Investigation of mid-loop operation with loss of RHR at INER integral system test (IIST) facility Original Research Article

A series of seven experiments was conducted at the INER integral system test (IIST) facility to investigate the thermal hydraulics of the PWR mid-loop operations with loss of residual heat removal. The measured results of the controlling phenomena for several different plant configurations and core powers are exhibited in explicit curves as a function of time. It is found that in a closed system with higher core decay heat, reflux condensation as well as upflow side flooding and both-side liquid holdup may occur in the steam generator U-tubes. A detailed description of these mechanisms is discussed in this paper.