Atmospheric deposition fluxes of <Superscript>7</Superscript>Be, <Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po at Xiamen,China

The atmospheric deposition fluxes of ⁷Be, ²¹⁰Pb and ²¹⁰Po at Xiamen were measured. The samples were collected from March 2004 to April 2005 and the sampling period was one month. The ⁷Be and ²¹⁰Pb activity were measured using HPGe γ-spectrometer after concentration using Fe(OH)₃ co-precipitation method. The ²¹⁰Po was counted with an α-spectrometer after the sample was digested and spontaneous plated onto a silver planchet. At Xiamen, the atmospheric deposition fluxes of ⁷Be varied between 0.11 and 2.93 Bq·m⁻²·d⁻¹ and the average was 1.64 Bq·m⁻²·d⁻¹; ²¹⁰Pb fluxes varied between 0.04 and 0.85 Bq·m⁻²·d⁻¹, and the average was 0.51 Bq·m⁻²·d⁻¹; ²¹⁰Po fluxes varied between 0.002 and 0.133 Bq·m⁻²·d⁻¹, and the average was 0.061 Bq·m⁻²·d⁻¹. There were positive correlations between the deposition fluxes of ⁷Be, ²¹⁰Pb or ²¹⁰Po and the amount of precipitation. The residence time of aerosols varied between 6.0 and 54.0 days with a mean of 27.1 days, which were calculated by ²¹⁰Po/²¹⁰Pb fluxes ratios.     

Etude de quelques reactions nucleaires induites par les neutrons rapides de pile

Conclusion Dans une première partie, l’étude des réactions engendrées par les neutrons rapides de pile sur douze éléments a montré que certaines de celles-ci pouvaient être utilisées pour un dosage quantitatif. Dans une seconde partie, nous proposons un dosage radiochimique du silicium par la réaction²⁸Si(n, p)²⁸Al qui a, dans nos conditions de travail, sa limite de détermination à 620 μg. A titre de comparaison, signalons que cette limite se situe par irradiation avec des neutrons de 14 MeV, produits au moyen d’un accélérateur (flux de 5·10⁸ n·cm⁻²·sec⁻¹), à environ 10 μg. Le dosage non destructif du silicium dans le diméthylpolysilane est décrit.

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In the first part, the fast-neutron flux available in reactor cores was utilized to define experimentally the sensitivity for the determination of 12 different elements, based on fast-neutron nuclear reactions. The fluxes available with our AGN-201 P reactor are in the range of 10⁹–10¹⁰ n·cm⁻²·sec⁻¹ in the 1–4 MeV region. A good sensitivity was obtained for²⁷Al,⁵²Cr,⁵⁶Fe,²⁸Si,²³Na [by (n, p) reaction],²⁷Al,³¹P,⁸⁹Y [by (n, α) reaction] and¹⁹⁷Au,¹⁸³W,⁸⁹Y [by (n, n′) reaction]; the elements Cl, Ca, Pb failed to give reactions. In the second part, a non-destructive method for the determination of silicium based on the reaction²⁸Si(n, p)²⁸Al is proposed. The limit of determination is about 0.6 mg for a neutron flux of 10⁹ n·cm⁻²·sec⁻¹. As an example, Si in dimethylpolysilane was determined.

     

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.     

Determination des fonctions d'excitation des reactions19F(p, α0)16O et7Li(p, α0)4He entre 150 et 1800 keV

The experimental device used is described. Excitation functions are given for an angle of observation 150° with respect to the incident beam. The possibilities of applying these reactions to the measurement of surface lithium and fluorine concentrations are considered. The detection limits for these two elements are shown to be 5·10⁻³ μg·cm⁻² with protons of energy between 1,350 and 1,500 keV. The method is compared with that based on the detection of prompt γ-rays from the reactions⁷Li(p, γ)⁸Be and¹⁹F(p, α γ)¹⁶O.      

Interference by neutron induced second order nuclear reaction in activation analysis of rare earths

In determining the trace impurities existing in high-purity rare earth samples by the neutron activation analysis, there are much interference due to nuclides induced from neutron induced second order nuclear reaction. This paper presents the degree of interference calculated over the ranges of irradiation time from 10⁵ to 10⁷ sec and of thermal-neutron flux from 1·10¹² to 1·10¹⁵ n·cm⁻²·sec⁻¹. According to the results of these calculations, degree of interference under the neutron irradiation condition for 288 hrs in the thermal-neutron flux of 3·10¹³n·cm⁻²·sec⁻¹ is concluded to be 6.4·10⁶ ppm Gd in Eu, 2.2·10⁴ ppm Sm in Eu, 1.9·10⁴ ppm Ho in Dy, 1.1·10³ ppm Eu in Sm, 1.1·10² ppm Ce in La and 1.1·10 ppm Tb in Gd, respectively. Especially, the Gd determination in the Eu target is extremely affected by¹⁵³Gd formed from the¹⁵¹Eu (n, γ) reaction. On the contrary, this reaction is effective in producing¹⁵³Gd activity.     

Nuclear and atomic activation with heavy ion beams

Heavy ion activation has been studied as a method for determining hydrogen. The reactions used [e.g.¹H(⁷Li, n)⁷Be] are the “inverse” of well known reactions [e.g.⁷Li(p, n)⁷Be]. Nuclear activation parameters for the ion beams of interest (⁷Li²⁺,¹⁰B²⁺) have been studied. The analytical feasibility is demonstrated with the determination of hydrogen in titanium at the 100 and 30 ppm levels with relative precisions of 8 to 10%. Detection limits in titanium are in the 0.1 to 0.5 ppm range. Heavy ion bombardment is also accompanied by the emission of characteristic X-rays (“atomic” activation). The parameters governing X-ray emission and background production have been investigated. Experimental K and L X-ray yields from thick targets have been measured for many elements excited by Oⁿ⁺ beams of 0.5 to 7 MeV/amu and Kr⁷⁺ beams of 0.5 to 1 MeV/amu. The simultaneous determination of trace elements at levels of 10 to several 100 ppm in microsamples (∼10⁻⁵ g) is demonstrated on biological specimens. K and L X-ray yields and corresponding detection limits have also been measured with the⁷Li²⁺ and¹⁰B²⁺ beams used for the nuclear activation of hydrogen. With these beams (∼6 MeV/amu) simultaneous nuclear and atomic activation is possible, yielding an unusual multielement trace analysis capability covering hydrogen and medium and high Z elements.     

The determination of carbon,nitrogen and oxygen in gases by neutron time-of-flight spectrometry

Carbon, nitrogen and oxygen were determined in gases by time-of-flight spectrometry of prompt neutrons from the respective reactions¹²C(d, n)¹³N,¹⁴N(d, n)¹⁵O and¹⁶O(d, n)¹⁷F, produced by a pulsed beam of deuterons of 2 MeV (for nitrogen) or 3 MeV. The analysis is non-destructive and requires about 15 min. per sample. The relative standard deviation for all three elements was about ±3%. Detection limits, using a total irradiation current of 20 millicoulombs, for carbon, nitrogen and oxygen, respectively, were 6·10⁻⁸ g, 2·10⁻⁷ g and 1.7·10⁻⁷ g per cm² cross-sectional area of irradiating beam.     

Trace determination of boron,silicon and sulfur with oxygen-18 ion bombardment

In order to determine traces of boron, silicon and sulfur, B(¹⁸O, x)²⁷Mg, Si(¹⁸O, x)⁴³Sc and S(¹⁸O, x)⁴⁷V reactions have been investigated between 15 and 44MeV. At 34 MeV, only a few of the systematically identified nuclear interferences produce²⁷Mg and the detection limit is 30ng boron for a 10 minute irradiation with a 0.3μA·cm⁻² oxygen-18 beam. Silicon analysis has shown nuclear interferences from Al, P and K; interference-free detection limit is 80 ng silicon for an hour irradiation with a 0.4 μA·cm⁻² beam at 39 MeV. There is no nuclear interference for the sulfur determination and the detection limit is 5 ng sulfur for a 30 minutes irradiation with a 0.5 μA·cm⁻² beam at 39 MeV. Thus a selective and sensitive sulfur determination can be achieved.     

Silicon determination in mine flue-dust by 14 MeV neutron activation analysis

The Si-contents of flue-dust and sedimented dust from Czechoslovak mines were determined by instrumental activation analysis with 14 MeV neutrons using a flux of 10⁷ cm⁻²·s⁻¹. The amounts determined range from 3 to 30 mg.     

Determination of low dose concentration profiles in solids by means of (n,p) and (n, α) reactions

The isotopes³He,⁶Li,⁷Be and¹⁰B exhibit extremely large cross sections, between 1 and 48 kilobarn, for (n, p) or (n, α) reactions with thermal neutrons. Together with now available extracted thermal neutron fluxes of 10⁽ n·cm⁻²·sec⁻¹ or more, these reactions present a highly sensitive method of detecting the mentioned light elements in any heavy matrix material. Through the experimentally determined energy losses of the emitted protons or α-particles, also well resolved depth profiles can be obtained, as demonstrated here for some relevant examples from semiconductor and fusion technology.     

Application d'un detecteur a semi-conducteur a l'analyse systematique de l'aluminium

Résumé Après une irradiation neutronique de 7 jours dans un flux de 3·10¹² n·cm⁻²·sec⁻¹, une trentaine d'éléments peuvent être dosés sans séparation chimique dans des échantillons d'aluminium de diverses provenances. Les modalités de mesure et de calcul des radioactivités sont précisées et nous indiquons les limites de détection obtenues. Elles sont comprises entre 5·10⁻² et 5·10⁻⁶ μg/g selon les éléments recherchés. Pour certains d'entre eux (Fe, Zn, Zr) ces limites peuvent être améliorées par une séparation chimique simple.     

Removal of zinc and mercury ions from aqueous solution by hydrous ceric oxide

The present work deals with study of uptake behavior of zinc and mercury ions by hydrous ceric oxide applying a radiotracer technique. The influence of various parameters such as concentration, temperature and pH have been examined. It was observed that the amount of zinc and mercury ions adsorbed at equilibrium increases with increase of adsorptive concentration (1.0·10⁻⁷ to 1.0·10⁻²M), temperature (303–333K) and pH (ca. 3–10). Concentration dependence data agree well with the classical Freundlich isotherm. The radiation stability of hydrous ceric oxide was also investigated by exposing it to a 11.1 GBq (Ra−Be) source associated with γ-dose of 1.72 Gy·h⁻¹ and also using a⁶⁰Co source (4.66 kGy·h⁻¹). Adsorption of these metal ions in the presence of some monovalent and divalent cations and complexing agents has also been included in the study.     

Determination of sulfanilamide based on the Mn(II)-catalyzed oscillating chemical reaction

A convenient and sensitive method for determination of sulfanilamide (SNA) was described based on the Mn(II)-catalyzed oscillating chemical reaction. Under optimum conditions, a linear relationship existed between the changes of oscillating period or amplitude and the negative of logarithm of SNA concentration in the range of 4.27 × 10⁻⁸ mol ·L⁻¹ ∼ 7.41 × 10⁻⁶ mol ·L⁻¹ (RSD, 0.85%) and 9.33 × 10⁻⁸ mol ·L⁻¹ ∼ 3.02 × 10⁻⁶ mol ·L⁻1 (RSD, 1.08%), respectively. The lower limit of detection was found to be 2.69 × 10⁻⁸ mol ·L⁻¹ and 6.03 × 10⁻⁸ mol ·L⁻¹, respectively.      

2-Oximinodimedone monoguanylhydrazone as spectrophotometric reagent for determination of iron

The synthesis, properties and analytical possibilities of 2-oximinodimedone monoguanylhydrazone as spectrophotometric reagent have been examined. A new method for the determination of iron has been developed in a concentration range varying from 0·2–5·0 ppm of iron; the molar absorptivity is 1·1×10⁴ litres mol⁻¹ cm⁻¹ at 600 nm and the relative error is ±0·3%. The method has been applied satisfactorily to the determination of iron in different inorganic samples.     

Reactions of hydroxyl radical (·OH) and oxide radical anion (O·−) with 2-aminopurine in aqueous medium

Pulse radiolysis has been used to investigate the reaction of hydroxyl radical (^·OH) and oxide radical anion (O^·−) with 2-aminopurine (2AP), a fluorescent analogue of adenine, in aqueous medium. The second-order rate constant for the reaction of ^·OH with 2AP was determined to be 3 × 10⁹ dm³ mol⁻¹s⁻¹ and for the reaction of O^·− it was 7.1 × 10⁸ dm³ mol⁻¹s⁻¹. The transient absorption spectrum obtained in the reaction of ^·OH at pH 7 has absorption maxima at 370 and 470 nm. The spectrum undergoes a time-dependent transformation at higher time-scale. The intermediate species was found to react with N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD). The yield of TMPD^·+ was calculated in terms of G(TMPD^·+) to be 3.3 × 10⁻⁷ mol J⁻¹ at pH 7. The ^·OH reactions were also carried out at pH 10 and the transient absorption spectra have λ _max at 400 and 480 nm. The transient spectra obtained in the reaction of O^·− at pH ≈14 have maxima at 400 and 480 nm. The transient intermediate species at pH 7 are assigned to the formation of 2AP-4-OH^· (54%), 2AP-5-OH^· (7%) and 2AP-8-OH^· (39%) based on the spectral evidence and TMPD^·+ build-up. Both 2AP-4-OH^· and 2AP-5-OH^· undergo OH⁻ elimination to form a radical cation. At higher pH (pH 10), the dehydration reaction of these OH-adducts leads to a N-centered radical (2AP-N(9)^·, 71%). Formation of 2AP-8-OH^· (29%) is also proposed at this pH. In the reaction of O^·− with 2AP, it is proposed that a similar nitrogen centered 2AP-N(9)^· radical is formed by an electron-transfer reaction at N(9).     

Fluorine analysis by activation with an isotopic fast-neutron source and counting Nitrogen-16

A rapid, nondestructive method has been developed for determination of fluorine by activation with fast neutrons from a²⁴¹Am-²⁴²Cm-Be source and counting the 6–7 MeV γ rays of the product nitrogen-16. The total neutron output of the source is 4.8·10⁹ unmoderated neutrons per second and the flux is 1.4·10⁸ fast n·cm⁻²· sec⁻¹. The γ-ray detectors consist of two opposing, matched cylindrical NaI(Tl) crystals 10 cm long and 10 cm in diameter. The sample is irradiated for 30 seconds, cooled for 4 seconds, and then counted for 30 seconds. The sensitivity is 4.8·10⁴ counts nitrogen-16 per gram fluorine, and the limit of detection is 0.4 mg fluorine in a 10-gram sample. A reproducibility of 0.24% is achieved. The relative standard deviation of the specific count rate of nitrogen-16 for 11 fluorine compounds is 1.31%.     

Experimental sensitivities for 3 MeV neutron activation analysis

The experimental sensitivity for 72 different elements using 3 MeV neutron activation has been investigated. Using a 200 kV Cockcroft-Walton neutron generator with a 3 MeV neutron flux of about 1.5·10⁶n·cm⁻²·sec⁻¹, γ-ray spectra of 51 elements were obtained with a sufficient number of photopeak counts for sensitivity calculations using a photopeak integration method. A useful table summarizing the sensitivity results is given. That 3 MeV neutron activation analysis is practical, is demonstrated by the experimental sensitivities obtained. Guest worker from the Institute of Nuclear Techniques, Academy of Mining and Metallurgy, Krakow, Poland, at the National Bureau of Standards, 1968–1969.     

Fallout of7Be in Damascus City

Atmospheric fallout of⁷Be was measured over a 2 year period (January 1995–January 1997) at Damascus city (33 N^o, 727 m above sea level). The annual total deposition of⁷Be was found to be 420 and 634 Bq·m⁻² for 1995 and 1996, respectively, reflecting a Mediterranean climate where two well recognized periods are dominant (wet and dry). The depositions in the wet periods were 303 Bq·m⁻² and 517 Bq·m⁻² for 1995 and 1996, respectively, while unexpected equal deposition rates in the two dry periods were found to be about 117 Bq·m⁻². In addition, monthly deposition rate of⁷Be showed a maxima in February in 1995 and January for 1996. Moreover, a comparison has been set for our measurements and other data obtained at different locations in the world.     

Fast-neutron activation analysis with short-lived nuclides

At the GKSS Research Center Geesthacht, a new 14 MeV activation facility—a 5·10¹² n/s neutron generator combined with a fast rabbit system (KORONA)—is being installed. Homogeneous neutron flux at a level of 5·10¹⁰ n·cm⁻²·s⁻¹ and sample transfer times of 140 ms to a 16m distant detector station are characteristic features of the facility described in the paper. With special consideration of short-lived nuclides and including cyclic activation, the analytical prospects with the intense neutron source are discussed, and sensitivities for 78 elements are presented.     

Determination of carbon impurities in epitaxial layers from semiconductor silicon by means of charged particles

The energy-dependent range of charged particles in activation analysis according to the reaction¹²C(d,n)¹³N permits the method to be applied to carbon determination in model epitaxial layers of sufficient thickness. We investigated 100 μm epitaxial layers of the n-type and undoped 50 μ layers as to p⁻ Czochralski substrates. Deuterons were slowed down with Cu and Ta foils having a limiting energy of 13.5 MeV, to 4.2 MeV and 2.9 MeV, respectively. In the resulting activation depths of 52 and 102 μm, the sensitivity of the method, which is 3·10¹⁴ at ·cm⁻³C at E_d=10 MeV in silicon, is reduced to 25% and 10%, respectively. An optimal flux of 0.9 μA·cm⁻² was maintained. After irradiation, 20 or 10 μm were etched off. The sample was inductively fused at 1500 K in a Pb₃O₄/B₂O₃ mixture.¹³N was passed with He as carrier gas into an absorption vessel kept at 77 K, and its activity was measured in γ, γ-coincidence.