Origin Story: Government scientist Bruce Banner hides in a remote desert bunker, preparing to detonate the world's first gamma bomb. Meanwhile, idiot teenager Rick Jones somehow manages to bypass government security, waltz out onto a restricted desert test area and stand on a big red "X" while picking his nose thoughtfully. Banner spots the teen and immediately realizes what he should do: detonate the bomb. Sadly, he listens to his conscience instead, telling his colleagues to delay the countdown while sprinting out into the desert to rescue the idiot.
What Banner doesn't know, though, is that his trusted colleague Igor Starsky... is a filthy, filthy Commie spy! With impeccable logic, Starsky reasons that if Banner is killed in the explosion, America will halt testing on gamma bombs, and glorious Russia will realize its dream of spreading its economically crippling socialist ideologies on an unsuspecting world. He and Hutch launch the gamma bomb just as Banner heroically pushes Rick into a nearby trench, taking the brunt of the gamma explosion head-on. It's tragic...
Or is it?
Comic Book Consequences: No! It's fucking awesome! Bruce Banner is transformed by life-giving radiation into the Hulk (who is incredible). He's enormous, incredibly strong and fueled by Bruce Banner's anger.
Would you like Bruce when he's angry? Good sirs, we humbly propose that you would not.
What Would Have Happened in Real Life: A gamma bomb (or "dirty bomb") is specifically designed to spread radioactive material with the intent to kill, using conventional explosives to help distribute it. From the perspective of Bruce banner at ground zero, getting hit with a gamma bomb would be no different than getting hit with a plain ol' bomb: You'd explode hilariously, which he does.
Meanwhile, all nearby towns within the blast radius of the detonation site-and, luckily, Teen Idiot Rick Jones-succumb to radiation poisoning over a period of weeks. The ensuing cover-up and media frenzy ignite the biggest American political fiasco of the century, as the front pages of respected newspapers showcase doe-eyed children trying pathetically to hold ice cream cones in their mutated flipper hands. The controversy halts America's burgeoning nuclear research effort. This is good news for Igor Starsky, who uses the gamma bomb blueprints to help the Commies take over the world. (And really, good for them. They worked hard and they earned it.)
A Second Possibility: Presuming that Bruce Banner managed to find a heretofore-undiscovered radioisotope, his gamma bomb does, in fact, turn him into a towering green monster when detonated-albeit a towering green dead one, since a gamma bomb still needs a conventional explosive to distribute it. A half hour after detonation, it then turns the populations of all nearby towns downwind of the blast site into towering green monsters. Since they are fueled by rage, and since getting transformed into a green mutant would make anyone irritable, they commence rampaging throughout North America, triggering the first Mutant War. The Russians make the best of America's confusion by, again, taking over the world (they're such dicks).