The radionuclides were released to the environment through MSSV in the base case. On the other hand, the in- containment relief valve prevents the release of the radionuclides to the environment.

As the adverse effect of ICRV, the release steam through ICRV increases pressure in containment building. And it reached 1.2 MPa, which is higher than 0.75 MPa of the base case pressure.

To reduce the adverse effect of ICRV, depressurization strategy in which the ICRV was connected to RDT was conducted. But it was ineffective because the capacity of the water in the RDT did not satisfy the release steam from steam generator

The overpressure which is adverse effect of the ICRV can be reduced by cavity flooding. The decay heat removal of the cavity flooding causes the depressurization with the steam condensation. The cavity flooding decreased the containment pressure from 1.2 MPa to 0.8 MPa in the ICRV case.

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