Determination of boron, fluorine and some medium Z elements in diet samples

As part of the study on “Reference Asian Man” project, dried food from different Asian countries, in powdered form, was analyzed applying different techniques. Boron was determined by measuring prompt alphas in ¹¹B(p,α)⁸Be reaction with 800 keV protons. Coulomb excitation was used for F and Na determination based on ¹⁹F(p,p'γ)¹⁹F (γ -rays: 110 and 197 keV) and ²³Na(p,p'γ)²³Na (γ -ray: 440 keV) reactions with 2.3 MeV protons. The elements Sc, Co, Zn, Rb, Ag and Ce were determined by neutron activation analysis. The elements Ca, Mn, Fe, Ni, Cu, Zn, Sr and Mo were determined by X-ray fluorescence technique. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of silicon dioxide in iron and steel-making slags and fluorspars by 14 MeV neutron activation and high-resolution gamma-ray spectrometry

Silicon as silicon dioxide in iron and steel-making slags and fluorspars was analyzed by 14 MeV neutron activation high-resolution γ-ray spectrometry. Silicon was detected by measuring the 1.78 MeV γ-ray of²⁸Al, the product of the²⁸Si(n, p) reaction, using a 30 cm³ coaxial Ge(Li) detector. A modified TPA method was used for the calculation.²⁸Al is also produced from phosphorus by the³¹P(n,α) reaction, and from aluminium by the²⁷Al(n,γ) reaction. The contribution from the former reaction could be corrected experimentally when the P₂O₅ content of the sample was known, while the latter reaction could be neglected in this neutron energy region. The experimental correction coefficient for phosphorus agreed well with the theoretical value calculated from the nuclear properties of silicon and phosphorus. Yields of²⁸Al from SiO₂, P₂O₅ and Al₂O₃ of the same weight percentages were calculated as 1, 0.426 (experimentally 0.44) and 0.0022, respectively. The results of this method agreed well with the results of the usual chemical methods. The limit of detection of SiO₂ in iron and steel-making slags and fluorspars was calculated as 0.07%. The coefficient of variation of repeated experiments was compared with the statistical one.     

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.      

Absolute intensity of the 140.5 keV gamma-ray of99Mo

The induced activity of the⁹⁹Mo isotope is mostly determined via the 140.5 keV γ-line, which is the strongest gamma-ray of its daughter,^99mTc. Some recent literature, however, indicates a direct feeding of this energy level from the mother isotope as well. Considering the importance of this line in practice as well as the large controversy and scattering in relevant nuclear data available at present, a combined effort was made to remeasure this questionable absolute intensity. A relative method of irradiating a Mo-target with reactor neutrons and repeatedly measuring its (n,γ) induced activity relative to the 181.1 keV and 739.5 keV gamma lines of⁹⁹Mo as internal references was used. The weighted average of different runs yielded γ(⁹⁹Mo, 140.5 keV)=(5.07±0.37)%. As a consequence, when the 140.5 keV gamma line is used, the contribution from the⁹⁹Mo mother isotope should always be taken into account, e.g. in neutron cross-section measurements and neutron activation analysis.     

The determination of fluorine in bones by non-destructive neutron activation analysis using 11.2 sec20F

A fast non-destructive determination of fluorine in bone samples by thermal neutron activation analysis using¹⁹F(n, γ)²⁰F reaction was developed. About 0.1–1 g samples is irradiated for 15 sec in TRIGA MARK II reactor at a thermal neutron flux of 5·10¹¹ n·cm⁻²·sec⁻¹. After 15–25 sec cooling, the 1633 KeV²⁰F activity (T=11.2 sec) is counted for 15 sec with a Ge(Li) spectrometer. A standard sample is prepared by mixing CaF₂ and CaCO₃ powders. The interference from²³Na(n, α)²⁰F is corrected by employing²⁴Na 2754 KeV double escape peak activities in samples and the²⁰F/²⁴Na peak area ratio observed previously for pure Na₂CO₃ powder. The precision is 7% for a bone sample containing 1020 ppm F and the sensitivity is about 10 ppm F.     

Neutron induced reactions at the Athens Tandem Accelerator NCSR “Demokritos”

The neutron facility at the 5.5 MV tandem T11/25 Accelerator of NCSR “Demokritos” can deliver monoenergetic neutron beams in the energy range from thermal to 450 keV, 4–11.5 MeV and 16–20.5 MeV via the ⁷Li(p,n), ²H(d,n) and ³H(d,n) reactions, respectively. The flux variation of the neutron beam is monitored by using a BF₃ counter and a liquid scintillator BC501A detector. The ²³²Th(n,2n)²³¹Th and ²⁴¹Am(n,2n)²⁴⁰Am as well as (n,2n), (n,p) and (n,α) reactions on natural Ge and Hf isotopes, have been investigated from threshold up to 11.5 MeV, by using the activation method. The cross section values have been determined relative to the ¹⁹⁷Au(n,2n)¹⁹⁶Au, ²⁷Al(n,α)²⁴Na and ⁹³Nb(n,2n) reference reaction cross sections.     

From potential to reality: Yeasts derived from ethanol production for animal nutrition

A chemical and radiochemical neutron activation analysis (CNAA/RNAA) method has been developed for the determination of three calcium isotopes (⁴⁸Ca,⁴⁶Ca, and⁴⁴Ca) in a single sample derived from urine. This method was developed in support of clinical research using a dual enriched stable isotope methodology to study bone mineralization in premature infants, juvenile rheumatoid arthritics, and cystic fibrosis. In these studies, one enriched isotope of calcium is administered orally, and one is administered intravenously. By making determinations of three isotopes (two enriched, one unenriched) within the same sample, the perturbation from natural isotopic ratios can be determined and used to calculate true absorption of calcium. In our method,⁴⁸Ca is determined via the⁴⁸Ca(n,γ)⁴⁹Ca reaction and 3084 keV gamma-ray,⁴⁶Ca via the⁴⁶Ca(n,γ)⁴⁷Ca reaction and 1296 keV gamma-ray, and⁴⁴Ca via the⁴⁴Ca(n,γ)⁴⁵Ca reaction and 256 keV (max) beta-particle. A pair of chemical separation steps are employed to separate calcium from urine as calcium oxalate with a yield in the range of 80–90%, and a radiochemical step is employed prior to the measurement of⁴⁵Ca to remove interfering radionuclides.     

Dose verification by activation in vivo following proton beam eye radiotherapy

This work presents the measurements of proton activation of a group of 15 patients following proton radiotherapy of the eye. Despite the heterogeneity in activation response and reaction cross section compared with the applied uniform dose, it can be shown that induced activity may be related to incident fluence volume and thus provide verification of applied dose. This proton treatment provides in vivo information that is normally unused. Up to 400 kBq was measured at 100-second post-treatment. Significant correlation of the ¹⁵O 511 keV activity with fluence volume is shown. The patient γ-ray spectra are tabulated and discussed. The longer-lived ⁷Be (T _1/2 = 53.1 d) activity, from O and C activation, may provide an additional means of dose verification. The potential of (p,p’γ) reactions was examined by irradiation of phantoms. High energy γ-rays from O and C were measured with a large NaI(Tl) detector, with a yield of 125 γ/cm²/mGy for the ¹⁶O(p,p’γ) reaction.     

Neutron activation analysis with PE moderated252Cf neutron source

The 1.369 MeV -rays emitted from²⁴Na²⁴Mg+^–+ after²³Na(n,)²⁴Na reaction were counted by high purity germanium (HPGe) detector and the half-life of²⁴Na was derived. This process was simulated by Monte Carlo Neutron and Photon Transport Code (MCNP-4A).²⁵²Cf neutron source was moderated by a polyethylene (PE) cylinder to increase the cross section of neutron absorption reaction and to decrease the biological hazard. NaCl powder of 20 cm³ and 40 cm³ volume in cylindrical polypropylene capsules were irradiated by the neutrons passed through the moderator. MCNP-4A was used to determine the optimum size of PE moderator, to assume the realistic geometry of the HPGe detector, and to assume the absolute efficiencies of the detector. The count rates for 1.369 MeV -rays in the HPGe detector were calculated by MCNP-4A for 20 cm³ and 40 cm³ NaCl. The accumulated counts calculated tumed out to be higher than those actually measured by 31% with a relative error of 3%. The half-life of²⁴Na measured within 4% and 1% for 20 cm³ and 40cm³ NaCl agrees with that of the reference. So, we can say that the result of MCNP-4A has about 30% of accuracy and 3% of precision in simulating the neutron activation analysis.     

The feasibility of utilizing the64Cu annihilation 511 keV line in INAA

This work demonstrates that the⁶⁴Cu 511 keV line can be used in INAA to determine trace amounts of Cu in biological and environmental materials. The method to reduce the serious interference in γ-ray spectroscopy from nuclides having high energy γ-rays is discussed. A simple INAA procedure is proposed and examined for 7 different SRM materials. An accuracy and precision better than 3% are achieved for tested samples with Na-to-Cu content ratio less than 1000. The minimum detectable Cu concentrations of less than several ppm are calculated for all the analysed samples. To retain the multi-element capability, the k₀-and the modified monostandard methods are applied by using the⁶⁴Cu 511 keV line as the comparator. With the aid of the program MULTINAA, maximum 32 elements are simultaneously determined with an accuracy better than 5% for most elements.     

Determination of silicon in aluminium by 14 MeV neutron activation analysis

A method has been developed for determining silicon in aluminium by fast neutron activation. It is based on the separation of two gamma lines by a Ge(Li) detector: the 1.73 MeV line from the product of²⁷Al(n, α)²⁴Na and the 1.78 MeV line from the²⁸Si(n, p)²⁸Al reaction. In the case of aluminium-silicon alloys 100 μg silicon can be determined, with an error of 10% in an aluminium sample of 1 g. This work was supported in part by the International Atomic Energy Agency.     

Determination of rare earth elements in recent and fossil shells by radiochemical neutron activation analysis

Seven rare earth elements (La, Ce, Sm, Eu, Tb, Yb and Lu) in marine shell samples were determined by neutron activation analysis. In order to measure γ-ray using a Ge(Li) detector without serious interference from the intense Compton background from²⁴Na, a simple radiochemical separation was performed by a co-precipitation method with hydrated iron(III) oxide. The chemical yields for shell samples (91–99%) were determined by a re-activation technique for Gd and Yb. The interference from the²³⁵U(n, fission) reaction was corrected for determination of La and Ce. The data obtained in this study showed the behavior of rare earth elements in shells during the process of fossilization.     

Determination of potassium in beet by 14 MeV neutron activation analysis

The applicability of 14 MeV neutron activation analysis for the determination of K in beet has been investigated by measuring the 2.167 MeV gamma-line from the decay of³⁸gK produced in the³⁹K(n, 2n) reaction. Beet samples were treated in different solutions of KCl and HgCl₂ to study the diffusion of K⁺ ions into the beet cells. The contribution of the gamma-line to the measured peak area from³⁸Cl produced in the³⁷Cl(n, γ) reaction was found to be 1%. Results obtained by fast neutron activation analysis and by flame spectrometry have been compared, and good agreements were found.     

The preparation of carrier-free102Rh and102m Rh

Long-lived rhodium radionuclides were produced by the following reactions:¹⁰³Rh(n, 2n)^102(m)Rh;¹⁰³Rh(γ,xn)¹⁰⁰Rh,¹⁰¹Rh,^102(m)Rh;¹⁰⁴Pd(d, α)^102(m)Rh; Ru(d, n)⁹⁹Rh,^101(m)Rh,^102(m)Rh; and . The average cross-section of the¹⁰³Rh(n, 2n)¹⁰²Rh reaction in a fission neutron spectrum is about 0.75 mb. Irradiation of rhodium in the bremsstrahlung spectrum of 50 MeV electrons yielded a¹⁰²Rh activity of 0.11 μCi/g after 3 days at a power of 2 kW. The thick target yield of the reaction¹⁰⁴Pd(d, α)¹⁰²Rh was 0.002 μCi/μAh for 12 MeV deuterons. The thick target yield of the reaction Ru(d,xn)¹⁰²Rh was 0.05 μCi/μAh for 12 MeV deuterons and 4.8 μCi/μAh for 18 MeV deuterons. The best yield was obtained by deuteron bombardment of ruthenium. The chemical separation of carrier-free Rh radionuclides from deuteron-irradiated ruthenium is described, with a chemical yield better than 90%. The same procedure has also been applied for the isolation of¹⁰⁵Rh from neutron-irradiated ruthenium. γ-Ray spectra of⁹⁹Rh,^101(m)Rh and^102(m)Rh from deuteron-irradiated ruthenium and of¹⁰⁵Rh from neutron-irradiated ruthenium, taken with a Ge(Li) detector, are shown; a number of γ-rays, not reported in the literature, were observed. The γ-ray energies were determined with a precision of ca. 0.3–0.4 keV.     

Serum aluminum determination by instrumental neutron activation analysis in long-term haemodialysis patients

Serum aluminum levels were determined by instrumental neutron activation analysis in 31 patients undergoing long-term haemodialysis. Aluminum-28 1.778 MeV (T _1/2=2.24 min) γ-rays produced by the thermal neutron reaction²⁷Al(n,γ)²⁸Al were detected. Successive irradiation of the samples at epithermal neutron fluence was performed to correct for the interference from the fast neutron reaction³¹P(n,α)²⁸Al. Serum aluminum level in this group of subjects was adequately represented by a lognormal distribution with a mean and variance of 16.5 μg/l and 16.8 μg/l, respectively. The results obtained were found to be in agreement with serum aluminum determination performed by electrothermal atomic absorption spectrophotometry (r ²=0.97). Instrumental neutron activation can provide a rapid technique to routinely monitor long-term haemodialysis patients in order to identify individuals at greater risk to develop aluminum toxicity.     

Nuclear data and measurements for the130Ba(n,γ)131Ba reaction

Although k₀-factors and related nuclear data for 122 radionuclides of interest in (n,) reactor neutron activation analysis have been tabulated, there are still some reactions attracting interest with respect to the accuracy of the literature data. The present paper deals with the reaction¹³⁰Ba(n,)¹³¹Ba, for which a more accurate half-life is proposed, together with re-evaluated Q₀ and k₀ factors. The new values are 11.53 days for T, 21.3 for Q₀, and for the k₀'s 3.90×10^–5, 2.75×10^–5, 1.92×10^–5 and 6.48×10^–5 for the -rays at 123.8 keV, 216.1 keV, 373.2 keV and 496.3 keV, respectively.     

Determination of aluminum levels in serum and red blood cells from long-term haemodialysis patients using instrumental neutron activation analysis

Aluminum levels of serum and red blood cell (RBC) were determined by instrumental neutron activation analysis (INAA) in 15 patients undergoing long-term haemodialysis. In the sample, aluminum was bombarded with thermal neutrons due to ²⁷Al(n,γ)²⁸Al and was determined by measuring 1779 keV gamma-ray of ²⁸Al (T _1/2 = 2.24 min) with a HPGe detector. Phosphorus, causing an important interference by the fast neutron reaction, ³¹P(n,α)²⁸Al, was determined by the photometric method to correct the net-area under the ²⁸Al gamma-peak. The one-sample Kolmogorov-Smirnov test was used to control the normality distribution of the aluminum levels in serum and RBC. The results obtained were found to be in agreement with the serum aluminum determination performed by electrothermal atomic absorption spectrophotometry. The statistical results show a correlation between the aluminum levels of serum and RBC. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rapid determination of tungsten in rocks using183mW

A rapid method has been developed for the determination of tungsten, especially in rocks. The reaction¹⁸²W(n, γ)^183mW (T=5.3 sec), with a thermal neutron capture cross-section of 0.5 b was used. The samples were irradiated in the fast pneumatic system of the FRM, which is described briefly. The low-energy γ-rays of the isomer^183mW were measured by a high-resolving Ge(Li) detector. The sensitivity of the method is 0.1 mg tungsten with an accuracy of about 5%; the minimum concentration is 0.1–0.2% W in geological samples. The analysis time is 2 min per sample.     

Observation of a Doppler broadening of the 4438 keV gamma-line of12C in processes12C(n,n′γ)12C and9Be(α, nγ)12C

A Doppler broadening is described of the 4438 keV spectral gamma-line observed by means of a Ge(Li) detector during the deexcitation of nuclei of¹²C in an inelastic scattering¹²C(n, n′γ)¹²C using an²⁴¹Am−Be source as well as during the reaction⁹Be(α, nγ)¹²C taking place in the Am−Be source. The FWHM of the spectral line is equal to (90±4) keV in the latter reaction and (64±8) keV in the former process. Experimental values agree well with theoretical ones. Presented at the Instrumental Activation Analysis Conference, IAA 79, June 4–8, 1979, Klučenice, Czechoslovakia.     

Prompt gamma rays from triton-induced reactions on oxygen and their use for analysis

Triton-induced reactions on oxygen were studied with a view to using the prompt γ-rays for analytical purposes. Five γ-rays were found to be potentially useful, of which three had a high intensity, the n(1, 0), n(2, 0) and p(1, 0) γ-rays, the other two being the n(3, 0) and the unresolved pair α(1, 0)–α(2, 0). The γ-rays are labelled according to the conventions(a,b), wheres is the light prompt product and the γ-photon is emitted by de-excitation from levela tob in the heavy product nucleus. The method had a relative precision of 2 to 3.5% for surface oxygen concentrations from 50 to 3 μg/cm². The sensitivity with 1 900 keV tritons was 0.13 μg/cm² on surfaces of steel or copper which did not yield interfering γ-rays, but 0.45 μg/cm² on aluminium where interfering γ-rays were emitted.