Systematics of nuclear charge distribution in fission the ZP model

An extension of the conventional Z_P model has been used with data for ten fission reactions and the method of least-squares for derivation of parameters that describe the nuclear charge-distributions. Data for light and heavy fission products for each reaction were treated together by consideration of the complementarity of average mass numbers of precursors (A′_L+A′_H=A_F). This treatment gave calculated yields that are essentially equal for complementary elements (Z_L+Z_H=Z_F). The parameters determined, , the Gaussian dispersion width parameter, a linear function of Δ_Z=|Z_P-A′(Z_F/A_F)|, Z_P being the Z at maximum of the curve, and and , the even-odd proton and neutron yield enhancement factors, represented most data (A_H⋟130–150 and the complementary light A's) moderately well, better than did oscillating functions of and Δ_Z. The values were found to be approximately constant (0.48 to 0.62) and, generally, to increase with the average number of neutrons emitted, . The Δ_Z values at A′=140 were in the range of 0.42 to 0.50, and the slopes, ∂Δ_Z/∂A′_H, ranged from 0.0 to 0.03. The factor was found to be several times larger than the factor and to decrease with increasing excitation energy and with A and/or Z of the fissioning nucleus, as has been reported previously. The adequacy of the Z_P model for representation of data and for prediction of yields in the high-yield mass-number regions mentioned above are discussed, and the large uncertainties that are involved in extrapolating the model to near symmetric or to very asymmetric mass and charge divisions are pointed out.     

High precision elemental abundances for tektites and crater glasses-thorium,uranium and potassium

Thorium, uranium and potassium mean abundances for 15 Ivory Coast tektites, 23 Australites, 10 Philippinites, 25 Thailandites, 16 Bediasites and 12 Moldavites are reported. Abundances are also reported for Muong Nong type tektites, Nordlinger Ries crater glass, Bosumtwi crater glass and Darwin crater glass. Previous measurements are reviewed. The value of the present work lies in the fact that high precision instrumental neutron activation analysis was employed to measure a large number of tektites encompassing the major strewn fields. Four independent measurements of thorium were made for each specimen with two Ge(Li) gamma spectrometers. Two of the measurements were based on the 312 keV gamma of²³³Pa, while the other two measurements were based on the uranium and X-rays which accompany the decay of²³³Pa. Internal consistency among the four thorium measurements is high. The uranium measurements were based on the 106 keV gamma of²³⁹Np, while potassium was measured from the 1524 keV gamma of⁴²K.     

Interferences in the determination of trace elements in high-purity tin

Reactor neutron activation analysis of antimony, indium and cadmium in high-purity tin is interfered with by nuclear reactions on the tin matrix. For a number of interfering reactions the cross-sections were determined. The following results were obtained:¹²²Sn(n,γ)^123mSn:σ_th=0.145 barn, I=0.79 barn;¹²²Sn(n,γ)¹¹³Sn:σ_th=0.52, I=25.4 barn;¹¹²Sn(n, 2n)¹¹¹Sn: microbarn;¹¹⁸Sn(n, α)¹¹⁵Cd: microbarn; and¹¹⁴Sn(n, p)^114m1In: microbarn.     

Calculation of average L shell fluorescence yields for the elements with 25≤Z≤101

Average L shell fluorescence yield , average L shell Auger yields and the total L shell X-ray fluorescence (LXRF) cross sections (σ _L ^x ) at 30 keV have been calculated theoretically for the elements with 25≤Z≤101. These calculated values have been compared with the other experimental and theoretical values.     

A method for experimental determination of effective resonance energies related to (n, γ) reactions

When making use of some single comparator or absolute standardization methods in reactor neutron and in epicadmium neutron activation analysis, the knowledge of the effective resonance energy ( ) is essential to correct for the effect of the nonideal epithermal flux distribution on the analysis result. can be calculated from neutron resonance data, but when these are incomplete, not accurate or even not known at all, experimental determination should be considered. Such a method, providing both and the resonance integral to 2200 ms^–1 cross-section ratio (Q_O), is described in this paper. Results are given for 11 isotopes.     

Mass transfer in shell-core inorganic TIP1 ion exchanger

The ion exchange processes of (OAc^–) and (OAc^–) proceeding in shell-core inorganic ion exchanger Ti (HPO₄)₂·1/2H₂O has been studied and the diffusion equation whose boundary conditions are satisfied by a shell-core model was solved. Based on the equation solved and experimental data, the diffusion coefficients corresponding to the exchange process (OAc^–) and Li⁺–H⁺ (OAc^–) at 17°C are found to be 7.7×10^–9 and 6.2×10^–8 cm² s^–1 and the activation energies 3.4×10⁴ and 5.0×10³ J mol^–1, respectively. Compared to the gel type of styrene-divinylbenzene strong acid exchanger with 20% cross linking, it can be concluded that the rate of or exchange is 3.5 times faster than that in the organic exchanger.TIP was obtained from the Salt Lake Institute of the Academy of Science of China.     

Photon-induced K-shell X-ray intensity ratio for elements with 74≤Z≤92

The K-shell X-ray intensity ratios and for W, Au, Tl, Pb, Bi, Th and U have been measured at a photon incident energy of 121.9 keV from⁵⁷Co radionuclide. A comparison between the experimental results and the theoretically calculated values shows that the experimental results are, in general, higher than the theoretical values. To the best of our knowledge, the measured intensities are reported for the first time.     

Critical evaluation of the effective resonance energy concept and the epithermal neutron spectrum shape-factorα for reactor NAA purposes

The epithermal reactor neutron spectrum shape-factor, and the associated effective resonance energy for a given nuclide, are examined theoretically in great detail. First the necessity, meaning and importance of the choice of a reference neutron energy in a non-ideal spectrum (0) are explained. Next, the definition and practical calculation of are discussed, showing that the relation between the reasonance integrals in ideal and non-ideal spectra cannot be described adequately by two independent parameters and . The exact meaning of the logarithmic expression defining an independent of is clarified, its limits of validity are established as a function of and, as a result, it follows that relatively large systematic errors on can be introduced by its use. It is shown that is dominated by the first lowest resonance energies for a given nuclide, making its vulnerability to literature updates of resonance parameters almost equal to those of individual resonances. The effect, on the epithermal and total activation of specific nuclides, of large systematic and statistical errors on and, is calculated for a series of nuclides (different I₀/₀ and ) and irradiation facilities (different and _the), and represented graphically.Finally, the effect of important errors on and is calculated for final NAA results in terms of concentrations, botained by a comparator technique based on the¹⁹⁷Au reference nuclide. Conclusions are drawn concerning the impact of the foregoing on the usefulness of comparator type reactor NAA as an alternative to classical NAA using multi-element standards.     

Laser-induced fluorescence study on the interaction of Eu(III) with polycarboxylates

Laser-induced fluorescence spectroscopy was applied to obtaining hydration structure of Eu(III) complexes with synthetic polycarboxylates of poly(acrylic acid), poly(maleic acid), poly(methacrylic acid), and poly(a-hydroxyacrylic acid). Dependence of (the number of water molecules in the first coordination sphere of Eu(III) ion) on pH and supporting electrolyte concentration was obtained for these complexes. The spectroscopic results show that Eu(III) is surrounded by the “cage” of polycarboxylate ligands. The pH-induced transition in conformation of poly(methacrylic acid) ligand was clearly observed in the plot vs. pH.     

Reactions of alkoxy and hydroxy radicals generated photochemically from hydroperoxide molecules

In the present work as well as HRO^. radicals were generated in the photochemical interaction of 1,2-benzanthracene with -ethyl phenyl hydroperoxide /HROOH/ in C₆H₆ and CCl₄ at 304 K. radicals were trapped by C₆H₆. The main reaction of HRO^. radicals is hydrogen abstraction from the hydroperoxide group of HROOH. Although OH radicals are less selective, the hydrogen abstraction is the main process during their interaction with aromatics in contrast to reactions in aqueous solutions, where addition to the benzene ring is the rate-determining process in CCl₄:

Substoichiometric exchange extraction of tantalum and gold with tetraphenylarsonium

The conditions for substoichiometric exchange extraction in the system have been investigated in order to establish the feasibility of substoichiometric separation of tantalum and its determination by activation.     

Absolute determination of the spontaneous fission yield of252Cf by radiochemical method

The distribution of mass in the spontaneous fission of²⁵²Cf has been investigated by the radiochemical determination of the absolute fission yields for 35 mass chains. A summation of the mass-yield curve gives a summed value of 199.4% which is in very good agreement with the value of 200% in fission. The mean masses of the light and heavy group are located at 106.39 and 141.82, respectively. The average number of neutron per fisson is 3.79±0.12. The peak-to-valley ratio is larger than 370. The width at one tenth of the maximum of the light and heavy group are 26.7 and 26.8 mass number, respectively. A comparison of previous investigators has resulted in recommended yields for 35 mass chains.     

Neutron generation in massive Cu-targets during the irradiation with 22 and 44 GeV carbon ions

An extended Cu-target was irradiated with 22 and 44 GeV carbon ions for about 11.3 and 14.7 hours, respectively. The upper side of the target was in contact with a paraffin-block for the moderation of secondary neutrons. Small holes in the moderator were filled with either lanthanum salts or uranium oxide. The reaction was studied via the decay of¹⁴⁰La(40h) using radiochemical methods, as has been published. The reaction was studied via the decay of²³⁹Np(2.3 d) as well as the reaction U(n,f) using radiochemical methods. In addition, solid state nuclear track detectors were used for fission studies in gold. The yields for the formation of (n,) products agree essentially with other experiments on extended targets carried out at the Dubna Synchrophasotron (LHE, JINR). To a first approximation, the breeding rate of (n, ) products doubles when the carbon energy increases from 22 to 44 GeV. If, however, results at 44 GeV are compared in detail to those at 22 GeV, we observe an excess of (37±9)% in the experimentally observed²³⁹Np-breeding rate over theoretical estimations. Experiments using solid state nuclear track detectors give similar results. We present a conception for the interpretation of this fact: There is the evident connection between anomalies we observe in the yield of secondary particles in relativistic heavy ion interactions above a total energy of approximately 30–35 GeV and increased yield of neutrons in this energy region.     

Studies on ion exchange equilibria and kinetics

¹⁶⁰Tb was used as radiotracer and the equilibria and kinetics of cation exchange with zeolite-Y were studied. The ion exchange isothems and the Kielland plots at 298 and 303 K were obtained. It was found that the ion exchange rate is controlled by particle diffusion. The integral interdiffusion coefficients for the direct and reverse exchanges at 298 K and 303 K were calculated. In addition, the isotopic ion exchange was studied too.     

Oscillatory variation in yields of I2 and the reactivity of γ-irradiated TiO2 in KI solution

The reactivity of preheated and -irradiated TiO₂ was observed in KI solution by studying the kinetics of liberation of I₂. The rate of the reaction was found to be low. species proposed on the surface of oxide probably dissociate into . surface sites which oxidize I^– ions to produce free I₂. During irradiation and are produced which are reducing in nature and therefore very low yields of I₂ are observed for low -doses. In further irradiation the reformation of –O–O–, peroxy linkages is proposed hence the observed higher yields. All the processes ultimately lead to an oscillatory variation in yields of I₂ with -doses.     

The sorption of uranyl ions on silica-titania mixed-hydroxide gels

SiO₂–TiO₂ mixed hydroxide gels were prepared and the apparent adsorption capacity for Na⁺ (1.30–1.60 mmol/g dry sample) determined by pH titration. The effect of solution pH on the sorption ability of the binary gels was studied. It is found that: (1) the sorption mechanism depends upon the pH, and the two most important factors are the nature of both counter ions in bulk solution and the surface of silica-titania gels, (2) the best pH range for the sorption of uranyl ions is 4–7. The thermodynamic functions were evaluated, suggesting that the reaction is chiefly attributed to physical adsorption rather than chemical one, and the opposite is the case of the reaction.     

A generalized separation reaction scheme for assessment of the radioanalytical method of concentration dependent distribution

For the assessment of the analytical error of concentration dependent distribution (CDD), complex-forming separation reaction was proposed in a generalized form of equilibrium , where n is the effective stoichiometric coefficient, i.e. the difference of mean ligand numbers and <n> of a mixture of complexes of analyte M with reagent L in the respective groups (distinguished by bars above the symbols) of the separation system. Calibration curve is derived from measurement of gross activity of complexes, A=A(ML_<n>) and . Theoretical relative error is expressed as a product of three terms, x/x=f₁f₂f₃. The first term f₁ depends on the degree of isotopic dilution, and the recommended ratio of amounts of nonradioactive (x) and radioactive (y) substance M is x/y(1;4). The second term f₂ depends first of all on the slope of distribution ratio (yield of separation ) vs. the analyte; reagent ratio, n(Z+1)/T. The form of slope is analyzed on the basis of the generalized separation reaction. Optimal conditions were discussed from this point of view and the ideal case is at f₂=1. The third term f₃ depends on the activities A and , i.e. on the distribution ratio, sample volumes, and the manner of counting. The ideal ratio of sample activities is A= and the optimal interval (0.2;0.8) is suggested     

Effect of dissolved oxygen on the inactivation of bacteriophages in water by gamma radiation: Important role ofH\dot O_2 radicalsradicals

The inactivation of bacteriophages by -radiation was studied in 0.1M Na phosphate buffer and in deionized water in the presence and absence of dissolved oxygen. From the results obtained it is possible to make conclusion that radicals /which are formed in radiolysis of water in the presence of oxygen/ have a marked inactivating effect on bacteriophages, but in the simultaneous presence of radicals an inactivation takes place between them.     

Extent of exchange of bromine-82 with bromamine-T in strong acid medium

The extent of exchange of bromine-82 with bromamine-T in strong acid medium is low due to the formation of at lower acid concentrations and bromine at higher acidities. formation occurs over a narrow acid concentration range and is less stable than .     

Cesium, strontium, europium(III) and plutonium(IV) complexes with humic acid in solution and on montmorillonite surface

The effect of Aldrich humic acid (HA) on the mobility of¹³⁷Cs,⁸⁵Sr,¹⁵²Eu and²³⁹Pu radionuclides was studied in Ca-montmorillonite suspensions. Verified 2-sites-2-species (2s2s) models correspond to an intensive interaction of all elements with humificated surface, what is in a remarkable contrast with the weak complexation of cesium and even strontium in solutions — the neutral ligand interaction constants β (l/mol) are log β<−9.9 and 7.56±0.21 for Cs and Sr, respectively. The result for europium complexation in solution, log β=12.49±0.18 is in a good agreement with literature data. For plutonium(IV) not only a high proton competitive constant in solution was obtained, log β β=(−0.67±0.32)+3pH, but also a strong chemisorption, which at high concentrations of humic acid (above 0.05 g/l) indicates the formation of bridge humate complexes of plutonium on the humificated surface. Logarithms of heterogeneous interaction constants ( ₂₄ l/g) of the elements with surface humic acid are 4.47±0.23, 4.39±0.08, and 6.40±0.33 for Cs, Sr, and Eu(III), respectively, and the logarithm of the proton competitive constant ( ₂₄, l/g) for Pu(IV) −3.80±0.72. Distribution coefficients of humic acid and metal humates between 0.01 g HA/l solution and montmorillonite were derived as logK _d(AH)=−1.04±0.11, logK _d(EuA)=1.56±0.11 and logK _d(PuA)=2.25±0.04, while the values for Cs and Sr were obtained with very high uncertainty. Speciation of the elements on montmorillonite surface is illustrated as a function of equilibrium concentration of humic acid in solution and of pH.