This kid has been showing up in news feeds, but only credulous pop media articles, not hard science reporting. What did he build, and what physics does his device do?
He built a fusor. It's basically a small particle accelerator designed to fuse atoms together. It can be used as a neutron source or to produce commercially useful radioisotopes. It doesn't produce any net power- the acceleration takes far more energy than the fusion produces even if all of that energy could be harnessed, so calling it a "nuclear reactor" is more than a little misleading.
You don't see it in hard science reporting because it's not notable from a scientific standpoint: anyone with 10 thousand dollars, some technical skills, and sufficient free time can build one in their garage.