• Nuclear Engineering and Technology
• /
• 제54권6호
• /
• pp.1962-1971
• /
• 2022

The liquid lead-lithium (Pb-17Li) blanket has many applications in fusion reactors due to its good tritium breeding performance, high heat transfer efficiency and safety. The compatibility of liquid Pb-17Li alloy with the structural material of blanket under magnetic field is one of the concerns. In this study, corrosion experiments China low activation martensitic (CLAM) steel and 316L steel were carried out in a forced convection Pb-17Li loop under 1.0 T magnetic field at 480 ℃ for 1000 h. The corrosion results on 316L steel showed the characteristic with a superficial porous layer resulted from selective leaching of high-soluble alloy elements and subsequent phase transformation from austenitic matrix to ferritic phase. Then the porous layers were eroded by high-velocity jet fluid. The main corrosion mechanism of CLAM steel was selective dissolution-base corrosion attack on the microstructure boundary regions and exclusively on high residual stress areas. CLAM steel performed a better corrosion resistance than that of 316L steel. The high Ni dissolution rate and the erosion of corroded layers are the main causes for the severe corrosion of 316L steel.

• Nuclear Engineering and Technology
• /
• 제53권1호
• /
• pp.61-68
• /
• 2021

Experiments of vertically upward steam-water two-phase flow have been carried out in single-side heated narrow rectangular channel with a gap of 3 mm. Flow patterns were identified and classified through visualization directly. Slug flow was only observed at 0.2 MPa but replaced by block-bubble flow at 1.0 MPa. Flow pattern maps at the pressure of 0.2 MPa and 1.0 MPa were plotted and the difference was analyzed. The experimental data has been compared with other flow pattern maps and transition criteria. The results show reasonable agreement with Hosler's, while a wide discrepancy is observed when compared with air-water two-phase experimental data. Current criteria developed based on air-water experiments poorly predict bubble-slug flow transition due to the different formation and growth of bubbles. This work is significant for researches on heat transfer, bubble dynamics and flow instability.

• Nuclear Engineering and Technology
• /
• 제54권11호
• /
• pp.4329-4337
• /
• 2022

Jet impinging device is designed for decay heat removal on horizontal fuel rods in a low temperature heating reactor. An experimental system with a fuel rod simulator is established and experiments are performed to evaluate water film covering capacity, within 0.0287-0.0444 kg/ms mass flow rate, 0-164.1 kW/m² heating flux and 13.8-91.4℃ feeding water temperature. An effective method to obtain the film coverage rate by infrared equipment is proposed. Water film flowing patterns are recoded and the film coverage rates at different circumference angles are measured. It is found the film coverage rate decreases with heating flux during single-phase convection, while increases after onset of nucleate boiling. Besides, film coverage rate is found affected by Marangoni effect and film accelerating effect, and surface wetting is significantly facilitated by bubble behavior. Based on the observed phenomenon and physical mechanism, dry-out depth and initial dry-out rate are proposed to evaluate film covering potential on a heating surface. A model to predict film coverage rate is proposed based on the data. The findings would have reliable guide and important implications for further evaluation and design of decay heat removal system of new reactors, and could be helpful for passive containment cooling research.

• 과학기술학연구
• /
• 제12권1호
• /
• pp.107-144
• /
• 2012

2011년 3월에 일본 후쿠시마에서 발생한 핵사고의 영향 때문에 최근 한국 사회에서도 에너지 미래에 대한 관심이 높아지고 있다. 한국 정부는 에너지 수요가 계속 증가할 것이라는 전제 하에 원자력 발전 확대 정책을 고수하는 반면, 한국의 시민사회와 진보정당들은 핵발전소를 단계적으로 폐지하자는 탈핵 주장을 잇달아 내놓고 있다. 최근 시민사회 쪽 연구자들에 의해 정부의 공식적인 시나리오와는 다른 대안적인 에너지 시나리오들이 발표되면서 앞으로 정부 쪽의 주류 시나리오와 시민사회 쪽의 대안적 시나리오 사이에 경합이 불가피한 상황이다. 이 글은 2008년에 결정된 제1차 국가에너지기본계획에 포함된 에너지 시나리오와 2012년에 발표된 시민사회단체들의 에너지 시나리오들의 내용을 인식론적이고 방법론적인 기반, 가치 지향성, 제도적 기반, 그리고 시나리오 등장의 사회적 배경 등의 측면에서 비교함으로써 한국의 에너지 시나리오를 둘러싼 '전문성의 정치'를 분석하고 있다. 전문성의 정치란 누구의 지식과 전문성을 정당한 것으로 인정할 것인지 혹은 어떤 지식과 접근법을 가치 있고 믿을만한 것으로 여겨야 하는가를 둘러싸고 사람들 사이에서 형성되는 갈등적 경합과정이다. 분석 결과, 정부의 에너지 시나리오는 과학주의적 인식론과 포캐스팅 방법론에 기반하고 있고, 가치중립성에 의거한 전문가주의를 표방하고 있으며, 에너지 수급에 대한 기존 추세를 전제로 주로 정부연구소의 신고전파 경제학자들에 의해 작성되었음을 알 수 있었다. 반면에 시민사회의 대안 시나리오는 구성주의적인 인식론과 백캐스팅 방법론에 기반하고, 시민참여와 같은 적극적인 가치개입을 주장하고 있으며, 후쿠시마 핵사고를 직접적인 계기로 하여 대학과 시민사회의 다양한 학문적 배경을 지닌 연구자들에 의해 작성되었다는 점을 발견할 수 있었다.

• Nuclear Engineering and Technology
• /
• 제40권2호
• /
• pp.127-132
• /
• 2008

An experimental loop operating with water at supercritical conditions(25MPa, $600^{\circ}C$ in the test section) is designed for operation in the research reactor LVR-15 in UJV Rez, Czech Republic. The loop should serve as an experimental facility for corrosion tests of materials for in-core as well as out-of-core structures, for testing and optimization of suitable water chemistry for a future HPLWR and for studies of radiolysis of water at supercritical conditions, which remains the domain where very few experimental data are available. At present, final necessary calculations(thermalhydraulic, neutronic, strength) are being performed on the irradiation channel, which is the most challenging part of the loop. The concept of the primary and auxiliary circuits has been completed. The design of the loop shall be finished in the course of the year 2007 to start the construction, out-of-pile testing to verify proper functioning of all systems and as such to be ready for in-pile tests by the end of the HPLWR Phase 2 European project by the end of 2009.

• Nuclear Engineering and Technology
• /
• 제42권6호
• /
• pp.690-703
• /
• 2010

Sampling based uncertainty analysis was carried out to quantify uncertainty in predictions of best estimate code RELAP5/MOD3.2 for a thermal hydraulic test (10% hot leg break LOCA) performed in the Large Scale Test Facility (LSTF) as a part of an IAEA coordinated research project. The nodalisation of the test facility was qualified for both steady state and transient level by systematically applying the procedures led by uncertainty methodology based on accuracy extrapolation (UMAE); uncertainty analysis was carried out using the Latin hypercube sampling (LHS) method to evaluate uncertainty for ten input parameters. Sixteen output parameters were selected for uncertainty evaluation and uncertainty band between $5^{th}$ and $95^{th}$ percentile of the output parameters were evaluated. It was observed that the uncertainty band for the primary pressure during two phase blowdown is larger than that of the remaining period. Similarly, a larger uncertainty band is observed relating to accumulator injection flow during reflood phase. Importance analysis was also carried out and standard rank regression coefficients were computed to quantify the effect of each individual input parameter on output parameters. It was observed that the break discharge coefficient is the most important uncertain parameter relating to the prediction of all the primary side parameters and that the steam generator (SG) relief pressure setting is the most important parameter in predicting the SG secondary pressure.

• 한국재료학회지
• /
• 제34권5호
• /
• pp.247-253
• /
• 2024

The separation of zirconium and hafnium using tributyl phosphate (TBP)-Dodecane extractants in nitric acid medium was performed. Zirconium oxychloride, used as extraction feed, was obtained from the synthesis of Kalimantan zircon sand concentrate smelted using NaOH. The extraction process was carried out by dissolving chloride-based metals in nitric acid media in the presence of sodium nitrate using TBP-Dodecane as an extractant. Some of the extraction parameters carried out in this study include variations in organic phase and aqueous phase (O/A), variations in contact time, and variations in nitric acid concentration. Extraction was carried out using a mechanical shaker according to the parameter conditions. X-ray fluorescence (XRF) was used for elemental (Zr and Hf) composition analysis of the aqueous solution. The results showed that zirconium was separated from hafnium at optimum conditions with an organic/aqueous ratio of 1:5, contact time of 75 min, and an HNO₃ concentration of 7 M. The resulting separation factor of zirconium and hafnium using TBP-Dodecane was 14.4887.

• Journal of Mechanical Science and Technology
• /
• 제19권5호
• /
• pp.1182-1193
• /
• 2005

The capability of TRAC-M code to predict downcomer boiling effect during reflood phase in postulated PWR LOCA is evaluated using the results of downcomer effective water head and Cylindrical Core Test Facility (CCTF) experiments, which were performed at JAERI. With a full height downcomer simulator, effective water head experiment was carried out to investigate the applicability of the TRAC-M best estimate LOCA code to evaluate the effective water head with superheated wall temperature in downcomer. In order to clarify the effect of the initial superheat of the downcomer wall on the system and the core cooling behaviors during the reflood phase, two sets of analysis were also performed with a CCTF. Results show that TRAC­M code tends to under-predict downcomer effective water head and core differential pressure. However, the code results show a good agreement with the experimental results in downcomer temperature, heat flux and pressure. Finally, both experiment and calculation showed that the downcomer water head with the superheated downcomer wall is lower than that of the saturated wall temperature.

• Nuclear Engineering and Technology
• /
• 제55권4호
• /
• pp.1300-1309
• /
• 2023

Simulated debris was synthesized using UO₂, Zr, and stainless steel and a heat treatment method under inert or oxidizing conditions. The primary U solid phase of the debris synthesized at 1473 K under inert conditions was UO₂, whereas a (U, Zr)O₂ solid solution formed at 1873 K. Under oxidizing conditions, a mixture of U₃O₈ and (Fe, Cr)UO₄ phases formed at 1473 K, whereas a (U, Zr)O_2+x solid solution formed at 1873 K. The leaching behavior of the fission products from the simulated debris was evaluated using two methods: the irradiation method, for which fission products were produced via neutron irradiation, and the doping method, for which trace amounts of non-radioactive elements were doped into the debris. The dissolution behavior of U depended on the properties of the debris and aqueous solution for immersion. Cs, Sr, and Ba leached out regardless of the primary solid phases. The leaching of high-valence Eu and Ru ions was suppressed, possibly owing to their solid-solution reaction with or incorporation into the uranium compounds of the simulated debris.

• Nuclear Engineering and Technology
• /
• 제28권4호
• /
• pp.415-422
• /
• 1996

Tritium removal from tritiated heavy water in a PHWR is the most effective way in reducing workers' internal dose and radioactivity emissions from Wolsong NPP. The optimum design of the Wolsong TRF (Tritium Removal Facility) was carried out using an approximate short-cut method with an assumption that the TRF, designed to extract 8 MCi per year of elemental tritium from a heavy oater feedstream, uses Liquid Phase Catalytic Exchange (LPCE) front-end process and Cryogenic Distillation (CD) process.