Contribution to the cyclotron targetry

The radionuclide¹⁸F is of considerable interest for biochemical and physiological studies using positron emission tomography (PET). Of all methods used for its production only two have found wide application since their yield is high enough and the chemical form of the product is suitable for fluorination of organic compounds. Proton irradiation of enriched water using¹⁸O(p,n)¹⁸F reaction and deuteron bombardment of gaseous neon²⁰Ne(d,)¹⁸F process are the commonly used effective cyclotron production procedures. In our previous papers^1,2 the different reactions and target parameters of the deuteron irradiation of neon gas were reported. In the present work, the production yields for the (d,), (d,n) and (d,p) reactions were determined.     

Simultaneous production of96Tc and111In by α-particle irradiation of stacked Nb and Ag foils,and their carrier-free separations

In order to produce routinely carrier-free⁹⁶Tc and¹¹¹In, their simultaneous production was examined by means of the stacked foil method. Both niobium and silver foils were arranged on the target holder so as the desired nuclear reactions took place effectively. Simultaneous irradiation of the target with 35 MeV -particles produced effectively¹¹¹In and⁹⁶Tc by the¹⁰⁹Ag(, 2n)¹¹¹In and⁹³Nb(, n)⁹⁶Tc reactions, respectively. Sufficient amounts of radioactivities for tracer uses are obtained by the irradiation at 5 A current for 2 hrs. In addition, carrier-free⁹⁶TcO₄ ^– in a perchloric acid solution could be prepared by the combined use of precipitation and anion-exchange methods. Separation of carrier-free¹¹¹In from the silver matrix was done by means of solvent extraction using acetylacetone as a chelating agent.     

A new detection method of99Tc by nuclear excitation

A new nuclear excitation process,⁹⁹Tc (, )^99mTc reaction, was applied for the first time to radioactivation analysis of technetium. Bremsstrahlung irradiation of⁹⁹Tc samples gave the reaction product^99mTc which emits -ray measurable with ease by a semiconductor detector. The production rate of^99mTc per g⁹⁹Tc was linearly correlated with the flux of bremsstrahlung. The detection limit of⁹⁹Tc was estimated to be nanogram order (0.63 Bq⁹⁹Tc) under the optimum irradiation condition. Possible interference by¹⁰⁰Ru(, p)^99mTc reaction was also studied, which could be discriminated from the (, ) reaction by simultaneously occurring⁹⁸Ru (, p)⁹⁷Ru reaction.     

Production of96Tc and95mTc via the93Nb(α, xn) Reactions

Relatively longer liver technetium tracers such as^95mTc (61 d) are useful for the development, evaluation and comparison of new technetium complexes for eventual development of^99mTc radiopharmaceuticals. The feasibility of producing⁹⁶Tc (4.35 d) and^95mTc (61 d) was studied by the alpha bombardment of pure Nb targets (⁹³Nb-100%).⁹⁶Tc was obtained in a yield of 30 Ci/Ah using 16 MeV alphas, but it contained significant activity of⁹⁵Tc (20 h) Relatively pure⁹⁶Tc and^95mTc was produced in yields of 18 Ci/Ah and about 1 Ci/Ah respectively with alphas of suitable energy and after allowing for suitable cooling periods after the end of bombardment (EOB).     

Accumulation of radicals in the photodecomposition of polypropylene hydroperoxide

Summary According to EPR data, upon UV irradiation both in the near (<300m) and the far (>300m) region decomposition of polypropylene hydroperoxide take place, accompanied by the accumulation of radicals at rates of 1.5·10¹⁴ and 6·10¹⁴ particles per minute, respectively.In conclusion I must thank M. V. Alfimov and V. A. Smirnov for their help in obtaining the spectra.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12 p. 2212–2214, December, 1964     

Behavior of triazines upon γ-irradiation

The behavior of triazines upon -irradiation from a⁶⁰Co source has been studied. The triazines selected were: atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], ametryne [2-ethylamino-4-(isopropylamino)-6-(methylthio)-s-triazine] and simazine [2-chloro-4,6-bis(ethylamino)-s-triazine]. The irradiation doses varied from 5.0 to 640.0 kGy, with a dose rate of 3 kGy h^–1. Following irradiation, the samples were analyzed by gas chromatography with flame ionization (FID) detection. The triazines remained stable after the irradiation process.     

Neutron activation analysis of zeolite catalysts

A new method for the determination of aluminum and silicon has been developed for zeolite catalysts. In contrast to previous methods, thermal neutrons are used for the analysis of both elements, and cadmium absorbers are not needed. The silicon determination utilizes a one-hour irradiation to observe the³¹Si produced by the (n, ) reaction of³⁰Si. A 15-second irradiation is used for the²⁷Al(n, )²⁸Al reaction. The²⁸Al activity is corrected for the contribution from the²⁸Si(n,p)²⁸Al reaction by using the analyzed weight of silicon in the sample and the data for a silicon standard irradiated simultaneously with the zeolite and the aluminum standard. The quantitation limits are 0.012 g for silicon and 3.3×10^–5 g for aluminum. Sodium presents a significant interference, but this element can be removed by taking advantage of the ion exchange properties of these materials.     

Measurement of the50Ti(n,α)47Ca reaction cross section averaged over a235U fission neutron spectrum

The²³⁵U fission neutron spectrum averaged cross section for the⁵⁰Ti(n,)⁴⁷Ca reaction was experimentally determined by irradiation of titanium with reactor neutrons. A value of (9.7±1.1) b was found for this cross section, using (307±11) b for the⁴⁸Ti(n,p)⁴⁸Sc spectrum-averaged cross section that was used as a standard. The⁵⁰Ti(n,)⁴⁷Ca spectrum-averaged cross section was also semiempirically evaluated by numerically integrating, through the ENDF/B-V representation of the²³⁵U fission neutron spectrum, the available experimental differential cross section data.     

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.     

Formation of monodisperse poly(1-methacryloxybenzotriazole) particles by radiation-induced dispersion polymerization

Radiation-induced dispersion polymerization of 1-methacryloxybenzotriazole (MABt) in ethyl propionate starts as homogeneous mixture and the resulting polymer precipitates as spherical particles. Formation, size, and shape of polymer particles are strongly dependent on the initial monomer concentration. Three regions can be distinguished: formation of deformed particles at concentrations of 15 w/v-% MABt; formation of spherical particles at concentrations from 18 to 35 w/v-% MABt; no precipitation of polymer at concentrations of 40 w/v-% MABt. The spherical particles at 20 w/v-% MABt had a diameter of 0.54 ± 0.31 m for 3 kGy irradiation and 2.93±0.68 m for 30 kGy. The number distribution of the microspheres shows that the spherical particles with small sizes formed at low irradiation dose (low conversion) disappears with increasing irradiation dose because of multi-coating by newly produced polymer.     

Gas-chromatographic technique for rapid isolation of uranium fission products

Summary A gas-chromatographic technique for a rapid separation of fission iodine or bromine from the other elements formed in nuclear fission was developed. Recoil-formed, volatile methyl bromide and methyl iodide were isolated within 1 min after the end of irradiation. An extension of this technique to other elements and to other nuclear reactions should be possible.The -ray spectra of both halogen fractions were measured. A dominating -ray at 0.79 MeV and a weaker -ray at 0.51 MeV were assigned to ⁸⁸Br (half life 16 sec). No -ray could be unambiguously attributed to ¹³⁷I (24 sec), a fact which makes unlikely the presence of highly intensive peaks in the -ray spectrum of this isotope. Further details of the spectra are discussed.

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Zusammenfassung Eine gaschromatographische Methode zur schnellen Isolierung von Spaltjod oder Spaltbrom aus dem Gemisch der bei der Kernspaltung entstehenden Elemente wurde entwickelt. Mittels Spaltrückstoß gebildetes, flüchtiges Methylbromid oder Methyljodid wurde innerhalb 1 min nach Bestrahlungsende isoliert. Die Methode sollte auf andere Elemente und andere Kernreaktionen übertragbar sein.-Spektren der beiden Halogenfraktionen wurden gemessen und ergaben für ⁸⁸Br (Halbwertszeit 16 sec) eine dominierende Linie bei 0,79 MeV und eine schwache Linie bei 0,51 MeV. In der Jodfraktion wurde keine -Linie beobachtet, die man eindeutig ¹³⁷J (24 sec) hätte zuordnen können, was sehr intensive Peaks im Spektrum dieses Isotops unwahrscheinlich macht. Weitere Einzelheiten der Spektren werden diskutiert.

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Dedicated to Prof. Dr. F. Strassmann on his 65th birthday.     

The determination of lead in environmental and geological materials by proton activation analysis

Lead is determined in environmental samples and in rocks using the^206,207,208Pb(p,xn)²⁰⁶Bi reaction. Bismuth is separated by anion exchange or by extraction with antimony diethyldithiocarbamate. Sources of errors such as volatilization of the matrix due to heating during the irradiation, variations of the abundance of the lead isotopes and the standardization were studied in detail. For concentrations between 11 mg/g and 3.7 g/g the relative standard deviation ranges from 2.6 to 5.4%. The detection limit is 10 ng/g.     

Radiation-Thermal Processes at the Surface of Pyrogenic γ-Alumina

The effects of ⁶⁰Co -radiation, 75-keV electrons, and thermal history (295–973 K) on the surface properties of pyrogenic -Al₂O₃ were studied by thermal desorption mass spectrometry. It was found that the state of a hydroxyl cover and the concentrations of surface acid–base sites and chlorine impurity atoms can be regulated by changing the conditions of oxide irradiation.     

Some problems associated with the use of boron carbide neutron filters for reactor epithermal neutron activation analysis (ENAA)

The radiation heating caused by the¹⁰B(n, )⁷Li-reaction in boron carbide (B₄ C) neutron filters used for epithermal neutron activation analysis has been examined by measuring rates of temperature rise and steady-state temperatures of sintered and powdered B₄C filters placed in dry air and reactor pool-water during irradiation, respectively. Maximum equilibrium temperatures of 195°C for air-cooled sintered, and 50°C for water-cooled powdered B₄C were observed, confirming the necessity for efficient cooling of the filter during irradiation. It is noted that the accumulation of the¹⁰B(n, )⁷Li-reaction products in B₄C and other boron compounds may severely limit the reuse of the filters in subsequent irradiations.     

Excitation functions and thick target yields of (α, αxn) and (α, 2p xn) reactions on159Tb

Cumulative cross-sections were determined by the stacked foil method for the (, xn) and (, 2pxn) reactions on¹⁵⁹Tb up to 90 MeV. Thick target yields were calculated as a function of the energy for the production of¹⁵³Tb,¹⁵⁵Tb,¹⁵⁶Tb,¹⁵⁸Tb and¹⁶⁰Tb.     

Polarographic determination of microgram amounts of thorium(IV)

Summary Among various salt solutions tested 0.01 N LiNO₃ proved to be most suitable as supporting electrolyte for the polarographic determination of microgram amounts of thorium. Well-developed, maxima-free and reproducible waves were obtained for a Th(IV) concentration range of 1.4–23 g/ml. The minimum detectable limit of the element was 0.8 g/ml. No relationship has been found between Th(IV) and H⁺-ion concentration.

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Polarographische Bestimmung von Mikrogramm-Mengen Thorium(IV)

Zusammenfassung Von verschiedenen untersuchten Salzlösungen hat sich als Grundelektrolyt 0,01 N LiNO₃-Lösung als am günstigsten erwiesen. Es wurden damit gut ausgebildete, maxima-freie und reproduzierbare Stufen für einen Konzentrationsbereich von 1,4–23 g Th(IV)/ml erhalten. Die Nachweisgrenze betrug 0,8 g Th(IV) in 1 ml Lösung. Es wurde kein Zusammenhang zwischen Thoriumkonzentration und H⁺-Ionenkonzentration nachgewiesen.

     

2,3-Dihydroxypyridine Loaded Amberlite XAD-2 (AXAD-2-DHP): Preparation, Sorption–Desorption Equilibria with Metal Ions, and Applications in Quantitative Metal Ion Enrichment from Water, Milk and Vitamin Samples

2,3-Dihydroxypyridine loaded (via –N=N–linker) Amberlite XAD-2 (AXAD-2-DHP) was prepared and characterized by elemental analyses, TGA and FT-IR spectra. It (1g packed in a column of 1cm diameter; surface area 135.5m²g^–1) was found to be an effective solid phase sorbent for enriching Zn²⁺, Mn²⁺, Ni²⁺, Pb²⁺, Cd²⁺, Cu²⁺, Fe³⁺ and Co²⁺ at pH 3.5 to 7.0 using flow rates between 1.0–5.0mLmin^–1. For desorption (recovery 97.0–99.8%) of the metal ions, 8 to 10mL of 2.0molL^–1 HCl or 1.5molL^–1 HNO₃ at a flow rate of between 2.0 and 4.0mLmin^–1 were found most suitable. The t_1/2 (time for 50% sorption) is between 2 and 10min when a 50mL solution (containing a total amount of metal of 2mg) was equilibrated with 0.5g of resin. Sorption of all metal ions except Pb²⁺ follows the Langmuir model, whereas for Pb the data fits with the Freundlich model. The sorption capacity is between 60.7 (for Cd) and 406.7 (for Cu) µmolg^–1. The resin can withstand an acid concentration of 6molL^–1 and can be reused for thirty cycles of sorption–desorption. The preconcentration factor varies between 100 and 300. For Cd, Ni and Cu the sorption capacity of 2,3-dihydroxypyridine loaded cellulose is lower than that of the present resin. The tolerance limits of electrolytes, humic acid, complexing agents, Ca²⁺ and Mg²⁺ in the enrichment of all metal ions are reported. The limits of detection are 3.88, 5.37, 8.72, 13.88, 4.71, 1.24, 0.59 and 0.30µgL^–1 for Zn²⁺, Mn²⁺, Ni²⁺, Pb²⁺, Cd²⁺, Cu²⁺, Fe³⁺ and Co²⁺, respectively. The calibration curves for flame AAS determination were linear in the ranges 0.018–1.0, 0.067–5.0, 0.2–5.0, 0.9–20, 0.028–2.0, 0.077–5.0, 0.19–10 and 0.1–3.5µgmL^–1, respectively. All the eight metal ions in river and synthetic water samples, Co in vitamin tablets and Zn in milk samples have been quantitatively enriched with Amberlite XAD-2-DHP and determined by flame atomic absorption spectrometry.     

Conformational studies of poly(N5-Ω-hydroxyalkyl-L-glutamine)s in reversed micelles

The molecular conformations of poly(N⁵-dihydroxyethylaminopropyl-L-glutamine) and poly(N⁵-dihydroxyethyl-L-glutamine) were investigated in reversed micelles of AOT as well as in aqueous solutions. Both poly(-amino acid)s assume disordered structures in pure water. The conformation of poly(N⁵-dihydroxyethylaminopropyl-L-glutamine) transits into-helix in the reversed micelles as the molar ratio of water to AOT (w₀=[H₂O]/[AOT]) becomes smaller. A similar conformational transition was also observed in aqueous solutions when a certain amount of AOT was added. Under these conditions, however, poly(N⁵-dihydroxyethyl-L-glutamine) did not undergo a conformational transition into-helix.     

Determination of neptunium in plutonium and mixed uranium-plutonium samples by isotope dilution gamma-spectrometry with243Am as a spike

A method was developed for isolating neptunium from Pu, U or mixed oxide (MOX) samples and its determination by isotope dilution -spectrometry (IDGS) using²³⁹Np (²⁴³Am) as a spike. Extraction chromatography with trilaurylamine fixed on a SGX-C18 support was used for the isolation of Np. The decontamination factors for U, Pu, Am and Pa vary between 1000–2000 and 100, respectively. The average separation yield of Np is (95±3)%. The amount of²⁴³Am required for spiking is about 0.2–0.3 g. It is recommended to use the pair of -rays 86.53 keV (²³⁷Np)-106.13 keV (²³⁹Np) for the assay of neptunium. A relative uncertainty of 4% or better is achievable in the analysis of plutonium samples, containing 0.4–80 g neptunium. The detection limit, under the proposed experimental conditions, is about 0.05 g Np. The results were compared with the results obtained by using high resolution -spectrometry (HRGS).     

Improved gas-chromatographic columns of liquid crystals supported on glass beads for analysis of polycyclic aromatic hydrocarbons

Summary Glass microbead columns withN, N-bis-(p-butoxybenzilidene) , -bi-p-toluidine (BBBT) a high-temperature smectic-nematic liquid crystalline stationary phase have been prepared. The best efficiency was obtained with BBBT from 0.025% w/w (ca. 1800 theoretical plates m^–1) to 0.1% w/w (ca. 2100 theoretical plates m^–1). Capacity ratios and separation efficiencies of columns packed with glass microbeads treated and untreated with a surfaceactive agent were studied as a function of analysis time. A separation of five methylchrysene isomers is shown.