> a problem in a secondary system (an added safety system) "Secondary" in nuclear parlance for a PWR refers to the loop of water that cycles through the steam

> a problem in a secondary system (an added safety system) "Secondary" in nuclear parlance for a PWR refers to the loop of water that cycles through the steam generators and turbines, while the "primary" loop cycles through the reactor and steam generators. Not to detract from your point, which is a good one, and the pressurizer relief valve that stuck open and through which the cooling water escaped was indeed an added safety system.