LiCl-KCl 공융염 내에서 희토류염화물들의 침전

조용준; 양희철; 은희철; 김응호; 김인태; Yung-Zun Cho; Hee-Chul Yang; Hee-Chul Eun; Eung-Ho Kim; In-Tae Kim

Journal of the Korean Industrial and Engineering Chemistry, Vol.18, No.4, 361-365, August, 2007

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LiCl-KCl 공융염 내에서 희토류염화물들의 침전

Precipitation of Rare Earth Chlorides in a LiC-KCl Eutectic Molten Salt

조용준 ^†, 양희철 , 은희철, 김응호 , 김인태

한국원자력연구원 선진핵연료주기개발단

Yung-Zun Cho^†, Hee-Chul Yang , Hee-Chul Eun, Eung-Ho Kim , and In-Tae Kim

Advaced Fuel Cycle Development, Korea Atomic Energy Research Institute, Daejeon 305-764, Korea

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초록

LiCl-KCl 공융염 내 존재하는 몇가지 희토류염화물(Ce/Nd/GdCl3)들의 산소와의 반응으로 인한 침전반응에 대한 연구를 수행하였다. 산소와의 반응으로 형성되는 희토류침전물의 형태와 산소분산 시간(최대 420 min) 및 공융염(450∼750 ℃) 온도가 침전물로의 전환율에 미치는 영향을 규명하였다. 본 연구결과 산소분산 시간 및 공융염의 온도와 무관하게 NdCl3 및 GdCl3는 옥시염화물(REOCl), CeCl3는 산화물(REO2)형태로 침전되었으며 이러한 실험결과는 반응 Gibbs free energy (△Gr) 를 이용한 예측 결과와도 일치하였다. 희토류염화물의 침전물로의 전환특성은 전환율 개념을 도입하여 파악하였다. 전환율은 산소분산 시간이 증가함에 따라서 지수적으로 증가하였으며 750 ℃의 공융염 온도 및 300 min 이상의 분산시간 조건에서 0.999 이상의 전환율을 나타내었다. 공융염 온도가 증가함에 따라서 전환율이 증가하였다. Ce의 경우에는 60 min 이상의 산소분산 조건에서 전 실험온도 범위에서 0.999 이상의 일정한 전환율을 나타내었다.

The precipitation reaction of some rare earth chlorides (Ce/Nd/GdCl3) in a LiCl-KCl molten salt has been carried out by reaction with oxygen. Identification of rare earth precipitates by reaction with oxygen and effects of oxygen sparging time (max. 420 min) and molten salt temperature (450∼750 ℃) on conversion were investigated. In this study, regardless of the oxygen sparging time and the molten salt temperature, oxychlorides (REOCl) for NdCl3 and GdCl3, and an oxide (REO2) for CeCl3 are formed as a precipitate, which are identical with the estimation results of Gibbs free energy of reaction (△Gr). The conversion of rare-earth chlorides into insoluble precipitates was described by using a conversion ratio. The conversion ratio increased exponentially with the oxygen sparging time and finally showed asymptotic value, over 0.999 at 750 ℃ of the molten salt temperature and over 300 min of sparging time conditions. The conversion ratios were increased with the molten salt temperature. In case of CeCl3, when the sparging time exceed 60 min, the values of the conversion ratio were nearly constant over 0.999 in all experimental temperature conditions.

Keywords:LiCl-KCl molten salt;oxygen sparging;rare earth element;precipitation

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[Related Articles]

[1] Kang YH, Hwang SC, Shim JB, Kim EH, Yoo JH, J. Korean Ind. Eng. Chem., 14(5), 645 (2003)

[2] Ackerman JP, Johnson TR, Chow LSH, Carls EL, Hannum WH, Laidler JJ, Prog. Nucl. Energy, 31, 141 (1997)

[3] Mcpheeters CC, Pierce RD, Mulcahey TP, Prog. Nucl. Energy, 31, 175 (1997)

[4] Garcia E, Dole VR, McNeese JA, Griego WJ, Los Alamos Science, 449 (2000)

[5] Smith DM, Neu MP, Garcia E, Dole VR, J. Alloy. Compd., 319, 258 (2001)

[6] Picard GS, Mottot YE, Tremillon BL, in Proc. 5th International Symposium on Molten Salts, M. L. Saboungi, K. Johnson, D. S. Newman, and D. Inman eds., pp. 189∼193, Pennington, NJ (1986)

[7] Katayama Y, Hagiwara R, Ito Y, J. Electrochem. Soc., 142(7), 2174 (1995)

[8] Fan LS, Gas-Liquid-Solid Fluidization Engineering, Butterworth Pub., MA (1989)

[9] Outokumpe web page : www.outokumpu.com/hsc

[10] Braunstein J, Manabtov G, Smith GP, Advances in Molten Salt Chemistry, vol. 2, Plenum, New York (1973)