There are two scenarios below, can you please answer the following questions for each:

$-$In a CANDU $9$ reactor, if there is excess feed flow due to the PHT feed valve failing open, what are the initial consequences, what control system tries to respond and how, and what should the unit operator do$?$

$-$In a CANDU $9$ reactor, if the pressurizer surge valve fails closed, what is the consequence if reactor power remains at $100\%$FP$,$ what is the consequence if reactor power decreases to $50\%$FP$,$ and what should the unit operator do$?$