Three-way valve operational to both transfer steam to a decontamination water tank under one accident situation and discharge the steam to atmosphere under a different accident situation

A nuclear power plant main steam system, which reduces the atmospheric discharge of radioactive materials generated in an accident, the system comprising:

• a decontamination water tank containing decontamination water;
• a connection pipe for connecting the decontamination water tank to a main steam pipe which connects a steam generator and a turbine;
• a main steam safety valve located upstream from the decontamination water tank;
• and
• an atmospheric dump valve,
• wherein the atmospheric dump valve is located upstream from the main steam safety valve,
• wherein the atmospheric dump valve is configured to discharge generated steam to atmosphere when an accident occurs within a design basis;
• wherein the main steam safety valve comprises a three-way valve configured to transfer the generated steam toward the turbine, to close to prevent transfer of the generated steam therethrough when an accident occurs within a design basis, and to transfer the generated steam to the decontamination water tank when a containment bypass accident occurs.