Radiolytic oxidation irradiated

In support of the development of graphite moderated reactors, an enormous amount of research has been conducted on the effects of neutron irradiation and radiolytic oxidation on the structure and properties of graphites. The essential mechanisms of these phenomena are understood and the years of research have translated into engineering codes and design practices for the safe design, construction and operation of gas-cooled reactors. 

A second example is the decomposition of methanol over zinc oxide irradiated with y-rays 120). The enhanced rate of decomposition was said to anneal out rapidly when irradiation was stopped, but the extent to which catalysis is responsible would be more certain if the decay had been measured. The value of the yield also speaks for catalysis rather than radiolysis, because it was about 4 x 10 molecules decomposed per 100 ev absorbed by the total system, an impossibly high number for a nonchain radiolytic process. Since the reaction involved is spontaneous at 400°, there is no requirement for a nonthermal source of energy. 

The radiolytic oxidation of porous reactor moderator graphite in C02 represents another effect induced by neutron irradiation in which the radiation-induced formation of structural defects is proposed to play an important role [245]. It has, however, been demonstrated that neutron irradiation also affects the electronic properties of various carbons [246] and one interpretation placed on such effects was that a dose of 1 neutron per cm2 created four electronic holes in the valence band per cm3. The... 

Radiolytic oxidation of Cr "-porphyrins in alkaline solutions also led to the formation of oxo-Cr -porphyrins. Further irradiation led to production of oxo-Cr -porphyrins. Pulse radiolysis studies indicated that Cr P under all conditions is oxidized first to the 7r-radical cation, Cr P-. This radical cation is unstable in aqueous solutions and undergoes disproportionation, but in CH2CI2 it is stabilized by the HCl (produced by fixe radiolysis). The radical cation was further oxidized by irradiation and the product was suggested to be a dication, Cr p2, also stabilized by the HCl. Furthermore, it was found that addition of base to Cr P converts this species into Cr P, and the process can be reversed by the addition of acid. 

The oxidative degradation of isotactic PP in the presence of air (as well as the postradiation oxidation) takes place frequently in industrial irradiation processes. The estimation of peroxy radicals, formed as a direct product of radiolytic oxidation reactions between oxygen and carbon-centred free radicals, is very useful in understanding the oxidation process. The application of electron spin resonance (ESR) is a practical method to follow the quantitative effect of this process [2],... 

In the experiments reported by Lucas (1985) the influence of additives to the solution and the gas phase on radiolytic oxidation of 1 was studied. At a composition of the test solution which was claimed to be quite similar to that assumed for the containment sump water, irradiation was carried out using a dose rate of 4 kGy/h. The results showed that in a closed vessel an h saturation concentration is reached at an integrated radiation dose of about 60 kGy the presence of CO2 in the gas phase resulted in an increase of the saturation level to about 20% I2 formation, while the presence of H2 did not significantly affect the results. By contrast, in an open system where I2 evolved from the test solution was trapped in a NaHCOs solution, no saturation I2 yield was obtained under such conditions, the I2 yield increased linearily with the dose rate, reaching about 55% at an integrated radiation dose of 0.24 MGy. 

Chemical interaction between fuel and cladding, or between coolant and cladding or structural materials, must be limited to a level giving an acceptably low probability of fuel element or plant component failure. The normal problems of chemical compatibihty are increased by the effect of irradiation in enhancing the rate of chemical attack. The radiolytic oxidation of graphite in a C02-cooled reactor, for example, raises problems of graphite erosion and mass transport to cooler regions of the primary circuit. 

Zhang, P, Song, C.L., Liang, J.F., Xin, R.X. 2003. Identification of radiolytic degradation products of y-irradiated 30% trialkylphosphine oxide-kerosene solution. Solvent Extr. IonExeh. 21 (1) 91-108. 

Phenothiazine radicals have been generated in various radiolytic experiments. Pulse radiolysis of phenothiazine in aerated cycloalkane solutions gives rise to phenothiazinyl (251). ° The mode of oxidation is believed to involve abstraction of H from the heterocycle by cycloalkylperoxyl radicals. Under similar conditions, 10-methylphenothiazine gives 261. Pulse radiolysis of phenothiazine in acetonitrile has also been documented. The reduction of phenothiazine dyes under radiolytic conditions has been reported. Several years ago, Ayscough and Thomson obtained paramagnetic products from X-irradiation of acid alcoholic solutions of Methylene Blue and other thiazine dyes. Low-resolution ESR spectra of the corresponding cation-radicals were recorded. 

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