• Nuclear Engineering and Technology
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• 제35권5호
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• pp.378-386
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• 2003

Recently failures of nuclear fuel rods in Korean nuclear power plants were reported and their failure causes have been investigated by using PIE techniques. Destructive and physico-chemical examinations reveal that the clad hydriding phenomena had caused the rod failures primarily and secondarily in each case. In this study, the basic mechanisms of the primary and the secondary hydriding failures are reviewed, PIE data such as cladding inner and outer surface oxide thickness and the restructuring of the fuel pellets are analyzed, and they are compared with the predicted behaviors by a fuel performance code. In addition, post-defected fuel behaviors are reviewed and qualitatively analyzed. The results strongly support that the hydriding processes, primary and secondary, played critical roles in the respective fuel rods failures and the secondary hydriding failure can take place even in the fuel rod with low linear heat generation rate.

• Nuclear Engineering and Technology
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• 제25권4호
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• pp.570-587
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• 1993

최근 전 세계적으로 내부2차수소 침투에 의한 것으로 보이는 핵연료의 심각한 파손이 잇달아 보고되었다. 본 논문에서는 결함 핵연료에서의 내부 수소 침투 현상이 개괄적으로 고찰된다. 먼저 핵연료의 피복관으로 사용되는 질코늄 합금의 개발사와 그 질코늄 합금이 사용되는 원자로 내의 운전조건이 소개되고 산화 질코늄 막에서의 수소의 투과성, 질코늄과 질코늄 합금에서의 수소의 최종 용해도와 침전도등 질코늄의 수소 침투에 관련된 기본 사항과 수소 침투가 기계적 강도에 미치는 악 영향등이 고찰된다. 결함 핵연료봉 내부에서 발생되는 수소의 대량 내부 침투의 메카니즘이 관찰된 제 현상을 중심으로 정성적으로 설명되고 이러한 수소의 대량 침투에 의한 핵연료치 파손심화를 줄이기 위한 노력의 일환으로 제시된 정량적 모델이 간단히 언급되고 이러한 정량적인 모델의 심도있는 개발을 위해 필요한 자료와 추후의 연구 내용이 설명된다.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2977-2983
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• 2023

During normal operation, some parts of the fission product in the defective fuel rods can release into the primary loops in PWR and the escape rate coefficients are widely used to assess quantitatively the release behaviors of fission products in the industry. The escape rate coefficients have been standardized and have been validated by some drilling experiments before the 1970s. In the paper, the model to determine the escape rate coefficients of fission products has been established and the typical escape rate coefficients of noble gas and iodine have been deduced based on the measured radiochemical data in one operating PWR. The result shows that the apparent escape rate coefficients vary with the release-to-birth and decay constants for different fission products of the same element. In addition, it is found that the escape rate coefficients from the defective rod with large defects are much higher than the standard escape rate coefficients, i.e., averagely 4.4 times and 1.8 times for noble gas and iodine respectively. The enhanced release of fission products from the severe secondary hydriding of several defective fuel rods in one cycle may lead to the potential risk of the temporary shutdown of the operating reactors.

• 한국수소및신에너지학회논문집
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• 제20권6호
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• pp.505-511
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• 2009

The hydriding and electrochemical characteristics of Zr-based $AB_2$ alloy produced by gas atomization have been extensively examined. For the particle morphology of the as-cast and gas-atomized powders, it can be seen that the mechanically crushed powders are irregular, while the atomized powder particles are spherical. The increase of jet pressure of gas atomization process results in the decrease of hydrogen storage capacity and the slope of plateau pressure significantly increases. TEM and EDS studies showed the increase of jet pressure in the atomization process accelerated the phase separation within grain of the gas-atomized alloy, which brought about a poor hydrogenation property. However, the gas-atomized $AB_2$ alloy powders produced by jet pressure of 50 bar kept up the reversible $H_2$ storage capacity and discharge capacity similar to the mechanically crushed particles. In addition, the electrode of gas-atomized Zr-based $AB_2$ alloy of 50 bar showed improved cyclic stability over that of the cast and crushed particulate, which is attributed to the restriction of crack propagation by grain boundary and dislocation with ch/discharging cycling.