J Hoste

Non-destructive proton activation analysis for nitrogen in refractory metals

The non-destructive determination of nitrogen in some refractory metals was studied by activation analysis with the 14N(p, n)14O reaction. The samples were irradiated with 12-MeV protons from a cyclotron. The proton beam intensity was normalized by means of a copper flux monitor. After chemical etching, the 14O activity (Eγ = 2313 keV, T12 = 70.5 s) of the sample was measured by means of a Ge(Li) or NaI(Tl) detector. Standardization was carried out by the “average cross-section” method with nylon 6 as a nitrogen standard. The method gives a sensitivity of 0.4–30 μg g−1 for analysis of Ta, W, Nb, and Ti, and 2000–4000 μg g−1 for Zr, Ni and Mo.

The determination of carbon in the refractory metals zirconium, niobium, tantalum and tungsten by instrumental deuteron activation analysis

Abstract Instrumental activation analysis is used for the determination of carbon in the refractory metals zirconium, niobium, tantalum and tungsten, based on the 12C(d, n)13N reaction induced by 5–7-MeV deuterons. 13N(t 1 2 = 10.0 min) is detected via its annihilation radiation. The contribution of 13N to the annihilation activity is separated from that of other β+-emitters by decay-curve analysis. The method is free of nuclear interferences. The possible spectrometric interferences are discussed. Concentrations of 65.1, 24.8, 1.04 and

Determination of cadmium, thallium and lead in environmental samples by proton activation analysis

Cadmium, thallium and lead are determined in environmental samples using the111,112,113Cd(p,xn)111In,203Tl(p,3n)201Pb and206,207,208Pb(p,xn)206Bi reactions.111In.201Pb and206Bi are chemically separated by anion exchange and anodic deposition of lead(IV). oxide. Detection limits are 6, 44 and 25 ng/g for cadmium, thallium and lead, respectively. The results obtained for certified reference materials are in good agreement with the certified values.

Sensitivities and interferences in activation-analysis with cyclotron-produced fast-neutrons

Fast neutrons are produced by irradiation of a thick beryllium target with deuterons from a cyclotron. The spatial neutron flux distribution was studied. Ge(Li) gamma-ray spectrometry was used to measure the radionuclides produced. Detection limits are tabulated along with the nuclear interferences.

Activation analysis with cyclotron-produced fast neutrons. Application to instrumental multi-element analysis and to the radiochemical determination of fluorine

Fast neutrons produced by irradiation of a thick beryllium target with 20–50 MeV deuterons are used for activation analysis. The spatial neutron flux distribution around the target is measured. A rotating sample holder is used for the simultaneous irradiation of samples and standards. Instrumental analysis can be applied for a number of elements. As an example, results for calcium and strontium in some reference materials are given. The19F(n, 2n)18F reaction is used for the radiochemical determination of fluorine in rocks with a fluorine concentration ranging from 9 to 5400 μg·g−1

The determination of trace-elements by charged-particle activation-analysis

Abstract Activation analysis with charged particles is now more readily available as compact, variable energy cyclotrons are more widespread. Standardization problems have been studied thoroughly so that accuracy could be significantly improved. Most applications of CPAA deal with the determination of light elements such as hydrogen, nitrogen and oxygen in metals and semiconductors. As surface layers can be removed by etching after irradiation, contamination problems can be avoided. For some metals concentrations of carbon and nitrogen were found several orders of magnitude lower than analysed by chemical methods. Due to its high accuracy and precision CPAA is often used as a reference method for certification analysis.

Determination of light elements in metals and semiconductors by charged particle activation analysis

The determination of boron, carbon, nitrogen and oxygen in metals and semiconductors by charged particle activation analysis (CPAA) is reviewed. It is shown that CPAA is a sensitive and accurate method suitable for the analysis of reference materials.

Determination of cadmium in environmental materials by fast neutron activation analysis

Abstract Cadmium is determined by activation analysis with fast neutrons, obtained by irradiation of a thick beryllium target with 14.5-MeV deutrons. Cadmium-111m, formed via the 112Cd(n, 2n)111mCd and 111Cd(n, n′)111mCd reactions, is separated by liquid—liquid extraction with zinc dithyldithiocarbamate in chloroform and measured with a Ge(Li) γ-spectrometer. For low concentrations, cadmium is precipitated as cadmium ammonium phosphate after the extraction. NBS and BCR reference materials were analyzed: for concentrations between 3 and 500 μg g−1, the relative standard deviation ranges from 5 to 3% The results obtained for sewage sludge are compared with those obtained by reactor neutron activation analysis.

Determination of fluorine in geological materials by fast neutron activation based on the 19F(n,2n)18F reaction

Abstract The determination of fluorine in geological materials by fast neutron activation analysis based on the 19 F( n , 2 n ) 18 F reaction is described. Fast neutrons are produced by irradiation of a thick beryllium target with 14.5 MeV deuerons. A rotating smple holder allows simultaneous irradiation of samples and standards. Fluorine-18 is separated by steam distillation of hexafluorosilicic acid or by extraction with triphenylatimony(V) dichloride and the annihilation radiation is measured with γ—γ coincidence equipment. The nuclear interference of recoil protons that induce the 18 O( p , n ) 18 F reaction is evaluated by means of synthetic samples: for a rock containing 43.4% of oxygen and 0.5% of hydrogen, the interference corresponds to 4.4 μg g −1 fluorine. The method was applied to USGS and NIMROC reference rocks: for concentrations between 6000 and 50 μg g −1 , the relative standard deviation ranged from 2 to 10%.

The determination of oxygen in copper by α-particle activation analysis

Abstract The determination of oxygen in copper by activation analysis with 45-MeV α-particles is described. The chemical separation of 18 F produced from oxygen consists of steam distillation as fluosilicic acid, followed by precipitation of the interfering gallium activities as the hydroxide and of the fluoride as lead chlorofluoride or of cation exchange followed by lead chlorofluoride precipitation. This allows a total decontamination from matrix radiation in excess of 10 6 . As standard, mica foils are used, while, for the purpose of flux monitoring, the activity induced in a thin copper or mica foil, placed before the sample is counted. Alternatively, the intensity of the particle beam is measured. The method, which allows determination of oxygen at the 1 μg g -1 level with a precision of about 10%, is applied to the determination of a concentration of 1.2 μg g -1 . Analysis of a reference material containing 70 μg O g -1 proves the accuracy of the standardization methods applied.