Solar, Man of the Atom (1992 Valiant Series) #1

Second Death. Part One: No Place Like Home

Finding himself floating above Earth, disoriented, Phil Seleski returns home, only to find another him in his apartment! Confused, he departs to stop a prison riot and raise a damaged Soviet nuclear sub. But, strangely, it seems the world isn't ready for a super-being doing good deeds. Finally realizing he has somehow come back through time, Phil cannot remember how. But he knows he's repressing a memory too terrible to bear!

Alpha and Omega. Part One

In chapter one, the experimental fusion reactor at the Edgewater Fusion Energy Research Center a.k.a. "the Edge" runs out of control, threatening to erupt into a sun-like fireball that will kill millions.

Doctor Phil Seleski, the principal designer of the device, realizing that his obsession with unlocking the secrets of fusion has led to catastrophe, races into the containment to attempt to shut the reactor down manually.