RELAP5/MOD3 simulation of the loss of RHR system during midloop operation experiment conducted at the ROSA-IV large-scale test facility

A computational investigation of the experiment involving the loss of residual heat removal (RHR) system during pressurized water reactor (PWR) midloop operations was simulated using the RELAP5/MOD3 thermal-hydraulic code. This experiment was conducted at the ROSA-IV large-scale test facility (LSTF) in Japan. The experiment involved a 5% cold-leg break in one loop along with the loss of RHR (Ref. 2). The computational simulation was run for 1000 s following the loss of RHR and a simultaneous break in the cold leg. The simulation showed that core boiling occurred at ∼500 s after the loss of RHR. The primary pressure also increased following the boiling of the liquid in the core. A maximum core rod surface temperature of 398 K was attained at the end of the simulation