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The radiolytic behaviors of aqueous ammonia solutions under γ-ray irradiation were investigated, focusing on several factors, including initial ammonia concentration, absorbed dose, and H3BO3 concentration. The main species including ammonia, H2O2, nitrogen oxides, and H2, were quantitatively analyzed. The results revealed the significant influence of the initial ammonia concentration on the radiolytic behavior of the aqueous ammonia solution. The existence of ammonia in the solution exhibited suppression of the concentrations of H2O2 and O2. Furthermore, the radiolysis of aerated aqueous ammonia solution led to the formation of nitrogen oxides (NO2− and NO3−). This process was driven by multiple oxidation reactions, in which O2 and ·OH played crucial roles. Interestingly, the addition of H3BO3 provided protection to ammonia during γ irradiation, while the concentration of H2O2 was increased. [ABSTRACT FROM AUTHOR]

In this work, the effects of the tungsten (W) converter and molybdenum target thickness on the 99Mo yield in the production of 99Mo via 100Mo(γ, n)99Mo photonuclear reaction were studied. The FLUKA program was applied to simulate the optimal size of the targets for the production of 99Mo under 50 MeV electron conditions, where the thicknesses of the W and Mo targets were 0.3 and 1.4 cm, respectively. The relative error between the calculation and the experimental results was less than 8%. The process of irradiating natural (natMo) and enriched (100Mo) molybdenum targets using electrons with a 1 mA average beam current was further simulated. The specific activity of enriched 100Mo is nearly ten times higher than that of natMo. The use of 100Mo targets also produces fewer radioactive impurities. This study provides a guidance on the size of W conversion and molybdenum targets, as well as the selection of molybdenum species, when producing 99Mo via photonuclear reaction. [ABSTRACT FROM AUTHOR]

A mathematical model of co-decontamination process (1A) containing U(VI), Pu(IV), Zr(IV), and Ru(III) was developed with a high-performance Iteration of Extraction Equilibrium (ITEE) algorithm. ITEE algorithm not only guarantees the positive solution set but also possesses better computational efficiency than L-BFGS-B and fsolve algorithms. This model was used to study the effects of the HNO3 concentration and the location of the feed stage on the extraction and decontamination efficiencies. The results show HNO3 is beneficial to the extraction of U, Pu, and Zr. More extraction stages boost the extraction of U and Pu into the organic phase. [ABSTRACT FROM AUTHOR]

Predicting the electrical corrosion potential (ECP) of type 304 stainless steel, the structural material of recirculation pipes in fusion power plants, is important because the growth rate of intergranular stress corrosion crack (IGSCC) of 304 stainless steel is closely related to ECP. In this work, a new model has been developed, by modifying existing models, to calculate the ECP of recirculation pipes in future fusion power plant. The calculation results indicate that merely injecting hydrogen cannot reduce ECP below EIGSCC if the dose rate exceeds a threshold, other assisted water chemistry controlling method is necessary. [ABSTRACT FROM AUTHOR]

The separation and recovery of U(VI) and Th(IV) from rare earths are very important to avoid environmental pollution. A functional fibrous hierarchically bimodal mesoporous silica (F-SiO-DP) as an high efficient adsorbent for selective adsorption of uranium and thorium, which had hierarchically bimodal mesoporous structure and specific surface area of ca. 474.1 m g, was prepared by post-modification method using 2,9-diamide-1,10-phenanthroline. The synthesized adsorbent was characterized by HR-TEM, SEM, FT-IR, N adsorption-desorption, TGA techniques, XRD and NMR spectroscopy. The effects of pH, contact time, initial U(VI) and Th(IV) concentration, temperature and the presence of competitive metal ions on U(VI) and Th(IV) adsorption behavior were studied in detail. The hierarchically bimodal mesoporous structure endows F-SiO-DP with faster adsorption rate, which can reach equilibrium within 10 min, as well as higher adsorption capacities for U(VI) and Th(IV) compared with unimodal mesoporous silica like MCM-41 functionalized with 2,9-diamide-1,10-phenanthroline. The maximum adsorption capacities reach 416 mg g for U(VI) at pH 5.0 and 277 mg g for Th(IV) at pH 3.8, which are much higher than most of previously reported mesoporous silica-based adsorbents. The selectivity coefficient of U(VI) and Th(IV) over Ce(III), Nd(III), Sm(III), Eu(III), Gd(III), Y(III) and Yb(III) is all larger than 9 at pH 3.8, indicating that F-SiO-DP possesses a good simultaneously selective adsorption performance for U(VI) and Th(IV). This work demonstrates that F-SiO-DP with hierarchically bimodal mesoporous structure has promising application in adsorption and separation of actinides from lanthanides, which is crucial to the environmental protection. [ABSTRACT FROM AUTHOR]

The oxidation processes of the radiation-generated, three-electron-bonded intermediates AcMet 2 [S∴S] + and AcMet [S∴Br] were investigated by pulse radiolysis via their reactions with tryptophan (TrpH). These intermediates were derived from N-acetyl-methionine amide ( N-AcMetNH 2) and N-acetyl-methionine methyl ester ( N-AcMetOMe). The bimolecular rate constant k of the reaction between each intermediate and l-tryptophan (TrpH) was measured. For N-AcMetNH 2, k for the reaction of AcMet 2 [S∴S] + with TrpH were 3.4 × 10 8 and 2.2 × 10 8 dm 3 mol −1 s −1 at pH = 1 and 4.5, respectively. For N-AcMetOMe, k for the reaction of AcMet 2 [S∴S] + with TrpH were 4.0 × 10 8 and 2.8 × 10 8 dm 3 mol −1 s −1 at pH 1 and 4.5, respectively. The rate constants for the intermolecular transformation of Met [S∴Br] into TrpH + or Trp were also estimated. For N-AcMetNH 2, k for the reaction of AcMet 2 [S∴Br] with TrpH were 2.6 × 10 8 and 3.3 × 10 8 dm 3 mol −1 s −1 at pH 1 and 4.5, respectively. Related mechanisms were discussed. [ABSTRACT FROM AUTHOR]

Transient radicals (hydrated electron, (SCN)[sub 2][sup .-] and CO[sub 3][sup .-]) formed in supercritical water have been observed by the pulse radiolysis technique. The change of spectra of these radicals with temperature has been measured. It was found that the spectra and absorption coefficients of the radicals, e[sup -][sub aq] and (SCN)[sub 2][sup .-], are strongly dependent on the temperature of the water. Since it was found that the absorption spectrum and molar absorption coefficient of CO[sub 3][sup .-] radical seem to be almost independent of temperature, G-values of OH and e[sup -][sub aq] could be derived. Then, the absolute values of the absorption coefficients for the radicals could be calculated. The G-values of the radical products in water radiolysis tend to increase with increasing temperature up to 400°C. Based on the above observation, radiolysis of supercritical water is discussed. [ABSTRACT FROM AUTHOR]