System and method for reducing atmospheric release of radioactive materials caused by severe accident

A system for reducing the atmospheric release of radioactive materials caused by a severe accident, the system comprising:

• a steam generator disposed in a containment building, configured to generate steam by using heat of a coolant heated in a nuclear reactor, connected to a main steam line and supplying the steam through the main steam line;
• a decontamination tank connected to the steam generator through the main steam line and a connection line and containing decontamination water for decontaminating the steam delivered from the steam generator and released into the atmosphere for reducing the atmospheric release of radioactive materials when a severe accident occurs;
• and
• a depressurizing power generation unit disposed on the connection line and configured to generate emergency power while depressurizing the steam delivered from the steam generator toward the decontamination tank when the severe accident occurs.