility that also exists at The University of Texas at Austin.     

An241Am−Be source based thermal neutron activation analysis facility at KFUPM

An instrumental thermal neutron activation analysis facility based, on a 16 Ci²⁴¹ Am–Be source, a high resolution -ray spectrometry setup and a PC-based data acquisition system at KFUPM is described. The thermal neutron flux distribution was determined from the induced activities of high purity indium foils. The absolute thermal neutron flux was calculated from the activities of bare and cadmium-covered gold foils at a position of 3 cm from the soource at which the flux reaches a maximum. The facility tests were carried out with the determination of manganese concentrations in six types of industrially important steel samples. The result of 1.33% manganese in SS-304 steel sample was in excellent agreement with the literature value. The method is nondestructive, economical and ideal for bulk analysis.