Epithermal Activation Research Articles

A simplified method to replace the Westcott formalism in k 0-NAA using non-1/v nuclides

The Westcott formalism was developed to accurately describe the activation of nuclides whose neutron capture cross-sections do not follow the 1/v-law and it was incorporated in the k 0-method about 20 years ago. However, its implementation in the original fashion is not easy, requiring the use of a different formalism for the non-1/v nuclides, with a g(T n) factor for the thermal neutron activation and an s 0 factor for epithermal activation, the measurement of the neutron spectral index of the irradiation channel and the irradiation of a temperature monitor with each batch of samples as well. In this work we investigated the accuracy of maintaining the simpler formula of the Hogdahl convention for all nuclides and introducing the g(T n) factor for the thermal neutron activation for non-1/v nuclides. The epithermal activation is calculated using a Q 0-value estimated from the measured s 0-value for non-1/v nuclides. This new approach has been shown, by calculations with the parameters of the neutron spectra of five irradiation channels, not to give a significant loss of accuracy relative to the Westcott formalism.

Neutron activation analysis in the life sciences

Development of methods for instrumental neutron activation analysis (INAA) and their applications in the life sciences are reviewed. Emphasis is placed on epithermal activation with reactor neutrons (ENAA), and the advantages of this technique in analysis of environmental objects are shown. The results of applied INAA studies in the field of the life sciences carried out at the world’s leading nuclear centers are reported. Experience in employing a radioanalytical complex at the IBR-2 reactor (Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna) for such studies is summarized.

A new method for the analysis of titanium, barium, and arsenic in obsidian via epithermal neutron activation analysis

A new instrumental epithermal neutron activation analysis procedure to quantitatively determine titanium, barium, and bromine in obsidian with improved sensitivity has been developed. The advantage of epithermal activation for Ti, Ba, and Br is demonstrated with multiple geological standards and the ability to determine arsenic in obsidian is demonstrated. The results for titanium are compared to previous electron-microprobe results for Kenyan obsidian.

Measurement of partial gamma-ray production cross-sections and k0-factors for radionuclides with chopped-beam PGAA—Part II

As a continuation of our previously reported experiments, the partial gamma-ray production cross-sections ( σ γ) and k 0-factors of 12 short- and medium-lived radionuclides were determined using a chopped beam of cold neutrons. This technique avoids several problems associated with epithermal activation, sample transportation and dead-time effects in neutron activation analysis (NAA) measurements. Our k 0-values were determined with internal standardization, using stoichiometric compounds or water solutions of known compositions.

Epithermal neutrons activation analysis, radiochemical and radiometric investigations of evaporitic deposits of Slanic-Prahova (Romania) salt mine

Summary. Three highly sensitive analytical methods: epithermal neutron activation analysis (ENAA), radiometric assay and UV/Vis spectroscopy were used to investigate the elemental composition of both halite and mineral fractions (sediments) of salt collected from the Slanic-Prahova salt mine, near the location of Low Background Radiation Laboratory. For halite with all three methods and within experimental uncertainties, it was not possible to observe the presence of any natural radioactive elements. For the mineral fraction both radiometric and ENAA showed the presence of 40 K, 232 Th and 238 U in concentrations comparable to the upper continental core (UCC). The same was true for the distribution in the mineral fraction of 7 other major (Na, Al, Cl, K, Ca, Ti and Fe) and 29 trace elements (Sc, Cr, V, Mn, Ni, Co, Zn, Cu, As, Br, Rb, Sr, Zr, Mo, Sn, Sb, Cs, Ba, La, Ce, Ne, Eu, Sm, Tb, Hf, Ta, W, Th, U) as determined by epithermal neutron activation analysis (ENAA), which demonstrates a continental origin of the sediments in the existing salt deposit.

INAA of geological materials using a combination of epithermal activation and Compton suppression: Prediction of possibilities

Nuclear data relevant to the determination of elements in geological materials by instrumental neutron activation analysis using a combination of epithermal neutron activation and Compton suppression counting are presented. The feasibility of this combination is discussed considering data for desired as well as interfering nuclides. Among elements determined after short irradiation, the conditions for Sr, Zr, I, Cs, Eu and U should be improved. After long epithermal irradiation and appropriate decay, Compton suppression should lead to improvement in determination of As, Rb, Sr, Mo, Sn, Sb, Ba, Gd, Ho, Tm, W, Au, Th, and U. In the case of Ga, Se, Ag, In, Cs, Tb, Yb, Hf, Ta, and W, the use of Compton suppression in connection with epithermal activation is not recommended because the radionuclides concerned decay with coincident γ-rays. In general, the use of Compton suppression should improve the determination of trace elements in geological materials by epithermal neutron activation analysis, but more work is needed to better quantify these improvements.

Different methodologies in neutron activation to approach the full analysis of environmental and nutritional samples

Different methodologies of neutron activation analysis (NAA) are now available at the Technological and Nuclear Institute (Sacavem, Portugal), namely Compton suppression, epithermal activation, replicate and cyclic activation, and low energy photon measurement. Prompt gamma activation analysis (PGAA) will be implemented soon. Results by instrumental NAA and PGAA on environmental and nutritional samples are discussed herein, showing that PGAA — carried out at the Institute of Isotope Research (Budapest, Hungary) — brings about an effective input to assessing relevant elements. Sensitivity enhancement in NAA by Compton suppression is also illustrated. Through a judicious combination of methodologies, practically all elements of interest in pollution and nutrition terms can be determined.

Epithermal Neutron Activation Analysis at the IBR-2 reactor of the Frank Laboratory of Neutron Physics at the Joint Institute for Nuclear Research (Dubna)

Experience of the Neutron Activation Analysis (NAA) Department in employing epithermal activation in life sciences and materials science is summarized. The potential of a combination of epithermal activation and the suppression of Compton scattering and contributions from cascade-photon-emitting elements for raising NAA-based analytical studies up to a new level are discussed.

Measurement of Neutron Capture Resonance Integrals on Bromine Isotopes

Neutron capture resonance integrals of the reactions 79Br(n, γ)80Brm, 79Br(n, γ)80Brg, 81Br(n, γ)82Brm, 81Br(n, γ)82Brg, and 81Br(n, γ)82Brm+g have been measured under 1-mm-thick cadmium covers inside the core of the RA-6 research reactor. The measured values are, respectively, (29.2 ± 3.1) b, (86.1 ± 8.9) b, (40.9 ± 2.3) b, (5.1 ± 1.1) b, and (46.8 ± 2.3) b. Resonance integrals of the reactions 79Br(n, γ)80Brm and 81Br(n, γ)82Brm were also measured by a direct method using the gamma ray from the isomeric transition. The results are (30.3 ± 2.6) b and (42.7 ± 4.0) b, respectively. All measured resonance integrals are referred to the standard value (1562 ± 48) b, corresponding to the reaction 197Au(n, γ)198Au. Spectrum unfolding with the STAY’SL code showed the 1/E behavior of the neutron energy spectrum in the epithermal range. Good agreement was found between the results of this work and others published in the literature. Perturbations of epithermal activation due to the presence of cadmium covers are discussed and corrected in the cases where differential cross-section data are available.

Validation study of the Monte Carlo code MVP for analysis of two-region TCA critical experiments with PWR-type MOX fuels

A series of critical experiments containing PWR-type MOX fuels conducted at the TCA facility of Japan Atomic Energy Research Institute have been analyzed. The cores were composed of a central 4.91 wt% plutonium enriched mixed-oxide (PuO 2–UO 2) 10 × 10 test lattice with water-to-fuel volume ratio of 2.40 or 2.96, surrounded by 2.6 wt% enriched UO 2 driver lattice with water-to-fuel volume ratio of 1.50 with a water gap in-between. The fissile plutonium content was 91.4 wt%. The critical water level, the power distribution in the test region, and the neutron activation distribution of Au-wire were measured for six different cores of which two contain soluble boron of 309.4 and 554.0 ppm, one contains four equidistant water holes in the central test lattice and one contains cross water gap at the core center. Calculation of corresponding effective multiplication factor, the fission reaction-rate distribution in the test region, and the capture reaction-rate distribution of Au have been performed using a continuous-energy Monte Carlo code MVP with two nuclear data sets based on JENDL-3.2 and JENDL-3.3. The calculated results agreed to the measurements within a maximum difference of 0.27% for the effective multiplication factors, 3.0% for the power distributions, 5.9% for the thermal activation distributions throughout the whole region, and 4.3% for the epithermal activation distributions in the core region.

Measurement of partial γ-ray production cross-sections and k0 factors for radionuclides with chopped-beam PGAA

The partial γ-ray production cross-sections ( σ γ) and k 0 factors for 16 short- and medium-lived radionuclides were determined with prompt gamma activation analysis (PGAA) in a chopped beam of cold neutrons. This technique avoids some problems of usual standardization measurements done in neutron activation analysis (NAA), e.g. epithermal activation, counting at varying count rates, and also offers better selectivities than continuous-beam PGAA. The k 0 values were determined with internal standardization using stoichiometric compounds or water solutions of known compositions. Calculation of the uncertainties is also discussed in detail.

Trace element contamination in industrial regions of Poland studied by moss monitoring.

The use of terrestrial mosses as biomonitors in large-scale multi-element studies of heavy metal deposition from the atmosphere is a well established technique in Europe. In such studies it is advantageous to determine as many elements as possible in order to distinguish between different source categories. A combination of INAA and AAS has been found very useful in this respect, in particular when epithermal activation is used for instrumental neutron activation analysis. A total of 33 elements (Al, Cl, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Ag, Cd, Sb, I, Cs, Ba, La, Ce, Tb, Yb, Hf, Ta, W, Au, Pb, Th, and U) in Pleurozium schreberi (Brid.) Mitt. moss samples from the Silesia-Kraków Industrial Region and Legnica-Głogów Copper Basin and from the control (background) area in Northeast Poland were identified. The highest concentrations of the majority of trace elements were found in mosses growing in the Silesia-Kraków Industrial Region, only Cu and As concentrations were higher in mosses in the Legnica-Głogów Copper Basin. These results are in conformity with the load of trace elements emissions in these areas.

Epithermal neutron activation analysis of food

Food samples were irradiated with thermal and epithermal neutrons. The average ratios of thermal to epithermal activity were determined for80Br,49Ca,38Cl,60mCo,42K,27Mg,56Mn,24Na, and86mRB. They were equal to 2.1, 26, 24, 6.6, 19, 16, 11, 23 and 1.9, respectively. Then, 57 food samples were analyzed by epithermal neutron activation analysis for Br and Rb. The concentrations (in ppm) of Br and Rb were in asparagus (2) 2.3, 11.5; beets (3) 0.5, 0.8; beef (3) 1.7, 3.6; cabbage (5) 0.5, 10.8; carrot (3) 0.2, 3.7; chicken (3) 0.6, 4.4; chocolate (7) 11.1, 18.7; egg (3) 0.9, 1.9; french bean (3) 0.3, 1.0; goose (2) 1.3, 9.3; lettuce (2) 0.9, 1.7; pork (1) 1.5, 4.4; potato (7) 1.0, 1.2; sausage (3) 0.6, 4.0; strawberry jam (3) 0.4, 1.4; tomato (1) 13.5, 14.6; turkey (3) 1.2, 4.9. respectively. The number of samples analyzed is indicated in parentheses.

Neutron activation analysis of an Egyptian monazite ore sample

The absolute sensitivity of a gamma-ray line following thermal or epithermal neutron activation is expressed as a product of four terms, namely, the intrinsic, irradiation, decay and measurement factors. The total absolute sensitivity is the sum of the absolute sensitivities due to thermal and epithermal activation. A. FORTRAN computer program was prepared on the TANDY 3000 NL PCA to calculate the total absolute sensitivity of the intensive gamma-ray lines from the thermal and epithermal neutron activation of all the naturally occurring nuclides. Another program was prepared for the determination of the total absolute sensitivity for gammarays emitted by radioactive daughters such as233Pa from233Th and239Np from239U. Long time irradiation periods (about 48 hours) for specimens of the monazite ore sample were carried out at the (ET-RR-1) reactor core periphery. The monazite ore sample was separated from the associating minerals in the sand of Abou-Khashaba of Rashied (Rosetta) area on the Mediterranean (North of Egypt). The separated monazite ore sample was provided by the Nuclear Material Authority of Egypt. The cadmium difference method was applied to thin gold foils for absolute thermal and epithermal neutron flux determination. The gamma-ray spectra were measured using a spectrometer with a HPGe coaxial detector. The evaluated absolute sensitivity tables were helpful in identifying the radioisotopes contributing to the gamma- ray spectra and in evaluating the elemental concentration of the monazite constitutents. Most of the rare earth elements were observed and their concentrations are reported. La, Ce, Nd, Sd and Th were found as major elements, U, Tb, Hf and Eu as minor elements.

Intercomparison and determination of environmental standard samples by instrumental neutron activation analysis

To identify and improve the analytical technique for air pollution research, four kinds of environmental standard samples, i.e., airbome particulate matter, coal flyash, soil and pine needle supplied from the NIST and the IAEA were analyzed using thermal and epithermal neutron activation techniques. Sample irradiation was done at the irradiation facilities (neutron flux, 1 · 1013 n·cm−2·s−1) of the TRIGA MARK-III Research Reactor in the Korea Atomic Energy Research Institute. The accuracy and precision for the analysis of 40 trace and toxic elements in the samples were compared with the certified and reported values, respectively. In the analytical results of all standard reference materials, the relative standard deviation were within the 15% except for 11 elements and the relative error were agreed within the 10–20% except for 13 elements. The benefit of epithermal activation was investigated and the optimum analytical condition is reported.

Quality of high count rate high resolution short-time activation analysis

The fast transfer system was modified to enable a fixed counting geometry with high reproductibility using an endcap geometry. The optimal count rate for short time activation analysis by means of the loss free counting system was found to be within 100–140 kcts/s, if a high accuracy is needed (1%). The method of calculating the peak area after the dead time and pile up corrections was modified by changing the peak fitting parameters gradually with increasing count rates. Epithermal activation by a6LiD converter was found to be an ideal irradiation technique for short time activation analysis especially for heavy elements due to the lower contribution of24Na and28Al (up to 30 fold).

Neutron activation analysis of final molasses from Cuban sugar industry

Thermal and epithermal non-destructive activation analyses have been performed on samples of final molasses from 14 different sugar factories, covering the most important regions in Cuba. From the first measurement after irradiation at the Triga Mark reactor (VTT), the concentration of more than 15 elements is reported. The almost constant elemental composition shows that they can be used equally for different purposes as animal foodstuff and for the manufacture of biotechnological products. This work is part of a research project developed in order to establish a complete characterization of Cuban sugar molasses.

Spectral Characterization of the Epithermal Neutron Beam at the Brookhaven Medical Research Reactor

This paper discusses neutron spectrum measurements performed on the aluminum-oxide-filtered neutron beam at the Brookhaven Medical Research Reactor (BMRR). Two independent measurement techniques are used in the spectrum characterization: foil activation spectrometry and proton-recoil spectrometry. Activation foil assemblies are irradiated at the exit port of the beam facility. Dominant resonances in selected activation reactions are used to measure the epithermal neutron spectrum. The intermediate and fast energy ranges of the neutron spectrum are measured by threshold reactions and the {sup 10}B-filtered {sup 235}U fission reaction. Neutron spectral data are derived form the activation data by two approaches: an analysis that yields neutron flux values at the energies of the dominant or primary resonances in the epithermal activation reactions and an analysis that utilizes all the activation data simultaneously in a spectrum unfolding process using the FERRET data adjustment code. Hydrogen-filled proton-recoil proportional chambers are used at the beam port exit to acquire data of a higher energy resolution than that obtainable through foil activation techniques. These measurements ar made to determine if structure in the aluminum scattering cross section would produce significant structure in the filtered spectrum in the fast neutron region.

Calibration of the fission-track dating method: Is Cu useful as an absolute thermal neutron fluence monitor?

Thermal neutron fluence measurements have been performed with Au and Co standard monitors at the one side and Cu monitors (foils and wires) at the other. using three reactor channels with different neutron energy spectra and two calibrated Ge detectors. Care was taken to eliminate errors caused by epithermal activation and neutron self-shielding while special attention was also paid to the problem of incomplete annihilation of the 64Cu β + radiation. Our new measurements reveal consistent fluences between Cu and the Au and Co standard monitors, when using the recommended and/or recently evaluated nuclear parameters for the 63Cu(n,γ) 64Cu reaction. However, we do not endorse the usage of Cu as a standard fluence monitor for fission-track dating because from a metrological standpoint too large uncertainties still exist on some of its relevant nuclear parameters such as the thermal neutron activation cross-section ( σ 0) of 63Cu.

Epithermal neutron activation analysis using the monostandard method

A method is described for epithermal neutron activation analysis of 17 elements in granite rock samples using a single standard. Gold has been used as a single comparator due to its relatively high resonance integral value (I0=400 barn). In addition, it is preferable to Co in order to obtain a large epithermal activation in a short irradiation. The method of calculation is simple and rapid and can be done using a small calculator. Epithermal activation is able to overcome the difficulty arising from changing irradiation position as well as increasing the number of determinable elements by eliminating the interference from undesired isotopes which have relatively high thermal cross section values (σ0), when reactor neutron flux is used. The coupling of epithermal activation with the monostandard method has the advantage of using a small Cd-cover which overcomes most of the difficulties arising in the relative method with large volume cadmium filters.