Since, containment integrity is the main issue under accidental conditions. Radiological consequences of LWR under accident have the grievous impact on the reactor building and its surrounding environment. Iodine is one of the most hazardous fission product releases in the serious accidents. So in this paper, the iodine source term has been evaluated for two-loop PWR under severe accident initiated due to LOCA. The TMI-2 reactor is considered as the reference reactor. The modeling and simulations are carried out by developing a MATLAB base program that uses the post-accident conditions and core inventory as input. The containment response, in order to mitigate the environmental and in-containment iodine source term is studied in normal, emergency, and isolation states of containment. The In-containment iodine source term is calculated with, and without the operation of engineering safety features (ESFs). The mitigation is determined by the activation of ESF. The environmental iodine source term is calculated as the function of containment response. The iodine dependency on the containment retention factor is also studied in all said states of containment. Results indicate the weak sensitivity of Iodine with activation of ESF towards exhaust rate values, under ESFs Operation.