The 2021 IAEA software intercomparison for k0-INAA

In order to establish the variation between results in mass fractions due to software implementation, as measured by the k0-method for INAA, the IAEA has organized a software intercomparison. A complete set of test spectra and associated information was assembled. Efficiency curves, neutron spectrum parameters, correction factors and mass fractions were calculated with the participating programs (k0-IPEN, k0-INRIM, k0-DALAT, k0-IAEA and KayWin) using identical peak areas. In this paper, we report on the observed discrepancies, causes, remedies and future software developments. The test data, as well as intermediate results and observed mass fractions of the certified reference material BCR-320R “channel sediment” are available through the IAEA on request. The variations in concentrations attributed to differences between the programs were initially found to be 5.6 and 7.9%, for certified and uncertified concentrations, respectively. After the certified concentrations had been made available to the participants and they had been allowed to improve their programs, the variations found were 2.7 and 3.4%, respectively. The main identified remaining causes of variation are differences in the procedures used for detector efficiency characterisation and neutron spectrum parameter determination.

Estimation of 99Mo production rates from natural molybdenum in research reactors

Molybdenum-99 is one of the most important radionuclides for medical diagnostics. In 2015, the International Atomic Energy Agency organized a round-robin exercise where the participants measured and calculated specific saturation activities achievable for the ⁹⁸Mo(n,γ)⁹⁹Mo reaction. This reaction is of interest as a means to locally, and on a small scale, produce ⁹⁹Mo from natural molybdenum. The current paper summarises a set of experimental results and reviews the methodology for calculating the corresponding saturation activities. Activation by epithermal neutrons and also epithermal neutron self-shielding are found to be of high importance in this case.

Multi-elemental composition of Slovenian milk: analytical approach and geographical origin determination

The main objective in multi-elemental analysis in food is to obtain the best results in the shortest time and with minimal contamination and reagent consumption. Three different methods were investigated in the present study to obtain the elemental content in milk samples: energy dispersive X-ray fluorescence spectrometry (EDXRF), k₀-instrumental nuclear activation analysis (k₀-INAA) and the inductively coupled plasma mass spectrometry (ICP-MS). Quality assurance including intercomparison exercises of these measurements proved entirely satisfactory and was typical of that previously established for this technique. It was found that EDXRF was the cheapest, simplest and environmental friendly method for analysis of multi-elemental composition (P, S, Cl, K, Ca, Zn, Br, Rb, Sr) in milk samples, while for determination of Mn, Fe, Cu, Se content and possible identification of pollutants such as As, Cd and Pb ICP-MS was a method of choice due to its excellent sensitivity and accuracy. These two methods were also used to determine the multi-elemental composition in Slovenian raw cow milk from different geographical regions: Alpine, Mediterranean. Dinaric and Panoninan in December 2013. Linear discriminant analysis (LDA) was used to explore multi-elemental analysis of milk samples to obtain classification according to geographical regions. Regional discrimination was most successful taking into account Ca, S, P, K, and Cl with prediction ability of 66.7%.

Application of k0-method of neutron activation analysis for determination of trace elements in various mineral samples: a review

<p>Various trace elements in different types of arsenic (orpiment, As₂S₃; realgar, As₄S₄; lorandite, TlAsS₂), antimony (stibnite, Sb₂S₃), copper (brochantite, Cu₄SO₄(OH)₆; chalcanthite, CuSO₄·5H₂O; chalcopyrite, CuFeS₂; covellite, CuS; native copper, Cu) and iron based geological materials (hematite, Fe₂O₃; pyrite, FeS₂; chalcopyrite, CuFeS₂) were determined using <em>k</em>₀-method of neutron activation analysis (<em>k</em>₀-NAA) in both forms: instrumental (<em>k</em>₀-INAA) and radiochemical (<em>k</em>₀-RNAA). In order to avoid interferences from the matrix element (As, Sb, Cu and Fe), various procedures were applied for its removal. Elimination of the matrix element enabled investigation from 35 to 47 trace elements in the samples using short (up to few minutes) and long (up to 20 hours) irradiations in typical irradiation channels of TRIGA reactor. The minerals were collected from various localities within the Republic of Macedonia, except covellite, which was obtained from Bor, Serbia.</p>

Proposed design for the PGAA facility at the TRIGA IPR-R1 research reactor

BACKGROUND

This work presents an initial proposed design of a Prompt Gamma Activation Analysis (PGAA) facility to be installed at the TRIGA IPR-R1, a 60 years old research reactor of the Centre of Development of Nuclear Technology (CDTN) in Brazil. The basic characteristics of the facility and the results of the neutron flux are presented and discussed.

FINDINGS

The proposed design is based on a quasi vertical tube as a neutron guide from the reactor core, inside the reactor pool, 6 m below the room's level where shall be located the rack containing the set sample/detector/shielding. The evaluation of the thermal and epithermal neutron flux in the sample position was done considering the experimental data obtained from a vertical neutron guide, already existent in the reactor, and the simulated model for the facility.

METHODS

The experimental determination of the neutron flux was obtained through the standard procedure of using Au monitors in different positions of the vertical tube. In order to validate both, this experiment and calculations of the simulated model, the flux was also determined in different positions in the core used for sample irradiation. The model of the system was developed using the Monte Carlo code MCNP5.

CONCLUSION

The preliminary results suggest the possibility of obtaining a beam with minimum thermal flux of magnitude 10(6) cm(-2) s(-1), which confirm the technical feasibility of the installation of PGAA at the TRIGA IPR-R1 reactor. This beam would open new possibilities for enhancing the applications using the reactor.

Determination of trace elements in iron minerals by instrumental and radiochemical neutron activation analysis

The method for determination of major and trace elements in iron oxide [hematite (Fe2O3)] and sulfide [pyrite (FeS2) and chalcopyrite (CuFeS2)] minerals using the k 0-method of neutron activation analysis in both forms: instrumental (k 0-INAA) and radiochemical (k 0-RNAA) was suggested. In order to avoid interferences from iron on the determination of elements present in trace levels, radiochemical separation was made. Determination of the investigated elements in the aqueous phase was performed by k 0-RNAA after extraction of iron by isoamyl acetate (IAA) and diisopropyl ether (DIPE) from hydrochloric acid solution. The distribution of 35 elements in extraction systems (with intermediate/medium and long half-lived radionuclides) present in the studied minerals was investigated.

Estimation of uncertainty arising from different soil sampling devices: the use of variogram parameters

In the frame of the international SOILSAMP project, funded and coordinated by the National Environmental Protection Agency of Italy (APAT), uncertainties due to field soil sampling were assessed. Three different sampling devices were applied in an agricultural area using the same sampling protocol. Cr, Sc and Zn mass fractions in the collected soil samples were measured by k(0)-instrumental neutron activation analysis (k(0)-INAA). For each element-device combination the experimental variograms were calculated using geostatistical tools. The variogram parameters were used to estimate the standard uncertainty arising from sampling. The sampling component represents the dominant contribution of the measurement uncertainty with a sampling uncertainty to measurement uncertainty ratio ranging between 0.6 and 0.9. The approach based on the use of variogram parameters leads to uncertainty values of the sampling component in agreement with those estimated by replicate sampling approach.

Total mercury, methylmercury and selenium in mercury polluted areas in the province Guizhou, China

The province of Guizhou in Southwestern China is currently one of the world's most important mercury production areas. Emissions of mercury from the province to the global atmosphere have been estimated to be approximately 12% of the world total anthropogenic emissions. The main objective of this study was to assess the level of contamination with Hg in two geographical areas of Guizhou province. Mercury pollution in the areas concerned originates from mercury mining and ore processing in the area of Wanshan, while in the area of Quingzhen mercury pollution originates from the chemical industry discharging Hg through wastewaters and emissions to the atmosphere due to coal burning for electricity production. The results of this study confirmed high contamination with Hg in soil, sediments and rice in the Hg mining area in Wanshan. High levels of Hg in soil and rice were also found in the vicinity of the chemical plant in Quingzhen. The concentrations of Hg decreased with distance from the main sources of pollution considerably. The general conclusion is that Hg contamination in Wanshan is geographically more widespread, due to deposition and scavenging of Hg from contaminated air and deposition on land. In Quingzhen Hg contamination of soil is very high close to the chemical plant but the levels reach background concentrations at a distance of several km. Even though the major source of Hg in both areas is inorganic Hg, it was observed that active transformation of inorganic Hg to organic Hg species (MeHg) takes place in water, sediments and soils. The concentration of Hg in rice grains can reach up to 569 microg/kg of total Hg of which 145 microg/kg was in MeHg form. The percentage of Hg as MeHg varied from 5 to 83%. The concentrations of selenium can reach up to 16 mg/kg in soil and up to 1 mg/g in rice. A correlation exists between the concentration of Se in soil and rice, indicating that a portion of Se is bioavailable to plants. No correlation between Hg and Se in rice was found. Exposure of the local population to Hg may occur due to inhalation of Hg present in air (in particular in Hg mining area) and consumption of Hg contaminated food (in particular rice and fish) and water. Comparison of intake through these different routes showed that the values of Hg considerably exceed the USA EPA Reference Concentration (RfC) for chronic Hg exposure (RfC is 0.0004 mg/m(3)) close to the emission sources. Intake of Hg through food consumption, particularly rice and fish, is also an important route of Hg exposure in study area. In general, it can be concluded that the population mostly at risk is located in the vicinity of smelting facilities, mining activities and close to the waste disposal sites in the wider area of Wanshan. In order to assess the real level of contamination in the local population, it is recommended that biomonitoring should be performed, including Hg and MeHg measurements in hair, blood and urine samples.

Effect of arsenic trioxide on metallothionein and its conversion to different arsenic metabolites in hen liver

The metabolism of arsenic, its affinity to metallothionein (MT), its influence on selenium levels, and its biotransformation to different metabolites in the liver tissue of laying hens exposed to arsenic trioxide (As2O3) was investigated. The experiment was performed with two groups of hens fed for 19 d with either a standard diet or with the same diet enriched in arsenic (30 microg/g). The major findings were as follows: 1. After 19 d exposure, about 65% of the total liver As was found in the water-soluble phase (100,000g centrifuged supernatant). In liver supernatant, As binding was found mostly in the range of very low-molecular-weight proteins (Mr < 10,000). Although after exposure the amount of MT-like proteins increased, the As bound to it was only in trace amounts. The protein was identified by convential procedures as Zn,Cu-thionein with traces of selenium and arsenic. 2. Arsenic exposure resulted in almost unchanged Se levels regarding its tissue concentrations and distribution between supernatant and pellet, where about 10% of total Se was found in the supernatant. On the contrary, As exposure did affect Cd levels. Tissue Cd concentration was slightly diminished, but the percentage of tissue Cd found in the water-soluble phase was increased from 20% to 40%. 3. In methanol extracts of tissue and supernatant of the As-exposed group, only two arsenic compounds were detected, As(III) and dimethylarsinic acid (DMA), the latter prevailing.