• Nuclear Engineering and Technology
• /
• 제49권8호
• /
• pp.1711-1716
• /
• 2017

Uranium tetrafluoride ($UF_4$) is the most used nuclear material for producing metallic uranium by reduction with Ca or Mg. Metallic uranium is a raw material for the manufacture of uranium silicide, $U_3Si_2$, which is the most suitable uranium compound for use as nuclear fuel for research reactors. By contrast, ammonium uranyl carbonate is a traditional uranium compound used for manufacturing uranium dioxide $UO_2$ fuel for nuclear power reactors or $U_3O_8-Al$ dispersion fuel for nuclear research reactors. This work describes a procedure for recovering uranium and ammonium fluoride ($NH_4F$) from a liquid residue generated during the production routine of ammonium uranyl carbonate, ending with $UF_4$ as a final product. The residue, consisting of a solution containing high concentrations of ammonium ($NH_4^+$), fluoride ($F^-$), and carbonate ($CO_3^{2-}$), has significant concentrations of uranium as $UO_2^{2+}$. From this residue, the proposed procedure consists of precipitating ammonium peroxide fluorouranate (APOFU) and $NH_4F$, while recovering the major part of uranium. Further, the remaining solution is concentrated by heating, and ammonium bifluoride ($NH_4HF_2$) is precipitated. As a final step, $NH_4HF_2$ is added to $UO_2$, inducing fluoridation and decomposition, resulting in $UF_4$ with adequate properties for metallic uranium manufacture.

• 한국방사성폐기물학회:학술대회논문집
• /
• 한국방사성폐기물학회 2003년도 가을 학술논문집
• /
• pp.395-400
• /
• 2003

사용후핵연료 금속전환체의 장기저장 안정성 확보를 위해 금속전환체의 주성분인 금속우라늄과 산화 안정화 후보물질인 Nb, Ti, Ni, Zr, Hf 등을 첨가한 모의금속전환체 합금을 제작하여 $200^{\circ}C~300^{\circ}C$ 온도구간에서 순수 산소분위기로 산화시험을 수행하였다. U-Nb, U-Zr, U-Ti 합금은 순수 금속우라늄보다 무게증가 측면에서의 산화저항성이 높았으나, U-Hf, U-Ni 합금의 경우에는 오히려 순수 금속우라늄보다 산화 저항성이 낮게 나타났다. 시편에 대한 미세성분 및 조직을 광학현미경, SEM, EPMA 등을 통해 분석하였다. 각 합금의 산화율 및 활성화에너지를 구한 결과 U-Nb 합금의 활성화에너지가 높고 산화 저항성이 가장 양호한 것으로 나타나 산화 저항성 후보물질로 선정하였다.

• 한국방사성폐기물학회:학술대회논문집
• /
• 한국방사성폐기물학회 2003년도 가을 학술논문집
• /
• pp.689-695
• /
• 2003

Electrochemical decontamination process has been applied for recycle or self disposal with authorization of large amount of metallic wastes contaminated with uranium compounds such as $UO_2$, ammonium uranyl carbonate (AUC), ammonium di-uranate (ADU), and uranyl nitrate(UN) with tributylphosphate(TBP) and dodecane, which are generated by dismantling the contaminated system components and equipment of a retired uranium conversion plant in Korea Atomic Energy Research Institute (KAERI). Electrochemical decontamination for metallic wastes contaminated with uranium compounds was evaluated through the experiments on the electrolytic dissolution of stainless steel as the material of the system components in neutral salt electrolytes. The effects of type of neutral salt as the electrolyte, current density, and concentration of electrolyte on the dissolution of the materials were evaluated. Decontamination performance tests using the specimens taken from a uranium conversion plant were quite successful with the application electrochemical decontamination conditions obtained through the basic studies on the electrolytic dissolution of structural material of the system components.

• 한국세라믹학회지
• /
• 제37권9호
• /
• pp.833-838
• /
• 2000

기존의 핵연료재료 습식처리 공정 대체를 위한 건식 처리 공정 기초 연구로서 산소 플라즈마 기체에 의한 금속우라늄과 이산화우라늄의 산화 연구를 수행하였다. 연구결과 산소 플라즈마를 사용할 경우 $UO_2$는 40$0^{\circ}C$에서 약 300% 정도, 50$0^{\circ}C$에서는 70% 정도의 산화율 증가가 일어났으며 금속우라늄의 경우에도 35$0^{\circ}C$에서 50% 정도의 증가를 확인할 수 있었다. 이들 산화율은 플라즈마 출력이 증가함에 따라 비례적으로 증가하였는데 이는 출력 증가에 따른 플라즈마내 산소 원자의 발생과 일치하여 이러한 산화율 증가 현상은 플라즈마내 산소 원자가 주도하는 것으로 드러났다. 이들 실험 결과는, 기존의 실험 결과와 길이, 시간에 따라 산화량이 선형적으로 증가하는 것으로 나타나 산소 플라즈마 산화 반응은 표면 반응이 주요 반응이라는 것이 밝혀졌다.

• 자원환경지질
• /
• 제13권4호
• /
• pp.241-246
• /
• 1980

Some components in uranium-bearing formations which consist mainly of black shale, slate. and low grade coal-bearing formation of Ogcheon Belt were processed statistically in order to find out the geochemical correlations with uranium. Geochemical enrichment of uranium, vanadium and molybdenum in low grade coal-bearing formations and surrounding rocks is remarkable in the studied area. Geochemical correlation coefficient of uranium and molybdenum in the rocks displays about 0.6, and that of uranium and fixed carbon about 0.4. Uranium and vanadium in uranium-bearing low grade coals denote very high correlation with fixed carbon, which is considered to be responsible for enrichment of metallic elements, especially molybdenum. Close geochemical correlation of uranium-molybdenum couple in the rocks can be applied as a competent exploration guide to low grade uranium deposits of this area.

• 한국주조공학회지
• /
• 제20권2호
• /
• pp.80-88
• /
• 2000

Continuous casting equipment was designed to cast the metallic uranium rods, and a thermal analysis was carried out to calculate the temperature and solidification profiles. Fluid flow and heat transfer analysis model including the effects of phase change was used to simulate the continuous casting process by finite volume method. In the design of continuous casting equipment, the casting speed, pouring temperature and cooling conditions should be considered as significant factors. In this study, the effects of casting speed, pouring temperature, and air gap between the uranium and mold were investigate. The results represented that the temperature and solidification profiles of continuous casting equipment varied with the casting speed, pouring temperature, and air gap.

• 환경위생공학
• /
• 제22권3호
• /
• pp.77-87
• /
• 2007

The ion exchange resins have been synthesized from chlormethyl styrene - 1,4 - divinylbenzene(DVB) with 1%, 3%, and 5%-crosslinking and macro cyclic ligand of OenNen-$H_4$ by copolymerization method and the adsorption characteristics of uranium(VI), iron(II) and samarium(III) metallic ions have been investigated in various experimental conditions. The synthesis of these resins was confirmed by content of chlorine, element analysis, and IR-spectrum. The effects of pH, time, dielectric constant of solvent and crosslink on adsorption of metallic ions were investigated. The uranium ion was showed fast adsorption on the resins above pH 3. The optimum equilibrium time for adsorption of metallic ions was about two hours. The adsorption selectivity determined in ethanol was in increasing order uranium ${UO_2}^{2+}>Fe^{2+}>Sm^{3+}$ ion. The adsorption was in order of 1%, 3%, and 5% crosslink resin and adsorption of resin decreased in proportion to order of dielectric constant of solvent.

• 환경위생공학
• /
• 제20권3호
• /
• pp.27-35
• /
• 2005

The ion exchange resins have been synthesized from chlormethyl styrene - 1,4 -divinyl-benzene(DVB) with $1\%,\;4\%,\;and\;10\%$-crosslinking and macrocyclic ligand of cryptand type by copolymerization method and the adsorption characteristics of uranium(VI), calcium(II) and lutetium(III) metallic ions have been investigated in various experimental conditions. The synthesis of these resins was confirmed by content of chlorine, element analysis, and IR-spectrum. The effects of pH, time, dielectric constant of solvent and crosslink on adsorption of metallic ions were investigated. The uranium ion was showed fast adsorption on the resins above pH 3. The optimum equilibrium time for adsorption of metallic ions was about two hours. The adsorption selectivity determined in ethanol was in increasing order uranium $(UO_2^{2+})>calcium(Ca^{2+})>lutetium(Lu^{3+})$ ion. The adsorption was order of $1\%,\;4\%,\;and\;10\%$ crosslink resin and adsorption of resin decreased in proportion to order of dielectric constant of solvents.

• 공업화학
• /
• 제22권6호
• /
• pp.697-702
• /
• 2011

1%, 2%, 5% 및 15%의 가교도를 가진 클로로메틸화된 스타이렌-1, 4-디비닐벤젠에 $OenNdien-H_4$ 거대고리 리간드를 공중합반응으로 결합시켜 이온교환 수지를 합성하여 우라늄(${UO_2}^{2+}$), 칼륨($K^+$), 네오듐($Nd^{3+}$) 금속 이온들의 흡착 특성을 여러 가지 실험 조건하에서 조사하였다. 이들 합성수지의 확인은 염소 함량과 원소 분석 그리고 IR-스펙트럼으로 하였으며, 수지에 대한 금속 이온들의 흡착에 미치는 pH, 시간 그리고 수지의 가교도에 따른 영향들을 조사한 결과 우라늄 이온은 pH 3 이상에서 큰 흡착률을 보였으며, 금속 이온들의 흡착 평형은 2 h 정도였다. 한편, 메탄올용액에서 수지에 대한 흡착 선택성은 우라늄(${UO_2}^{2+}$) > 칼륨($K^+$) > 네오듐($Nd^{3+}$) 이온이었고, 금속 이온의 흡착력은 1%, 2%, 5% 및 15%의 가교도 순이었다.

• Nuclear Engineering and Technology
• /
• 제40권6호
• /
• pp.497-504
• /
• 2008

In a study of the optimum operational condition for a melting decontamination, the effects of the basicity, slag type and slag composition on the distribution of depleted uranium were investigated for radioactively contaminated metallic wastes of iron-based metals such as stainless steel (SUS 304L) in a direct current graphite arc furnace. Most of the depleted uranium was easily moved into the slag from the radioactive metal waste. The partitioning ratio of the depleted uranium was influenced by the amount of added slag former and the slag basicity. The composition of the slag former used to capture contaminants such as depleted uranium during the melt decontamination process generally consists of silica ($SiO_2$), calcium oxide (CaO) and aluminum oxide ($Al_2O_3$). Furthermore, calcium fluoride ($CaF_2$), magnesium oxide (MgO), and ferric oxide ($Fe_2O_3$) were added to increase the slag fluidity and oxidative potential. The partitioning ratio of the depleted uranium was increased as the amount of slag former was increased. Up to 97% of the depleted uranium was captured between the ingot phase and the slag phase. The partitioning ratio of the uranium was considerably dependent on the basicity and composition of the slag. The optimum condition for the removal of the depleted uranium was a basicity level of about 1.5. The partitioning ratio of uranium was high, exceeding $5.5{\times}10^3$. The slag formers containing calcium fluoride ($CaF_2$) and a high amount of silica proved to be more effective for a melt decontamination of stainless steel wastes contaminated with depleted uranium.