The temperature of the Unit 1 core coolant increased from to during the 36 minutes required to re-energize the A-side bus. Throughout the event, non-vital power was continuously available to Unit 1 from off-site sources. However, the Vogtle electrical system was not designed to permit easy interconnection of the Unit 1 vital busses to non-vital power or the Unit 2 electrical busses. Since this incident, Plant Vogtle has implemented changes to the plant that allow the non-vital electrical buses to transfer power to the vital buses in this type of scenario.