Rodney was helping people on a planet in Pegasus, with permission, to upgrade their tech to run clean nuclear energy as a power source. While he was on the planet, a rival faction/nation captured him and forced him to do the same for them, only they wanted the nuclear tech weaponized, or they don't listen to him and create a huge nuclear accident.
Rodney is crushed, depressed, and angry when one side nukes the other. He is upset because, as he tells his sister (or whomever they visited after), all they had to do was ask for help, and he would have helped them.
So he is back on Earth, trying to get over his captivity, when the story opens. He opens up about what happened throughout the story. No other scientists were held, just him.
Thanks for any info. I don't think the story is 'Catalyst'.