The Korea Atomic Energy Research Institute (KAERI) in Daejeon, South Korea was established in 1959 as the sole professional research-oriented institute for nuclear power in South Korea, and has rapidly built a reputation for research and development in various fields. In 1995 KAERI designed and constructed the nation's first multipurpose research reactor, HANARO based on the Canadian MAPLE design. KAERI is dedicated to finding a wide range of uses for atomic energy. As examples, KAERI developed the world's first radiopharmaceutical "Milican injection" for treating liver cancer.KAERI has made significant contributions to the nation's nuclear technology development. After Korea achieved self-reliance in nuclear core technologies, KAERI have transferred highly developed technologies to local industries for practical applications. The Korea Institute of Nuclear Safety (KINS), responsible for supporting the government in regulatory and licensing works, and the Nuclear Environment Technology Institute, responsible for low and medium level radioactive waste management, are also originally spin-offs from KAERI. KAERI established the present KEPCO E&C (full name: KEPCO Engineering & Construction Company, INC., formerly: KOPEC), responsible for not only the architect engineering works of nuclear power plants, but also for designing nuclear steam supply systems. KAERI also established the present Korea Nuclear Fuel Co., Ltd. (KNFC), responsible for designing and manufacturing PWR as well as PHWR fuels..
Understanding the dissolution behavior of UO 2 in carbonate-bearing groundwater is critical for predicting the long-term release of uranium from spent nuclear fuel in geological disposal environments. This study investigates the pH-dependent interfacial dissolution of UO 2 in these environments to identify distinct reaction regimes governed by surface chemistry. Two uranium oxide models with contrasting structural characteristics were examined: structurally disordered electrodeposited UO 2+x films and well-crystallized sintered UO 2 pellets exhibiting terrace-step morphologies. Dissolution processes were monitored using a combination of quartz crystal microbalance (QCM), atomic force microscopy (AFM), Raman spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS). Both materials exhibit consistent biphasic dissolution kinetics, characterized by an initial rapid uranium release followed by a slower, steady-state regime. Dissolution is accelerated under mildly acidic carbonate conditions (pH 6.0) and suppressed under highly alkaline conditions (pH 12.0). Under representative groundwater conditions (pH 8.0), the UO 2 surface develops a relatively stable interfacial layer involving partial oxidation and surface-bound carbonates. These findings demonstrate that pH-controlled interfacial chemistry and initial defect density fundamentally dictate uranium dissolution, providing critical mechanistic insights for predicting radionuclide release in deep geological repositories.
SA508 low-alloy steel is a candidate material for main steam line piping, and its microstructure and mechanical properties are significantly influenced by the cooling rate after austenitizing. This study quantitatively analyzed the effect of cooling rate–induced microstructural changes on J -R fracture resistance. As the cooling rate increased, the fraction of coarse ferrite and pearlite decreased, while the formation of low-temperature transformation microstructure increased. As a result, the strength increased, whereas the J -R fracture resistance increased up to the air cooling (AC) and subsequently decreased with a further increase in the cooling rate. These changes in mechanical properties are considered to be associated with these low-temperature microstructures induced by the increased cooling rate. The relationship between microstructure and J Ic was quantitatively evaluated using a predictive model incorporating grain size and strength. For specimens with mixed microstructures of ferrite, pearlite, and bainite (FC, AC, AQ), the predicted values of J Ic showed good agreement with experimental results. However, for WQ, the experimental J Ic was approximately 140 kJ/m 2 lower than the predicted value.
Low-temperature growth of crystalline GaN remains challenging for plasma-enhanced atomic layer deposition (PEALD) because limited adatom mobility often leads to poorly ordered films. Here, we investigate a cycleintegrated atomic layer annealing (ALA) strategy to enhance the crystallinity of GaN thin films grown on Al2O3(0001) by PEALD at 300 degrees C. Trimethylgallium and NH3 plasma were used as the Ga and N sources, and an Ar plasma ALA step was inserted after each PEALD cycle to promote plasma-assisted atomic rearrangement. The ALA duration was varied from 0 to 60 s for non-pretreated samples, and NH3-plasma-pretreated samples were examined at 30 and 90 s ALA. X-ray diffraction and rocking-curve analysis show that the GaN(002) rocking-curve FWHM decreases from approximately 5.9 degrees without ALA to 0.050 degrees at 60 s ALA, indicating strongly enhanced outof-plane c-axis orientation. At the same 30 s ALA duration, NH3 plasma pre-treatment suppresses the secondary GaN-related diffraction component observed in the non-pretreated film, while the fitted FWHM values of ALA30 (0.083 degrees) and P-ALA30 (0.078 degrees) differ only slightly and are not interpreted as statistically different. Within the pretreated series, P-ALA90 exhibits a broader rocking-curve FWHM (0.091 degrees) than P-ALA30; because a nonpretreated ALA90 control was not included, no specific degradation mechanism is assigned. Cross-sectional TEM and selected AFM and XPS measurements provide complementary microstructural, morphological, and chemical-state characterization. These results establish an ALA-duration-dependent process-window perspective for the low-temperature PEALD growth of highly c-axis-oriented GaN thin films on sapphire.
A bubble pressure-based model was developed to predict the formation of high burnup structure (HBS) in nuclear fuel pellets. In contrast to existing models that predominantly focus on burnup, the proposed model comprehensively considers physically relevant parameters, including fission gas concentration, bubble size, bubble density, and porosity, based on the hypothesis that HBS formation is driven by grain subdivision resulting from bubble over-pressurization. The model was implemented in the FRAPCON-4.0 Patch 1 fuel performance code and validated against in-pile experimental data. The influence of power history on HBS evolution was investigated, indicating that the onset and width of HBS are significantly affected by the time-dependent behavior of fuel temperature and fission gas distribution. These findings demonstrate that the coupled effects of power history, temperature, and fission gas behavior play a critical role in accurately modeling HBS formation, enhancing the reliability of high burnup fuel performance predictions.
In Level 3 probabilistic safety assessment (Level 3 PSA), offsite radiological risk is quantified through pathway-specific dose assessments based on atmospheric dispersion and deposition analyses. Dose coefficients play a critical role in this process by converting environmental radionuclide concentrations and intakes into estimates of human radiation doses, thereby directly influencing the results of offsite consequence analysis. This study evaluates the impact of three representative dose coefficient frameworks commonly applied in offsite radiological consequence assessment: those based on ICRP Publications 26, 60, and 103, issued by the International Commission on Radiological Protection, as well as a fourth framework based on Federal Guidance Report No. 13 (FGR 13), published by the U.S. Environmental Protection Agency. Offsite consequence simulations were performed using the RCAP and MACCS codes. Differences among the four frameworks were assessed in terms of spatial dose distribution, protective action distances, evacuation criteria, and emergency planning zone boundaries. The results indicate that the application of the ICRP 26-based framework generally produces higher dose estimates than the other three frameworks. Consequently, it leads to larger reference distances for the implementation of protective actions and the delineation of emergency planning zones. These findings demonstrate that the selection of a dose coefficient framework can meaningfully affect offsite consequence estimates, emergency-response decisions, and the overall reliability and comparability of Level 3 PSA results. They also indicate a potential need to reassess regulatory approaches that continue to rely on dose coefficients derived from ICRP 26.
