Spent nuclear fuel continues to be generated domestically and abroad, and various studies are actively being conducted for interim dry storage and disposal of spent nuclear fuel. The characteristics vary depending on the type of spent nuclear fuel and the initial specifications, and based on these characteristics, it is essential to estimate the burnup and enrichment of spent nuclear fuel as a nondestructive assay. In particular, it is important to estimate the characteristics of spent nuclear fuel with non-destructive tests because destructive tests cannot be performed on all encapsulated spent nuclear fuel in case of intrusion traces in safeguards. Data is made by measuring spent nuclear fuel directly to evaluate burnup of spent nuclear fuel, but computer simulation research is also important to understand its characteristics because past burnup history is not accurately written, and destructive testing is difficult. In Sweden, the dependency of the burnup history in source strength and mass of light-water reactor-type spent nuclear fuel was evaluated, and this part was also applied to MAGNOX in consideration of the possibility of being used to verify DPRK’s denuclearization. SCALE 6.2 TRITON modeling was performed based on public information on DPRK’s 5 MWe Yongbyon reactor, and the source strength of Nb-95, Zr-95, Ru-106, Cs-134, Cs-137, Ce-141, Ce- 144, Eu-154 nuclides were evaluated. Since the burnup of MAGNOX is lower than that of lightwater reactors, major nuclides in decay heat were not considered. The cooling period was evaluated based on 0, 5, 10, and 20 years. In case the discharge timing was different, the total period of discharge and reloading was the same, and the end-cycle burnup was the same, calculations showed that the source strength emitted from major nuclides was evaluated within 2-3% except for Ru-106 and Ce-144 nuclides. Even the burnup step of nuclear fuel is the same, and the reloaded length after discharge is different, i.e., the cooling period between is different at 5, 10, and 20, the source strength of Nb-95, Zr-95, Ce-144, and Cs-137 was evaluated as an error of 1%. Except for Ru-106 and Ce-144, nuclides are highly dependent on burnup. Compared to the case of light-water reactors, the possibility of a decrease in error needs to be considered later because the specific power is low. As a result, radionuclides in released fuel depend on the effects of burnup, discharged and reloaded period, and a cooling period after release, and research is needed to correct the cooling period within the future burnup history. In addition, in this study, it is necessary to select a scenario -based burnup because the standard burnup due to the statistical treatment of discharged fuels was not considered as conducted in previous studies.

Spent fuels (SFs) are stored in a storage pool after discharge from nuclear power plants. They can be transferred to for the further processes such as dry storage sites, processing plants, or disposal sites. One of important measures of SF is the burnup. Since the radioactivity of SF is strongly dependent on its burnup, the burnup of SF should be well estimated for the safe management, storage, and final disposal. Published papers about the methodology for the burnup estimation from the known activities of important radioactive sources are somewhat rare. In this study, we analyzed the dependency of the burnup on the important radiation source activities using ORIGEN-ARP, and suggested simple correlations that relate the burnup and the important source activities directly. A burnup estimation equation is suggested for PWR fuels relating burnup with total neutron source intensity (TNSI), initial enrichment, and cooling time. And three burnup estimation equations for major gamma sources, 137Cs, 134Cs, and 154Eu are also suggested.

Spent nuclear fuel (SNF) characterization is important in terms of nuclear safety and safeguards. Regardless of whether SNF is waste or energy resource, the International Atomic Energy Agency (IAEA) Specific Safety Guide-15 states that the storage requirements of SNF comply with IAEA General Safety Requirement Part 5 (GSR Part 5) for predisposal management of radioactive waste. GSR Part 5 requires a classifying and characterizing of radioactive waste at various steps of predisposal management. Accordingly, SNF fuel should be stored/handled as accurately characterized in the storage stage before permanent disposal. Appropriate characterization methods must exist to meet the above requirements. The characterization of SNF is basically performed through destructive analysis/non-destructive analysis in addition to the calculation based on the reactor operation history. Burnup, Initial enrichment, and Cooling time (BIC) are the primary identification targets for SNF fuel characterization, and the analysis mainly uses the correlation identified between the BIC set and the other SNF characteristics (e.g., Burnup - neutron emission rate) for characterizing. So further identification of the correlation among SNF characteristics will be the basis for proposing a new analysis method. Therefore, we aimed to simulate a SNF assembly with varying burnup, initial enrichment, and cooling time, then correlate other SNF properties with BIC sets, and identify correlations available for SNF characterization. In this study, the ‘CE 16×16’ type assembly was simulated using the SCALEORIGAMI code by changing the BIC set, and decay heat, radiation emission characteristics, and nuclide inventory of the assembly were calculated. After that, it was analyzed how these characteristics change according to the change in the BIC set. This study is expected to be the basic data for proposing new method for characterizing the SNF assembly of PWR.

The Air-shiter is a new product possible ventilation at the same time cooling or heating with combined refrigerator and heat recovery ventilator. And a key device of this system is the air shifter. The air shifter device is to convert the outdoor air, room air, supply air and exhaust air flow. Therefore, an experimental study has been carried out to investigate the operating performance for this system. The results, it is possible to ventilate at the same time of heating by outside air above 30℃ in summer. and of heating by outside air within 3℃ in winter. The indoor discharge temperature is over 40℃, and the coefficient of performance is 3.4 in winter.

The Air-shiter is a new products possible ventilation at the same time cooling or heating with integrated refrigeration and ventilation units. and is a key component of the air shifter devices and bypass damper. The air shifter devices are to convert the outdoor air, room air, supply air and exhaust air flow. And the bypass damper is device to determine a ventilation. After research and development of these systems were as follows. It is confirmed that the Air-shiter is possible ventilation at the same time cooling or heating, and outdoor air cooling in the spring or fall.

사용후핵 연료 심지층 처분의 목적은 그 독성이 인간 및 자연환경에 영향을 미치지 않도록 장기간 동안 격리하고, 방사성물질의 누출을 지연시키는 것이다. 이러한 심지층 처분장 설계시 주요한 요건은 처분시스템의 건전성 유지를 위하여 폐기물로부터 발생된 열로 인하여 완충재의 온도가 를 넘지 않도록 하는 것이다. 따라서, 원자력 발전소에서 방출된 후의 사용후핵연료 냉각기간은 심지층 처분장 설계시 효율 및 경제성을 위한 중요한 고려인자이다. 본 연구에서는 가장 적절한 사용후핵연료 냉각기간 설정을 위하여 처분시스템 온도요건을 만족하는 심지층 처분장 배치에 필요한 처분터널-처분공 간격 및 그에 따른 면적, 열하중에 대한 분석을 수행하였다. 이를 위하여, 기준 처분개념을 바탕으로 사용후핵연료의 냉각기간 및 처분터널/처분공 간격을 다양하게 설정하여, 처분시스템에서의 열적 안정성을 해석하고 그 결과를 비교분석하였다. 그리고 분석 결과를 바탕으로 처분면적 측면에서 효율적인 사용후핵연료 냉각기간을 도출하였다. 그 결과, 사용후핵연료의 냉각기간이 짧을수록 처분장에서 설계온도 제한치 범위내 최고온도에 이르는 시간은 빨라지고, 사용후핵연료 냉각기간이 길수록 처분장에서 온도상승 및 하강속도는 완만해지는 것으로 나타났다. 또한, 본 연구에서 고려대상으로 삼은 처분장 규모와 사용후핵연료를 심지층에 처분한다고 할 때 그 냉각기간을 40-50년으로 함이 적합한 것으로 나타났다.

동결 과정 중 필수적인 단계중 하나인 냉각(cooling)과 냉각 후 배양시간이 생쥐 난자의 방추체의 형태와 염색체의 배열에 미치는 영향을 알아봄으로서 냉각 후 손상되었던 난자의 방추체와 염색체가 정상적으로 회복하는데 필요한 최적의 배양시간을 알아보기 위해 본 실험을 실시하였다. 생후 4-6주령의 암컷 B6C3Fl 생쥐를 과배란 처리하여 metaphase II상태의 난자를 회수하여 다음과 같이 처리하였다. 대조군은 난자를 냉각처리하지 않았으며 실험군은