Veritasium did a great video showcasing such sites, it's 3 years old though so the Fukushima bits have become a lil bit safer and the Chernobyl cover is much more complete
Yeah, the core is still pretty hot, hard to explore robotically, but with how the Fukushima reactors melted down, it's far safer than Chernobyl, which straight-up exploded. Fukushima just kinda popped a hole in the roof with steam pressure and fizzled into the floor