Post irradiation effect

Aqueous plutonium photochemistry is briefly reviewed. Photochemical reactions of plutonium in several acid media have been indicated, and detailed information for such reactions has been reported for perchlorate systems. Photochemical reductions of Pu(VI) to Pu(V) and Pu(IV) to Pu(III) are discussed and are compared to the U(VI)/(V) and Ce(IV)/(III) systems respectively. The reversible photoshift in the Pu(IV) disproportionation reaction is highlighted, and the unique features of this reaction are stressed. The results for photoenhancement of Pu(IV) polymer degradation are presented and an explanation of the post-irradiation effect is offered. 

Host irradiated polymers show a continuing change in properties for a long period after irradiation. These post-irradiation effects may be attributed to (1) trapped radicals which react slowly with the polymer molecules and with oxygen which diffuses into the polymer (2) peroxides formed by irradiation in the presence of air or trapped within polymers irradiated in vacuum or an inert atmosphere) and slowly decompose with formation of reactive radicals, usually leading to scission, (3) trapped gases in glassy and crystalline polymers which cause localized stress concentrations. 

The consequences of post-irradiation effects in polymer materials are progressive reduction in strength, cracking and embrittlement. Some reduction in these effects can be achieved by annealing of the trapped radicals, addition of appropriate... 

Figure 9. 77ie post-irradiation effect on the bending angle of polypropylene syringe barrel flange... 

Nguyen and Kausch [1984] found that the presence of phenyl groups in poly(styrene-co-acrylo-nitrile), SAN, protects PMMA in the blend, during radiolysis (Table 11.9). SAN and PMMA were dissolved in dimethyl formamide, 50- J,m-thick films were cast, and then dried under vacuum. Transparent bar specimens were compression-molded from the film. Mixing the polymers by co-precipitation from methanol resulted in opaque samples. Gamma irradiations were done in evacuated and sealed glass tubes, at a dose rate of 3 kGy/h. Comparison of freshly irradiated samples with irradiated and annealed ones showed the absence of any post-irradiation effects. 

Rivaton, A., Lalande, D., Gardette, J., Influence of the structure on the y-irradiation of polypropylene and on the post-irradiation effects. Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 2004, 222, 187-200. 

The mechanical degradation that arises after irradiation with y-rays has been shown to be independent of the conditions of irradiation (air or vacuum) [93]. The post-irradiation effects of oxygen dominate, which will lead to a drop in both the tensile strength, modulus of elasticity, and elongation over time. Table 52.6 gives some changes for isotactic... 

First, vitamin E scavenges free radicals propagating oxidation. It is hence not surprising to observe that it significantly reduces the post irradiation effects observed in UHMWPE. Kinetic curves in post irradiation phase always display the same characteristic shape with a maximal increase rate at the beginning of post irradiation (Figure 3.13). 

Vitamin E offers the possibility to trap residual radicals and avoid some post irradiation effects. However, it directly competes with crosslinking. It could be an interesting strategy for add vitamin E by an impregnation method in the crosslinked UHMWPE. 

E. Suljovrujic. Post-irradiation effects in polyethylenes irradiated under various atmospheres. Radiation Physics and Chemistry 89,43-50, August (2013). 

MetaHoelement complexes may be useful for the post-irradiation treatment of radiation injury, based on the observation that several of these compounds accelerate recovery of, among other things, lympho/hemopoiesis. Preirradiation Mn2(0)(DIPS)g increases the survival of y-irradiated mice (103). Treatment of mice that have been exposed to an LD q q dose of y-rays plus Mn2(0)(DIPS)g either 1 or 3 h after irradiation also increases survival, which supports the hypothesis that this compound is an effective radiorecovery agent (105). Again, this increase in survival may result from the resynthesis of radiation-depleted Mn-dependent enzymes that facHitate the recovery of immunocompetence and tissue repair, as reported for Cu(II)2(DIPS)4. 

Studies of the influence of irradiation on the kinetics of oxidation have been confined to post-irradiation work. In general, prior irradiation increases reactivity, although there are considerable inconsistencies in the enhancements obtained The effects can be derived from an increased surface area associated with the swelling voids produced in the metal by the irradiation, and can also probably arise to a lesser extent from chemical effects of the fission products. 

Picosecond pedestal, 143 Pin-hole camera, 128 Plasma channels, 112, 147, 148 Plasma defocusing, 84, 91 Plasma frequency, 166 Plasma index of refraction, 147 Plasma mirror (PM) technique, 194 Plasma wakefield acceleration, 172 Plasma wavelength, 166 Plasma-induced effects, 83 Polarization, 97 Polarization control, 87 Ponderomotive force, 170 Population inversions, 19 Post-irradiation spectroscopy, 156 Pre-pulse, 143 Propagation, 81 Protein, 102 Pump depletion, 151... 

Gray, R. and Stevenson, M.H. (1989a). The effect of post-irradiation cooking on the ESR signal in irradiated chicken drumsticks. Int. J. Food Sci. Technol. 24.447. 

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