I read this story 1 or 2 years ago.
My details are a little bit foggy, but the main gist of the story is that an astronaut learns that some dastardly villain (I think he was posing as a philanthropist?) planned to launch missiles/nukes at the Earth. The night before the attack, the astronaut gets rid of the fuel (probably plutonium), and as he dies from radiation, he thinks about his wife and everybody back on Earth. Back on Earth, he's celebrated for his heroic deeds.