Abstract: IMPROVEMENT OF TRPO EXTRACTION SYSTEM FOR REMOVAL OF ACTINIDES FROM HLWYANG DAZHU；JIAO RONGZHOU；DOU SHIREN；ZHU YONGJUN（Institute of Nuclear Energy Technology，Tsinghua University，P.O. Box 1021，Beijing 102201）ABSTRACT The formation of the third phase in the treatment of high level waste by TRPO extractionhas been observed．The influence of diluting the feed solution and intreducing additives to the or-ganic solution on thc formation of the third phase and the extraction coefficient of Am have beenstudied．The radiation stability of TBP-TRPO-kerosene has been tested. Key words HLW TRPO Extraction Third phase Additive Actinides