Abstract: THES TUDY ON THE COUNTER CURRENT EXTRACTION PROCESS OF HIGH ENRICHED URANIUMWANG JIANCHEN；JIAO RONGZHOU；LIU BINGREN（Institute of Nucler Energy Technology，Tsinghua University，Beijing，102201）WANG SULAN（BeiJing Institute of Nuclear Engineering，l00840）ABSTRACT The counter current extraction process of high enriched uranium with critically nuclear safemixer-settler has been studied． The distribution curves of acidity and uranium have been ob-tained．The results fit these of test tube extraction cascade experiments well．The interface heightand the ratio of the contract phases have been examined．The height of the liquid surface lowerthan the critically nuclear safe limit．The rate of recovery of uranium is more than 99．9％. Theextraction efficiency of stage is more than 85％.Key words Mixer-settler High enriched uranium Critically safe