EE INSTRUCTED TO MOUNT 500 HP MOTOR TO A DISCONNECTED/ISOLATER BOOSTER PUMP FOR MC-1 PLANT. EES OPENED 13.8 KV TRANSOFRMER WHICH FEEDS POWER TO THE BOOSTER PUMP AND A TAILS PUMP. (EE OPENED 13 .8 KV TRANSFORMER-DUAL WHILE TAILS PUMP WAS IN OPERATION.TRANSFORMER VAPORIZED WHEN OPENED. FIR CONTAINED WITHIN CABINET. EES NOT INJURED.) ""NEAR MISS INCIDENT"".