The Primary Coolant Loop Test Facility [Primӓrkreislӓufe Versuchsanlage (PKL)] PKL I2.2 Benchmark experiment for an intermediate-break loss-of-coolant accident (IB-LOCA) with a 13% or 17% break at the cold leg was performed in the Organisation for Economic Co-operation and Development/PKL-4 project at PKL in Erlangen, Germany. Analysis of Thermal-Hydraulics of LEaks and Transients (ATHLET) 3.1A was used at Karlsruhe Institute of Technology for its posttest calculations. Crucial predicted parameters were compared with measured data. The calculated trend of the selected parameters fits well with that of the experimental data except for the phenomenon of core heatup and the value of the peak cladding temperature. A fast Fourier transform–based method was chosen to quantify the matching of the parameter trends. According to the quantitative assessment, the IB-LOCA scenario and its detailed phenomena can be predicted well by ATHLET. Additionally, some discrepancies, i.e., insufficient reliable predictions for break mass flow and for reactor pressure vessel collapsed water level, were also observed, possibly deserving another study to undergo deeper scrutiny.