Yep, the USA build a bunch of them and ran several tests, so they are very qualified to know how bad an idea this is. Radioactive pollution in the air + the risk of an active nuclear reactor falling from the sky. Supposedly some Russians have already died in 2019 when recovering a missile that crashed in 2017.

A much more in depth article than the wiki article, but with more speculation: https://basicint.org/brief-burevestnik/