Prompt Gamma Neutron Activation Analysis Research Articles

On the accuracy of protein determination in large biological samples by prompt gamma neutron activation analysis

A prompt gamma neutron activation analysis (PGNAA) facility has been developed for the determination of nitrogen and thus total protein in large volume biological samples or the whole body of small animals. In the present work, the accuracy of nitrogen determination by PGNAA in phantoms of known composition as well as in four raw ground meat samples of about 1kg mass was examined. Dumas combustion and Kjeldahl techniques were also used for the assessment of nitrogen concentration in the meat samples. No statistically significant differences were found between the concentrations assessed by the three techniques. The results of this work demonstrate the applicability of PGNAA for the assessment of total protein in biological samples of 0.25–1.5kg mass, such as a meat sample or the body of small animal even in vivo with an equivalent radiation dose of about 40mSv.

The comparison of two MCNP models used for prompt gamma in vivo detection of cadmium and mercury

In vivo detection of trace elements is one of the most important research areas at the Medical Physics and Applied Radiation Sciences Department at McMaster University. Prompt gamma neutron activation analysis (PGNAA) used for detection of cadmium and mercury takes place simultaneously at two different experimental sites; the McMaster Nuclear Reactor (MNR) and the 238Pu/Be neutron source site. This particular study consists of two parts. In the first part the water phantoms (125mL) were used in MCNP simulations. The water phantoms were doped with different concentrations of Cd, Hg and HCl. This is done in order to compare the (n, γ) prompt gamma reaction rate; in fact, the rate of neutron capture by the nuclides of interest; 113Cd, 199Hg and 35Cl. The second part involves, the neutron and photon dosimetry calculations that were performed for both sites using MCNP compatible body builder software developed in Los Alamos. The output of this program is the actual MCNP geometry description for various human anthropomorphic phantoms (different sex and ages). This phantom geometry output is incorporated into the original MCNP geometry and the dosimetry calculations were performed for various organs at risk.

Phantom studies of Cd, Hg and Cl by prompt gamma neutron activation analysis using a 238Pu–Be neutron source

Prompt gamma neutron activation analysis is a means of non-invasive monitoring for occupational exposure to toxic heavy metals such as Cd and Hg. Preliminary kidney detection limits from previous phantom studies at McMaster were 13.6±0.2ppm for Cd (125mL phantom) and 315±24ppm for Hg (125mL phantom) using the 238Pu–Be neutron source and 0.88±0.01ppm for Cd (125mL phantom) and 16.91±0.05ppm for Hg (30mL phantom) using the thermal neutron beam port at the McMaster Nuclear Reactor. The detection limits vary greatly between the two methods due to differences in experimental set-up, neutron energy spectra and a difference in dose by more than a factor of 100. The Hg detection limit from preliminary data is much higher than expected for both neutron source types. In order to explain the apparent detection limit discrepancy, measurements of Hg and Cd phantoms were performed using the 238Pu–Be neutron source. The results were compared to phantom measurements of Cl, a well-known neutron activation element.

Gamma-ray yield dependence on bulk density and moisture content of a sample of a PGNAA setup: A Monte Carlo study

Monte Carlo calculations were carried out to study the dependence of γ-ray yield on the bulk density and moisture content of a sample in a thermal-neutron capture-based prompt gamma neutron activation analysis (PGNAA) setup. The results of the study showed a strong dependence of the γ-ray yield upon the sample bulk density. An order of magnitude increase in yield of 1.94 and 6.42 MeV prompt γ-rays from calcium in a Portland cement sample was observed for a corresponding order of magnitude increase in the sample bulk density. On the contrary the γ-ray yield has a weak dependence on sample moisture content and an increase of only 20% in yield of 1.94 and 6.42 MeV prompt γ-rays from calcium in the Portland cement sample was observed for an order of magnitude increase in the moisture content of the Portland cement sample. A similar effect of moisture content has been observed on the yield of 1.167 MeV prompt γ-rays from chlorine contaminants in Portland cement samples. For an order of magnitude increase in the moisture content of the sample, a 7 to 12% increase in the yield of the 1.167 MeV chlorine γ-ray was observed for the Portland cement samples containing 1 to 5 wt.% chlorine contaminants. This study has shown that effects of sample moisture content on prompt γ-ray yield from constituents of a Portland cement sample are insignificant in a thermal-neutrons capture-based PGNAA setup.

Performance improvement of a PGNAA setup due to change in moderator design: A Monte Carlo study

Effect of neutron source-moderator geometry has been studied on the performance of a thermal neutron capture-based prompt gamma neutron activation analysis (PGNAA) setup. In the study prompt gamma-ray and thermal neutron yield was calculated for various positions of the neutron source inside 3–10 cm long high density polyethylene moderators. The study has been carried out for a Portland cement sample using Monte Carlo calculations. The maximum yields of the thermal neutrons and prompt gamma-rays have been observed for a neutron source at a distance of 1 cm from the sample. The maximum yield of the 1.94 and 6.42 MeV prompt gamma-ray from a Portland cement sample has been observed for moderators having length equal to or greater than 7 cm. The yield of both gamma rays is 2.57 times higher than the previously reported value for a PGNAA setup with the source placed outside a 5 cm thick moderator. The higher yield of gamma rays will result in higher sensitivity of the PGNAA setup.

Influence of the effective mass on the relative neutron density distribution inside a large sample in prompt-gamma neutron activation analysis

A Monte Carlo study was carried out to determine the influence of the effective scattering mass (M e) of the atoms on the neutron density profile inside and outside the sample illuminated by a thermal neutron beam as in large-sample prompt-gamma neutron activation analysis (LS-PGNAA). From theory it is known that the spatial neutron density distribution (n(r)) inside a large sample is not the same for atoms with the same macroscopic scattering and absorption cross-section (Σ s and Σ a) but different M e, due to anisotropic scattering at low M e. The probability of neutron absorption in the sample was found to be the same for materials with equal Σ s and Σ a but different M e, even though the neutron density distribution in the sample was found to change slightly. In view of typical sample, collimator and detector dimensions, it is concluded that M e does not need to be taken into account in a correction method for neutron self-shielding in LS-PGNAA.

Application of cold neutron prompt-gamma activation analysis in environmental studies of aquatic plants

This paper describes the use of cold-neutron prompt-gamma activation analysis (CNPGAA) to determine carbon, nitrogen, and phosphorus in the aquatic plant Typha domingensis, commonly known as cattail, during spring and fall seasons. According to studies of the Florida Everglades, cattail replaces sawgrass as a result of nutrient enrichment from farm water runoff. Nutrient enrichment, especially phosphorus, in sediment and the water column can lead to undesirable expansion. Early signs of this expansion are apparent in the Apalachicola River floodplain near Apalachicola, Florida, USA. This research project is designed to use cattails as biomonitors of nutrient enrichment in the lower Apalachicola River floodplain. Determination of carbon, nitrogen, and phosphorus in cattail using cold neutron prompt-gamma activation has been developed in our previous studies at the CNPGAA facility at the National Institute of Standards and Technology (NIST), USA. The results of numerous field samples, collected from the study area during spring and fall seasons in 2002, will be presented in this paper.

Development of a non-invasive method for the determination of the macroscopic neutron cross sections of a sample matrix in large-sample prompt-gamma neutron activation analysis

In order to correct for neutron self-shielding in large-sample prompt gamma NAA, a method has been developed to determine the macroscopic scattering and absorption cross sections, i.e., Σ a and Σ s, using four Cu flux monitors placed around the sample. With Monte Carlo computations, the neutron densities throughout the sample and the resulting and the corresponding self-shielding factor as calculated from the Σ a and Σ s as obtained through the Cu monitors were compared to the true values. The derived Σ a and Σ s were found to be sufficiently accurate as long as Σ t = Σ a + Σ s was less than 0.6 cm−1 and Σ s/Σ t was greater than 0.1.

Validation experiment for large-sample prompt-gamma neutron activation analysis

A method is proposed for the implementation of large-sample prompt-gamma neutron activation analysis (LS-PGNAA). The method was tested with four different sample materials at the thermal PGNAA facility at JAERI, Japan. The macroscopic scattering cross section (Σ s) and absorption cross section (Σ a) of the samples were determined by monitoring the neutron flux in four positions just outside the sample container. With the Σ s and Σ a determined, the spatial neutron density distribution [n(r)] inside the sample material was derived. Taking n(r) and the gamma-ray self-absorption into account simultaneously, the effective geometric gamma-ray detection efficiency for large samples as a function of gamma-ray energy was calculated. Taking silicon as test element, the concentrations found agreed to within 7% with the known concentrations in the four sample materials examined, both when using relative standardization and with absolute standardization.

Evaluation of spatial sensitivity of a prompt gamma neutron activation analysis facility for the in vivo determination of nitrogen in small animals

We investigated the spatial dependence of the sensitivity of nitrogen measurement with a prompt gamma neutron activation analysis (PGNAA) system for small animals and developed an analysis procedure that permits the reduction of systematic errors due to that dependence. The analysis procedure is based on neutron and photon transport calculations performed using the MCNP code in order to evaluate the sensitivity of the PGNAA facility. The system can be calibrated experimentally using a small number of phantoms of known size and composition. The calculation approach can then be used to predict responses for animal body sizes and shapes relatively to those experimentally determined and to include the effect of tissue inhomogeneities. Our calculations were verified by experimental measurements performed for a set of cylindrical inhomogeneous phantoms. The calculated to experimental ratios observed were within 6%.

Neutron resonance capture analysis and applications

In this paper we discuss the use of neutron resonances to determine the elemental composition of objects non-destructively. Resonances are observed from about 1 to 3000 eV by the time-of-flight technique using the pulsed neutron source of the GELINA facility in Geel (Belgium). Prompt capture γ-radiation is used to signal capture events. Some aspects of the neutron resonance capture analysis (NRCA) are compared with prompt gamma neutron activation analysis (PGNAA).

Interferences in Prompt γ Analysis of corrosive contaminants in concrete

An accelerator-based Prompt Gamma Neutron Activation Analysis (PGNAA) setup has been developed to measure the concentration of corrosive chloride and sulfate contaminants in concrete. The Minimum Detectable Concentration (MDC) limit of chlorine and sulfur in the concrete depends upon the γ-ray used for elemental analysis. For more interfering γ-rays, the MDC limit is higher than that for less interfering γ-rays. The MDC limit of sulfur in concrete measured for the KFUPM PGNAA setup was calculated to be 0.60±0.19 wt%. The MDC limit is equal to the upper limit of sulfur concentration in concrete set by the British Standards. The MDC limit of chlorine in concrete for the KFUPM PGNAA setup, which was calculated for less interfering 1.165 MeV γ-rays, was found to be 0.075±0.025 wt%. The lower limits of the MDC of chlorine in concrete was 73% higher than the limit set by American Concrete Institute. The limit of the MDC can be improved to the desired standard by increasing the intensity of neutron source. For moreinterfering 5.715 and 6.110 MeV chlorine γ-rays the MDC limit was found to be 2–3 times larger than that of 1.165 MeV γ-rays. When normalized to the same intensity of the neutron source, the MDC limits of chlorine and sulfur in concrete from the KFUPM PGNAA setup are better than MDC limits of chlorine in concrete obtained with the 241Am–Be source-based PGNAA setup. This study has shown that an accelerator-based PGNAA setup can be used in chlorine and sulfur analysis of concrete samples.

Partitioning and budget of Li, Be and B in high-pressure metamorphic rocks

Partitioning and budget of Li, Be and B in high-pressure metamorphic rocks from the island of Syros (Greece) were studied, using secondary ion mass spectrometry, inductively coupled plasma optical emission spectrometry and prompt gamma neutron activation analysis. Partitioning between coexisting mineral phases was found to be rather constant and independent of element concentrations. For several mineral pairs, apparent partition coefficients vary in a narrow range, while concentrations vary by more than an order of magnitude. Hence, it was possible to establish sets of inter-mineral partition coefficients for Li, Be and B among 15 different high-pressure minerals. This data set provides important information on the behaviour of the light elements in different lithologies within subducting slabs from the onset of metamorphism to the eclogite stage. It is essential for modelling trace-element and isotope fractionation during subduction and dehydration of oceanic crust.

Occupational nuclear medicine: Trace element analysis of living human subjects

Several trace elements are toxic when present in excessive amounts. Such overloads occur most commonly in the occupational setting, although some environmental exposures are also of concern. The relationship between chronic exposure and health effects is best explored with the aid of knowledge of the quantity of element in question stored in the body. In vivo elemental analysis can provide this knowledge non-invasively for a number of elements of toxicological importance. In vivo analysis presents specific challenges, particularly the fact that the body is an extended medium, giving rise to extensive scattering and absorption. Also of primary importance, the radiation dose must be kept as low as reasonably possible and must in every case be within the range of other diagnostic procedures. Both the incident radiation and the detected signal must have an adequate mean free path in human tissue. This means that neutron activation analysis (NAA) and X-ray fluorescence (XRF) are the two most studied techniques. For some elements, analytical methods are established while others are under active development. For still others, no promising technique is currently available. The most fully developed techniques are for lead and cadmium. For lead three different XRF approaches have been put forward, although one, 109Cd excited K XRF is most widely used. For cadmium, both prompt gamma NAA and XRF have been developed to the extent of full human studies. Amongst elements for which application to human studies has begun or is likely to begin shortly are aluminum and manganese, both using NAA.

The analysis of C 60 and C 70 fullerenes by prompt gamma neutron activation

The capabilities of prompt gamma neutron activation analysis (PGAA) are examined for fullerene samples. As shown PGAA is a promising instrumental technique for the determination of the light elements of the periodic table. These elements (C, H, O, N and B) were inaccessible by instrumental neutron activation analysis (INAA) as done by the authors in previous publications.

Determination of Ti, K, Sm and Gd Values in Geological Survey of Japan Reference Materials by Prompt Gamma Neutron Activation Analysis

Prompt gamma neutron activation analysis was applied to the determination of the titanium, potassium, samarium and gadolinium contents of nine Geological Survey of Japan (GSJ) reference materials (JB‐1, 1a, 2, 3; JA‐1, 2, 3; JR‐1, 2). Firstly, the values in JB‐1 were determined by the standard addition method: pressed powder disks of JB‐1 were used for neutron irradiation and gamma‐ray measurements, after known quantities of standard reagents had been added. Secondly, the contents of eight other reference materials were determined by comparison methods using JB‐1 as the comparative standard. The precision of analyses were obtained by replicate determinations on these samples. The relative standard deviation was generally less than 5%. For most samples, analysed values agreed well (< 5%) with the recommended values.

In situ determination of salinity by PGNAA

Salinity is a very important environmental issue all around the world. In many cases salinity was produced from human activities like farming and mining. Different soluble salts contribute to salinity, however, NaCl is the most common salt producing salinity. This work deals with the application of the prompt gamma neutron activation analysis (PGNAA) technique for in situ determination of salinity. The technique is based on the measurement of chlorine, a component of the common salt, by PGNAA.

A Novel Method For The Diffusion Of Boron In 60-80 Micron Size Natural Diamond Type II/A Powder

ABSTRACTThe purpose of this paper is to report the experimental results of boron doping on 60-80 micron size diamond particles using Field Enhanced Diffusion with Optical activation (FEDOA) [1-5]. Diamond is a wide band gap material with unique combinations of optical, thermal, mechanical and electronic properties that can be useful for a number of applications including optoelectronic applications and micro sensor technology. The incorporation of boron into diamond has been proven to change its electrical properties and convert the diamond from insulator to a p-type semiconductor [3]. A promising technique for incorporation of impurities into diamond is FEDOA. FEDOA drives impurities into single crystalline diamond material and we have used this method in this study [5-7]. FEDOA uses a combination of thermal diffusion with bias plus thermal ionization and optical ionization I simultaneously. A modified version of FEDOA was implemented for the diffusion of boron in natural diamond type II/a powder of size 60-80 microns (Figure 1). The diamond powder was obtained from Microdiamant and has 99.9% purity. The boron powder used in the experiment was amorphous, 325 mesh 90 %(Assay), Mg (5%) nominal obtained from AESAR. A ratio of 3:1 Boron-Diamond mixture was used for the doping process. A heating element and a diamond-boron powder mixture holder were designed and incorporated in the FEDOA system. Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) were used to study the diamond-doped morphology and identify impurities. Boron and hydrogen concentration results in the doped samples were studied using Prompt Gamma Neutron Activation Analysis (PGNAA) at the University of Missouri Research Reactor (MURR). Raman analysis of the treated samples was done as part of this work. The experimental results and analysis show that the samples were doped with boron. It was also found that samples with high boron concentration exhibited a high electrical conductivity. This work presents additional evidence that boron can be diffused into natural diamond powders. It also demonstrates that the FEDOA diffusion process is not only a powerful technique for the diffusion of impurities into wide band-gap materials in the form of single crystal plates, polycrystalline plate but also in a powder form with the modified FEDOA process.

Automated lithology prediction from PGNAA and other geophysical logs

Different methods of lithology predictions from geophysical data have been developed in the last 15 years. The geophysical logs used for predicting lithology are the conventional logs: sonic, neutron–neutron, γ (total natural- γ) and density (backscattered γ– γ). The prompt gamma neutron activation analysis (PGNAA) is another established geophysical logging technique for in situ element analysis of rocks in boreholes. The work described in this paper was carried out to investigate the application of PGNAA to the lithology interpretation. The data interpretation was conducted using the automatic interpretation program LogTrans based on statistical analysis. Limited test suggests that PGNAA logging data can be used to predict the lithology. A success rate of 73% for lithology prediction was achieved from PGNAA logging data only. It can also be used in conjunction with the conventional geophysical logs to enhance the lithology prediction.

Measurement of lime/silica ratio in concrete using PGNAA technique

Prompt gamma neutron activation analysis (PGNAA) technique has been used to determine lime/silica ratio in concrete samples using an accelerator-based PGNAA facility. The ratio was determined from the measured yield of 6.42 MeV prompt γ-rays of calcium and 4.93 MeV γ-rays of silicon from the six concrete samples. The experimental results were compared with the results of the Monte Carlo simulations. An excellent agreement has been achieved between the two. The study has demonstrated successful use of the accelerator-based PGNAA setup in non-destructive analysis of the concrete samples.