Stress mitigating arrangement for working fluid dam in turbine system

A steam turbine (ST) system, the ST system comprising:

• at least one of a high pressure (HP) turbine and an intermediate pressure (IP) turbine;
• a casing including a body having an open interior for enclosing the at least one of the HP steam turbine and the IP steam turbine;
• a first working fluid flow path defined in the body for directing a first working fluid flow in the open interior in a first direction;
• a second working fluid flow path defined in the body for directing a second working fluid flow in the open interior in a second direction that is opposed to the first direction;
• and
• a steam dam extending radially and axially in the body between the first working fluid flow path and the second working fluid flow path to redirect the first and second working fluid flows to the at least one of the HP steam turbine and the IP steam turbine, the steam dam including a stress-mitigating slot extending radially therein;
• and a fill member mounted in the stress-mitigating slot.