Calculation of primary nuclear interferences occurring in neutron activation analysis with a slowpoke reactor

The cross-sections for (n, p) and (n, α) reactions which may interfere with (n, γ) reactions used in thermal neutron activation analysis have been calculated systematically using an empirical formula in conjunction with published σ-values. The interference factors (IF) have been subsequently calculated for flux conditions that prevail in a SLOWPOKE II reactor and both cross sections and interference factors have been listed in a tabulated form. The significance and usefulness of IF's thus obtained is discussed from the standpoint of trace analysis. For a number of low-Z matrices, their magnitude is such that the measurement of certain constituents at the ppm level by instrumental analysis is rendered virtually impossible, as for the following matrix—trace element pairs=Al/Mg, Na/Al, P/Si, S/P and Cl/S. For higher Z elements, interferences can be neglected in most instances.     

The epithermal neutron flux distribution in a nuclear reactor and its effect on epithermal neutron activation analysis

The shape of the epithermal neutron energy distribution has been determined in two irradiation positions of the University of London CONSORT II reactor. The method applied involves cadmium ratio measurements using a series of resonance detectors. Principles of the method and some considerations relative to epithermal neutron activation analysis in connection with the deviation of the epithermal neutron flux distribution from the 1/E law are given.     

Rapid multielement neutron activation analysis with a slowpoke reactor

The SLOWPOKE nuclear reactor meets many modern elemental analysis requirements; rapid multielement analysis of most types of samples is possible. The variable neutron flux (maximum 10¹² n cm^-2 s^-1) is stable, homogeneous and reproducible from day to day over a period of months. Sensitivities for 78 elements analyzed by neutron activation, with short irradiation and counting periods, have been determined; the conditions allow rapid multielement analysis with short sample turn-round time. Examples of the application of the technique to complex practical samples are given.     

Single-comparator methods in reactor neutron activation analysis

A critical evaluation of different comparator methods is given. The method based on experimentally-determined and convertible comparison factors (k) is considered to be the most suitable for general use. An alternative method is proposed, introducing generalized k₀ factors which are independent of irradiation and measuring conditions. This approach combines the simplicity of the absolute methods with nearly the same accuracy attained by the relative ones. It is suggested that k₀ factors be compiled in all cases when using single-comparator methods, to allow a continuous re-evaluation.     

ko-measurements and related nuclear data compilation for (n, γ) reactor neutron activation analysis

k_o-factors of 35 isotopes used in reactor neutron activation analysis were measured with a high degree of accuracy (1–2%). To minimize systematic errors, measurements were carried out using different reactor types, irradiation conditions (18 < Φ_s/Φ_e), Ge(Li) detectors, sample detector geometry, etc. Analyst-oriented tabulations including all necessary nuclear data, “best values”, as well as recommended k_o-values are given to facilitate analytical work with the new method. Some practical aspects as well as limitations of the k_o-method are also outlined together with the applied neutron flux and cross-section conventions. Research associate of the National Fonds voor Wetenschappelijk Onderzoek, Belgium     

Measurement of the neutron flux distribution in a research reactor by neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - The neutron flux distribution in the core region of the JRTR was measured through the neutron activation analysis method. Sample mount and a tool...     

Computer program for neutron activation analysis with the SLOWPOKE reactor

A FORTRAN computer program for automatic neutron activation analysis is presented. The program locates and identifies peaks in a gamma-ray spectrum, calculates peak areas and the concentrations of the elements of interest in the sample. This program was specifically designed for the SLOWPOKE reactor, it uses a semi-absolute method and does not need standards or flux monitors. The program was written so as to minimize the computation time, and a typical 4096-channel spectrum is processed in five seconds by an IBM 360/75 computer.     

Multielement standards in routine reactor neutron activation analysis

The application of multielement standards (MES) in routine neutron activation analysis brings a whole range of advantages. This paper deals with the experience obtained during many years of application of these MES. Nine of these MES contain a total of 50 elements in suitable combinations and concentrations; thus, the determination of most of the common elements by NAA can be carried out simultaneously. This refers to the following elements: Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Mo, Ag, Cd, In, Sb, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, W, Re, Au, Hg, Th and U. For the determination of the remaining elements such as Zr, Ta, Ir etc., single element standards (SES) are used.     

k0-measurements and related nuclear data compilation for (n, γ) reactor neutron activation analysis

Recommended k₀-factors and related nuclear data for use in (n, γ) activation analysis are given for 72 isotopes. In addition the basic nuclear constants and experimental parameters needed in the k₀ standardization method are reviewed. For convenient data reduction, computer programs were developed.     

k0-Measurements and related nuclear data compilation for (n, γ) reactor neutron activation analysis

The determination of k₀-factors has been continued covering now the relevant gamma-lines of 112 analytically interesting radionuclides. Experimental details are given, and an extended tabulation is presented of complex activation decay types and the associated expression for the parameters involved in the k₀-method.Deceased May 1988.     

Uncertainties in neutron activation analysis resulting from reactor noise

The stochastic processes of activation, disintegration and counting have been studied, taking into account reactor noise. Deviation of the variance of the number of counts from Poisson limit is shown to result. Explicit expressions for the variance in the case of Markovian autocorrelation function of the neutron flux density are presented and their relevance to neutron activation analysis is discussed.Presented at the MTAA-8 Conference, September 16–20, 1991, Vienna, Austria.     

Trace element analysis of motor oil by reactor neutron activation analysis

Normal motor oil have been analyzed by RNAA using thermal neutrons and single comparator method. The samples were taken from the oil carter of an engine. The concentration of trace elements have been measured as a function of running kilometers by -ray spectrometry. The trace elements which have been detected are Na, Mg, Al, Cl, V, Mn, Cu, Cr, Fe, Co, Zn, Br, Sb and Cd.     

Determination of characteristic neutron flux parameters of nuclear reactors for thermal neutron activation analysis

The characteristic neutron spectrum parameters for thermal neutron activation analysis have been determined for the most important irradiation positions of the reactors BR1 and BR2 at Mol (Belgium), HFR at Petten (Netherlands) and FRJ2 at Jülich (Federal Republic of Germany). The method of determination is described.     

Quantitative aspects of neutron activation analysis and isotope production with a small reactor

The use of “small” research reactors with applicable thermal neutron fluxes of ≤10^12.cm^−2.s⁻¹ in (instrumental) activation analysis based on γ-spectrometry, and in isotope production for radiotracer experiments is surveyed on the absis of the experience at ECN, Petten, The Netherlands and elsewhere. The aim is to provide a practical guideline for the application of “small” reactors in both fields. Reproducibility and knowledge of the physical parameters of irradiation and counting are essential and thus the first task of the radioanalyst. Emphasis is laid on the use of short-lived radionuclides. This implies the elimination of an additional source of bias in γ-spectrometry. Some suggestions are made on eventual projects of current interest.     

Instrumental neutron activation analysis of lanthanides and other elements employing CIRUS reactor as a thermal neutron source

The high thermal neutron flux provided by the CIRUS reactor (1×10¹³ n cm^–2s^–1) has been used to determine elements having long half-lives or poor thermal neutron crosssections. Selective cooling time and the use of a high resolution HPGe detector in conjunction with a PC based MCA unit have made it possible to analyze many elements in a single irradiation run. The method developed has been used for the analysis of ores such as Ilmenite, Rutile, Sillimanite, Garnet, Zircon and Monazite.     

A semi-automatic system for activation analysis using the WWR nuclear reactor

A semi-automatic pneumatic transport system for nuclear reactors is described. The sealed polyethylene capsules containing the sample are placed into transport containers. Ten such containers are placed manually into a feeding device. All subsequent operations (irradiation, removal of the capsule from the container, and transport of the capsule to the laboratory for activity measurement) are automated. Total time from the completion of irradiation to the beginning of measurement is 10–20 sec.     

Characterization of household plastics for heavy metals using neutron activation analysis

Highly enriched concentrations of several heavy metals have been found in municipal solid waste incinerator (MSWI) ash. In an effort to identify possible sources of these metals in MSWI ash, a variety of disposable household plastic products was examined for heavy metal content. Using both thermal and epithermal neutron activation analysis (NAA) along with Compton suppression techniques, concentrations of several trace and heavy metals including Ag, As, Au, Ba, Br, Cd, Cr, Cu, Fe, Mn, Ni, Sb, Se, Sn, Sr, V, W and Zn were determined. Results indicate a wide range of concentrations for these elements, with large variations in plastics of similar color and intended use. As limits dealing with heavy metal content of consumer products are lowered, NAA techniques will provide a useful method for verification of product compliance.     

Nuclear interferences of thorium fission products in reactor neutron activation analysis

The study is concerned with nuclear interferences of thorium in the determination of Zr, Mo, Ru, Te, Ba, La, Ce and Nd by the method of NAA under the conditions of neutron activation in a nuclear reactor core.Dedicated to Prof. V. D. Nefedov on the occasion of his 70th birthday     

Determination of copper in high-purity tin by reactor neutron activation analysis

For the determination of very low concentrations of copper in tin, an analytical method involving reactor neutron activation was developed whereby the copper activity was separated from the tin matrix by extraction of the Cu(I) cuproin complex in n-amyl alcohol. A new decontamination technique was sought in order to remove the copper contamination present on the tin surface. Pre-irradiation removal of the tin surface combined with post-irradiation etching appeared to be the most efficient.     

Problems and solutions in the standardization of reactor neutron activation analysis

A discussion is held on some selected topics of importance in the standardization of reactor neutron activation analysis. The topics are related to the accuracy and the consistency of the nuclear data, the occurrence of flux gradients in the irradiation container, the extensions and modifications of the k₀-method, and the determination of uranium via the counting of²³⁹Np and²³⁹U with a large Ge-detector or a LEPD.