• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3164-3182
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• 2023

The CRUD on the fuel cladding under the pressurized water reactor (PWR) operating condition causes several issues. The CRUD can act as thermal resistance and increases the local cladding temperature which accelerate the corrosion process. The hideout of boron inside the CRUD results in axial offset anomaly and reduces the plant's shutdown margin. Recently, there are efforts to revise the acceptance criteria of emergency core cooling systems (ECCS), and additionally require the modeling of the thermal resistance effect of the CRUD during the performance analysis. There is an urgent need for the evaluation of the effect of the CRUD deposition on the cladding heat transfer under PWR operating conditions, but the experimental database is very limited. The experimental facility called DISNY was designed and constructed to analyze the CRUD-related multi-physical phenomena, and the performance analysis of the constructed DISNY facility was conducted. The thermal-hydraulic and water chemistry conditions to simulate the CRUD growth under PWR operating conditions were established. The design characteristics and feasibility of the DISNY facility were validated by the MARS-KS code analysis and separate performance tests. In the current study, detailed design features, design validation results, and future utilization plans of the proposed DISNY facility are presented.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2288-2297
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• 2023

Current designs of both large reactor units and small modular reactors utilize a nuclear fuel with increasing enrichment. This increasing demand for better nuclear fuel utilization is a challenge for nuclear fuel handling facilities. The operation with higher enriched fuels leads to reduced reserves to legislative and safety criticality limits of spent fuel transport, storage and final disposal facilities. Design changes in these facilities are restricted due to a boron content in steel and aluminum alloys that are limited by rolling, extrusion, welding and other manufacturing processes. One possible solution for spent fuel pools and casks is the burnup credit method that allows decreasing very high safety margins associated with the fresh fuel assumption in spent fuel facilities. This solution can be supplemented or replaced by an alternative solution based on placing the neutron absorber material directly into the fuel assembly, where its efficiency is higher than between fuel assemblies. A neutron absorber permanently fixed in guide tubes decreases system reactivity more efficiently than absorber sheets between the fuel assemblies. The paper summarizes possibilities of fixed neutron absorbers for various nuclear fuel and fuel handling facilities. Moreover, an absorber material was optimized to propose alternative options to boron. Multiple effective absorbers that do not require steel or aluminum alloy compatibility are discussed because fixed absorbers are placed inside zirconium or steel cladding.

• 전기화학회지
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• 제12권1호
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• pp.26-33
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• 2009

The phase-shift method and correlation constants, i.e., the unique electrochemical impedance spectroscopy (EIS) techniques for studying the linear relationship between the behavior ($-{\varphi}$ vs. E) of the phase shift ($90^{\circ}{\geq}-{\varphi}{\geq}0^{\circ}$) for the optimum intermediate frequency and that ($\theta$ vs. E) of the fractional surface coverage ($0{\leq}{\theta}{\leq}1$), have been proposed and verified to determine the Langmuir, Frumkin, and Temkin adsorption isotherms of H and related electrode kinetic and thermodynamic parameters at noble metal (alloy)/aqueous solution interfaces. At a Zr/0.2 M ${H_2}{SO_4}$ aqueous solution interface, the Frumkin and Temkin adsorption isotherms ($\theta$ vs. E), equilibrium constants (K = $1.401{\times}10^{-17}\exp(-3.5{\theta})mol^{-1}$ for the Frumkin and K = $1.401{\times}10^{-16}\exp(8.1{\theta})mol^{-1}$ for the Temkin adsorption isotherm), interaction parameters (g = 3.5 for the Frumkin and g = 8.1 for the Temkin adsorption isotherm), rates of change of the standard free energy (r = $8.7\;kJ\;mol^{-1}$ for g = 3.5 and r = $20\;kJ\;mol^{-1}$ for g = 8.1) of H with $\theta$, and standard free energies ($96.13{\leq}{\Delta}G^0_{\theta}{\leq}104.8\;kJ\;mol^{-1}$ for K = $1.401{\times}10^{-17}\exp(-3.5{\theta})mol^{-1}$ and $0{\leq}{\theta}{\leq}1$ and ($94.44<{\Delta}G^0_{\theta}<106.5\;kJ\;mol^{-1}$ for K = $1.401{\times}10^{-16}\exp(-8.1{\theta})mol^{-1}$ and $0.2<{\theta}<0.8$) of H are determined using the phase-shift method and correlation constants. At 0.2 < $\theta$ < 0.8, the Temkin adsorption isotherm correlating with the Frumkin adsorption isotherm, and vice versa, is readily determined using the correlation constants. The phase-shift method and correlation constants are probably the most accurate, useful, and effective ways to determine the adsorption isotherms of H and related electrode kinetic and thermodynamic parameters at highly corrosion-resistant metal/aqueous solution interfaces.

• 자원리싸이클링
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• 제26권6호
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• pp.3-9
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• 2017

본 연구에서는 anode로 Kroll 공정 처리된 Ti 스폰지를 사용하여 아크 전류, 아크 전압, 플라즈마 가스 종류에 따른 플라즈마 아크 재용해 거동을 조사하였다. 진공펌프의 토출 압력 범위($200{\sim}300kgf/cm^2$)에서는 토출 압력 증가에 따라 주어진 아크 길이에서 아크 전압이 크게 달라지지 않았다. 이것은 작업하는 동안 진공챔버내 압력이 거의 변화하지 않고, 주어진 분위기 압력을 잘 유지함을 의미한다. 여러가지 아크 전류 조건(700~900A)에서, 아크 전류 증가에 따라 아크 전압이 약간 증가하였고, anode 재료변화에 대한 효과도 이전 연구결과와 비교하였다. 분위기 가스가 Ar에서 He으로 변경되는 경우에는 정상상태의 출력이 2배 정도 향상되는 효과가 관찰되었다. 플라즈마 아크 장치의 출력 증가는 Ti 스폰지의 재용해 속도 증가와 함께 잉곳 표면도 양호해졌다. New 스크랩인 타이타늄과 old 스크랩인 지르코늄 합금을 플라즈마 아크 재용해한 결과, 매우 양호한 표면을 갖는 잉곳을 제조할 수 있었다.

• 대한환경공학회지
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• 제33권11호
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• pp.855-859
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• 2011

원자력산업에서의 지르코늄합금 튜브 제조공정은 튜브 산세 시 질산과 불산을 사용하고 있어 세척 시 발생되는 폐수의 주요 오염물질은 질산성질소와 불소성분으로 이루어져 있다. 오염물질인 불소와 질산성질소의 처리를 위해, 다양한 실험을 거쳐 처리기술을 검토한 결과를 토대로, 당사의 폐수처리공정은 1차 화학응집처리에 의한 불소성분 제거공정, 황산화 탈질반응을 이용한 SOD (Sulfur Oxidation Denitrification)공법에 의한 독립영양탈질공정, 2차 화학응집처리공정으로 구성하여 운영하고 있다. 본 폐수처리공정의 특징은, 질산성질소제거를 위해 황산화 탈질공법(SOD Process)을 적용한 것이다. SOD공법은 기존의 황탈질공법과는 달리 황과 알칼리성물질을 일체화한 충진담체(JSC Pellet)를 사용한 기술로, 유기탄소원이 전혀 없는 무기계폐수의 탈질기술로서 주목받고 있다. 현재까지 폐수처리장의 운영결과를 보면, 유입수의 평균 T-N농도가 설계값인 100 mg/L를 상회하는 147.55 mg/L이었지만, 처리수의 평균 T-N농도는 12.72 mg/L로 91%의 높은 제거율을 안정하게 유지하고 있다. 이상의 결과로, SOD공법이 무기계 산업폐수의 질산성질소제거에 매우 유용한 공법임이 확인되었으며, 신규 개발한 미생물활성화제(특허출원 중)를 사용함에 의해 증식속도가 늦은 독립영양미생물의 활성이 안정적으로 유지되었다.

• 한국세라믹학회지
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• 제51권5호
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• pp.435-441
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• 2014

Silicon carbide-based ceramics and their composites have been studied for application to fusion and advanced fission energy systems. For fission reactors, $SiC_f$/SiC composites can be applied to core structural materials. Multilayered SiC composite fuel cladding, owing to its superior high temperature strength and low hydrogen generation under severe accident conditions, is a candidate for the replacement of zirconium alloy cladding. The SiC composite cladding has to retain its mechanical properties and original structure under the inner pressure caused by fission products; as such it can be applied as a cladding in fission reactor. A hoop strength test using an expandable polyurethane plug was designed in order to evaluate the mechanical properties of the fuel cladding. In this paper, a hoop strength test of the multilayered SiC composite tube for nuclear fuel cladding was simulated using FEA. The stress caused by the plug was distributed nonuniformly because of the friction coefficient difference between the inner surface of the tube and the plug. Hoop stress and shear stress at the tube was evaluated and the relationship between the concentrated stress at the inner layer of the tube and the fracture behavior of the tube was investigated.

• 대한기계학회논문집A
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• 제24권1호
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• pp.206-214
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• 2000

The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and it's containment vessel. If a flaw is found during the periodic inspection from the pressure tube s. the integrity evaluation must be carried out. and the safety requirements must be satisfied for continued service. In order to complete the integrity evaluation, complicated and iterative calculation procedures are required. Besides, a lot of data and knowledge for the evaluation are required for the entire: integrity evaluation process. For this reason. an integrity evaluation system, which provides efficient of evaluation with the help of attached databases, was developed. The developed system was built on the basis of ASME Sec. XI and FFSG(Fitness For Service Guidelines for zirconium alloy pressure tubes in operating CANDU reactors) issued by the AECL, and covers the delayed hydride cracking(DHC). This system does not only provide various databases including the 3-D finite element analysis results on pressure tubes, inspection data and design specifications but also is compatible with other commercial database software. In order to verify the developed system, several case studies have been performed and the results were compared with those from AECL. A good agreement was observed between those two results.

• 비파괴검사학회지
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• 제23권4호
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• pp.342-348
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• 2003

Zr(1.32mm) 판재 위 $Be-Zr(100{\mu}m)$ 합금층의 평가를 목적으로 후방산란 초음파 의 입사각 의존성인 프로파일이 여러 입사위치에서 측정되었다. 누설 램(Lamb)파로부터 후방복사된 초음파 프로파일에는 4개의 주요 세부 프로파일이 발견되었다. 세부프로파일들의 정점각과 정점세기는 Be 확산층의 강화효과로 인해 감소하였다. 세부 프로파일들의 존재와 변화가 시편재질의 음향학적 특성, 램파모드들의 군속도 집단적 변화 그리고 표면파의 누설율 차이 등으로 설명되었다 판재 위 얇은 확산층의 평가를 위한 유용한 평가 기법으로 판재로부터의 후방복사 세부 프로파일이 제안되었다.

• 대한치과보철학회지
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• 제55권2호
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• pp.212-217
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• 2017

임플란트의 협설 측으로 잔존 골조직이 불충분할 경우 골증대술을 시행하지 않기 위해서는 작은 직경의 임플란트를 사용할 수 있다. 작은 직경 임플란트의 경우는 파절 저항성이 낮고, 골과 임플란트의 접촉 면적이 좁아 구치부에는 부적절한 것으로 여겨져 왔다. 최근의 연구에서는 새로운 임플란트 합금의 개발 및 표면 처리방법의 발전으로 구치부에서도 표준 직경 임플란트와 유사한 성공률이 보고되고 있다. 이 증례에서는 구치부 상실 부위 잔존골의 협설 폭이 부족한 상황에서 작은 직경 임플란트를 이용하여 심미적, 기능적으로 만족스러운 치료 결과를 보였다. 현재까지 추적 검사 기간은 4년 이상 되었고 특이할만한 합병증 없이 유지되었다. 향후 장기적인 안정성에 대한 추가적인 연구가 필요할 것으로 사료된다.

• Tribology and Lubricants
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• 제22권3호
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• pp.144-148
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• 2006

The experimental investigation was performed to find the associated changes in characteristics of fretting wear with various water temperatures. The fretting wear tests were carried out using the zirconium alloy tubes and the grids with increasing the water temperature. The tube materials in water of $20^{\circ}C,\;50^{\circ}C\;and\;80^{\circ}C$ were tested with the applied load of 20 N and the relative amplitude of $200{\mu}m$. The worn surfaces were observed by SEM, EDX analysis and 2D surface profiler. As the water temperature increased, the wear volume was decreased, but oxide layer was increased on the worn surface. The abrasive wear mechanism was observed at water temperature of $20^{\circ}C$ and adhesive wear mechanism occurred at water temperature of $50^{\circ}C,\;80^{\circ}C$. As the water temperature increased, surface micro-hardness was decreased, but wear depth and wear width were decreased due to increasing stick phenomenon. Stick regime occurred due to the formation of oxide layer on the worn surface with increasing water temperatures