[en] Nuclear materials were first used to end the World War II. They were produced and maintained during the cold war for global security reasons. In the succeeding 50 years since the Atoms for Peace Initiative, nuclear materials were produced and used in global civilian reactors and fuel cycles intended for peaceful purposes. The Nonproliferation Treaty (NPT) of 1970 established a framework for appropriate applications of both defense and civilian nuclear activities by nuclear weapons states and non-nuclear weapons states. As global inventories of nuclear materials continue to grow, in a diverse and dynamically changing manner, it is time to evaluate current and future trends and needed actions: what are the current circumstances, what has been done to date, what has worked and what hasn't? The aim is to identify mutually reinforcing programmatic directions, leading to global partnerships that measurably enhance international security. Essential elements are material protection, control and accountability (MPC and A) of separated nuclear materials, interim storage, and geologic repositories for all nuclear materials destined for final disposal. Cooperation among key partners, such as the MPC and A program between the U.S. and Russia for nuclear materials from dismantled weapons, is necessary for interim storage and final disposal of nuclear materials. Such cooperative partnerships can lead to a new nuclear regime where a complete fuel cycle service with fuel leasing and spent fuel take-back can be offered to reactor users. The service can effectively minimize or even eliminate the incentive or rationale for the user-countries to develop their indigenous enrichment and reprocessing technologies. International cooperation, supported by governments of key countries can be best to facilitate the forum for formation of such cooperative partnerships

[en] This study is to research the maturity of advanced nuclear fuel and cladding technology and to explore the suitability of existing technology for addressing the emerging requirements for Generation IV reactors and emerging thermal/fast spectrum reactors, while simultaneously addressing nuclear waste management, and proliferation resistance concerns

[en] Several options for weapons fissile-material disposition, such as once-through mixed- oxide (MOX) fuel in reactors or immobilisation in waste glass, would result in end products requiring geologic disposal. The criticality potential of the fissile end products containing U-235 and Pu-239 and the associated consequences in a geologic setting are important considerations for the final disposal of these materials. The possibility of underground criticality, and especially autocatalytic criticality, is affected by (1) groundwater leaking into a failed waste container, (2) preferential leaching of neutron absorbers or of fissile material from a failed container, and (3) preferential deposition of fissile material in the surrounding rock. Bowman and Venneri have pointed out that fissile material mixed with varying compositions of water and silica can undergo a nuclear chain reaction. Some configurations can become autocatalytically supercritical resulting in considerable energy release, terminated finally by disassembly. Some reviews rejected the Bowman and Venneri warning as implausible because of low probabilities of scenarios that could lead to such configurations. Sanchez et al. reported possible supercritical conditions in systems of Pu-SiO₂-H₂O and Pu-tuff-H₂O but concluded that the probability of forming such combinations is extremely low. Kastenberg et al. studied the potential for autocatalytic criticality of plutonium or highly enriched uranium in the proposed Yucca Mountain geologic repository. They concluded that plutonium or uranium could, theoretically, become supercritical, but that such criticality is unlikely given the hydrology, geology and geochemistry of the Yucca Mountain site. These studies are not definitive. The possibility of criticality exists. Detailed mechanisms have not been sufficiently studied for clear conclusions on the probabilities of occurrence. More technical analysis is needed to understand the potential for underground autocatalytic criticality and the associated consequences. Here we present our calculations of possible conditions and a mechanism for criticality in a container containing fissile material in various different chemical forms, including conditions for autocatalytic criticality. We discuss criteria for designing waste solids for the disposition of weapons fissile material so that long-term dissolution of a neutron-absorber or of fissile material would not cause criticality. These results for simplified geometries outline the conditions for a more detailed analysis of practical systems. The potential for underground criticality is also studied for other fissile waste forms, including spent fuel from commercial reactors, research reactors, and naval reactors, all of which may be destined for geologic disposal. If not carefully resolved on scientific grounds, underground criticality could potentially become the 'Achilles heel' of programmes to dispose of weapons materials and nuclear wastes. 6 refs

[en] Now, the Korean utility is planning to apply the risk information derived from its PSAs in many licensing areas such as modification of technical specifications, in-service inspection, etc. In order to meet the utility's growing demand for the application of risk information, it is essential for the regulatory body to prepare a riskinformed regulatory framework, including the technical basis and philosophy used in regulatory decision making. This paper summarizes the risk-informed inspection approach which was developed to apply the risk-information or risk-insights to future regulatory inspection of NPPs in order to enhance regulatory efficiency and effectiveness

[en] In the PSA of nuclear power plants, it is impossible to enumerate all the cut sets due to high memory requirements and long computation time. To determine a set of minimal cut sets with adequate accuracy, Minimal Cut Sets (MCSs) with probabilities less than a specified probability cut-off value are discarded. The application of the cut-off technique entails the need to estimate the truncation error, i.e., the probability of system failure due to truncated cut sets. In this paper, the treatment status of truncation error in PSA application is summarized and a new truncation error evaluation method, which is based on the trend of MCS results in terms of newly established event space coverage, is developed

[en] In order to provide the technical rationale for future risk-informed regulatory applications, four essential regulatory areas, i.e., PSA regulatory audit model, quality certification procedure on PSA, risk-informed performance indicator, and risk monitoring were surveyed, and the corresponding state-of- technology for each area was summarized. Actually, this study was performed by way of the analysis and in-depth survey on the previous experience done by any individual organizations like USNRC or US NEI, as well as the international organizations like IAEA or OECD/NEA. Through the survey results, we might look for the regulatory positions on national development

No abstract available

[en] The dynamic qualification of the structure of the traveling water screen for nuclear power plant will be accomplished by analysis using finite element model of the equipment. The equipment will be mathematically modeled by finite elements using ANSYS, version 5.5. All operating loads on the equipment to be qualified which could be present during the seismic event will be included in the analysis. These loads will include dead weight, maximum traveling screen load, torque load of the drive unit, seismic inertia load and pipe nozzle loads. Depending on the results of modal analysis, the dynamic qualification will proceed. Three components of earthquake motion are combined by taking the Square Root of the Sum of the Squares(SRSS)

[en] We have investigated structural and electrical properties of PbZr_0.3Ti_0.7O₃ (PZT) thin films deposited by pulsed laser deposition methods. In order to improve the ferroelectric properties of PZT thin films, we have controlled grain size or surface morphology by changing bottom electrode or deposition time. PZT thin films have been deposited on La_0.5Sr_0.5CoO₃ (LSCO) or LaMnO₃ (LMO) bottom electrodes with LaAlO₃ substrates during different deposition times. X-ray diffraction data have shown that all the PZT films and bottom electrodes are highly oriented with their c-axes normal to the substrates. The thickness of each film is determined by field-emission scanning electron microscope. We have also observed alternation of grain sizes (80 ∼ 180 nm) by using atomic force microscopy mode and surface potential distribution and retention behavior of ferroelectric domains by using Kelvin force microscopy mode. A PZT/LMO structure has shown superior ferroelectric and retention properties to a PZT/LSCO structure.

No abstract available