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In some reactors, ammonia and its radiolytic product (H2) are used to scavenge the oxidizing species (H2O2, O2, and •OH). A reducing chemical environment is thus created and the pH of the coolant is regulated simultaneously. In the present study, the radiolytic behaviors of deoxygenated ammonia solution were studied in the γ-ray field. The impacts of N2 pressure, gas-liquid volume ratio, and temperature on deoxygenated ammonia solution radiolysis were investigated. The pH and the concentrations of residual ammonia, H2, and nitrogen oxides (NO2- and NO3-) were analyzed. The results revealed that the variation of N2 pressure (0.5~5.0 MPa) and gas-liquid volume ratio had no influence on the concentrations of residual ammonia and nitrogen oxides. NO2- and NO3- concentrations were approximately 1 mg/L at room temperature when the absorbed dose was 28.8 kGy. However, the apparent concentration of H2 significantly decreased with the N2 pressure and gas-liquid volume ratio. The loss fraction of ammonia considerably declined from 26.5% to 8.4% when the temperature increased from 25 to 200 ℃, demonstrating that the radiolysis of ammonia was suppressed at the elevated temperature. However, the concentrations of NO2- and NO3- increased to 34 and 3 times, respectively, at 200 ℃ compared to those at 25 ℃. In addition, a radiolysis model of ammonia-containing coolant was established in the present study. The maximum relative error between experimental data and calculation results at any temperature was 4.1%. The model was thereafter used to calculate residual ammonia concentration with the absorbed dose under different initial ammonia concentrations. The results revealed that it was necessary to replenish ammonia regularly when using it alone to inhibit oxidizing species.

Copper and copper alloys are widely used in the field of nuclear materials. The effects of aqueous solutions that have undergone copper ion radiolysis on the generation of H2O2, O2, and H2 must be considered for material corrosion control and hydrogen explosion risk assessment. In this study, a γ-radiolysis experiment of an aqueous solution containing copper ions was conducted to explore the effects of different absorbed doses, absorption dose rates, and Cu2+ concentrations on the generation of H2O2, O2, and H2. The results showed that with an increase in the absorbed dose (0-1.80 kGy), the concentrations of H2O2 and H2(g) firstly increased and then tended to stabilize under steady-state concentrations of 5.41×10-6 and 7.91×10-5 mol/L, respectively, whereas the concentration of O2(g) remained at 9.04×10-4 mol/L. The presence of Cu2+ enhanced the equilibrium concentrations of H2 and H2O2 by one and two orders of magnitude, respectively, which in turn promoted the generation of H2O2 and H2; however, it had a negligible effect on O2 generation. The equilibrium concentrations of H2O2 and H2 increased with an increase in the absorption dose rate. Specifically, when the absorption dose rate was increased from 1.40 to 46.93 Gy/min, the equilibrium concentrations of H2O2 and H2 increased from 4.56×10-6 and 1.78×10-5 mol/L to 2.46×10-5 and 3.81×10-4 mol/L, respectively, whereas O2 remained essentially unaffected within this absorption dose rate range. In addition, based on the kinetics of water radiolysis and two-film theory of gas-liquid mass transfer, we constructed a calculation model for the radiolysis of aqueous solutions containing copper ions. Compared with the experimental data, the absolute values of the normalized mean bias in the simulation results were mostly between 1% and 7%, with a maximum of approximately 24%, thereby demonstrating the effectiveness and correctness of the calculation model. Accordingly, the model was used to calculate the radiolytic behavior of an aqueous solution containing copper ions under C6+ ion irradiation, and the simulation results matched well with the experimental data reported in the literature, indicating that the model can be expanded to other applications.

In this study, the γ-radiolysis of boric acid-lithium hydroxide-ammonia coolant was investigated under different conditions, including boric acid concentration, absorbed dose, and absorbed dose rate. The concentrations of H2O2, NO2-, and NO3- were determined using UV-visible spectroscopy and ion chromatography. With an increase in boric acid concentration, the concentrations of H2O2 and NO2- in the coolant system did not change significantly within a pH range commonly used in pressurized water reactor operation. Specifically, the concentration of H2O2 varied from 9.28×10-5 to 1.07×10-4 mol/L, while that of NO2- changed from 0.9×10-5 to 1.5×10-5 mol/L. In contrast, the concentration of NO3- fluctuated significantly, ranging from 4×10-5 to 8×10-5 mol/L. With an increase in the absorbed dose (1-30 kGy), the equilibrium concentration of H2O2 and NO2- in boric acid-lithium hydroxide-ammonia system increased to 1.28×10-4 mol/L and 1.30×10-5 mol/L, respectively. Meanwhile, the concentration of NO3- did not change significantly (4×10-5 to 6×10-5 mol/L). The concentrations of the three radiolytic products were not significantly affected within the given absorbed dose rate range (1.27 to 18.86 Gy/min). Overall, this work provides valuable basic data for optimizing the new boric acid-lithium hydroxide-ammonia coolant system.

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]

γ-raysand pulse radiolysis of aqueous solutions of Ni2+ionsin the presence of polyacrylate (PA–) and 2-propanolleads to the formation of metastable species absorbingat 540 nm that are ascribed to “pink” oligomeric clustersof a few nickel atoms only. The molar absorption coefficient is evaluatedas ε540 nm= 3300 ± 300 L mol–1cm–1per Ni0atom. The successive stepsfrom the reduction of Ni2+into Ni+ions tothe formation of the pink clusters at 540 nm under conditions of complexationby PA–are investigated by pulse radiolysis. Theyield of the formation of pink clusters increases markedly with theirradiation dose rate, demonstrating the occurrence of the disproportionationof the [Ni+, PA–] complex after a singleelectron pulse. The reduction and nucleation mechanisms, includingrate constants, in competition with the back oxidation by protons,particularly at low dose rate, are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Radiolysis mechanism and radiolytic pathways of DAPhen were investigated. • Radiolysis of DAPhen is mainly through the cleavage of amide bonds and N C bonds. • HNO 3 enhanced the extraction and An/Ln separation performance of DAPhen after irradiation. • Radiolytic products of DAPhen were verified by DFT calculations to have extraction ability for U. The stability of organic extractant molecules against radiolysis is critical in the field of actinides and lanthanides (An/Ln) separations. In order to evaluate the radiolytic effects on the extraction performance, the solutions of N,N '-diethyl- N,N '-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) in n -octanol were subjected to γ-irradiation in the presence and absence of 3 mol/L HNO 3 aqueous phase. Et-Tol-DAPhen diluted in n -octanol was almost completely decomposed after irradiation and exhibits decreased extraction ability at an absorbed dose of about 384 kGy, along with the appearance of various degradation products. Et-Tol-DAPhen, which was diluted in n -octanol, was completely decomposed upon irradiation in the presence of 3 mol/L HNO 3 aqueous phase. However, it exhibited higher D U and SF U/Eu values than before irradiation, as well as degradation products that were also generated. The structures of some isomers of radiolytic products were investigated by density functional theory (DFT) calculations, the radiolysis pathways and products of Et-Tol-DAPhen extractants were obtained, and the radiolysis pathways and products of Et-Tol-DAPhen extractants was proposed. The radiolytic products mainly originated from amide bond and N C bond cleavage of side group substituents, and some resulted from interaction with n -octanol radicals generated during radiolysis. The presence of HNO 3 can inhibit the radiolysis of Et-Tol-DAPhen to a certain extent and cause enhanced extraction ability. Moreover, the DFT calculations reveal that the radiolytic products produced in presence of 3 mol/L HNO 3 aqueous phase also have efficient extraction performance towards UO 2 2+. The understanding of the radiolysis pathways and products of extractants, based on radiation chemical effects is expected to be helpful for developing new strategies for extractants with long-term performance. [ABSTRACT FROM AUTHOR]

Predicting the effects of coolant water radiolysis induced by neutron and gamma radiation in the International Thermonuclear Experimental Reactor (ITER) is important, as oxidizing species like O 2 and H 2 O 2 will corrode structural materials, increasing maintenance costs and potentially compromising safety. In this work, a new model has been developed, by modifying existing models, to evaluate the water radiolysis behaviors in different Primary Heat Transfer Systems (PHTSs) in ITER. The new model takes the circulation of coolant, and the combined gamma and 14 MeV neutron radiation into consideration. We recommend injection of about 5 cc H 2 under standard temperature and pressure (STP) per kilogram of H 2 O into the First Wall/Blanket (FW/BLKT) PHTS to both efficiently suppress water radiolysis and avoid problems caused by addition of excessive H 2 . [ABSTRACT FROM AUTHOR]