The delay of hair regrowth of mice after irradiation was examined to investigate its possibility as a biological dosimeter in the cases of localized over exposure. Hairs on the dorsal skin of mice were shaved and irradiated with a 90Sr/90Y β-ray source in early anagen or midanagen stage of hair cycle. Skin doses were 0.5-10Gy and 1-4Gy, respectively. Hair regrowth was observed with a scaling loupe. Hair regrowth delay was dose dependent, fitting the linear-quadratic function and the linear function according to the stages of hair. Histological observations indicated that the hair matrix cells death was the main cause of hair regrowth delay in the midanagen stage. Dose estimation functions, derived from the dose-effect relationship curves, could be applied for the dosimetey of the skin over exposure. It could detect a dose over 1Gy, and as early as a few days after the exposure.
An outline survey of indoor and outdoor 222Rn concentrations in South Korea was carried out with electrostatic integrating 222Rn monitors (EIRM) from Sept. 1995 to Feb. 1997. The annual mean indoor and outdoor 222Rn concentrations at the six central cities across Korea were 26.1Bq·m-3 and 9.0Bq·m-3, respectively. The outdoor 222Rn concentrations in seashore areas were lower than those of inland areas. Relatively high outdoor 222Rn concentrations were found at the inland cities in Korea, which may be explained as the geological structure. The ratios of indoor to outdoor 222Rn concentrations ranged from 1.6 to 3.8 with an average of 2.9. The seasonal pattern seems to be relatively high during spring to summer and relatively low during autumn to winter for both indoor and outdoor 222Rn concentrations. Passive integrating 222Rn cup monitors were also used to measure the indoor 222Rn concentrations at Seoul. The results showed that the concentrations in basements were clearly higher than those in usual living/working places, and the averages were 43.8Bq·m-3 and 24.2Bq·m-3, respectively.
The effect of storage on the track registration property of CR-39 has been studied. Pieces of CR-39 plate were irradiated with normally incident α particles and fission fragments by using a 252Cf source before and after their storage in air for one to six months at different temperatures of -80°C, -23°C, 4°C, 23°C and 35°C. The bulk etch rate and α-track sensitivity were obtained from the etch pit diameters of α and fission tracks. It was shown that the bulk etch rate and the α-track sensitivity both tend to decrease during storage time and from the effect of storage temperatures. The most significant effect was observed on α-track sensitivity at 35°C, which was reduced 55% for six months. It was also shown that the storage effect is attributed not to a fading of latent tracks, but to changes in the detector itself.
Plutonium (Pu) is one of the most important elements from the viewpoint of radiotoxicology and protection. The International Commission on Radiological Protection (ICRP) recently revised the respiratory tract model and biokinetic models for selected elements, including Pu. The monitoring quantities for inhaled 239Pu such as lung retention and daily excretion rate have been computed. The aerosols of 5μm Activity Median Aerodynamic Diameter (AMAD) and 1μm AMAD were treated by using these new models. The conversion coefficients from the monitoring quantities to the effective dose of 239Pu have been obtained. Besides the graphical representation, the computed monitoring quantities have been approximately represented by a summation of exponential functions. The present results provide useful data for the design of monitoring programs and for the interpretation of the monitoring results in occupational exposure.
Air kerma rates in the basin of the Ashida River of Hiroshima Prefecture were measured by a NaI (Tl) scintillation spectrometer. It was found that they were distributed from 5.4×101nGy h-1 to 1.2×102nGy h-1 and had a mean value of (7.9±1.8)×101nGy h-1, which was about 30% higher than the air-absorbed dose rates determined by the National Institute of Radiological Science. It also became clear from a comparison of gamma-ray spectra measured there that two kinds of parent rocks whose components of radionuclides were very much different from each other would be the sources of the gamma ray exposure in this area.