Li-Cd 합금을 이용한 환원추출방식을 LiCl-KCl 기반의 drawdown 공정에 적용하게 되면, LiCl-KCl 공융염의 조성이 파괴되므로 공정온도를 높여야 하며, 전해정련 및 전해제련과 같은 공정에 LiCl-KCl 용융염을 재사용할 수 없게 된다. 따라서, 본 연구에서는 공융염 조성에 적합한 Li-K-Cd 합금을 제조하였으며, 이를 이용하여 U와 Nd가 포함된 LiCl-KCl 염에 투입하여 용 융염 내 UCl3의 제거가 가능한지 평가하였다.

LiCl-KCl 용융염에서 광학적으로 투명한 텅스텐 망으로 제작된 작업전극에 대해 사마륨의 전기화학적 거동을 Cyclic voltammetry와 Potential step chronoabsorptometry의 전기화학적 및 분광전기화학적 방법으로 조사하였다. Cyclic voltammogram 으로 결정된 Sm3+/Sm2+의 산화환원 반응의 가역성을 기반으로 형식전위와 확산계수를 계산하여 각각 –1.99 V vs. Cl2/Cl- 와 2.53×10-6 cm2·s-1를 얻었다. 작업 전극에 –1.5 V vs. Ag/AgCl (wt%)로 전압을 인가하여 측정한 Chronoabsorptometry 를 통해 사마륨 이온의 특성 파장으로 Sm3+에 대해 408.08 nm, Sm2+에 대해 545.62 nm를 확인하였다. Voltammogram에서 얻은 환원 피크 전압과 산화 피크 전압을 이용하여 Potential step chronoabsorptometry를 수행하였다. 545.63 nm의 흡광 피크 값을 분석하여 2.15×10-6 cm2·s-1의 확산계수를 얻었으며 이 값은 동일한 온도에서 Cyclic voltammtry 분석으로 얻은 값과 큰 차이를 보이지 않았다. 실험결과로부터 고온 용융염에서 광학적으로 투명한 작업전극을 이용한 분광전기화학적 방 법이 용융염에 용해된 이온의 종류를 확인하며 전기화학적 거동을 조사하는데 유용한 도구로 활용될 수 있음을 확인하였다.

In order to develop a new commercial Al-12%Si casting alloy with improved physical properties, we investigated the effect of adding Sr and TiB to the alloy. Al-12%Si alloys were prepared by die casting at 660 oC. The eutectic temperature of the Sr-modified Al-12%Si alloy decreased to 9 oC and the mushy zone region increased. The shape of the Si phase changed from coarse acicula to fine fiber with the addition of Sr. The addition of TiB in the Al-12%Si alloy reduced the size of the primary α-Al and eutectic Si phases. When Sr and TiB were added together, it worked more effectively in refinement and modification. The density of twins in the Si phase-doped Sr increased and the width of the twins was refined to 5 nm. These results are related to the impurity induced twinning(IIT) growth.

Densities of molten salt mixtures of eutectic LiCl-KCl with UCl3, CeCl3, or LaCl3 at various concentrations (up to 13 wt%) were measured using a liquid surface displacement probe. Linear relationships between the mixture density and the concentration of the added salt were observed. For LaCl3 and CeCl3, the measured densities were significantly higher than those previously reported from Archimedes’ method. In the case of LiCl-KCl-UCl3, the data fit the ideal mixture density model very well. For the other salts, the measured densities exceeded the ideal model prediction by about 2%.

사용후핵연료 파이로프로세싱에서는 방사성 희토류 염화물(RECl3)을 함유한 LiCl-KCl 공융염폐기물이 발생되며, 핫셀시설에서 운영을 목적으로 단순한 형태의 공융염폐기물 처리공정을 개발하는 것이 필요하다. 본 연구에서는, LiCl-KCl 공융염폐기물 내 희토류 핵종 분리/고화공정의 단순화를 목적으로 Li2O-Al2O3-SiO2-B2O3계의 무기합성매질을 이용하여 LiCl-KCl 공융 염 내 희토류 핵종(Nd)을 분리한 후 분리생성물을 바로 고화하는 시험을 실시하였다. 공융염 내 희토류 염화물(NdCl3) 대비 0.67의 무게비에 해당하는 무기합성매질의 양으로도 Nd 핵종을 98wt% 이상 분리할 수 있었고, 이 때 얻은 희토류 핵종 포집생성물은 약 50wt% 수준의 희토류 산화물 함량을 보유하고 있었으며, 이 포집생성물을 화학적 내구성이 우수한 단일상의 균질한 유리고화체로 제조할 수 있었다. 이 결과들은 LiCl-KCl 공융염폐기물 내 희토류 핵종의 분리/고화공정을 단순화하기 위한 방안수립에 활용될 수 있을 것이다.

산화물 사용후핵연료에 대한 전해환원의 금속전환체를 양극으로 한 전해정련공정에는 LiCl-KCl 공융염에 우라늄 원소뿐 아 니라 초우란 원소 및 희토류 원소들이 용해되므로 우라늄을 선택적으로 회수하기 위해서는 우라늄과 다른 원소들이 음극에 전착되는 거동에 대한 연구가 필요하다. LiCl-KCl 공융염 내 희토류 원소의 농도에 따른 음극에서의 전착거동을 고찰하기 위 해 U 및 Ce를 기준으로 한 U, Ce, Y 그리고 Nd 원소들의 분리계수에 대한 연구를 수행하였다. Ce 금속을 희생 양극으로 이용 하여 정전류 정련반응을 통해 용융염 상과 전착물 상의 U, Ce, Y 그리고 Nd 원소의 농도를 분석하여 이로부터 분리계수를 얻 었으며 UCl3 농도와 CeCl3/UCl3 농도비에 따른 분리계수로부터 우라늄을 선택적으로 회수할 수 있는 조건들을 고찰하였다.

The US Department of Energy’s Idaho National Laboratory (INL) has been operating a molten salt electrorefiner at their facility since 1996. The baseline method for disposal of the radioactive salt is the ceramic waste process which generates glass bonded sodalite loaded with chloride salts. This process starts with the high temperature absorption of the salt into zeolite-4A. The salt-loaded zeolite is then blended with glass frit and heated to form a sintered, glass-bonded sodalite. INL is currently assessing alternatives for disposal of the ER salt because of the lengthy processing times, costly equipment and large volume of waste associated with the baseline process. An alternative process was studied, where protonated zeolite was used instead of alkali metal-substituted zeolite. It was found that the metals contained in the salt can replace the protons in the zeolite which are evolved via formation of HCl. From the standpoint of generating a nuclear waste form, the evolution of HCl gas should reduce the weight of the final waste. It has been estimated that the volume of waste produced from immobilizing the INL electrorefiner salt could be reduced by a factor of three using this process followed by sintering the fission product loaded zeolite. Equipment requirements in the hot cell would be significantly simplified, and the time to process all of the waste salt would be reduced by almost a factor of 4. An investigation into the new process has been presented here.

사용후핵연료 파이로프로세싱에서 발생하는 방사성폐기물의 양을 최소화하기 위해서는 방사성 핵종 함유 염폐기물을 효과 적으로 처리할 수 있는 기술개발이 필요하다. 이를 위해 탄산화물(Li2CO3, K2CO3)을 이용한 반응증류공정에서 LiCl-KCl 공융 염 내 NdCl3의 분리특성을 관찰하였다. HSC-Chemistry 프로그램을 이용한 탄산화물과 NdCl3의 반응모델결과에서 NdCl3는 탄산화물의 주입조건 및 온도변화에 따라 산염화물(NdOCl) 또는 산화물(Nd2O3) 형태로 전환됨이 확인되었으며, 탄산화물 의 주입조건에 따른 LiCl-KCl-NdCl3계의 반응증류시험에서 반응모델결과와 유사한 경향을 확인하였다. 이 결과들을 이용하 여 LiCl-KCl 공융염 내 NdCl3를 고화가 용이한 산화물 형태로 분리하기 위한 공정조건을 도출하였다.

Recently, applied areas of nonferrous materials have been expanded in terms of efficiency of materials used and cost reduction. And, in accordance with compactness and accuracy of parts, the need of joining of dissimilar materials is raised. Accordingly, this study aimed at finding out the optimal welding current value(6.3～6.5kA) considering tensile strength, fracture test and welding residue after joining with various welding conditions by means of copper pipe(Φ7.0 × t0.5) and aluminium pipe(Φ7.0 × t0.7) using an eutectic diffusion bonding machine.

The deformation properties of a TiC-Mo eutectic composite were investigated in a compression test at temperaturesranging from room temperature to 2053K and at strain rates ranging from 3.9×10−5s−1 to 4.9×10−3s−1. It was found that thismaterial shows excellent high-temperature strength as well as appreciable room-temperature toughness, suggesting that thematerial is a good candidate for high-temperature application as a structure material. At a low-temperature, high strength isobserved. The deformation behavior is different among the three temperature ranges tested here, i.e., low, intermediate and high.At an intermediate temperature, no yield drop occurs, and from the beginning the work hardening level is high. At a hightemperature, a yield drop occurs again, after which deformation proceeds with nearly constant stress. The temperature- andyield-stress-dependence of the strain is the strongest in this case among the three temperature ranges. The observed high-temperature deformation behavior suggests that the excellent high-temperature strength is due to the constraining of thedeformation in the Mo phase by the thin TiC components, which is considerably stronger than bulk TiC. It is also concludedthat the appreciable room-temperature toughness is ascribed to the frequent branching of crack paths as well as to the plasticdeformation of the Mo phase.

Al-based alloys have recently attracted considerable interest as structural materials and light weight materials due to their excellent physical and mechanical properties. For the investigation of the potential of Al-based alloys, a surface porous Al88Cu6Si6 eutectic alloy has been fabricated through a chemical leaching process. The formation and microstructure of the surface porous Al88Cu6Si6 eutectic alloy have been investigated using X-ray diffraction and scanning electron microscopy. The Al88Cu6Si6 eutectic alloy is composed of an α-Al dendrite phase and a single eutectic phase of Al2Cu and α-Al. We intended to remove only the α-Al phase and then the Al2Cu phase would form a porous structure on the surface with open pores. Both acidic and alkaline aqueous chemical solutions were used with various concentrations to modify the influence on the microstructure and the overall chemical reaction was carried out for 24 hr. A homogeneous open porous structure on the surface was revealed via selective chemical leaching with a H2SO4 solution. Only the α-Al phase was successfully leached while the morphology of the Al2Cu phase was maintained. The pore size was in a range of 1~5μm and the dealloying depth was nearly 3μm. However, under an alkaline NaOH, aqueous solution, an inhomogeneous porous structure on the surface was formed with a 5 wt% NaOH solution and the morphology of the Al2Cu phase was not preserved. In addition, the sample that was leached by using a 7 wt% NaOH solution crumbled. Al extracted from the Al2Cu phase as α-Al phase was dealloyed, and increasing concentration of NaOH strongly influenced the morphology of the Al2Cu phase and sample statement.

In the DBC (direct bonding of copper) process the oxygen partial pressure surrounding the AlN/Cu bonding pairs has been controlled by Ar gas mixed with oxygen. However, the direct bonding of Cu with sound interface and good adhesion strength is complicated process due to the difficulty in the exact control of oxygen partial pressure by using Ar gas. In this study, we have utilized the in-situ equilibrium established during the reaction of + 1/2 by placing powder bed of CuO or around the Cu/AlN bonding pair at . The adhesion strength was relatively better in case of using CuO powder than when powder was used. Microstructural analysis by optical microscopy and XRD revealed that the interface of bonding pair was composed of , Cu and small amount of CuO phase. Thus, it is explained that the good adhesion between Cu and AlN is attributed to the wetting of eutectic liquid formed by reaction of Cu and .

Recently, ultrafine grained (ufg, typically 100 > d > 500 nm) Ti-Fe eutectic materials have been highlighted due to their extraordinarily high strength and good abrasion resistance compared to conventional coarse grained (cg, d > 1μm) materials. However, these materials exhibit limited plastic strain and toughness during room temperature deformation due to highly localized shear strain. Several approaches have been extensively studied to overcome such drawbacks, such as the addition of minor elements (Sn, Nb, Co, etc.). In this paper, we have investigated the influence of the addition of Gd and Y contents (0.3-1.0 at.%) into the binary Ti-Fe eutectic alloy. Gd and Y are chosen due to their immiscibility with Ti. Microstructural investigation reveals that the Gd phase forms in the eutectic matrix and the Gd phase size increases with increasing Gd content. The improvement of the mechanical properties is possibly correlated to the precipitation hardening. On the other hand, in the case of Ti-Fe-Y alloys, with increasing Y contents, primary phases form and lamellar spacing increases compared to the case of the eutectic alloy. Investigation of the mechanical properties reveals that the plasticity of the Ti-Fe-Y alloys is gradually improved, without a reduction of strength. These results suggest that the enhancement of the mechanical properties is closely related to the formation of the primary phase.

사용후핵연료 건식처리공정(pyrochemical process)에서 LiCl-KCl 공융염의 회수는 방사성폐기물 부피 감량과 원료물질 회수를 위해 반드시 필요하다. 본 논문은 진공증류공정을 이용하여 희토류 침전물(희토 류 산염화물 또는 산화물)내 잔류하는 LiCl-KCl 공융염 회수에 관한 것이다. 진공증류시험장치에서 희토 류 침전물내 공융염은 효과적으로 휘발 및 분리되었다. 분리된 공융염은 감압증류시험장내 세 지점에서 침적되거나 필터에 포집되으며, 침적되거나 포집된 공융염을 회수하는 것은 쉽지 않았다. 이 문제점을 해 결하기 위해 감압조건에서 온도구배를 이용하여 공융염 거동을 제어할 수 있는 공융염 진공증류/응축회 수 시스템을 개발하였으며, 이 장치를 이용하여 휘발된 공융염을 회수용기에서만 응축시켜 쉽게 회수할수 있음을 확인하였다.