Isolation Condenser (IC) System

The IC is used in older boiling water reactor designs. The IC system transfers residual and decay heat from the reactor coolant to the water in the shell side of the heat exchanger resulting in steam generation. The steam generated in the shell side of the heat exchanger is then vented to the outside atmosphere. The system employs natural circulation as the driving head from the reactor steam side, through the isolation condenser tubes, and back to the reactor.

The IC system is automatically initiated if a high reactor pressure condition is sustained for 15 seconds. The time delay prevents unnecessary system initiation during turbine trips. Also at most plants, the IC system automatically initiates on a low vessel water level to aid in reducing reactor pressure for small line breaks. The IC system is designed to provide core cooling regardless of whether electrical power is available.

The initial system study is documented in "Isolation Condenser System Reliability, 1987-1993" (NUREG/CR-5500, Volume 6 ). The links below provide the current information for the study and latest results.

Current Results (SPAR-based):

Historical Results (SPAR-based):

Historical Results (LER-based):

Supporting Information:

Page Last Reviewed/Updated Thursday, March 16, 2023