Korean Association for Radiation Application

Dr. Haruyuki Ogino, a member of the Japan Health Physics Society (JHPS), was awarded the 2021 Bo Lindell Medal by the International Commission on Radiological Protection (ICRP). To commemorate this, the “Joint JHPS-KARP-ARPS program for young radiation protection (RP) scientists to discuss the future of RP” was organized via a web meeting system. First, Dr. Ogino gave a lecture, and then young researchers selected from each academic society made presentations on the future of RP. After the presentations by the three researchers, a free talk was held— young researcher groups of each country being active is a great opportunity to collaborate and exchange information. It was emphasized that the low awareness of knowledge related to radiation has been common to all of the participating countries. Thus, it is necessary to utilize communication via web technology, as done for this program, effectively. One of the biggest advantages for Asia and Oceania is that we do not have a significant time difference. The round-table discussion was concluded by expressing the hope of active exchange and development of young researchers in the future.

Radon exposure in schools is different from that in dwellings because the residence pattern is very different each other. So, when effective dose is calculated in schools, different approach should be considered from in dwellings. The aim of this study was to estimate actual effective dose due to inhaled radon considering the residence time in schools. It could help avoid overestimation when effective dose is calculated in schools. The range of radon concentration in 376 schools was 18.1-2810 Bq m-3 and that of annual effective dose was estimated 0.0902-8.92 mSv y-1 considering the residence time in spring and autumn semesters.

Background: Any real application of Bayesian inference must acknowledge that both prior distribution and likelihood function have only been specified as more or less convenient approximations to whatever the analyzer’s true belief might be. If the inferences from the Bayesian analysis are to be trusted, it is important to determine that they are robust to such variations of prior and likelihood as might also be consistent with the analyzer’s stated beliefs. Materials and Methods: The robust Bayesian inference was applied to atmospheric dispersion assessment using Gaussian plume model. The scopes of contaminations were specified as the uncertainties of distribution type and parametric variability. The probabilistic distribution of model parameters was assumed to be contaminated as the symmetric unimodal and unimodal distributions. The distribution of the sector-averaged relative concentrations was then calculated by applying the contaminated priors to the model parameters. Results and Discussion: The sector-averaged concentrations for stability class were compared by applying the symmetric unimodal and unimodal priors, respectively, as the contaminated one based on the class of e-contamination. Though e was assumed as 10%, the medians reflecting the symmetric unimodal priors were nearly approximated within 10% compared with ones reflecting the plausible ones. However, the medians reflecting the unimodal priors were approximated within 20% for a few downwind distances compared with ones reflecting the plausible ones. Conclusion: The robustness has been answered by estimating how the results of the Bayesian inferences are robust to reasonable variations of the plausible priors. From these robust inferences, it is reasonable to apply the symmetric unimodal priors for analyzing the robustness of the Bayesian inferences.

For safety reasons, it is desirable to measure radiation as remotely as possible. For remote measurement of gamma radiation, the fiber-optic sensor (FOS) was developed in this study by combining a plastic optical fiber and an inorganic scintillator. To identify the best shape of the sensing probe of the FOS in terms of its detection efficiency, three different shapes of probe were fabricated using an inorganic scintillator: a cylinder and two bundles of different lengths (30 and 10 mm). To identify the best reflector for the sensing probe, the side of each probe was wrapped with one of three different reflectors: Teflon tape, TYVEK 1056D, and aluminum foil. In this study, a total of twelve different sensing probes were prepared: three different shapes of sensing probes with three different reflectors, and three different shapes of the sensing probes without reflectors. To measure gamma radiation, a cesium-137 source (1 Ci) in a disk shape, 26 mm in diameter, was attached to the end of the sensing probes. The measurements showed that bundle shape II (a bundle of 26 inorganic scintialltors, 1 mm in diameter and 10 mm in length) was the best shape for the sensing probe, and aluminum foil was the best reflector.

32P measurements of urine samples and internal dose assessments were conducted for workers in life science laboratories. A procedure for sample pre-treatment was established and validation was performed to exclude interference and to detect 32P levels accurately. The detection conditions for Cherenkov radiation were evaluated and the accuracy of Cherenkov radiation measurements validated. The analytical and measurement procedures were applied to urine samples collected from 11 workers from life sciences laboratories. The results of the measurements generally indicated very low background radiation levels, but daily urine samples from two workers were above the minimum detectable activity. The 32P concentrations for two of the workers were 29.3 ± 10.4 Bq•d−1 and 24.1 ± 11.8 Bq•d−1, respectively, at intake levels of 4.12 kBq and 2.61 kBq. The effective doses for these two workers were 4.6 μSv and 2.9 μSv. Overall, the results indicate very low levels of radioactivity, except for cases related to specific working conditions.