1 sec Alarms sound within the control room. 2 sec Because heat is no longer being transferred to the secondary loop, water pressure and water temperature in the primary loop rise. This is normal and no cause for concern. 4 sec Backup pumps within the secondary loop automatically turn on. However, these pumps are disconnected from the system by cutoff valves.
Operators assume that the pumps are doing what they're supposed to do.
The control rods , made of boron and silver, are lowered, which slows down the nuclear chain reaction within the core. Heat is still generated, though. In this state, the core produces enough energy to light 18,000 homes. The PORV light goes out, indicating that the valve is now closed. The valve is actually still open.