14.8 MeV neutron activation cross-sections for (n,p) and (n, α) reactions of some rare earth nuclides

The activation cross-sections for sixteen (n, p) and (n, α) reactions on rare earth nuclides were measured at 14.8 MeV neutron energy. A Ge(Li) detector was used for the radioactivity measurements. The measured cross-sections are compared with the semi-empirical predictions of LEVKOVSKII³ and BAYHURST and PRESTWOOD.¹⁶     

Epithermal neutron activation analysis using (n,n′) reaction

The (n, n′) reaction with the epithermal and fast neutrons of a nuclear reactor has been studied for activation analysis of Sr, Cd, In, Ba, Hf, Os, Au, Hg and Pb. For some elements (In, Os, Au, Hg and Pb) the use of a cadmium sheet reduced the activity by less than a factor of two, while the interferences from the most abundant elements have been reduced by more than two orders of magnitude.     

The reaction117Sn (n,n′)117mSn as a primary interference in (n, γ) neutron activation analysis

The¹¹⁶Sn (n, γ)^117mSn reaction commonly used in reactor-neutron activation analysis (RNAA) turned out to be seriously interfered by the¹¹⁷Sn (n, n′)^117mSn reaction, as observed from irradiation in channels with largely different neutron thermalization. To estimate the magnitude of this primary interference an attempt was made to determine the relevant fission neutron averaged cross-section, yielding approximately σ_{n, n}, (¹¹⁷Sn)==0.09±0.01 barn. This value—believed to be the first measured and published—is remarkably high especially when compared to the 2200 m·s^?1 cross-section σ_o[¹¹⁶Sn(n, γ)^117mSn]=0.006 barn.     

Cross section measurements for (n, p) and (n, 2n) reactions of rare-earth isotopes at neutron energies from 13.5 to 14.6 MeV

Cross sections for (n, p) and (n, 2n) reactions have been measured on some rare-earth isotopes at neutron energies of 13.5-14.6 MeV using activation technique. Data are reported for the following reactions:¹⁵⁰Nd(n, 2n) ¹⁴⁹Nd, ¹⁴⁸Nd(n, 2n) ¹⁴⁷Nd, ¹⁴²Nd(n, 2n) ¹⁴¹Nd, ¹⁶⁰Gd(n, 2n) ¹⁵⁹Gd, ¹⁵⁸Gd(n, p) ¹⁵⁸Eu, ¹⁴⁶Nd(n, p) ¹⁴⁶Pr, ¹⁴¹Pr(n, p) ¹⁴¹Ce and ¹³⁹La(n, p) ¹³⁹Ba. The neutron fluences are determined by the cross sections of ²⁷Al(n, a) ²⁴Na and ⁹³Nb(n, 2n) ^92mNb reactions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Activation cross-sections for some (n, 2n), (n,p) and (n, γ)-reactions

The average fission neutron cross-sections of the reactions²³³U(n, 2n)²³²U,⁶⁰Ni(n, p)⁶⁰Co and²⁷Al(n, p)²⁷Mg and the resonance integrals of the (n, γ)-reactions of the nuclides¹⁸¹Ta,¹⁷⁶Lu,¹⁷⁵Lu,⁶⁴Ni,⁵⁹Co and²⁶Mg have been determined by the activation method following the well-known conventions. The results verify some of the existing values and present data for hitherto unknown or poorly known reactions.     

The monostandard method in thermal neutron activation analysis of geological, biological and environmental materials

Summary A simple method is decribed for instrumental multielement thermal neutron activation analysis using a monostandard. For geological and air dust samples, iron is used as a comparator, while sodium has advantages for biological materials.To test the capabilities of this method, the values of the effective cross sections of the 23 elements determined were evaluated in a reactor site with an almost pure thermal neutron flux of about 9·10¹² n·cm^–2·s^–1 and an epithermal neutron contribution of less than 0.03%. The values obtained were found to agree mostly well with the best literature values of thermal neutron cross sections. The results of an analysis by activation in the same site agree well with the relative method using multielement standards and for several standard reference materials with certified element contents. A comparison of the element contents obtained by the monostandard and relative methods together with corresponding precisions and accuracies is given.

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Die Monostandardmethode bei der Aktivierungsanalyse mit thermischen Neutronen von geologischem, biologischem und Umweltmaterial

Zusammenfassung Die Monostandardmethode wurde erstmals auf die Aktivierungsanalyse mit rein thermischen Neutronen aus der thermischen Säule des Reaktors FRJ-2 (mit epithermischen Anteilen von < 0,03%) angewendet. Hier sind die theoretischen Verhältnisse und damit auch Gleichungen besonders einfach. — Die bei einem Neutronenfluß von 9·10¹² n·cm^–2·s^–1 ermittelten effektiven Neutroneneinfangquerschnitte stimmen häufig gut mit den Literaturwerten überein. — Für geologische Proben wurde Eisen, für biologisches Material Natrium als Komparator, d.h. Monoelementstandard, verwendet. Es konnten über zwanzig Elemente in Andesit, Granit, Flugstaubasche, Luftstaub, Pflanzenmaterial und Obstblättern bestimmt werden.

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Dedicated to Professor Dr. Kurt Starke, University of Marburg/ Lahn on the occasion of his 70 th birthday

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Fourth Communication on Improvement of Instrumental Analysis for Service Analysis

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Guest Scientist from Egypt.

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Guest Scientist under IAEA-Fellowship from the Faculty of Chemistry, University of Sofia, Bulgaria

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This paper is an extract of the more detailed Report Jül-1822 (ISSN 0366-0885), January 1983.     

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     

Effective threshold energies for (n, 2n) reactions induced in a fission neutron spectrum

The table presents computed values of effective threshold energies, E_eff, for (n, 2n) reactions induced in a fission neutron spectrum. E_eff-values are given for the (n, 2n) reactions for which the charge of the target nucleus is greater than 11 and for which the reaction product cannot be formed by (n, γ) reaction on another stable isotope. A closed expression is given for the integral of a fission neutron distribution of the Cranberg type, N(E), and for the mean energy of the fission neutrons with spectral distribution N(E).     

Optimization of Linac-based neutron source for thermal neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - A 20&nbsp;MeV electron Linac based neutron beam has been shaped for neutron activation analysis (NAA) technique. A beam shaping assembly (BSA)...     

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.     

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.     

The average cross section of the 102Pd(n,p) 102,102mRh and 103Rh(n, 2n) 102, 102m Rh reactions in a fission neutron spectrum

The mean cross sections of the ¹⁰²Pd(n,p)^102,102mRh and ¹⁰³Rh(n,2n)^102,102m Rh reactions were experimentally determined by irradiating palladium and rhodium samples for 1 week at an equivalent fission flux of 3 × 10¹³ n. cm⁻² . s⁻¹. The equivalent fission neutron flux was determined using six reference threshold reactions [⁴⁷Ti(n,p)⁴⁷Sc; ⁵⁸Ni(n,p)^58,58mCo; ⁵⁴Fe(n,p)⁵⁴Mn; ⁴⁶Ti(n,p) ⁴⁶Sc; ⁹²Mo(n,p) ^92mNb and ⁵⁵Mn(n,2n) ⁵⁴Mn] and appeared to be unperturbed.Thorough radiochemical decontaminations were required in order to separate the ^102,102mRh activities from the high thermal neutron induced palladium, silver and/or iridium activities.The results are compared with the values predicted by empirical relationships.     

Average cross-sections for (n, α) and (n,p) reactions on titanium in a fission-type reactor spectrum

The average cross-section in a fission-type reactor spectrum was determined experimentally for the reactions:⁴⁶Ti(n,p)⁴⁶Sc,⁴⁷Ti(n,p)⁴⁷Sc,⁴⁸Ti(n,p)⁴⁸Ti(n,α)⁴⁵Ca and⁵⁰Ti(n,α)⁴⁷Ca. In order to obtain the (n,p) cross-sections, reactor irradiation of titanium was followed by measurement of the induced scandium activities with a Ge(Li) detector of calibrated detection efficiency. For this no chemical separations had to be carried out. For the (n,α) reactions, however, the induced calcium activities were separeted and purified by oxalate precipitation, after the bulk of the radioactivity had been removed by precipitation of titanium hydroxide. The⁴⁷Ca disintegration rate was determined in the same way as for the scandium isotopes, whereas for⁴⁵Ca liquid scintillation counting was carried out. The shape of the reactor spectrum was investigated by irradiating reference threshold detectors with different effective threshold energies. To correct for (n,γ) interferences, irradiations were carried out with and without cadmium shielding. On the basis of \(\bar \sigma _F = 0.64\) mb for the reaction²⁷Al(n,α)²⁴Na, the average cross-sections were as follows:⁴⁶Ti(n,p)⁴⁶Sc:10.5±0.4 mb;⁴⁷Ti(n,p)⁴⁷Sc: 16.3±0.6 mb;⁴⁸Ti(n,p)⁴⁸Sc:0.272±0.005 mb;⁴⁸Ti(n,α)⁴⁵Ca: 34μb;⁵⁰Ti(n,α)⁴⁷Ca: 8.1±0.3 μb.     

A compilation of the fission spectrum average neutron cross-sections for (n, α) reactions

The (n, α) cross-sections averaged over the²³⁵U thermal fission neutron spectrum are compiled. The original values and whenever possible renormalized values are presented in parallel. The methods used for measurements and calculations are briefly discussed.     

Possibilities of the short-term thermal and epithermal neutron activation for analysis of macromycetes (mushrooms)

Summary Fruitbodies of wild-growing macromycetes (mushrooms) of various genera and species collected in localities with different geochemical features and man-made burden in the Czech Republic were analyzed using the short-term instrumental neutron activation, with both thermal and epithermal neutrons. Analytical possibilities of these methods were compared. Na, Mg, Al, Cl, K, Ca, V, Mn, Cu, and Br were determined regularly, whereas S, Ti, Rb, Cs, Ba, and Dy were determined occasionally with thermal neutron activation at irradiation-decay-counting times mode of 1-10-10 minutes. Because of high concentration of K and P in the macromycete dry matter (2-7% and 0.5-1%, respectively) and also high Cl concentration in some genera (up to 2.5%), all “1/v” absorbers, epithermal neutron activation in Cd box (1 mm thick wall) substantially suppresses their macroactivities and enhances sensitivity in the determination of elements with significant resonance integrals. Cu, Se, Rb, Ag, Hf, and sometimes Ba are determinable in the mode of 60-30-60 seconds, while K, Cu, As, Br, Rb, In, I, U (in some species also Co, Zn, Cs, Ba, and Hg) in the mode of 1-13-13 minutes. However, Na, Mg, Al, Cl, and Mn determination is not possible this way, as the (n,p) and (n,α) interfering reactions with fast neutrons and high K, P, and other interfering elements content make great interference contributions. Information about content of the essential and toxic elements in mushrooms is important in nutritional studies, because mushrooms form a non-negligible part of diet in many countries.     

The determination of ko factors and their application to the neutron activation analysis of pure zirconium metal by the single-comparator method

The procedures followed for the determination of standardization factors and their use in the single-comparator method for multi-element reactor neutron activation analysis are described. The method is applied to the determination of Cr, Mn, Fe, Ni and Mo in pure zirconium metal. The matrix could serve as the single comparator and as a bi-isotopic thermal-to-epithermal neutron flux ratio monitor.     

Symmetry nonintegrability for extended K(m, n, p) equation

Journal of Mathematical Chemistry - In the present paper we study symmetries of extended K(m,&nbsp;n,&nbsp;p) equations and prove that the equations from this class have no generalized...     

Determination of70Ge(n,p)70Ga and74Ge(n,p)74Ga reaction cross sections for a fission neutron spectrum

The fission neutron spectrum averaged cross-sections for the reactions⁷⁰Ge(n,p)⁷⁰Ga and⁷⁴Ge(n,p)⁷⁴Ga have been determined. The averages of four determinations are, respectively, (3.10±0.30) mb and (0.00938±0.00059) mb. The present values are, to the authors' knowledge, the first experimental data on the fission averaged cross-section for these reactions.     

Radiochemical thermal neutron activation analysis of fish solubles

A rapid and simple method has been developed for the determination of Mn, Zn, Cr and Ag by radiochemical thermal neutron activation analysis, involving solvent extraction and precipitation technique. Mn, Zn, Cr and Ag can be determined with an accuracy of 8.9, 5.8, 7.7 and 7.6%, respectively. The method has been employed for determination of the elements in fish solubles. Two samples and a standard can be analyzed in three hours.