Pulse radiolysis study on aqueous solution of nicotine

Nicotine has been studied for the first time by pulse radiolysis techniques. It has been found that hydrated electrons, hydrogen radicals and hydroxyl radicals can react with nicotine to produce anion radicals and neutral radicals, respectively, and the related rate constants have been determined.     

A study of low-energy ion induced radiolysis of thiol-containing amino acid cysteine in the solid and aqueous solution states

The radiolysis of cysteine under plasma discharge and irradiation of low-energy ion beam was investigated. The damage of cysteine in aqueous solution under discharge was assessed via the acid ninhydrin reagent and the yield of cystine produced from the reaction was analyzed by FTIR. In addition, the generation of hydrogen sulfide was also identified. The destruction of solid cysteine under low-energy ion beam irradiation was estimated via monitoring IR bands of different functional groups (–SH, –NH₃, –COO^?) of cysteine, and the production of cystine from ion-irradiated solid cysteine after dissolution in water was also verified. These results may help us to understand the inactivation of sulphydryl enzymes under direct and indirect interaction with the low-energy ion irradiation.     

Effect of nitrate on corrosion of austenitic stainless steel in boiling nitric acid solution containing chromium ions

The oxidation behavior of chromium and the corrosion behavior of austenitic stainless steel in boiling nitric acid solution containing highly concentrated nitrates were investigated using UV-visible spectroscopic measurements, Raman spectral measurements, immersion tests, and potentiodynamic polarization measurements. The oxidation rate measurement of chromium from Cr(III) to Cr(VI) was performed by 1 M boiling nitric acid solution containing each highly concentrated nitrates: Al(NO₃)₃, Nd(NO₃)₃, Ca(NO₃)₂, Mg(NO₃)₂, and NaNO₃ as a simulant of uranium nitrate in uranium concentrator in reprocessing plants. As a result, the rate of chromium oxidation was different depending on the added nitrates even at the same nitric acid concentration. In addition, the oxidation rate of chromium was increased with increasing the calculated partial pressure of nitric acid in consideration of the hydration of cation of nitrates. Furthermore, the corrosion rate of type 310 stainless steel was accelerated by the solution having a high chromium oxidation rate containing nitrates. These results indicated that the acceleration of the corrosion rate in the solutions depending on the oxidation rate of chromium, and the rate is affected by the salt-effect of nitrates.     

High dose radiolysis of aqueous solutions of chloromethanes: Importance in the storage of radioactive organic wastes

The radiolysis of aqueous solutions of chloromethanes (dichloromethane, CH₂Cl₂; chloroform, CHCl₃; and carbon tetrachloride, CCl₄) was performed with γ-rays to doses sufficient to completely decompose the solute in order to estimate the effects of radiation on the long-term storage of mixed waste in enclosed containers. One of the main relevant products was the inorganic chloride anion, which increased in concentration with increasing radiation dose due to the reactions of radiolytic decomposition products of water with the chloromethane. The pH of the solutions was observed to decrease with irradiation due to the formation of H₃O⁺ as the counter ion to Cl⁻, i.e. the main radiolytic decomposition product is hydrochloric acid. Polymer formation was observed in aerated solutions as a precipitate while deaerated solutions exhibited a slight turbidity.     

On the solution and migration of single Xe atoms in uranium dioxide - An interatomic potentials study

Atomic scale simulation techniques based on empirical potentials have been considered in the present work to get insight on the behaviour of single Xe atoms in the uranium dioxide matrix. In view of the high activation energies commonly observed for Xe migration, this work has focused on the so-called “static calculations” (i.e. energy minimization based calculation) of incorporation and migration energies of Xe in UO₂, using empirical interatomic potentials to describe atom interactions. A detailed study of these results enables to determine the solution and the migration properties of Xe in the different stoichiometry regimes, and can be applied as well for the in-pile behaviour of xenon.     

Electrical ignition sources in nuclear power plants: statistical, modelling and experimental studies

Electrical ignitions of fires in nuclear power plants (NPPs) were studied by analysing statistical information from both nuclear and non-nuclear installations, modelling the most common simple physical ignition processes, and finally carrying out experiments on some of the modelled scenarios. Statistical assessment indicated cables to be a significant cause of electrical ignitions in all kinds of installations. Modelling of some relevant scenarios of cable fires and carrying out a number of experiments gave quantitative information on the circumstances and physical processes of the dangerous cable ignition situations.     

On the velocity dependence for negative ionization of atoms sputtered from cesiated surfaces: An experimental study

The experiments here reported were performed to study the velocity dependence of the negative ions M⁻ ejected from a metal M when the surface work function is lowered by adsorption of cesium atoms.The decrease in the work function induces very similar exponential increases for all initial energies. The measured variations, reaching 3 to 5 orders of magnitude, are attributed essentially to variations of ionization probabilities. Thus the velocity dependence, predicted by theoretical studies derived from the initial work of Blandin et al. could not be established for the negative metallic ions. Besides, some other investigated ion species, H⁻, P⁻ and O⁻, experience more direct velocity dependent ionization processes. Chemical bonds may alter the ionization process. In all cases, the ionization process can still be attributed to an electron attachment on an acceptor level of the ejected particle. However, multielectronic transitions or electronic excitations during the ejection have to be considered. Such an approach has been proposed by Sroubek for positive ion emission.     

Analyses of organics in irradiated aqueous N, N-diettiyihydroxylamine solution

The organics in γ-ray irradiated aqueous N, N-diethylhydroxylamine （DEHA） solution, which is used as a reducing agent in reprocessing spent nuclear fuel, were analyzed with gas chromatography equipped with FFAP capii- lary colunm and flame-ionization detector. It was found that irradiated DEHA solutions contained acetaldehyde, ethanol, and acetic acid. For DEHA of 0.2 mol/L irradiated to 10-1000 kGy, the concents of acetaldehyde, ethanol and acetic acid are （9.7-18.7）×10^3, （0.4-23.4）×10^3 and （6.5-11.7）×10^3 mol/L, respectively. The concentration of DEHA decreases obviously with the dose.     

LBE-water interaction in sub-critical reactors: First experimental and modelling results

This paper concerns the study of the phenomena involved in the interaction between LBE and pressurised water which could occur in some hypothetical accidents in accelerator driven system type reactors. The LIFUS 5 facility was designed and built at ENEA-Brasimone to reproduce this kind of interaction in a wide range of conditions. The first test of the experimental program was carried out injecting water at 70 bar and 235 °C in a reaction vessel containing LBE at 1 bar and 350 °C. A pressurisation up to 80 bar was observed in the test section during the considered transient. The SIMMER III code was used to simulate the performed test. The calculated data agree in a satisfactory way with the experimental results giving confidence in the possibility to use this code for safety analyses of heavy liquid metal cooled reactors.     

An experimental study of the rigidity of perforated plates

An experimental study of the effective rigidity of perforated flat plates is described, which forms part of a general study of perforated plates with particular reference to concrete reactor pressure vessels. Consideration is given to circular perforations on an equilateral triangular grid pattern, the perforation being unstiffened. The experimental results are compared with previous theories and with a new analytical approach based on a “thick cylinder” analogy.     

吲哚荷尔蒙自由基脉冲辐解光谱及其酸基平衡和还原电位性质研究

The Absorption spectral, acid-base equilibrium potential properties and formation and decay kinetics of four kinds of radicals from natural existing indole hormones were studied by pulse radiolysis.One of the most important properties for these four indolyl hormones, melatonin, 5-methoxygramine (MTA),5-methoxy-N, N-dimethylthytrytamine (DMM TA) and 5-methoxy-N, N-diethylthytrytamine (DEMT A), which are involved in biochemical processes and play crucial roles in many neuropathy and cancer related diseases, is their facile one electron oxidation with formation of radical cations or their conjugated base, the indolyl radicals.Formation kinetics and properties of the radicals were investigated by pulse radiolysis using the Linac accelerator with fast time-resolving optical system in UTNL.In the present study, these radicals were generated through oxidation of the corresponding hormone with azide radical in radiation induced process. Their spectroscopic properties were investigated and it was found that the transient spectra in all these cases exhibit similar absorption and pH dependence: in acidic solution, the radicals are characterized with three absorption maxima around 320-350, 440-460, 520-550nm. The spectra of MTA at various pH were shown as an example. From the absorption changes as a function of pH, two pK values were determined to be around 5 and 9 for the indolyl radicals except for melatonin, in which, only one pK was distinguished to be 4.4. Formation kinetics of the radicals was measured by following the growth of their absorption peaks and it was found that these indolyl derivatives transfer an electron to N3, with different rate constants, i.e.1.2×1010, 4.5×109, 4.9×109, 1.6×109 dm3 mol-1 s-1 for melatonin, MTA, DMMTA, and DEMTA, respectively.Reduction potentials of the radicals vs their molecules were also determined and they are dependent on the pH of medium. At pH 7, the reduction potentials were estimated to be 1.10, 1.18, 1.18, 1.20eV for melatonin, MTA,DMMTA and DEMTA, respectively. Because of its relatively high contents in human brain cells, melatonin is the main antioxidant among hormones against the oxidizing species in brain cells.     

The spectral, acid-base equilibrium and reduction potential properties of indole hormone radicals ： a pulse radiolysis study

The Absorption spectral, acid-base equilibrium potential properties and formation and decay kinetics of four kinds of radicals from natural existing indole hormones were studied by pulse radiolysis.     

First results of an experimental study of the residual activity induced by high-energy uranium ions in steel and copper

First results of an experimental study of the residual activity induced by high-energy uranium ions are presented. As a preparatory work for constructing the FAIR facility at GSI, samples of stainless steel and copper were irradiated by 500 MeV/u ²³⁸U ions and investigated by gamma-ray spectroscopy. The isotopes that contribute dominantly to the residual activity have been identified and their contributions have been quantified. Depth-profiles of residual activity of individual isotopes have shown that target activation due to projectile fragments and neutrons extends far beyond the range of primary particles and reaches the same level as in the region irradiated by primary particles.     

Stability constants of nitrate complexes of trivalent plutonium in aqueous and tributyl phosphate solutions

The extractability of nitrate complexes of trivalent plutonium from an aqueous phase at various concentrations was investigated. It was shown that tributyl phosphate (TBP) will extract trivalent plutonium from nitric acid solutions in the form of Pu(NO₃)₃. TBP at nitrate ion concentrations up to 1.2 M. Under the conditions studied, the distribution coefficient of trivalent plutonium depended very little on the concentration of hydrogen ions. The stability constants of the complexes Pu(NO₃)₃ · 3TBP, Pu(NO₃)₃, Pu(NO₃) ₂ ⁺ and Pu(NO₃)²⁺ were determined and equaled 0.75 ± 0.1; 14.4 ± 0.8; 14.3 ± 0.8 and 5.9 ± 0.5.     

Alpha induced reactions on Cd and Cd: An experimental study of excitation functions

Excitation functions of alpha induced reactions on enriched ¹¹⁴Cd and ¹¹⁶Cd targets, leading to the formation of the ^117m,119mSn, ^{114m₁,115m,116m,117m,g}In, ^115gCd isotopes, were studied by the stacked foil activation technique. Reaction cross-sections were measured from their respective thresholds up to E_α = 38.9 MeV. Quantification of induced isotopes has been made by gamma and X-ray spectrometry. The experimental cross-sections are compared, where available, with values reported previously in literature. Thick target yield for the medically important radionuclide ^117mSn is calculated based on discrete values of measured cross-sections.     

X-ray radiolysis induced formation of silver nano-particles: A SAXS and UV-visible absorption spectroscopy study

We show that X-ray irradiation of metal salt aqueous solutions in the absence of any stabilizer leads to the synthesis of metal nano-particles, similarly to γ-ray irradiation. The chemical route is the reduction of silver metal ions induced by radiolysis of water. Moreover, X-rays used for the synthesis allow following in situ the formation of silver nano-particles by Small Angle X-ray Scattering associated with UV-visible absorption spectroscopy. The synthesized nano-objects appear spherical with a radius of about 14 nm.     

水峰抑制(WEFT)技术在~1H NMR中研究糖类化合物的变旋现象

在FX-100型核磁共振仪器上,将WEFT技术用于观察糖类化合物六元环结构中与氧原子直接联结的C_1上的α、β构型质子峰高的变化,从中获取糖类化合物在水溶液中的变旋行为信息,得到α、β构型的平衡时间,以及最后平衡浓度α、β各占的百分比;通过变旋的动力学过程,跟踪了一般~1H NMR无法观察到的C_2位质子峰的化学位移。     

EB degradation of perfluorooctanoic acid and perfluorooctane sulfonate in aqueous solution

Electron beam (EB) degradation of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in aqueous solutions was studied.It suggested that PFOA and PFOS degradation followed the pseudo-firstorder kinetics,and degradation rates increased with increasing initial pH.Radical scavengers' experiments indicated that hydrated electron and hydrogen radical were important in the electron beam degradation of PFOA and PFOS,especially hydrated electron.The decomposition efficiencies were 95.7％ for PFOA and 85.9％ for PFOS,by EB irradiation in an anoxic alkaline solution (pH =13).The potential degradation pathways of PFOA and PFOS by electron beam irradiation through defluorination and the removal of CH2 unit were proposed.     

Fundamental aspects of the radiolysis of solid polymers, crosslinking and degradation

Possibly, the two most important processes in the radiolysis of polymers are crosslinking and degradation. This is true in both a fundamental and applied sense. In order to discuss these radiation induced processes, many of the fundamental, i.e. initial short lived events are considered. The techniques used are primarily rapid subnanosecond pulsed radiolysis with pulses of 0.4 mev electrons, and irradiation at low temperatures, coupled with spectroscopic techniques. In some instances it is instructive to compare and contrast the radiolytic data with similar studies using pulsed laser methods, where the energies are much less, while the resulting radiation induced processes are simpler.From a chemical view point, much can be gained from considering similar radiolytic process in simple liquids. In order to cover a reasonable gambit, the following three polymers, polyethylene, polyvinyl alcohol, and polystyrene, receive particular attention, and are compared to the radiolysis of hydrocarbons, alcohols, and alkyl benzene. Data on copolymers of the above are also reported, and compared to the radiolysis of comparable liquid mixtures.In a nutshell, the paper incorporates recent fast pulsed radiolytic, spectroscopic and laser studies to describe early radiation induced events in polymer systems. The discussion of mechanism also brings in data from other laboratories in this area of research.     

An experimental study on rewetting phenomena in transient conditions of bwrs

It is known that rod temperature rise after boiling transition (BT) is not excursive and that the peak cladding temperature (PCT) is suppressed by rewetting to return to nucleate boiling, even if BT occurs under severe conditions exceeding abnormal operational transients for a BWR. The purpose of this study is to develop and verify the rewetting correlation. The rewetting correlation was developed based on single rod data, as a function of quality, mass flux, pressure and heat flux. The transient thermal-hydraulic code used in the BWR design analysis (SCAT) with this rewetting correlation was compared with transient rod temperature result after the occurence of BT obtianed by the 8×8 and 4×4 rod bundle. It is concluded that the transient code with the developed rewetting correlation predicts the PCT conservatively, and the rewetting time well.