Die Bestimmung von53Mn,Welches in Meteoritischem Material Durch Kosmische Strahlung Erzeugt Wurde,mit Hilfe der Neutronenaktivierung

Among a number of stable and unstable nuclides formed in material exposed to cosmic radiation the spallation nuclide⁵³Mn (T=2·10⁶ a) is investigated in meteoritic manganese by combined techniques of neutron activation and advanced γ-spectrometry. The need for an economic use of precious meteorites is so ensured best. Intense neutron bombardment transforms the long-livedK-emitter⁵³Mn into⁵⁴Mn, which is detected by its 0.84 MeV γ-rays. Using the (n,γ) cross section—recently derived byMillard—⁵³Mn-values in the range of 60–600 dpm/kg (10⁻¹¹ g/g) are found in a larger number of iron meteorite samples, which are only 1–3 g in weight. The determination is very specific and under appropriate conditions unaffected by side reactions. The attempt to use the⁴⁴Ti (n,γ)⁴⁵Ti reactions for the analysis of spallogenic titanium failed, because the σ_therm of⁴⁴Ti was found to be unexpectedly low (10 barns). Additionally,⁴⁵Sc was determined after (n,γ) reaction by the⁴⁶Sc γ,γ-cascades.      

Determination of chromium in blood by neutron activation analysis

A procedure for the determination of chromium in blood has been developed with a sensitivity of 5×10⁻³ μg Cr. Dried blood was irradiated with a neutron flux of 10¹² n·cm⁻²·sec⁻¹ in the VVRS reactor for 4 weeks, then the sample was mineralized and the chromium isolated by extraction as perchromic acid. The determination of the chromium content was accomplished by measuring the 0.32 MeV gamma energy of⁵¹Cr. In order to make correction for the interfering reaction⁵⁴Fe(n,α)⁵¹Cr, the formation of chromium from high-purity iron was investigated. The chromium content of the blood samples was between 1.03×10⁻² and 5.2×10⁻² ppm Cr.     

Metallobiochemistry of current environmental levels of trace metals: A new method of cyclotron production of48V for toxicological studies

No-carrier-added⁴⁸V at 37 Mbq (mCi) levels was produced at the JRC-Ispra cyclotron by (, n) reactions on a scandium target and used to label environmental and physiological levels of vanadium for metallobiochemical investigations. The radiochemical separation of⁴⁸V from Sc is very simple and rapid and involves a single chromatographic step after fast dissolution of the bombarded target. The yield of the separation and the radioisotopic purity of the separated⁴⁸V were nearly 100% A summary of the main results concerning different metabolic investigations on rats including absorption, retention, transfer of⁴⁸V from mothers to newborns, binding with enzymes as well as uptake by cell culture system is reported.At the time of this study visiting scientists at the^4,5Radiochemistry and³Functional Materials Divisions of the JRC-Ispra.     

Recoil implantation reaction in geometrical isomers of tris/benzoylacetonato/chromium/III/

Hot atom chemical reaction by⁵⁰Cr/n, /⁵¹Cr and⁵²Cr/, n/⁵¹Cr reactions, and recoil implantation reaction by⁵¹V/p, n/⁵¹Cr reaction were investigated using geometrical isomers /mer and fac/ of tris/benzoylacetonato/ chromium/III/ /Cr/ba/₃/. The production of counter isomer was observed for both mer- and fac-targets, although the yield of labelled parent isomer was larger. The observed mer/fac yield ratio suggests that the main formation mechanism of⁵¹Cr/ba/₃ is the reaction of ba^– and Cr/ba/ ₂ ⁺ which has the same geometrical configuration of target complex, and the substitution reaction of central metal atom by recoil⁵¹Cr. Furthermore, implantation gave rise to a much higher yield of labelled Cr/ba/₃ compared to the case of in situ nuclear recoils.     

The development of nuclear microprobe techniques for the spatial determination of13C and13C/12C ratios

Sensitive and selective nuclear reaction methods have been sought for the nuclear microprobe measurement of the spatial distributions of¹³C and¹³C/¹²C ratios. The¹³C(α, n)¹⁶O reaction, with neutron detection, is the most selective for¹³C, and has a sensitivity of ca. 100 ppm. The reactions¹³C(d, p)¹⁴C and¹²C(d, p)¹³C, with proton detection, are the most sensitive for the simultaneous measurement of¹³C and¹²C, with detection limits of 30 and 2 ppm respectively. Less sensitive alternative reaction pairs are;¹³C(³He, p)¹⁵N and¹²C(³He, p)¹⁴N;¹³C(d, nγ)¹⁴N and¹²C(d, pγ)¹³C;¹³C(³He, pγ)¹⁵N and¹²C(³He, pγ)¹⁴N. The conditions governing their use, particularly light element interferences, are detailed.     

Isotopic analysis of lithium by prompt alpha measurement during deuteron irradiation

Charged particle spectrometry was used to determine the isotopic concentration of lithium in lithium fluoride targets irradiated with a deuteron beam of 4.0 MeV. Alpha particles emitted by the⁶Li(d, α)⁴He and⁷Li(d, α)⁵He reactions were used as a measure of⁶Li and⁷Li, respectively. From the⁶Li/⁷Li α-count ratio the isotopic concentration of⁶Li was determined for isotopic concentrations over the range 7.42 (natural) to about 30 atom%⁶Li, with a relative standard deviation of±4.1%. Alpha particles from the¹⁹F(d, α)¹⁷O reaction could also be measured as an internal standard, extending the measurements from natural to 100 atom%⁶Li and giving a relative standard deviation of ±1.9%. The effect of target thickness on the accuracy of the determinations was investigated.     

A compilation of charged particle production cross sections by 14 MeV neutrons for Ti,V, Cr and Mn isotopes

A compilation of the cross sections (n, p), (n, n′ p), (n, α), (n, n′ α) and (n, He³) for Ti-46,-47,-48,-49,-50; V-51; Cr-50,-52,-53,-54 and Mn-55 by 14 MeV neutrons is presented in the form of a table containing the results of some 170 different measurements, mainly obtained by activation analysis. Brief assessments of the experimental methods and the data status are given.     

The elemental and isotopic determination of lithium by the coincidence measurement of complementary particles

The coincident measurement of both nuclear products at their complementary angles was used to determine⁶Li by the reactions⁶Li(d, α)⁴He and⁶Li(p, α)³He, and⁷Li by the reaction⁷Li(p, α)⁴He. Elemental lithium was determined in natural samples or samples of known isotopic composition. Isotopic analyses could be carried out over the entire range from 0 to 100 atom% with a relative standard deviation of about 4%. The CMCP technique is highly specific and effectively eliminates interference and background.     

Instrumental method for the determination of trace elements in water samples by neutron activation analysis

Thermal neutron activation analysis and a large-volume high-resolution Ge(Li) gammaray spectrometer, connected on-line to a DEC PDP 8/L computer, have been used to measure the concentrations of Na, Sc, Cr, Fe, Co, Ni, Zn, As, Se, Br, Rb, Ag, Sb, Cs, W and Hg in some Italian subsurface water samples. The instrumental method requires neither a chemical separation technique nor a pre- or post-concentration of the trace elements to be detected. As a consequence, this method eliminates many inherent errors associated with chemical determinations. The technique is sensitive, precise and particularly suitable for routine analysis of many trace elements at both natural and pollution levels in water samples. The interferences due to fast neutron (n, p) and (n, α) reactions are not appreciable, with the only exception of the⁵⁴Fe(n, p)⁵⁴Mn and⁵⁸Ni(n, p)⁵⁸Co reactions. Losses of volatile, elements, e. g. As, Br and Hg, during irradiation proved to be negligible.     

Radiochemical determination of the yields of transuranium nuclides produced from natural uranium irradiated in a reactor

Transuranium nuclides were produced by irradiating a pellet of natural uranium sulfide in the Japan Material Testing Reactor (JMTR). After irradiation, a successive separation of uranium, plutonium, americium and curium was carried out. The fractional concentrations of the nuclides²³⁸Pu,²³⁹Pu,²⁴⁰Pu,²⁴¹Am,²⁴³Am,²⁴²Cm and²⁴⁴Cm were determined by α-ray spectrometry, and those of²⁴¹Pu and^242mAm were estimated from the build-up of α-emitting daughters,²⁴¹Am and²⁴²Cm, respectively. As the yield of²⁴²Pu was too slight to be detected by α-counting, the neutron activation analysis of the plutonium fraction based on the²⁴²Pu(n, γ)²⁴³Pu reaction was carried out by γ-ray spectrometry, and it was shown that a few pg of²⁴²Pu could be determined. A burn-up of²³⁵U was also estimated by neutron activation analysis. The experimental results are compared with the calculated ones.     

Computer assisted multielement analysis of terrestrial and extraterrestrial materials and studies on long-lived cosmogenic53Mn by neutron activation

In a large number of alpine rocks and respective mineral separates the beryllium distribution was studied via “non-destructive” photon activation. The detection limit of the assembly was ∼20 ppb. The existence of Be-rich areas was revealed. A selection of individual rocks was analysed by instrumental as well as by radiochemical neutron activation analysis for main and trace elements as: Na, K, Sc, Cr, Mn, Fe, Co, Rb, Cs, La, Eu, Yb, Ta, W, Au, and U. The latter was determined by counting the²³⁵U-fission tracks. The data supply an insight into the complex processes leading to the formation of metamorphic rocks. The hardware and the computer evaluation of the γ-spectra is described in some detail. A further application is the determination of traces of⁵³Mn (in the order of 10⁻¹² g/g) produced by the interaction of cosmic rays with stony meteorites. From a comparison of the²⁶Al- and⁵³Mn-values it is concluded that the depth dependent production of these two radionuclides differs slightly.     

Isomer yield ratios and cross sections for110(4.9 h)In/110(69 min)In and108(58 min) In/108(39.6 min)In produced by alpha reactions on silver

This paper reports the determination of absolute excitation functions and cross section ratios for the production of 110(4.9 h)/110(69 min) In and^{108(58 min)/108(39.6 min)}In in reactions of -particles with natural silver. Target stack foils of silver were bombarded with the 55.0 MeV -particle, beam available at the Buenos Aires synchrocyclotron. The -spectrometry was used for the identification and for the determination of the absolute activity of^{110(4.9 h)}In and^{110(69 min)}In from¹⁰⁷Ag/, n/ and¹⁰⁹Ag/, 3n/ reactions and of^{108(58 min)}In and^{108(39.6 min)}In from¹⁰⁷Ag/, 3n/ and¹⁰⁹Ag/, 5n/ reactions by means of Ge intrinsic detector.This work has been sponsored by the Subsecretaria de Ciencia y Tecnología Argentina.     

The determination of radium-226 and radium-228 in soils and plants,using radium-225 as a yield tracer

Recovery of²²⁶Ra in analysis is determined using²²⁵Ra separated by anion exchange from²²⁹Th and²³³U. Radium is coprecipitated with barium, and purified by ion exchange.²²⁶Ra and²¹⁷At (decay product of²²⁵Ra) are measured by α-spectrometry.²²⁸Ra is determined both by β-counting²²⁸Ac and²²⁵Ac separated from²²⁸Ra and²²⁵Ra, and by α-counting its daughters after the decay of²²⁵Ra. Sources for α-spectrometry are prepared by electrodeposition (molecular plating).     

Isotope effect in retention value between55Cr and51Cr in recoll chemistry of Cr/acac/3

Recoiling behaviour of⁵⁵Cr produced by⁵⁴Cr/n, /⁵⁵Cr reaction was studied by choosing solid Cr/acac/₃ or its benzene solution as target material and by using rapid separation technique. The approximate retention value /R-value/ of⁵⁵Cr, defined as the percentage of the activity retained in the benzene phase which was not extracted with an oxalic acid solution, was found to be higher than that of⁵⁵Cr for practically all experimental runs tested /15 runs/. The ratio (⁵⁵Cr/⁵¹Cr) was 1.115±0.027.     

On achieving measurement quality in air pollution studies employing nuclear techniques

In order to study the metabolism of physiological amounts of⁵¹Cr (10 μg/100 g of body wt.) intragastrically administered in rats, the activable enriched stable isotope Cr-50 compound Cr₂O₃ was used as a tracer. The absorption and distribution of⁵¹Cr(III) in rats with time were studied. Significant⁵¹Cr contents were found in all the organs and tissues of interest. The kidney, liver and bone contain higher amounts of⁵¹Cr than others. The fact that specific activities of⁵¹Cr are notably high in kidney, bone, spleen and pancreas and decrease gradually with time suggests that there are tighter binding of chromium in these organs. The excretion of⁵¹Cr at various time intervals was also studied. Almost totally intragastrically administered dose was excreted in the feces. The increased urinary excretion of⁵¹Cr with time indicates that the urine-chromium is the metabolic derivative of organism. In view of the tissues distribution and excretion, it can be concluded that no more that 1% of the dose was absorbed from the gastrointestinal tract.     

Mapping of neutron flux gradient at NIST reactor to optimize neutron activation analysis of53Mn

Determination of⁵³Mn in meteorites by neutron activation analysis requires a thermal neutron flux high enough to ensure adequate production of⁵⁴Mn from⁵³Mn with a sufficiently low fast neutron component to minimize its production through fast neutron reactions. Thermal and fast neutron fluxes were mapped as a function of sample position within the NIST research reactor in order to determine the optimum position for irradiation of⁵³Mn.     

Radionuclide concentrations in two sewage treatment plants on Western Lake Ontario,Canada

Radionuclide concentrations in digester sludge and effluent samples from Hamilton and Dundas sewage treatment plants, located at the western tip of Lake Ontario, have been determined by high-resolution γ-ray spectrometry. The radionuclides⁵¹Cr,⁷⁵Se and¹³¹I, which are used in nuclear medicine procedures, were found in sludge samples. Very low concentrations of⁵¹Cr, entering Lake Ontario through the Hamilton plant effluent discharge, have little effect on lake water quality.     

A new method for the measurement of spallogenic53Mn by neutron activation

Résumé Des recherches précises sur les noyaux de spallation de longue période et extrémement peu abondants, produits par l'interaction de rayons cosmiques et de matières exposées, sont d'un grand intérêt pour la géo et la cosmochimie. Ces produits de réaction sont utiles pour la recherche des profils de profondeur d'activité et l'estimation des périodes de radiation. Le⁵³Mn est prometteur par sa relativement forte section efficace de production et sa longue période de radioactivité. Ce noyau émetteur K est transformé par capture neutronique en⁵⁴Mn, facilement mesuré par son rayonnement γ. L'avantage de cette technique est que le niveau d'activité est accru d'un facteur >10⁴. On étudie systématiquement et on corrige les interférences dues aux réactions (n,p) et (n,2n). La constante de décroissance insuffisamment connue jusqu'ici a été recherchée par une transmutation partielle de⁵³Mn météoritique en⁵⁴Mn donnant⁵⁴Cr stable au moyen d'une intense irradiation dans un réacteur pendant 587 jours. Les différences constatées dans le niveau de production de⁵⁴Mn au début et à la fin de l'irradiation permettent alors de rechercher la section efficace de capture σ₅₃=66±7 barn. On en déduit le produit T₅₃·σ₅₃=(260·32)·10⁶ barn·années, conduisant alors à une période de décroissance de T₅₃=(3,9±0,6)·10⁶ années. La quantité absolue de⁵³Mn, produite dans des matériaux de la surface lunaire, est de l'ordre de 2 à 7·10⁻¹² g/g.      

Simultaneous determination of boron and lithium by activation analysis

Simultaneous determination of boron and lithium is done by double irradiation with protons. One irradiation with 1.55 MeV protons and another with 7.4 MeV protons, measuring in both cases the amount of⁷Be formed /⁷Li/p,n/⁷Be and¹⁰B/p,/⁷Be/. Deuteron bombardment was not found to be of much advantage.