Pre-irradiation Dose Research Articles

Preparation of perfluorinated ion exchange membranes and their application in acid recovery

The preirradiation grafting of crosslinked sulphonated styrene monomer (CSS) and a crosslinked aromatic monomer (ARM) onto ethylene-tetrafluoroethylene (ETFE) film was studied. The dependence of the grafting reaction on temperature, concentration of monomer, crosslinking agent, concentration of inhibitor and on the preirradiation dose was investigated. Interaction between monomer diffusibility and the viscosity of the monomer bath controls the grafting reaction. Other factors such as the mutual reactivity of monomer and crosslinking agent contribute to explaining the results of the grafting reaction. The properties of some membranes were also determined. The application of these membranes to acid recovery by dialysis, electrodialysis and electro-electrodialysis (EED) showed their excellent performance.

Investigation of post-radiation grafting of acrylamide onto polypropylene films

A study has been made on the post-radiation grafting of aqueous acrylamide (AAm) onto polypropylene films (PP). A good hydrogel supported on the polymer substrate was obtained by grafting of AAm onto preirradiated PP films. The effect of grafting conditions such as solvent and inhibitor concentration, preirradiation dose, monomer concentration and reaction temperature on the initial rate and grafting yield was determined. It was found that the addition of 0.05 wt% Mohr's salt into the reaction medium effectively reduced the homopolymerization of AAm and the grafting process was successfully achieved. The dependence of the initial rate of grafting on the preirradiation dose and AAm concentration was found to be of the order 1.3 and 1.7, respectively. Two overall activation energies for this grafting system were found: 31.1 and 13.5 kcal mol −1 below and above 35°C, respectively. Some selected properties of the prepared graft copolymer were investigated and the possibility of its practical use discussed.

Graft polymerization of styrene onto nylon 6 fiber by pre-irradiation in air.

Styrene was grafted onto nylon 6 fibers by a pre-irradiation technique in air. The effects of experimental conditions, such as the pre-irradiation dose, the irradiation intensity and the polymerization temperature, on the apparent percent graft as well as on the molecular weight and mole number of grafted polystyrene were investigated. The molecular weight of the grafted polystyrene was determined by the intrinsic viscosity measurement after the hydrolysis of the backbone in concentrated hydrochloric acid. An optimum irradiation dose was observed to attain the highest apparent percent graft and the highest molecular weight of grafted polystyrene. The molecular weight of grafted polystyrene decreased with the increase in the number of grafted polystyrene and the rise in the polymerization temperature, when compared at a fixed irradiation dose.

Radiation grafting of α,β,β‐trifluorostyrene onto poly(ethylene–tetrafluoroethylene) film by preirradiation method. I. Effects of preirradiation dose, monomer concentration, reaction temperature, and film thickness

AbstractPreirradiation grafting of α,β,β‐trifluorostyrene onto poly(ethylene–tetrafluoroethylene) film was studied. The trapped radicals formed upon irradiation were able to induce graft polymerization under appropriate conditions. The influences of the grafting conditions were analyzed kinetically. The grafting rate dependency on the preirradiation dose was found to be of order 0.3, and the monomer concentrations, 1.0. The overall activation energies for this grafting were calculated to be 6.2 × 104 and 9.3 × 103 J/mol below and above 50°C. The grafting rate was found to be independent of the film thickness, which ranged from 25 to 100 μm.

Effect of trunk polymer orientation on ionic vinyl monomer grafting reaction

Mono- and bioriented ethylene-vinyl alcohol (EVAL) copolymer films were grafted by means of the electron beam pre-irradiation method with the potassium salt of styrenesulphonic acid (SSKS). The influences of pre-irradiation dose, reaction temperature and monomer concentration on grafting degree were determined for EVAL films with different drawing orientations. The dependence of the initial grafting rate on these parameters was found to be influenced by the morphology of the trunk polymer. The inhibitory effect of tert-butyl catechol, ferric chloride and Mohr salt on homopolymerization, as well as on the grafting reactions, was followed. Promotion of grafting by sodium acetate was established. Film dimension changes, induced by grafting, revealed a significant influence of EVAL morphology on the location of SSKS grafted chains.

The effect of preirradiated tumour bed on the response of a murine fibrosarcoma to elevated temperatures.

The effect of pretransplantation irradiation of tumour beds (tumour bed effect or TBE) on the response of tumours to elevated temperatures and on the kinetics of thermo-tolerance was studied. Animal tumours were early generation isotransplants of a fibro-sarcoma, FSa-II in C3Hf/Sed mice. The tumour bed or murine foot was irradiated with 0.8 or 16 Gy in air, and tumour cell suspensions were transplanted 1-35 days thereafter. Hyperthermia of various durations was given in a 45.5 degrees C water bath when tumours reached an average diameter of 6 mm (110 mm3), and the tumour growth (TG) time to reach 500 mm3 was obtained. Dose-response curves between the TG time and the treatment time were less steep for tumours in preirradiated tumour beds than for tumours in non-irradiated tumour beds, indicating that the tumours in preirradiated tumour beds were more resistant to hyperthermia compared to the tumours in normal tumour beds. This resistance appeared to increase with increasing preirradiation dose. Thermotolerance was equally developed in tumours in normal and preirradiated tumour beds. The time required to develop the maximum thermotolerance was identical for both tumours. This indicated that the TBE has no effect on the kinetics of thermotolerance. The implication of these results in clinical trials may be that the tumour which recurred after radiotherapy may not be a good candidate for hyperthermia.

Synthesis of perm-selective membranes by grafting acrylic acid into air-irradiated Teflon-FEP films

Grafting acrylic acid into air-irradiated Teflon-FEP films was investigated. Pre-irradiation doses ranged from 0.5 to 10 kGy. Grafting occurred at 45 or 60°C. Homopolymerization inhibitors, ferrous ions or methylene blue, were added to the system. It was found that after completion of the reaction, within 40–100 min, membranes were obtained with very low electric resistivities. The influence of added inhibitors, pre-irradiation dose and grafting temperature was studied. From the results it is concluded that the initiating centers in air-irradiated Teflon-FEP are, on the one hand, peroxides of structure POOP′, in which P is a polymeric radical and Pprime; a small fragment, and on the other trapped PO . 2 radicals. The latter only react after losing their oxygen. In the presence of polymerization inhibitors, initiation involves a redox process which reduces the overall activation energy.

Gasification of different types of carbon in steam and carbon dioxide in the presence of γ-radiation

Studies have been made of the formation of H 2 and CO at temperatures between 20 and 500°C on reacting graphite, activated charcoal and semicoke with steam and carbon dioxide, respectively, in the presence of γ-radiation. The highest rates of H 2 and CO formation were observed on the gasification of semicoke. At 500°C, gas formation rates are W( H 2) − W( CO) = 2.0 × 10 13 molec/ cm 3 s for semicoke in steam and W( CO) = 1.37 × 10 13 molec/ cm 3 s for semicoke in carbon dioxide. Investigation has been made of the temperature of semicoke production from lignite and also of the effect of preirradiation dose on the rate of CO formation in the semicoke/CO 2 system. An increase in the semicoke production temperature from 500 to 700°C reduced its reactivity with carbon dioxide by a factor of 1.4. Preirradiation of the semicoke with 200 kJ/kg decreases the reactivity by a factor of 2.8. A discussion is given of the mechanism of the effect of γ-radiation on the gasification processes of different carbons in steam and carbon dixoide.

Radiation grafting of hydrophilic monomers onto poly(4‐methylpentene‐1), I. Grafting of acrylic acid

AbstractRadiation grafting of acrylic acid (AAc) onto poly(4‐methylpentene‐1) (TPX) with different crystallinity has been investigated under various conditions. Free radicals formed by pre‐irradiation of TPX in vacuum were more stable than those in the presence of air and might initiate the grafting reaction if come in contact with the AAc. Grafting yields increased with increasing preirradiation dose, grafting temperature, and concentration of AAc. Lower crystalline TPX (24%) showed a higher initial grafting rate compared with higher crystalline one. The distribution of grafting was observed by X‐ray microanalyzer. The grafting reaction proceeded gradually with time from the surface of the film to the inner part. In high crystalline TPX (34%) the grafting distribution in the final stage depended on the film thickness, while in lower crystalline TPX it was homogeneous regardless the film thickness.

Performance Characteristics of a High-Level Solid-State Personnel Dosimetry System in Pulsed Radiation Environments

The Health Physics Research Reactor at Oak Ridge National Laboratory was used to evaluate performance characteristics of a high-level, solid-state, personnel dosimetry system developed for the US Army for the rapid measurement of total (gamma plus neutron) radiation doses to soldiers in locations where tactical nuclear weapons could be used. The gamma sensitive element of the dosemeter consists of a silver-activated phosphate glass and the neutron detector is a silicon diode. Areas considered in this evaluation included pre-irradiation dose indication; accuracy and precision of gamma, neutron, and total dose measurements; time dependence; and temperature effects. Study results indicate that for doses above about 0.4 Gy, the system can provide rapid and accurate dose estimates within accuracy limits specified by several international regulatory and standards agencies for criticality accident dosimetry. However, theoretical and observed lower limits of detection for this system are somewhat higher than the 0.25 Gy minimum dose of interest for general accident dosimetry.

Evaluation of temperature effects in p-type silicon detectors

A theoretical investigation concerning sensitivity variations in semiconductor detectors used in the short-circuit mode at different temperatures and pre-irradiation dose levels has been compared with experimental results. Initially, a sensitivity drop of more than 15% kGy-1 and a sensitivity increase with temperature of less than 1% per 10 degrees C was found for p-type silicon detectors. After a pre-irradiation dose of 5 kGy with 20 MeV electrons these values were changed to about 6.5% kGy-1 and 3% per 10 degrees C, respectively. As a temperature rise of about 10 was obtained in the detector when applied to a patient, the change in sensitivity has to be taken into consideration when the detector is used in patient dosimetry.

Hydrophilization of polyethylene film by preirradiation method

The preirradiation method of radiation grafting has been employed to produce polyethylene (PE) films as hydrophilic materials. The effects of radiation dose, atmosphere of preirradiation and monomer concentration on the grafting of methacrylic acid and its salts (NH 4,K) on low density polyethylene have been studied. The degree of grafting increases with the dose of preirradiation, time and concentration of both acid and salt form of monomer. Irradiation in air leads to a higher degree of grafting than in N 2 or in vacuum. Hydrophilic properties of grafted polyethylene film expressed as an electric resistance have been found to depend on the degree of grafting and the type of monomers used. The PE film with 90–95% grafting of methacrylic acid has been found to have electric resistance lower than 1 10 2 mΩ·cm 2. The same conditions of grafting for the salt form give the film an electric resistance higher than 1 10 6 mΩ·cm 2.

Some investigations on the post radiation grafting of acrylamide onto polyethylene films

A study has been made on the post radiation grafting of aqueous acrylamide onto low density polyethylene film. It was found that the addition of 0.05 wt % Mohr's salt reduced effectively the homopolymerization of acrylamide and the grafting process was successfully achieved. The dependence of the grafting rate on the preirradiation dose and monomer concentration was found to be of 1.43 and 1.4 order, respectively. The overall activation energy for the graft polymerization was found to be 13.5 and 1.95 Kcal/mol below and above 45°C, respectively. Some properties of the graft copolymer such as swelling behaviour, electrical conductivity, and reverse osmosis desalination of saline water (water flux and salt rejection), were also investigated and the possibility of its uses in the practical applications was discussed.

The influence of regenerated thermoluminescence on low-dose dosimetry.

The contribution of regenerated thermoluminescence to low doses is studied for the case of CaF2-Dy (TLD-200). A component of 2 mrad was found for pre-irradiation doses of 70 rad, 1 krad and for 10 days' regenerating time. The results are discussed and the conclusion is that for measurements of extremely low dose it is better to use virgin crystals.

Implication of regenerated thermoluminescence on low dose measurements

In several TL and ESR dating methods the annual dose rate is usually measured by sensitive TL dosimeters, such as CaF 2-Dy, CaSO 4-Dy, etc. These phosphors have been found to exhibit high regenerated thermoluminescence. The contribution of regenerated thermoluminescence to low dose dosimetry is studied. A component of 20 μGy for pre-irradiation doses of 70 cGy and for 10 days regeneration time was found. The results are discussed and the conclusion is that for measurements of extremely low doses, where and when an accuracy in the order of μGys is acquired, it is better to use virgin crystals.

Membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether)

AbstractSome properties of the membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene‐perfluorovinyl ether) copolymer (PFA) films have been investigated. The dimensional change caused by grafting and swelling behavior, water uptake, electrical conductivity, and mechanical properties of the grafted films were found to increase as the grafting proceeds. The influence of the preparation conditions (such as preirradiation dose, monomer concentration, grafting temperature, and film thickness) on those properties was studied. These properties were found to be dependent mainly on the degree of grafting regardless of grafting conditions, except at higher monomer concentration (>40 wt %). The electric conductivity and mechanical properties for the membranes obtained at higher AAc concentrations were lower than those obtained at lower ones. Analysis by x‐ray microscopy of the grafted films revealed that the grafting begins at the part close to the film surface and proceeds into the central part with progressive diffusion of monomer to give finally homogeneous distribution of the electrolytes in the whole bulk of the polymer. The membranes show good electrochemical and mechanical properties which make them acceptable for practical use as cation‐exchange membranes.

Kinetic study of preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether) copolymer

AbstractA kinetic study has been made on the preirradiation grafting of acrylic acid (AAc) onto poly(tetrafluoroethylene–perfluorovinyl ether) (PFA) film. The effect of grafting conditions was investigated. The dependences of the grafting rate on preirradiation dose and monomer concentration was found to be of the order of 0.5 and 1.3, respectively. The final degree of grafting was found to increase with dose and monomer concentration. However, it decreases as the grafting temperature increase. The overall activation energy for the graft polymerization was calculated from Arrhenius plots to be 5.6 kcal/mol. The activation energy for this grafting system was found to be independent of preirradiation dose used in the range from 10 to 100 kGy. The relationship between the grafting rate and film thickness gave a negative first‐order dependence. The results suggest that the grafting proceeds by radical mechanism with bimolecular termination of growing chain radicals. It was reasonable concluded that this grafting proceeds from the surface to the center of film with progressive monomer diffusion through the grafted layer which swells in the monomer solution.

Preirradiation grafting of N‐vinyl‐2‐pyrrolidone onto poly(tetrafluoroethylene) and poly(tetrafluoroethylene‐hexafluoropropylene) films

AbstractPreirradiation grafting of N‐vinylpyrrolidone (NVP) onto poly(tetrafluoroethylene) (PTFE) and poly(tetrafluoroethylene‐hexafluoropropylene) (FEP) films was investigated. The influence of grafting parameters such as preirradiation dose, monomer concentration, and grafting temperature on the rate and grafting yield was studied. Different solvents were used for diluting the monomer and it was found that the aqueous monomer solution at a concentration of 80 wt% was suitable for this grafting system. However, the graft polymerization of NVP in benzene terminated within a short time without significant grafting yield. The dependence of the grafting rate on preirradiation dose and monomer concentration was 1.2 and 1.07 order, respectively, for grafting onto PTFE films and 1.1 and 1.2 order, respectively, for grafting onto FEP films. Arrhenius plots for grafting onto PTFE films showed a breaking point at ca. 35°C and the overall activation energies were calculated as 23.6 and 9.0 Kcal/mol below and above 35°C, respectively. For grafting onto FEP films, however, no break was observed in the Arrhenius plots; the overall activation energy was 11.9 Kcal/mol. The swelling behavior and electric resistance of the grafted materials were investigated.

The isothermal luminescence of γ-irradiated 3-methylpentane glass at 77 K

The isothermal luminescence (ITL) at 77 K of pure 3-methylpentane was investigated. The influence of dose on ITL intensity, spectral distribution and decay was examined. The effect of pre-irradiation dose on ITL was found. The results were explained assuming the recombination of e - t -cation (in the low dose range) and anion-cation (in the high dose range, ⪞ 10 23 eV dm -3). The recombining anions and cations are formed as a result of charge transfer from primary ions to the radicals as well as to stable radiolysis products.

Effects of radiation damage on p-type silicon detectors

A p-type silicon radiation detector has been constructed and the effect of radiation damage on sensitivity and dose rate dependence has been studied. The dose rate dependence showed, in contrast to an n-type silicon detector, a linear dose rate response for clinically relevant radiation qualities, dose rates and preirradiation doses.