Thermal neutron cross section and resonance integral of the reaction of135Cs(n,γ)136Cs: Fundamental data for the transmutation of nuclear waste

To determine the cross sections of the¹³⁵Cs(n,γ)¹³⁶Cs reaction, a sample of¹³⁵Cs included in a “standardized solution” of¹³⁷Cs was used as a target and irradiated in a reactor. The ratio of the atom number of¹³⁵Cs to that of¹³⁷Cs was determined to be 0.89±0.03 with a quadrupole mass spectrometer. The thermal cross section and the resonance integral measured in this study were determined to be 8.3±0.3 and 38.1±2.6 b respectively.     

Cross section measurements for 141Pr(n,γ)142Pr reaction at neutron energies from 13.5 to 14.8?MeV

Activation cross-sections were measured for the ¹⁴¹Pr(n,??)¹⁴²Pr reaction at three different neutron energies from 13.5 to 14.8?MeV. The fast neutrons were produced via the ³H(d,n)⁴He reaction on Pd-300 neutron generator. The natural high-purity Pr₂O₃ powder was used as target material. Induced gamma activities were measured by a high-resolution gamma-ray spectrometer with high-purity germanium detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The neutron fluences were determined by the cross section of ²⁷Al(n,??)²⁴Na reaction. The neutron energy in the measurement were by the cross section ratios of ⁹⁰Zr(n,2n)^89m+gZr and ⁹³Nb(n,2n)^92mNb reactions. The data for ¹⁴¹Pr(n,??)¹⁴²Pr reaction cross sections are reported to be 3.3?±?0.2, 2.7?±?0.2 and 2.2?±?0.2 mb at 13.5?±?0.2, 14.1?±?0.2, and 14.8?±?0.2?MeV incident neutron energies, respectively. Results were discussed and compared with some corresponding values found in the literature.     

An alternative route for the preparation of the medical isotope 99Mo from the 238U(γ, f) and 100Mo(γ, n) reactions

The radionuclide ⁹⁹Mo, which has a half-life of 65.94 h was produced from ²³⁸U(γ, f) and ¹⁰⁰Mo(γ, n) reactions using a 10 MeV electron linac at EBC, Kharghar Navi-Mumbai, India. This has been investigated since the daughter product ^99mTc is very important from a medical point of view and can be produced in a generator from the parent ⁹⁹Mo. The activity of ⁹⁹Mo was analyzed by a γ-ray spectrometric technique using a HPGe detector. From the detected γ-rays activity of 140.5 and 739.8 keV, the amount of ⁹⁹Mo produced was determined. For comparison, the amount of ⁹⁹Mo from ²³⁸U(γ, f) and ¹⁰⁰Mo(γ, n) reactions was also estimated using the experimental photon flux from ¹⁹⁷Au(γ, n)¹⁹⁶Au reaction. The amount of ⁹⁹Mo from the detected γ-lines is in agreement with the estimated value for ²³⁸U(γ, f) and ¹⁰⁰Mo(γ, n) reactions. The production of ⁹⁹Mo activity from ²³⁸U(γ, f) and ¹⁰⁰Mo(γ, n) reactions is a relevant and novel approach, which provides alternative routes to ^235,238U(n, f) and ⁹⁸Mo(n, γ) reactions, circumventing the need for a reactor. The viability and practicality of the ⁹⁹Mo production from the ²³⁸U(γ, f) and ¹⁰⁰Mo(γ, n) reactions alternative to ^235,238U(n, f) and ⁹⁸Mo(n, γ) reactions has been emphasize. An estimate has been also arrived based on the experimental data of present work to fulfill the requirement of DOE.     

On the Relation Between the Effective Resonance Energy and the Infinite Dilution Resonance Integral for (n,γ) Reactions

In this paper a possible relation between the effective resonance energy and the infinite dilution resonance integral of (n,) reactions is discussed. These two parameters are important data in thermal neutron activation analysis when using the single comparator method based on the Høgdahl convention. The values for these two parameters of more than one hundred (n,) reactions are considered, and the possibility of a — 2/3 power function is proposed.     

The reaction between HO and (H2O) n (n?=?1, 3) clusters: reaction mechanisms and tunneling effects

The reaction between the HO radical and (H₂O)n (n?=?1, 3) clusters has been investigated employing high-level quantum mechanical calculations using DFT-BH&HLYP, QCISD, and CCSD(T) theoretical approaches in connection with the 6-311?+?G(2df,2p), aug-cc-pVTZ, and aug-cc-pVQZ basis sets. The rate constants have also been calculated and the tunneling effects have been studied by means of time?Cdependent wavepacket calculations, performed using the Quantum?CReaction Path Hamiltonian method. According to the findings of previously reported theoretical works, the reaction between HO and H₂O begins with the formation of a pre-reactive complex that is formed before the transition state, the formation of a post-reactive complex, and the release of the products. The reaction between HO and (H₂O)₂ also begins with the formation of a pre-reactive complex, which dissociates into H₂O??HO?+?H₂O. The reaction between HO and (H₂O)₃ is much more complex. The hydroxyl radical adds to the water trimer, and then it occurs a geometrical rearrangement in the pre-reactive hydrogen-bonded complex region, before the transition state. The reaction between hydroxyl radical and water trimer is computed to be much faster than the reaction between hydroxyl radical and a single water molecule, and, in both cases, the tunneling effects are very important mainly at low temperatures. A prediction of the atmospheric concentration of the hydrogen-bonded complexes studied in this work is also reported.     

Production of cationic 198Au3+ and nonionic 198Au0 for radionuclide therapy applications via the natAu(n,γ)198Au reaction

¹⁹⁸Au (??_max?=?0.96?MeV (98.6?%), ??_max?=?0.412?MeV (95.5?%) and T _1/2 ?=?2.7?days) is a radionuclide with very appealing characteristics. ¹⁹⁸Au has been widely used to treat the uterus, bladder, cervix, prostate, melanoma, breast, skin and other cancers. In the present study, cationic ¹⁹⁸Au⁺³ and nonionic ¹⁹⁸Au⁰ are prepared following thermal neutron irradiation of commercially available natural gold compounds in Tehran Research Reactor via the ^natAu(n,??)¹⁹⁸Au reaction. The prospects in the production of pure ¹⁹⁸Au⁰ and ¹⁹⁸Au⁺³ for radionuclide therapy are discussed and effect of reduction on the activity of radioactive gold is evaluated. Au⁰ particles were synthesized via NaBH₄ reduction of aqueous solutions of hydrogen tetrachloroaurate trihydrate. Then two quartz tubes were charged with cationic ¹⁹⁸Au³⁺ and nonionic ¹⁹⁸Au⁰. After irradiation by thermal neutrons, the samples were analyzed for a period of 1?month by liquid scintillation counter and high purity germanium detector. As a result, ^natAu³⁺ reduction process had no significant effect on the activity of the ¹⁹⁸Au sample. In conclusions, natural gold thermal neutron activation cross section is reasonably high for medical application.     

Breakdown of the pseudopotential approximation for magnetizabilities and electric multipole moments: test calculations for Au, AuF, and Sn(n) cluster (n ≤ 20)

The response of the electronic wavefunction to an external electric or magnetic field is widely considered to be a typical valence property and should, therefore, be adequately described by accurately adjusted pseudopotentials, especially if a small-core definition is used within this approximation. In this paper we show for atomic Au and Au(+), as well as for the molecule AuF and tin clusters, that in contrast to the case of the static electric dipole polarizability or the electric dipole moment, core contributions to the static magnetizability are non-negligible, and can therefore lead to erroneous results within the pseudopotential approximation. This error increases with increasing size of the core chosen. For tin clusters, which are of interest in ongoing molecular beam experiments currently carried out by the Darmstadt group, the diamagnetic and paramagnetic isotropic components of the magnetizability tensor almost cancel out and large-core pseudopotentials do not even predict the correct sign for this property due to erroneous results in both the diamagnetic and (more importantly) the paramagnetic terms. Hence, all-electron calculations or pseudopotentials with very small cores are required to adequately predict magnetizabilities for atoms, molecules and the solid state, making it computationally more difficult to obtain this quantity for future investigations in heavy atom containing molecules or clusters. We also demonstrate for this property that all-electron density functional calculations are quite robust and give results close to wavefunction based methods for the atoms and molecules studied here.     

Gold bearing ore assays using 197Au(γ,n)196Au photonuclear reaction

We performed computational and experimental studies of the feasibility of the gold bearing ore assay utilizing the ¹⁹⁷Au(γ,n)¹⁹⁶Au photonuclear reaction. Gold bearing silicate samples were irradiated using bremsstrahlung produced by an electron accelerator with endpoint energies ranging from 25 to 40 MeV. ¹⁹⁶Au yield simulations were benchmarked and experimental results were in good agreement with the predictions. Optimum electron beam energy for photon activation analysis was found to be around 32 MeV which corresponded to a detection limit of 80 ppb. Two-hour gamma-spectroscopy measurements were repeated every 24 h and the optimum sample cooling time was found to be about 100–160 h.     

37Cl(n,γ)38Cl reaction in binary mixtures of carbon tetrachloride with ethanol, heptanol and octanol

³⁷Cl(n,)³⁸Cl reaction in mixtures of CCl₄ with ethanol, heptanol and octanol exhibit a dependence on the tendency of the -COH group to cleave into CO and H. This tendency, shown here, correlates with the order of acidity of alkanols.The author wishes to thank the Reactor Staff of the Research Centre Demokritos for their kind cooperation in the irradiation of samples, Dr. Dimitris Tsiourvas for the drawing the figures and Miss Rena Nisiotou for the purification of carbon tetrachloride.     

Measurements of activation cross-sections for the 101Ru(n,p)101Tc reaction for neutrons with energies between 13 and 15 MeV

In this study, activation cross-sections were measured for the ¹⁰¹Ru(n,p)¹⁰¹Tc reaction at three different neutron energies from 13.5 to 14.8 MeV. The fast neutrons were produced via the ³H(d,n)⁴He reaction on K-400 neutron generator. Induced gamma activities were measured by a high-resolution gamma-ray spectrometer with high-purity germanium detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The data for ¹⁰¹Ru(n,p)¹⁰¹Tc reaction cross-sections are reported to be 15.7 ± 2.0, 18.4 ± 2.7 and 22.0 ± 2.4 mb at 13.5 ± 0.2, 14.1 ± 0.2, and 14.8 ± 0.2 MeV incident neutron energies, respectively. Results were compared with the previous works.     

(n,γ)-radiolysis of magnesium iodate

The initial retention of thermal neutron irradiated magnesium iodate tetrahydrate was found to be 47% and increased to 54% for the dehydrated salt. The post irradiation isothermal annealing followed the characteristic pattern both in hydrated and dehydrated salts; the rate of increase in retention in the hydrated salt being faster than in the dehydrated form. At an annealing temperature of 453 K, 100% retention was achieved by the hydrated salt but the corresponding value for the dehydrated magnesium iodate was not higher than 88%. The role of water of crystallization in the retention studies of magnesium iodate is discussed.     

Measurement of neutron-capture cross section and capture γ-ray spectrum of 105Pd(n,γ)106Pd reaction

We measured the neutron-capture cross section and the capture γ-ray spectrum of the ¹⁰⁵Pd(n,γ)¹⁰⁶Pd reaction with about 550 keV neutrons produced from the ⁷Li(p,n)⁷Be reaction at a 3-MV Pelletron accelerator. The capture yields of the palladium or gold sample were obtained by applying a pulse-height weighting technique to the corresponding net capture γ-ray pulse-height spectra. The neutron-capture cross section of the ¹⁰⁵Pd(n,γ)¹⁰⁶Pd reaction was determined with errors less than 5 % by using the standard capture cross sections of ¹⁹⁷Au. The neutron-capture γ-ray spectrum was obtained by unfolding the observed capture γ-ray pulse-height spectra. Theoretical calculations of cross sections and γ-ray spectra with the Empire code have been performed by utilizing the Hauser-Feshbach statistical model. The calculated results have a good agreement with present measurements.     

Rh(Ⅱ) and Zn(Ⅱ) co-catalyzed multi-component reaction for the synthesis of vicinal diols

Oxonium ylide intermediates generated fromα-diazocarbonyl compounds and water were trapped by Zn(Ⅱ)-activatedα-dicarbonyl compounds.The reaction gaveα,β-dihydroxyl acid derivatives in moderate yield.     

Activation cross sections for the 110Pd(n,2n) reaction and the isomeric cross-sections ratio of 109m,gPd in the neutron energy range of 13–15 MeV

Journal of Radioanalytical and Nuclear Chemistry - The 110Pd(n,2n)109m,gPd reaction cross-sections and the isomeric cross section ratios (σm/σg) in the neutron energy range of...     

Measurement of isomeric-yield ratios for the 197Au(γ,n)196m,gAu reactions induced by bremsstrahlung

We measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions with bremsstrahlung energies of 50-, 60-, 70- MeV, and 2.5-GeV at the two different electron linac of the Pohang accelerator laboratory by using the activation method. The photons were produced when a pulsed electron beam hit a thin tungsten target. The well-known photoactivation method was used and hence the induced activities in the irradiated foils were measured with the high-resolution γ-ray spectrometric system consisting of lithium drifted high-purity Germanium detector and a multichannel analyzer. The measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions were (4.95 ± 0.51) × 10^?4, (5.72 ± 0.72) × 10^?4, (6.03 ± 0.50) × 10^?4, and (9.27 ± 0.83) × 10^?4 for 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies, respectively. The present results measured with the bremsstrahlung energy higher than 60-MeV are the first measurement.     

Experimental cross section evaluation for innovative 99Mo production via the (α,n) reaction on 96Zr target

The high-specific activity ⁹⁹Mo accelerator-based production, via the (α,n) reaction on ⁹⁶Zr-enriched target, has been investigated in the present work. The excitation function measurement has been performed in the energy range 8–34 MeV at the ARRONAX facility, using the well-known stacked foils technique on natural zirconium as target. A general good agreement in the cross section trend has been observed, once compared to former measurements. A different (i.e. higher) peak value and a shift of about 2 MeV towards larger energies have however been found. Assuming a fully enriched ⁹⁶Zr target irradiated by an α-beam at suitable energy (E = 25 MeV), the ⁹⁹Mo production yield has thus been estimated. At last the alternative production routes, based on the ⁹⁶Zr(α,n)⁹⁹Mo and ¹⁰⁰Mo(p,x)⁹⁹Mo/^99mTc reactions, are compared.