IC8 was created for hot zero power of RC pressure near 2200 psia and Tavg 560ºF. By opening the left side single ADV and lock it open, a flow rate about 500 lb/s is discharged from loop A. It overcools the RCS. As a result, moderator temperature reactivity causes return to criticality and a power surge. PCTRAN’s result (about 20% peak) is greater than the MHI prediction of 5%. Depressurization in the RCS initiates HSPI and its boron reactivity suppresses the total reactivity back to sub-critical.
Apparently MHI’s analysis has assumed that all MSIV’s were closed so the intact side not affected by the ADV opening. We assumed that they were still open so both decreased