60Co Gamma Radiation Research Articles

Wood plastic composite at different urea concentrations

Wood plastic composite (WPC) has been prepared with a low grade wood simul ( Salmalia malabarica) of Bangladesh under Co-60 gamma irradiation using MMA as the bulk monomer combined with methanol as the swelling solvent at different urea concentrations. Effect of a second solute such as NVP, TPGDA and TMPTA in the impregnating solution is evaluated. NVP appears to be the best co-additive/second solute among all the additives used to yield the composite with the highest polymer loading (PL) and tensile strength (TS) at 0.5% urea concentration.

Relative biological effectiveness of proton medical beam at Moscow synchrotron determined by the Chinese hamster cells assay

Assessment of relative biological effectiveness (RBE) of the proton medical beam at Moscow synchrotron. The study was performed at Moscow proton medical facility (Institute for Theoretical and Experimental Physics). Relative biological effectiveness of the synchrotron proton beam was assessed at the entry of the unmodulated 179 MeV beam and in the center of spread out Bragg peak (SOBP), from measurements of the survival of Chinese hamster cells (clone 431). Gamma-radiation of 60Co was used as a reference source. According to the linear regression model, mean RBE values at 37% survival level were found to be 1.10 +/- 0.04 at the beam entry and 1.14 +/- 0.05 in the center of SOBP. Values of RBE obtained using the linear-quadratic model for 10% and 37% survival levels were 1.09 and 1.07, respectively, at the beam entry and 1.07 and 1.08, respectively, in the center of SOBP. The data obtained indicate that (a) the RBE values at the entry of the unmodulated beam and at the center of the SOBP are in close agreement, with an average of about 1.10; (b) protons are radiobiologically somewhat more effective than 60Co gamma rays; and, (c) high pulse dose rate of the medical beam does not significantly affect biological effects of the beam.

Wood-Plastic Composite with Methylmethacrylate in Presence of Novel Additives

Abstract Wood–plastic composites (WPC) were prepared with kadom and mango wood of Bangladesh under Co-60 gamma irradiation using methylmethacrylate (MMA) as the bulk monomer mixed with methanol (swelling solvent) at different proportions in presence of a number of additives such as N-vinyl pyrrolidone, tripropylene glycol diacrylate, trimethylol propane triacrylate, copper sulfate, sulfuric acid, and urea. Composites prepared with urea, NVP, and CuSO4 possess better tensile and protective properties.

Calculation and measurement of the dose to points outside the primary beam for CO-60 gamma radiation

Purpose: In radiation therapy one sometimes needs to estimate the dose to points in the body outside the primary beam. Therefore a generalized model is developed to calculate this dose with reasonable accuracy. Methods and Materials: Measurements were made for a cobalt beam to determine separately the contribution of leakage radiation, radiation scattered from the collimator, scattered from the floor and radiation scattered inside the patient. Results: The radiation scattered in the patient shows a strong dependence on field size and distance to the beam axis and is predominant only at short distances. The radiation scattered from the collimator also depends strongly on distance and field size and is more important than the leakage radiation. With appropriate factors, correcting for patient dimensions and field shape, the total dose outside the primary beam can be calculated with an accuracy better than ±30%. The results are in accordance with published data. Conclusion: Using the measured data it is possible to calculate the dose at any point of the body outside the primary beam for Co-60 gamma radiation. The accuracy is considered to be adequate for risk assessment. Gonadal dose, Radiation therapy, Risk assessment.

Use of Co-60 Gamma Irradiation to Simulate Decomposition of Tetraphenylborate Precipitates from High Level Radioactive Waste

Savannah River Plant nuclear waste requires the decontamination of approximately 100 million gallons of salt solution. The radioactive Cs-137 will be removed by precipitating it as a tetraphenylborate (TPB) salt. This radioactive precipitate will be stored in large, underground steel tanks for approximately two years until it is consigned to the Defense Waste Processing Facility (DWPF) for immobilization in glass. During the processing and storage, the tetraphenylborate precipitate will be subjected to intense beta and gamma irradiation which will cause partial decomposition leading to the production of many organic compounds. The purpose of this project was to qualitatively and quantitatively identify the organic products formed from the radiolysis of soluble and insoluble tetraphenylborate salts.

EFFECTS OF γ IRRADIATION ON LOSS CHARACTERISTICS OF SINGLE MODE OPTICAL FIBERS DOPED WITH RARE EARTH Er3+

This papers presents the effects of Co-60 gamma irradiation on the absorption loss of single mode optical fibers doped with rare earth Er3+. The parameters of optical fibers are measured, prior to irradiation and after irradiation and UV bleaching. It has been found that absorption loss in the wavelength range of 0.80-1.60μm is greatly lager than those of unirra-diated fibers. Its increase law of absorption loss is similar to that of β ray irradiation. This similarity can be explained by Compton's effect. The induced loss can be partly bleached by UV, resulting in a better effect than heat annealing. In order to improve radiation resistivity, the elements with smaller atomic number should be selected as dopants in both core and cladding of the fiber.

Geometrical aspects of scatter‐to‐primary ratio and primary dose

Using an approximation of Bjarngard and Petti [Phys. Med. Biol. 33, 21-32 (1988)] that the scatter-to-primary ratio SPR(r,d) is a linear function of the geometrical parameter z = rd/(r + d) (where r is the radius of photon beam and d is depth in phantom), a method was developed to determine primary dose directly from depth-dose data, measured within the range of fields with lateral electronic equilibrium. This method was evaluated using tabulated TAR data for Co-60 gamma radiation in water. The results for primary dose agree within approximately 1% of those from other studies. It was shown that this method is applicable within the energy range of therapeutic x rays. Primary dose was determined in the case of 6- and 18-MV x rays using proposed method.

Messung kleiner Aktivitäten mit Teletherapie-Ionisationskammern: Ermittlung des Kalibrierfaktors Ner

Under given clinical circumstances the air kerma rate produced by brachytherapy sources at photon energies between 150 and 600 keV must be measured with teletherapy-type ionisation chambers positioned in air at some distance from the source. According to the presented experiments and calculations the chambers should be used with a) the wall thickness adaption caps provided for Co-60 gamma radiation together with an air kerma calibration factor interpolated for the photon spectrum of the specified nuclide, b) the shape- and distance-dependent Kondo/Randolph correction factors which permit source to chamber distances as low as twice the chamber diameter. Ionization chamber signals of sufficient resolution (100 digits) have been obtained with activities of about 100 MBq (3 mCi) using a 30 cm3 cylindrical chamber.

Subsurface layers with degenerate hole gas arising in germanium immersed into liquid helium under 60Co-gamma irradiation

Abstract The subsurface layers with quasi-metal hole conductivity have been observed in n- and p-Ge immersed into liquid He under the 60Co-gamma-irradiation. three conditions are to be fulfilled simultaneously for the production of the layers: low temperature, direct contact between helium and germanium and gammairradiation.

Radiation Induced Dissolution of UO2

ABSTRACTIn order to be able to model the effect of water radiolysis on the dissolution of fuel in the disposal vault it is essential to study the oxidation mechanism. Radiolysis of water produces radicals and molecules, amongst them the oxidizing species H2O2 and OH radicals, and, in aerated solutions, O2- as well. These species are probably responsible for the oxidation and dissolution of UO2 observed in a number of experiments. In the present investigation the effect of the oxidizing species has been studied separately using suitable scavengers. A polished specimen of UO2 was immersed in water and irradiated at ambient temperature with Co-60 gamma radiation. After irradiation the amount of uranium which had dissolved, or deposited elsewhere than the sample surface, was measured, and the oxidation of the surface was determined, using ESCA and SIMS. In 50 mM H2O2 (without irradiation) the corrosion rate was 5±3 μg.cm−2d−1 after 6 d exposure at pH 8. Corresponding rates for oxidation by O2- and OH radicals were about 3 μg.cm−2d−1, (dose rate 600±90 Gy/h.)

Effect of gamma radiation on low density polyethylene

AbstractLow density monofilaments of polyethylene with varying draw ratios were subjected to high energy radiation using Co60 gamma radiation source. It was found that the tensile strength is sharply improved with the increasing dose up to 20 Mrd beyond which a sharp decrease in tenacity and initial modulus was observed. The swelling behaviour also decreased with the increased in dose of irradiation. However, density showed an increasing trend. The shrinkage behaviour of all the filaments was found to increase with increasing dose and draw ratios. The results have been explained in terms of continuous increase in crosslink density with the increasing dose of irradiation along with loss of crystallinity, which appears to be more severe in the latter stages of exposure. The samples exhibited memory effect after redrawing at 100°C and cooling under tension followed by further heating at 110°C under relaxed condition. The shrinkage was still much higher but independent of draw ratio.

Effect of bias on the response of metal-oxide-semiconductor devices to low-energy x-ray and cobalt-60 irradiation

The response of metal-oxide-semiconductor (MOS) transistors and capacitors to high-energy Co-60 gamma and low-energy x-ray irradiation is evaluated as a function of gate bias during exposure. It is demonstrated that, in contrast to previous expectations, the relative response of MOS devices to Co-60 gamma and 10 keV x-ray irradiation cannot be explained simply in terms of electron-hole recombination and dose enhancement effects.

Radiation induced interface trap limited storage times in 10 micron cutoff wavelength (Hg,Cd)Te MIS capacitors

Dark storage times were measured as a function of temperature over a temperature range of 50 to 80 K for 10- mu m cutoff wavelength (77 K) p-type (Hg,Cd)Te/anodic oxide/ZnS metal-insulator-semiconductor (MIS) capacitors prior to and after Co-60 gamma irradiation to doses of 5*10/sup 5/ and 1*10/sup 6/ rad (Si). The radiation-induced interface trap density near midgap for these doses was 8*10/sup 11/ and 1.6*10/sup 12//eV-cm/sup 2/, respectively. A decrease in the storage time was observed for both doses and is attributed to thermal generation through the radiation-induced interface traps and to interface-trap-assisted tunneling. The radiation-induced dark current responsible for the storage time degradation is 1.8*10/sup -4/ A/cm/sup 2/ at 50 K after a dose of 1*10/sup 6/ rad (Si). >

Total dose radiation characteristics of SOI MOSFETs fabricated using ISLANDS technology

Total-dose-radiation results for n- and p-channel silicon-on-insulator (SOI) MOSFETs fabricated using ISLANDS (oxidation of porous silicon) technology and subjected to Co-60 gamma radiation are reported. The back-gates of both n- and p-channel transistors were hard to 1 Mrad(Si) with either -5 or 0 V on the substrate during irradiation. The buildup of radiation-induced interface traps at the back-gate of n-channel MOSFETs compensated for the threshold voltage shift due to oxide-trapped charges. The front-gate hardness was similar to that of bulk MOSFETs. >

Dose and temperature response of “opti-chromic” dosimeters

Opti-chromic dosimetry systems which are commercially available and consist of radiochromic dye solutions in plastic tubing have been tested for measurement of Co-60 Gamma radiation at dose range of 0–0.3, 0–2.5, 0–30 KGy using detector types of FWT-70-40 and FWT-70-83. The required doses have been delivered from a hot-spot 3000 Irradiator with a dose rate of about 4.25 KGy/hr, at two irradiation temperatures of 22 and 50 C respectively. The response of the above detectors has been measured with FWT-98 reader at wavelengths of 600, 656 and 680 nm as appropriate. The results of this study and certain characteristics of this dosimetry system are presented.

Cement mortar impregnated with poly(methyl methacrylate‐co‐styrene)

AbstractPolymer‐impregnated mortars were prepared by copolymerization of a monomer mixture of methyl methacrylate and styrene in the ratios of 13:87 and 40:60 using Co‐60 gamma radiation. The copolymerization characteristics viz. the rate of polymerization, the extent of monomer loss, polymer loading, etc., were studied. The nature and molecular weight of the extractable polymer from the composite were determined. The flexural strength of the copolymer‐impregnated composites was found to be better than that of the composites impregnated with component homopolymers.

Serum alkaline phosphatase (SAP) activity following exposure to cadmium and/or60CO gamma irradiation

Abstract Two hundred and sixteen male Sprague‐Dawley (S‐D) rats, 80 ± 5 days old and weighing 220–250 g each, were assigned at random to nine groups of 24 rats each. Rats were injected with cadmium (Cd) intraperitoneally every 3 days for 29 days for a total of nine injections. Injections doses were 0, 1.0, or 2.5 mg Cd kg−1 body weight. Twenty‐four hours after the last Cd injection (day 30), each rat received an acute whole‐body 60Co gamma radiation dose of 0, 3.62, or 5.43 Gray (Gy) at a dose rate of 3.304 Gy min‐1. Eight rats from each of 9 groups were sacrificed on day 1, 7, or 21. High dose radiation administered 24 hours following the last dosage of Cd caused significantly elevated serum alkaline phosphatase levels, whereas high dose cadmium caused the enzyme to be significantly depressed. When Cd and radiation were used as the co‐insult, the combination of high Cd‐high radiation was more effective than either cadmium or radiation alone, suggesting a previously reported cadmium metal protection against the radiation. Although the precise mechanism is unknown, we speculate that the protection afforded by cadmium against radiation might be attributed to different conformations of metal‐induced metallothionein cysteine clusters. Further, these clusters are likely dependent upon conversion between conformational forms requiring specific levels of metal ion site occupancy.

Spectral Investigations of the Effects of 60Co-Gamma Irradiation on Iodothyronine and Iodotyrosines

Solids of 3-iodo-, 3–5–di-iodotyrosine and 3,5-di-iodothyronine were irradiated by 60Co-gamma irradiation for a period of about twenty hours. The effects of irradiation were investigated through a study of the UV and IR spectra of irradiated samples. UV spectra showed the presence of a new band at 360 nm which was assigned to the formation of IO−. IR spectra showed a strong carbonyl absorption and the removal of the carboxylate band in the case of thyronine only. For comparison, the spectra of the studied compounds were investigated before irradiation.

Radiation Effects in High Electron Mobility Transistors: Total Dose Gamma Irradiation

AlGaAs/GaAs high electron mobility transistors (HEMTs) have been exposed to 90 Mrad(GaAs) of Co60 gamma radiation. Despite the heavy exposure, the peak transconductance for selected transistors was only diminished by approximately 4%. In addition, threshold voltage shifts of up to 80 mV were observed for both enhancement and depletion mode devices.

Response to Gamma Irradiation and Induced Virulent Mutation in Melampsora medusae of Poplars

AbstractWhen the urediniospores of three races of Melampsora medusae, the causal agent of leaf rust of poplars, were exposed to Co60 gamma irradiation (range 100–1000 Gy), there were significant differences in the radiosensitivity of the races as assessed, in vitro, by incubation period to flecking and the uredinial survivability percentage. In race 5A the frequency of mutation to virulence on Populus deltoides cv. T‐173, normally a resistant cultivar, was maximum (1.688 %) at an irradiation dose of 400 Gy. Importance of mutations as source of variability in pathosystems and usefullness of artificially induced mutations in the context of host‐pathogen interactions are discussed.