The Korea Atomic Energy Research Institute (KAERI) employs a methodology for evaluating the concentration of radionuclides, dividing them into volatile and non-volatile nuclides based on their characteristics, to ensure the permanent disposal of internally generated radioactive waste. Gamma spectroscopy enables the detection and radiation concentration determination of individual nuclides in samples containing multiple gamma-emitting nuclides. Due to the stochastic nature of radioactive decay, the generated radiation signal can interact with the detector faster than the detected signal processing time, causing dead time in the gamma spectroscopy process. Radioactive waste samples typically exhibit higher radiation levels than environmental samples, leading to long dead times during the measurement process, consequently reducing the accuracy of the analysis. Therefore, dead time must be considered when analyzing radioactive waste samples. During the measurement process, dead time may vary between a few seconds to several tens of thousands of seconds. More long dead time may also result in a temporal loss in the analysis stage, requiring more time than the actual measurement time. Long dead time samples undergo re-measurement after dilution to facilitate the analysis. As the prepared solution is also utilized in the nuclide separation processes, minimizing sample loss during dilution is crucial. Hence, predicting the possibility of dead time exceeding the target sample in advance and determining the corresponding dilution factor can prevent delays in the analysis process and the loss of samples due to dilution. In this study, to improve the issues related to gamma analysis, by using data generated during the analysis process, investigated methods to predict long dead time samples in advance and determining criteria for dilution factors. As a result of comparing the dead time data of 5% or long with the dose of the solution sample, it was concluded that analysis should be performed after dilution when it is about 0.4 μSv/h or high. However, some samples required dilution even at doses below 0.4 μSv/h. Also, re-measurement after dilution, the sample with a dead time of less than 32% was measured with less than 5% when diluted 10 times, and more than 32% required more than 10 times dilution. We suppose that with additional data collection for analyzing these samples in the future, if we can establish clearer criteria, we can predict long dead time samples in advance and solve the problem of analysis delay and sample loss.

It is essential to provide a safe working environment for radiation workers. At a research reactor decommissioning site in Seoul (KRR1 & KRR2), radioactive waste drum disposal work is in progress. Before performing radiation work, it is necessary to determine the radioactivity of the waste drum to ensure safety. In this reason, we conducted a study to determine the detection efficiency of waste drums using the EXVol code. Determination of the full energy absorption peak efficiency (detection efficiency) is one of the important processes of the gamma-ray activation analysis. For the large voluminous gamma-ray sources like waste drum, the geometrical and attenuation effect should be considered. EXVol (Efficiency calculator for eXtended Voluminous source) code is a detection efficiency calculation code using the effective solid angle method. EXVol can calculate both coaxial and asymmetric structure. In addition, the introduction of a collimator made it possible to reduce the radiation intensity of a high radiation source. And it is possible to determine the precise detection efficiency according to the energy of a gamma ray at a specific position of the volume source. To verify the performance of the EXVol, a high resolution gamma spectroscopy system was constructed and measurement and analysis were performed. Measurements were performed on coaxial, asymmetric and collimated structures with standard point source, standard 1 L liquid volume source and HPGe detector. The measured results were compared with the calculation results of EXVol. The relative deviation of the measurement and calculation in the coaxial and asymmetric structures was 10%, and that of the collimation structure was 20%. Results can be available in analysis of waste drums’ radioactivity determination at a specific position.

Lepidopteran hitchhikers were investigated in vessel at five major ports of Korea in 2013. These moths were collected by International Plant-Quarantine Accreditation Board (IPAB) during inspection on vessels for Asian Gypsy Moth (AGM). The results typically include the taxonomic identification, their origin localities, and information related to commodities and ship’s route. A total of 1,026 individuals were detected in vessels and identified with 236 species belonging to 21 families. Although most of the species are already known to the Korean fauna, the following three species are unknown: Lymantria xylina Swinhoe (Lymantriidae), Glyphodes actorionalis Walker (Crambidae), and Histia flabellicornis nigrinus Jordan (Zygaenidae). Interestingly, H. flabellicornis nigrinus Jordan was detected for two consecutive years. Although this species is not an important pest, it will be need to necessarily continual monitoring. L. xylina Swinhoe which is a great potential forest pest, was detected four times (16 specimens) at Busan port of entry. Therefore, it is necessary to provide comprehensive border surveillance monitoring and a valuable historical record of the array of lepidopteran hitchhikers transported to the Korea through inanimate pathway, in order to counter further potential importance of hitchhikers on international vessels at Korea.

In a faunistic survey for the family Coleophoridae (Lepidoptera: Gelechioidea) on Is. Yeonpyeong and Is. Baengnyeong in 2010 and 2006, respectively, eleven species of Coleophora were recognized. Among them, three species; Coleophora adjunctella Hodgkinson, C. chenopodii Oku, and C. kurokoi Oku are reported for the first time from Korea. For the newly recorded species, taxonomical remarks and illustration of adults and genitalia are given.