고준위 방사성 액체폐기물을 옥살산침전으로 처리할시 폐기물로 침전여액이 발생된다. 침전여액에는 옥살산과 아스코빅산과 같은 유기물질들이 함유되어 있고, 이들의 제거는 방사성 폐기물의 궁극적 처리처분에 대단히 중요하다. 본 연구에서는 모의 침전여액을 제조하고 모의 침전여액으로부터 유기물질(옥살산과 아스코빅산) 제거 연구가 수행되었다. 2가지 제거방법이 본 연구에 적용되었다. 하나는 과산화수소를 이용한 유기물제거로서, 모의 침전여액에 존재하는 Ru⁺⁴과 Fe⁺³은 과산화수소를 자체분해시키는 역할을 하기 때문에 유기물질 분해를 방해하는 것으로 밝혀졌다. 그리고 반응물의 C.O.D를 낮추는데 있어서 회분식보다 반회분식이 보다 더 효율적이었다. 또 다른 방법으로는 NaOH를 첨가하는 방법으로서 용액내 pH가 증가됨에 따라 침전이 발생하면서 C.O.D는 현격히 감소하는 경향을 보여주었다. 침전물은 Na₂C₂O₄로 확인되었고, pH9인 용액을 90℃에서 3시간 이상 유지시킨 후 과산화수소를 첨가하면 용액내 C.O.D는 98% 이상 감소된다.

At a treatment of high level liquid radioactive waste by oxalate precipitation, a filtrate is occurred as waste. Organic substances such as oxalic acid and ascorbic acid are included in the filtrate and removal of those is very important in viewpoint of ultimate treatment and disposal of waste. The purpose of the present studies is to find means for removing organic substances in the filtrate. To achieve this, the simulated filtrate was prepared and two methods for removing organic substances in the simulated filtrate have been employed in this study. One is decomposition method of organic substances by using hydrogen peroxide. As a result of this method, it was found that both Ru⁺⁴ and Fe⁺³ prevented organic substances from decomposition in the simulated filtrate due to self-decomposition of hydrogen peroxide by those ions and semibatch operation was preferred to batchwise one at lowering C.O.D in the simulated filtrate. The other method is increasing pH of the simulated filtrate by adding NaOH. C.O.D decreased due to precipitation of oxalate ion as Na₂C₂O₄ form with pH of the simulated filtrate. Finally, C.O.D could be decreased to over 98% by addition of H₂O₂ after the simulated filtrate kept at 90℃ for 3 hours.

Oxalic Acid Ascorbic Acid Filtrate Hydrogen Peroxide Decomposition

Kubota M, Fukase T, J. Nucl. Sci. Technol., 17(10), 783 (1980)
Skalberg M, Liljenziz JO, "Partitioning and Transmutation: the State of the Art," Nucl. Eng. Inter., Feb., 30 (1993)
IAEA-TECDOC-783: "Safety and Environmental Aspects of Partitioning and Transmutation of Actinides and Fission Products," International Atomic Energy Agency, Vienna (1995)
IAEA Technical Reports Series No. 214: "Evaluation of Actinide Partitioning and Transmultation," IAEA, Vienna (1982)
Tedder DW, Blomeke JO, "Actinide Partitioning and Transmutation Program Progress Report for Period April 1 to June 30, 1977," ORNL/TM-6056 (1977)
Kondo Y, Takitsuka T, "Technology Assessment of Partitioning Process(I)," JAERI-M94-067 (1994)
Forsberg CW, Nucl Technol., 40, 243 (1980)
Kobayash T, Morita Y, Kubota M, "Development of Partitioning Method: Method of Precipitation Transuranium Elecements with Oxalic Acid," JAERI-M88-026 (1988)
Kim EH, J. Nucl. Sci. Technol., 34(3), 283 (1997)
Rankin DT, Buency GA, Smith PK, Sission RD, Am. Ceram. Soc. Bull., 56(5), 478 (1977)
Kim EH, Shin YJ, Kim WH, Chung DY, Kim SS, Yoo JH, Choi CS, Korean J. Chem. Eng., 12(5), 557 (1995)
Kim EH, Kim YH, Chung DY, Shin YJ, Yoo JH, Choi CS, HWAHAK KONGHAK, 34(2), 249 (1996)
Kobayashi T, Shirahashi K, Kubota M, "Development of Partitioning Method: Precipitation Behavior of Other Elements in Separating the Transuranie Elements Group with Oxalic Acid," JAERI-M89-168 (1989)
Bishop DF, Storn G, Fleishman M, Marshall LS, Ind. Eng. Chem. Process Des. Dev., 7(1), 110 (1968) 
Shirahashi K, Kubota M, J. Nucl. Sci. Technol., 29(6), 559 (1992)
Agrawal A, Rao I, Gupta C, Mishra SK, Sharma PD, "Chemical Kinetics and Reaction Mechanism," ed. Gupta, K.S., RBSA Publishers, Jaipur (1991)
Mimura H, Akiba K, Kawamura K, J. Nucl. Sci. Technol., 31(5), 463 (1994)
IAEA Technical Reports Series No. 337: "Chemical Precipitation Process for the Treatment of Aqueous Radioactive Waste," IAEA, Vienna (1992)
Kirk RE, Othmer DF, "Encyclopedia of Chemical Technology," 3rd ed., Wiley, New York, 13 (1980)