And that's with incompetence and neglect.

http://chernobylgallery.com/chernobyl-disaster/cause/

Personnel had an insufficiently detailed understanding of technical procedures involved with the nuclear reactor, and knowingly ignored regulations to speed test completion

And a Japanese reactor that didn't melt down:

https://thebulletin.org/onagawa-japanese-nuclear-power-plant...

Before beginning construction, Tohoku Electric conducted surveys and simulations aimed at predicting tsunami levels. The initial predictions showed that tsunamis in the region historically had an average height of about 3 meters. Based on that, the company constructed its plant at 14.7 meters above sea level, almost five times that height. As more research was done, the estimated tsunami levels climbed higher, and Tohoku Electric conducted periodic checkups based on the new estimate.

There's just no good reason for either Chernobyl or Fukushima. Both were preventable by following simple safety procedures.