Organic insulating materials have been widely used as insulators for electrical elements in various environmental conditions. These investigations are further enhanced due to the increasing of organic insulating materials being used in radiation environment of space and nuclear power facilities. This paper describes the effects of gamma-rays irradiation on the discharge characteristics of organic insulating materials. The samples of modified polyphenylene oxide, polybutylene, epoxy resin and polybutylene terephthalate which were irradiated in air up to 100 kGy and 1 MGy with a dose rate of 10 kGy/h using a60Co gamma source. The experiment was carried out on the sample surface by applied a do impulse voltage between a plate and needle electrode. The solution droplet was placed on the plate of sample in contact with the needle electrode. The total dose effects on the discharge quantity, contact angles and extending length of droplet have been studied As the total doses are increased, the tendency of discharge quantity decreased with modified polyphenylene oxide, polybutylene and epoxy resin, on the other hand the discharge quantity increases with polybutylene terephthalate. The author found that the effects of gamma-rays irradiation on surface discharging quantity are due to radiation-induced degradation and cross-linking of organic insulating materials.
Radiation-induced luminescence, involving optically stimulated luminescence (OSL) and red thermoluminescence (RTL), was utilized to the evaluation of naturally accumulated dose using quartz grains. The purified quartz grains from coastal sands revealed the RTL properties with high dose-sensitivity, while the OSL offered poor dose-response. The luminescence was measured by an automated OSL/TL measuring system, installed with a small X-ray irradiator, using a single aliquot technique. The RTL -results gave the residual or naturally accumulated doses amounted to about 250 and 450 Gy for Kashiwazaki-Kariwa and Agano-river mouth regions. respectively. However, the OSL was resulted in negligibly weak intensity of natural luminescence. These background dose measurements based on natural luminescence from quartz grains will be preferable for the retrospective dose evaluation in the vicinity of nuclear facilities as well as in geological and archaeological fields.
The membrane characteristics controlling125I and36Cl transport across anion exchange paper membranes are examined using four different ion exchange capacities paper membranes treated with trim ethylhydroxypropylamino group. Nonequilibrium thermodynamic analyses for the paper membrane transport process are carried out based on transmembrane potential, membrane conductance, and ion flux measurements. The electroconductive membrane, permeabilities representing the solution membrane ion distribution due to electrostatic effects, and the diffusional membrane permeabilities, representing the migration speed of ions within the membrane phase, for125I are higher than those for36Cl in all cases. In the paper membrane treated with trim ethylhydroxypro-pylamino group, 125I diffusion or125I solution/membrane distribution process can be improved by increasing the concentration of anion exchange sites in the paper membrane. These findings indicate the potential utility of paper membranes prepared in this way for separating125I from radioactive waste that has been contaminated with chloride ions. The125I transport performance of such systems may be improved with the use of other anion-exchange groups.
Dose conversion coefficients from neutron fluence to operational quantities have been changed with the revision of radiation protection ordinances in Japan in April 2001. The influences of the revision were examined for the popularly used neutron dosemeters. It was shown, as a result, that the relative energy response to dose equivalent was not so changed by the revision. In addition, various dosemeters were examined on the ratios between the reading and true dose equivalent, when they were used in the various neutron fields. The percentages of the cases whose ratios were within 1-2 were 23-77% and 9-82% in 180 fields, for the representative rem counters and personal dosemeters, respectively, when the dosemeters were calibrated with252Cf source.