[en] Analysis of TLOFW(Total Loss of Feed-Water) has been performed using NPA based on MARS code with acceptance criteria considering design features for Kori 3 and 4. It is assumed that operator recognizes the event when the followings are satisfied : the loss of auxiliary feedwater, steam generator dryout, and pressurizer PORV automatic opening. Acceptance criteria are as follows : First, all the three PORV flow paths and all the two SI pumps have sufficient capacity to prevent core uncovery with two feet margin during a TLOFW event when all PORV flow paths are manually opened at 30minutes after the operator recognizes TLOFW. Second, two of three PORV flow paths in conjunction with one-of-two SI pumps have sufficient capacity to prevent core uncovery with two feet margin following a TLOFW event when two PORV flow paths are manually opened at recognition point of TLOFW. The analysis results show that the active core is covered with more than 2ft margin for the two cases, respectively