Firestorm: The Nuclear Man #23

It's one year after the events of Infinite Crisis, and Firestorm is working with Lexcorp testing a new nuclear device. The test goes awry, and Firestorm saves the day. It's revealed that Martin Stein has gone missing and that Jason now merges with Lorraine Reilly to become Firestorm. While separated, Jason and Lorraine are attacked. Both are taken down and Jason explodes because he and Lorraine must remain within a mile of each other.