Radiation chemistry of polymers

Results of basic and applied research in radiation chemistry of polymers in Russia and Belarus for the last 5–10 years are presented.     

Radiation chemistry of actinides

The paper presents data on the development of a mathematical model describing the radiation-chemical behaviour of plutonium in 3–6 mol/l HNO₃ with uranium present and absent. Using experimental data on the kinetics of Pu(VI) reduction and Pu(IV) oxidation, and comparing them with the calculated values, we succeeded in finding the previously unknown rate constants of many reactions between plutonium ions and HNO₃ radiolysis products, between plutonium ions and between plutonium ions and uranium ions. The mechanism of the radiation-chemical processes has been established.     

Radiation chemistry education in Australia

A segment on radiation chemistry should be included in every course on nuclear science because of its unique role and its being relatively far removed from nuclear explosives. Experience of courses at different levels is outlined. Particular attention is given to the use of radiation chemical techniques in the training of postgraduate research students.Honorary AINSE Fellow, formely Post Retirement Fellow, ANSTO Isotope Technology.     

Radiation chemistry and the nuclear fuel cycle

A global collaboration is currently developing solvent extraction separations for the nuclear fuel cycle of the future. The goal is to recover fissionable material for recycle, mitigate proliferation concerns, and mitigate the environmental impact of nuclear waste disposal. Relying on selective metal complexing agents, the radiation stability of these solvent extraction ligands will determine the efficiency and recycle lifetime of any solvent intended for use in this high-radiation environment. This paper reviews work at the Idaho National Laboratory regarding the radiation chemistry of nuclear solvent extraction ligands, with particular emphasis on the reactions of nitrogen-centered radicals.     

Radiation chemistry of poly(propylene oxide)

Atactic, isotactic, and optically active poly(propylene oxides), PPOx, were irradiated with both γ-rays and electron beams. Up to a dose of 37 Mrad no change could be detected in the optical activity. G values for hydrogen evolution decreased as compared to polypropylene in about the same ratio as G(H₂) of polyoxymethylene decreased as compared to polyethylene. G values for crosslinking and scission, estimated by means of gelation theories of Saito and Inokuti, were found to be greater for isotactic than for atactic PPOx. The behavior of transient infrared and ultraviolet absorption bands is discussed. Intrinsic viscosity data indicate a rapid initial chain degradation whereas CO gas and OH group production is linear with dose. Evidence for the conversion of one type of free radical to another on heating an irradiated sample from 77°K to room temperature is based on the behavior of transient infrared and ultraviolet absorption bands.     

Radiation chemistry of the gamma-irradiated carbon tetrachloride-benzene system

Summary In order to study the radiation chemistry of the γ-irradiated carbon tetrachloride-benzene system, irradiation products were identified by GC/MS and their quantities were relatively estimated by GC at different molar ratios and dose rates of reactants. The mechanism of formation of the main products was suggested. It was found that the yield of chlorobenzene depends linearly on the dose up to 234 kGy.The radiation chemical yield (G-value) of this product was determined to be 55 ^. 10^-3 μmol ^. J^-1.     

Radiation centre of institute of physical chemistry in Moscow

Radiation centre of the Institute of Physical Chemistry of Russian Academy of Sciences (Moscow) is described. It has four ⁶⁰Co γ-ray sources and four electron accelerators, three of them being linear ones. The brief consideration of researches and developments in radiation chemistry and radiation processing is conducted.     

Radiation chemistry of smart polymers (A Review)

Radiation chemistry methods used to prepare smart polymers are surveyed. The properties of these polymeric materials are considered. The benefits of radiation-chemical procedures for manufacturing smart polymers are discussed. The areas of their practical use are outlined     

Shock-initiated decomposition of tetramethylgermane and the reaction of methyl radicals with toluene

The shock-initiated decomposition of tetramethylgermane (1078–1242 K) has been found to involve successive elimination of methyl radicals with the rate constant k₁ for the first step given by In the presence of excess toluene the products were CH₄ (major), C₂H₄, and C₂H₆. Results relevant to the reaction of methyl radicals with toluene compared to methyl radical recombination are discussed.     

Radiation chemistry of xylenol orange in aqueous solutions at different acidities

The radiolytic decolourization and peroxide formation have been studied in aqueous solutions of xylenol orange (XO) at different acidities. The G(-XO) increases from 0.78 at pH 11, to 3.70 at pH 3. The peroxide yield also increases from 1.19 at pH 11, to 3.34 in 0.025 mol dm^-3 H₂SO₄. In alkaline solutions only the OH^. decolourizes XO whereas in acidic solutions both the H and OH^. decolourize XO though G(-XO) due to H-atoms is less. The ionization of the phenolic group in XO influences the e^-_aq reaction with it. In alkaline solution, the oxidized and reduced XO formed by OH^. and e^-_aq reactions, respectively, react together regenerating original XO. Near 0.025 mol dm^-3 H₂SO₄, there is an abstraction of H-atom from XO by HO₂ whereas at other acidities, H₂O₂ is formed by disproportionation of peroxides. Reaction schemes have been given to explain the various radiolytic yields.     

Radiation chemistry of Cu(II) tetrasulfophthalocyanine in water-methanol system

The effect of ionising radiation on copper(II) phthalocyanine 3,4′,4′′,4′′′ tetrasulfonic acid, tetrasodium salt (Cu(II)tspc^4-) in aqueous as well as in water-methanol solutions has been studied. The determined yields of complex decomposition (measured on the basis of absorption decay) depend on the composition of matrices and the dose applied. The rate constant of electron scavenging by Cu(II)tspc^4-, k = (1.3 ± 0.1) × 10¹⁰ M^-1 s^-1 in methanol-water (2:8 v/v) solutions has been determined using the pulse radiolysis technique. The rate constant k = (1.16 ± 0.1) × 10¹⁰ M^-1 s^-1 of scavenging of OH radicals applying the competion method with p-nitrosodimethylaniline (pNDA) has been determined in aqueous solutions.     

Radiation chemistry of aqueous iodine systems under nuclear reactor accident conditions

Radiation-chemical behavior of cesium iodide solutions was investigated using a once-through flow system in relation to the behavior of radioactive iodine under the condition of nuclear reactor accidents. It was found that several factors such as initial concentration of CsI, pH and O₂ concentration have a large influence on the oxidation-reduction reactions in the radiolysis of the iodide solutions. A pulse radiolysis technique was applied to this system to obtain clearer understanding of the radiolysis mechanism, and the rate constants were measured with the several important reactions involved.     

Radiation chemistry of polysaccharides: 4. Free-radical mechanisms of formaldehyde formation

Based on an analysis of author’s experimental results and published data on the radiolysis of polysaccharides, three main reaction paths of CH₂O formation related to the transformations of primary radicals with unpaired electrons on C1, C5, and C6 atoms were revealed. The formaldehyde molecule was formed in the primary event of C5 radical conversion or through the steps of formyl radical formation in the other two cases.     

Radiation chemistry of aqueous poly(ethylene oxide) solutions. I

The γ radiolysis of aqueous high molecular weight poly(ethylene oxide) solutions has been studied. The crosslinking and eventual gelation of these solutions appears to occur via an indirect effect. Solubility measurements on the gelled solutions showed that the ratio of crosslinking to degradation is about four. G(H₂) increased from 1.3 in neutral solutions to 3.5 in 0.1N HCl solutions. In heavy water solutions, HD is the major gaseous product. Solvated electrons are not important precursors to hydrogen at neutral pH. Intramolecular crosslinking appears to be an important phenomenon in solutions of high molecular weight polymers.     

Radiation protection relevant to nuclear chemistry in the light of recent international recommendations

The paper discusses the requirements for radiation protection in nuclear chemistry which are related to the recent recommendations of the International Commission on Radiological Protection. These recommendations have been incorporated into the updated International Basic Safety Standards issued by the International Atomic Energy Agency as well as into new relevant Directives of the European Union based on which the legislation of the EU Member States has to be updated. The new international requirements are aimed at the further improvement of strict control of radiation sources, their safety and security as well as the minimization of exposure to workers and members of the public. It would be appropriate for the nuclear chemistry community to become familiar with the changes in radiation protection so that it would be easier for nuclear chemists to adopt new requirements in their everyday practical work.