Gamma Neutron Activation Analysis Facility Research Articles

Collimator and sapphire filter using for the prompt gamma neutron activation analysis facility: modelling and simulation

Safety measures play an important role in ensuring any system, although nuclear systems always require more safeguards than necessary. From this principle comes the importance of this research, which aims to conduct a study of neutron simulations and modelling to ensure safe installation of PGAA devices in the NB1 channel from the TRIGA Research Reactor at the Maamoura Center for Nuclear Studies. During this study, we used the Monte Carlo method using the MCNP6/X code. This study aims to determine the neutron profile, neutron distribution, and secondary gamma rays produced during the passage of the neutron flux in the collimator channel, sapphire and the vacuum channel that is maintained for the immediate neutron activation analysis (PGAA).

Conceptual design of prompt gamma neutron activation analysis facility at Tehran Research Reactor for BNCT application

Abstract Since Tehran Research Reactor (TRR) is the only available neutron source , which can be used for Boron Neutron Capture Therapy (BNCT) in Iran, it is essential to provide an appropriate analysis system at TRR in order to determine 10 B concentration in sample tissue or blood. Based on the advantages, Prompt Gamma Neutron Activation Analysis (PGNAA) facility has been selected. Irradiation channels in TRR have been studied using Monte Carlo MCNPX2.6 code and evaluated to provide the appropriate neutron beam for PGNAA. Based on the results of neutron intensity and spectrum, F-beam tube is considered to be the most favorable for PGNAA, and has therefore been selected for further investigation and MCNP simulation. Bismuth blocks for decreasing gamma radiation , and Fluental™ as a filter for fast neutron have been used in F-beam tube. The convergent collimator with iron and polyethylene has been considered to shape the neutron beam and to reduce the neutron and gamma-ray fluxes at the position of the HPGe gamma-ray detector. The sensitivity of the designed system is determined, from MCNP simulation, to be 7.35 cps/ μ g.

Development of a prompt gamma neutron activation analysis facility for 10B concentration measurements at RA-3: Design stage

A PGNAA facility is being developed for (10)B concentration measurements at RA-3 reactor. Its design targets detection limits better than tenths of a microgram and irradiation times on the order of minutes. Computational models were developed, which estimated thermal neutron fluxes in irradiation position to be larger than 10(9) n cm(-2) s(-1). Calculated amounts of photons and fast neutrons make necessary for filter/moderator arrangements. An irradiation device was designed and numerically tested, which is being built and is to be used for performing characterizing measurements.

A benchmarked MCNP model of the in vivo detection of gadolinium by prompt gamma neutron activation analysis

Abstract Gadolinium (Gd)-based contrast agents are a valuable diagnostic aid for magnetic resonance imaging (MRI). The amount of free Gd deposited in tissues following contrast enhanced MRI is of toxicological concern. The McMaster University in vivo prompt gamma neutron activation analysis facility has been adapted for the detection of Gd in the kidney, liver, and the leg muscle. A simple model of the HPGe detector used for detection of the prompt γ-rays following Gd neutron capture has been created using Monte Carlo simulation. A separate simulation describing the neutron collimation and shielding apparatus has been modified to determine the neutron capture rate in the Gd phantoms. The MCNP simulation results have been confirmed by experimental measurement. The deviations between MCNP and the experiment were between 1% and 18%, with an average deviation of 3.8 ± 6.7%. The validated MCNP model is to be used to improve the Gd in vivo measurement sensitivity by determining the best neutron moderator/reflector arrangement.

Design, construction and characterization of a prompt gamma activation analysis facility at the Oregon State University TRIGA® 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.

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%.

An improved prompt gamma neutron activation analysis facility using a focused diffracted neutron beam

The performance of the prompt gamma neutron activation analysis (PGNAA) facility at the MIT Research Reactor has been improved by a series of modifications. These modifications have increased the flux by a factor of three at the sample position to 1.7 × 10 7 n/cm 2 s, and have increased the sensitivity, on average, by a factor of 2.5. The background for many samples of interest is dominated by unavoidable neutron interactions that occur in or near the sample. Other background components comprise only 20% of the total background count rate. The implementation of fast electronics has helped to keep dead time reasonable, in spite of the increased count rates. The PGNAA facility at the MIT Research Reactor continues to serve as a major analytical tool for quantifying 10B in biological samples for Boron Neutron Capture Therapy (BNCT) research. The sensitivity for boron-10 in water is 18 750 cps/mg. The sensitivity for pure elements suitable for PGNAA analysis is reported. Possible further improvements are discussed.

A prompt gamma neutron activation analysis facility using a diffracted beam

A prompt gamma neutron activation analysis facility has been constructed at the MIT Research Reactor using a diffracted beam from a multilayered graphite monochromator. A beam of 0.0143 eV neutrons of intensity 6 × 10 6 n cm 2 s is available at the sample position. Backgrounds are low due to the use of the diffracted beam and are further improved by a sapphire crystal in the beam line. This design allowed the Ge detecting crystal to be placed close to the sample position, ~ 4 cm, with a resultant high detection efficiency. The sensitivity of the facility is reported for several representative pure elements. The major impetus for the construction of this facility was the need for accurate analyses of 10B in biological samples for neutron capture therapy research. Detailed results for this type of analysis are provided. The sensitivity of this diffracted beam facility currently exceeds that of two representative direct beam facilities using reactors of twice the power of the MITR-II. Possible major improvements in sensitivity, more than an order of magnitude, and in background levels are outlined for future development.

Calibration of a prompt gamma in vivo neutron activation facility for direct measurement of total body protein in intensive care patients

The Auckland in vivo prompt gamma neutron activation analysis facility has been calibrated for direct measurement of protein and chlorine in intensive care patients without reliance on hydrogen as an internal standard. These patients often present with massive fluid overload and the technique using hydrogen as an internal standard may be invalidated. Eight variable anthropomorphic phantoms containing physiological amounts of the major body elements were constructed from commercially available flexible polythene tubes and used for calibration. These phantoms are easily disassembled and reassembled to a different size and shape. Accuracy and precision for protein and chlorine were assessed by repeated scanning of a 64 kg anthropomorphic minced-meat phantom followed by chemical analysis of the meat. Reproducibilities for protein and chlorine were 2.9% and 10.6% respectively, for a mean dose equivalent to a subject of approximately 0.15 mSv. Chemical analysis for protein and chlorine did not differ significantly from the scanning results.

The prompt gamma neutron activation analysis facility at Murr

A facility has been developed at the University of Missouri Research Reactor so that the unique features of prompt gamma-ray neutron activation analysis can be used to measure trace and major elements in samples. This facility consists of a radial beamport, external sample position with shielding, and a multi-mode counting system. A single-crystal silicon neutron filter installed inside the beamport passes most of the thermal neutrons while reducing fast neutron and gamma radiation associated with the beam. Using thin gold foils, the beam was measured at the sample position to be 5 × 10 8n cm −2 s −1, with a cadmium ratio of 42 1 . Background measurements of thermal and fast neutrons at the Ge(Li) detector yielded 1 and 2 n cm −2 s −1, respectively. The multimode counting system consists of a Ge(Li) detector surrounded by an annular NaI crystal both of which are controlled by a computer-based analyzer system. Prompt gamma-ray spectra were collected in the energy range from 0.05 to 11 MeV. To establish the performance capabilities of the facility, irradiations of pure element or simple compound standards were performed to identify the prompt gamma-ray energies from each element, their count rates, and their interferences. Preliminary results are presented demonstrating the application of this technique to the analysis of standard reference materials.