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Validation of the Radiation Sterilization of Pharmaceuticals
Published in James Agalloco, Phil DeSantis, Anthony Grilli, Anthony Pavell, Handbook of Validation in Pharmaceutical Processes, 2021
In some cases, radiolysis may be reduced by use of electron beam irradiation rather than gamma irradiation (Slegers and Tilquin, 2006). Here, dose rate may be an important factor. Although there is no general rule, many drugs show less breakdown at the higher dose rate, that is, with electron beam irradiation. This may be because of consumption of all the oxygen (which generally increases radiation damage), with sterilization being completed before oxygen can be replenished; and possibly because of too short a time for production of long-lived free radicals that may increase radiation-induced damage. On the other hand, the high dose rate could in some cases cause increased damage because of the “high concentration” of gamma photons close to the substrate.
Polymers and Their Composites for Water-Splitting Applications
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Tariq Altalhi, Polymers in Energy Conversion and Storage, 2022
Zahra Pezeshki, Zahra Heidari, Mashallah Rezakazemi, Mohammad Younas
Radiolysis can be used as a process to break down water into H2 and O2 gases with the help of fuel or nuclear waste. This process is divided into three stages: physical, physico-chemical, and chemical. During this process, water goes through a breakdown sequence into hydrogen peroxide, hydrogen radicals, and assorted oxygen compounds, such as ozone, which when converted back into oxygen releases great amounts of energy (Figure 17.28) [143,144]. Some of these releases are explosive. This decomposition is generated mostly by the α particles, which can be thoroughly absorbed by very thin layers of water. The radiolysis reaction can be written as: H2O→HO•.H•.HO2•.eaq−.H3O+.OH−.H2O2.H2
Ionizing Radiation
Published in Martin B., S.Z., of Industrial Hygiene, 2018
When ionizing radiation deposits energy in living tissue, it causes ionization of the atoms in the molecules composing that tissue. Direct radiation damage occurs when molecules are modified by the direct action of radiation. Indirect damage occurs when important molecules or structures are damaged by radiolysis products such as free radicals.
Optimization of dissolved hydrogen concentration for mitigating corrosive conditions of pressurized water reactor primary coolant under irradiation (1) evaluation of water radiolysis
Published in Journal of Nuclear Science and Technology, 2023
Kuniki Hata, Satoshi Hanawa, Yasuhiro Chimi, Shunsuke Uchida
Water radiolysis calculations have been conducted in each organization and NPP vendor [6–8]. For this objective, several data sets on chemical reactions were developed in each organization [6–9]. WRAC-J, which is one of the water radiolysis calculation programs, has been developed by Japan Atomic Energy Agency for BWR water chemistry with suitable G-value (chemical yields of species) and reaction constant sets [7]. Water radiolysis is affected by temperature, radiation dose rate, radiation qualities (neutrons, γ rays, and α rays), pH, and hydrogen concentration. Water temperature (285°C), energy depositions due to neutrons and γ-rays, and neutral pHR (room-temperature pH) (6.5–7.5) were major parameters of the water radiolysis in BWRs, whereas temperature (about 290°C), energy depositions due to α-rays resulting from 10B(n, α)7Li reaction, neutrons, and γ-rays, and high pHT (7.2–7.4) were major parameters in PWRs [6,10–12]. In this study, we applied the WRAC-J code to calculate PWR primary coolant conditions (higher pHT and temperature) by implementing the effects of α-rays.
Fit-for-purpose urban wastewater reuse: Analysis of issues and available technologies for sustainable multiple barrier approaches
Published in Critical Reviews in Environmental Science and Technology, 2021
Molecular exposure to a high energy flux of ionizing radiation causes cleavage of chemical bonds (radiolysis). Applied to water solutions, radiolytic processes split water molecules generating, in addition to a wider range of stronger oxidants than other AOPs (·HO, ·H, H2O2, H3O+), also strong reducing compounds (O−2, e−(aq)). Therefore, they combine the capabilities of AOPs and ARPs in a single process step. All these reactive species have half-life in the order of 10 μs (at 10−4 M concentration), with practically instantaneous degradation of a wider range of solute molecules compared to individual AOPs and ARPs (Capodaglio, 2017c). Radiolysis-based processes constitute a particular subclass of Advanced Oxidation Reduction Processes (AORPs) (Khan et al., 2019). Table 6 shows the comparative oxidation and reduction capacity of radicals generated by AOP, ARP and AORP methods and of other common oxidants. The advantage of AORPs is the speed of reaction kinetics, which is practically instantaneous (∼10−4 s) and thus does not require large process units. From the energetic point of view, EB-based systems are characterized by high energy transfer efficiency, with EEOs (Electric Energy per Order, a process yield efficiency parameter) lower or similar to other AOPs (Trojanowicz et al., 2017).
Re-evaluation of Radiation-Energy Transfer to an Extraction Solvent in a Minor-Actinide-Separation Process Based on Consideration of Radiation Permeability
Published in Solvent Extraction and Ion Exchange, 2021
Tomohiro Toigawa, Yasuhiro Tsubata, Takeshi Kai, Takuya Furuta, Yuta Kumagai, Tatsuro Matsumura
There are several well-established chemical dosimetry methods based on the metal redox reactions caused by the radiolysis products, such as the Fricke dosimeter. The dosimeters have been typically employed for the previous radiation-stability studies, but they were limited to evaluating for external radiation. Such methods could not be applied for a solution containing dissolved radionuclides. Indeed, in the solvent extraction system containing a mixture of aqueous and organic phases, dosimetry is difficult to perform. Therefore, the dose absorbed by the extraction solvent in a real MA-separation process has been evaluated analytically.[5,6] A typical procedure for such evaluation is as follows: (i) prepare concentrations of the radionuclides in the feed solutions, with considering fuel burn-up, cooling time, dissolution in acidic solution, and the pre-existing separation steps for the given process (i.e., uranium reprocessing in relation to the MA-separation process); (ii) distribute the radionuclides in the extraction solvent (organic phase) or the feed solution (aqueous phase) according to the extraction property for each nuclide in the process; (iii) obtain the energies classified according to the type of radiation (i.e., alpha, beta, and gamma radiation) with reference to the radioactive decay of each nuclide; and (iv) simulate the radiation-energy transfer to the extraction solvent for each radiation type. The calculation methods of (i)–(iii) have been previously addressed, and the former analyses suggest that the absorbed dose strongly depends upon the fuel-condition settings of the burn-up and cooling time after discharge.[5,6] However, regarding (iv), the effects of the permeability of radiation have yet to be fully evaluated where the extraction solvents are likely to receive radiation energy from radionuclides in the contacting aqueous solutions and vice versa.