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Narrow spectrum series from N-40 to N-120 were established according to ISO 4037:2019. This study was made through experimental measurements and the software modeling toolkit SpekPy v2.0. Experiments were performed to determine Inherent filtration (0.332 & 0.492 mm Al at 100 cm & 250 cm, respectively). The maximum deviation compared to ISO 4037:2019 of the measured HVLs values are not more then 0.10 mm Al and for modeling not exceed 0.09 mm Al; h range 0.91 to 0.97 for experimently and 0.89 to 0.96 for modeling (0.88 - 1, ISO 4037-1:2019). The maximum contribution of scattering is value 4.0% (< 5%, ISO 4037-1:2019). Radiation field uniformity of N-40 to N-120 should list all categories in detail 12.5, 11.0, 10.0, 9.0, 8.5 cm at 100 cm distance; and 35.5, 31.5, 29.0, 26.5, 24.5 cm at 250 cm beam center axis distance. On the basis of ISO 4037:2019, air kerma values at 100 cm and 250 cm have also been determined with uncertainties 3.85% to 5.18% for experimently and 3.41% to 4.19% for modeling (not exceed 10%, ISO 4037:2019). Therefore, the X-ray radiation field has been well established in compliance with the ISO 4037:2019, it can be used for calibrating survey meters and personal dosimeters.

The k0-based internal mono-standard (IM) method was first proposed for the concentration analysis of samples of non-standard geometry in the 2000s. The method has demonstrated several advantages such as the elimination of gamma-ray self-attenuation and geometrical effects. On the other hand, the accuracy of the method principally depends on the in situ relative detection efficiency, which requires to be obtained in each measurement. Therefore, the relative detection efficiency is always under consideration for the improvement of the analysis results. The present paper describes a simple and automatic procedure for the determination of the relative efficiency using one or more activation products emitting gamma rays over a considered range of the spectrum. The procedure can be applied for INAA and PGNAA analysis.

The k0-based internal monostandard INAA method (IM-NAA) has been investigated for the determination of elemental concentrations in non-standard geometry samples at the Dalat research reactor (DRR). The experiments were implemented at the rotary specimen rack of the DRR which the thermal neutron flux was (3.61 ± 0.11) × 1012 n cm−2 s−1. In this work, the concentration analysis of Montana II Soil (SRM 2711a) and Brick Clay (SRM 679) have been used to validate the method. The elemental concentrations of Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Rb, Sb, Sm, Ta, Th, Yb, Zn have been analysed and to be in good agreement with certified values. The IM-NAA method has been applied to determine elemental concentrations in clay bricks and ceramics at the Cat Tien archaeological site.

Nuclear data for the k0-based neutron activation analysis (k0-NAA) including: k0-factors – combination of nuclear constants (atomic mass, isotopic abundance, gamma-ray yield and thermal neutron capture cross section); Q0 – the ratio of the resonance integral to thermal neutron capture cross section; and Er – effective resonance energy, along with the related nuclear data are presented and evaluated in the presentation. Accuracy and capability of k0-NAA depends considerably on the reliability of the above mentioned nuclear data. In general, the evaluation of nuclear data is essential and necessary in the field of nuclear science and technology, and this work is conducted by the nuclear data centers on the world as well as the research institutions where the nuclear data are usedfor R&D. Therefore, the evaluation of the nuclear data used in k0-NAA should also be performed so that some of data may no longer be appropriate should be redetermined. The evaluation of nuclear data in k0-NAA would contribute to the improvement of accuracy and reliability of the method, moreover, it would also contribute to the establishment a nuclear database in Vietnam in the future.

The cyclic neutron activation analysis (CNAA) facility based on a pneumatic transfer system for short irradiation and rapid counting has recently been upgraded at the Dalat research reactor. The original facility was only designed for single irradiation. Therefore, this work has aimed to upgrade both hardware and software for the cyclic irradiation. In this paper, the upgrading of the facility for CNAA was described. Irradiation time of the facility were calibrated, thereby reducing irradiation time to seconds with precision. The accuracy and sensitivity of CNAA based-on the upgraded facility were assessed by determination of some short-lived nuclides.

Quality evaluation of the k 0-standardized neutron activation analysis (k 0-NAA) at Dalat research reactor (DRR) has been implemented by analyzing the SMELS, a synthetic multi-element standard material as well as the certified reference materials for purposes of validation and verification of the method. The results revealed that the k 0-NAA established at DRR has met the requirements of multi-element analysis for the intended applications with about 42 elements: Al, As, Au, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Cu, Dy, Eu, Fe, Hf, I, In, K, La, Mg, Mn, Mo, Na, Nd, Pr, Rb, Sb, Sc, Se, Sm, Sr, Ta, Tb, Th, Ti, U, V, W, Yb, Zn and Zr in matrices of environment, geology and biology among others. Evaluation criteria for the laboratory quality used in this work are the statistical analysis parameters namely: u-scores, laboratory result/certified value ratios and relative biases as well as the control charts those are shown in the paper.

The k 0-standardized neutron activation analysis (k 0-NAA) has been applied for determination of multiple elements (25 elements: Al, As, Ba, Br, Ca, Cl, Co, Cr, Cs, Cu, Eu, Fe, Hg, K, La, Mg, Na, Rb, Sc, Se, Sm, Th, Ti, V and Zn) in marine sediment and tuna fish. About 50 marine sediment and 9 tuna fish samples were collected in two coastal areas of Vietnam. The health risk index (HRI) values of As and Br were higher than 1.0 for the tuna fish. Also, HRI value of Hg was 8.92 × 10−1 indicating a relatively high potential health risk, whiles Co and Mn with HRIs = 1.56 × 10−4 and 8.56 × 10−4, respectively, have the lowest potential health risks. Average enrichment factors using Al as a reference element (EF Al) were higher than 1.5 for Eu, La, Zn, Th, Cs and As in which the highest EF Al value for As was higher than 10. This study showed that the HRI value of As in the tuna fish correlated positively with the EF Al value for the element in the marine sediment.

The combination and optimization of the cyclic modes in neutron activation analysis (NAA) at the Dalat research reactor were performed to determine short-lived nuclides. This work focused on determination of selenium in biological materials using 77mSe (T 1/2 = 17.4 s) as a case in point. The detection limit was significantly improved by a factor of 3–4 times in comparison with the conventional NAA. The precision was typically within the range of 4–6 % at the third or fourth cycle. It is a reliable technique for determination of selenium in biological materials at sub-ppm concentration levels.

ObjectiveDioxin (polychlorinated dibenzodioxins+polychlorinated dibenzofurans) is one of the most toxic chemical substances known. Although it is suspected to cause endocrine disruption, very few epidemiological studies have been carried out on its effects on human steroid hormones. The aim of this study was to elucidate the association of dioxin exposure with steroid hormone levels in the saliva and serum of Vietnamese women.Study designTwo areas, namely Phu Cat (hot spot) and Kim Bang (nonexposed area), were selected for the study. The study subjects consisted of 51 and 58 women respectively. Saliva, blood, and breast milk samples were collected from the subjects in both the areas.MethodsCortisol, cortisone, DHEA, androstenedione, estrone, and estradiol levels in serum and saliva were determined by liquid chromatography–tandem mass spectrometry; dioxin concentrations in breast milk were measured by gas chromatography–mass spectrometry.ResultsDioxin concentrations in the breast milk of women from the dioxin hot spot were three to four times higher than those in the breast milk of women from the nonexposed area. Good correlations were found between the levels of six steroid hormones in saliva and those in serum respectively. Salivary and serum cortisol and cortisone levels in women from the dioxin hot spot were significantly higher than those in women from the nonexposed area (PPConclusionThese results suggest that dioxin influences steroidogenesis in humans. Saliva samples can be used for hormone analysis and are therefore excellent specimens in epidemiological studies.

Size segregated suspended particulate matter (PM2.5 and PM2.5-10) were collected using Gent low-volume air sampler at four different receptor site-classes in Lagos Mega City, Nigeria. The particulate mass loading was quantified and the concentration was analyzed to examine the pattern and variation from one receptor site-class to another. The PM2.5/PM10 ratio varied among the site-classes with the residential and marine sites having the least and highest ratio of 0.31 +/- 0.13 and 0.49 +/- 0.17 respectively. Particulate loading was higher on weekdays than on weekends (by a factor of about 1.5) in all but the marine site-class.The mean PM2.5/PM10 ratio is 0.41 +/- 0.15, which suggests that traffic emission is not the principal source of the Particulate Matter (PM). The INAA assay of the particulates detected ten elements: As, Br, Ce, K, La, Mo, Na, Sb, Sm and Zn. Except for Br, Mo and Sb, the detected elements were more pronounced in the coarse-fractioned filter Principal Component Factor Analysis (PCFA) of the detected elements identified some common sources (traffic-related, traffic emission, sea-salt and industrial emission) for both PM fractions at the four receptor site-classes.