Sweden's first commercial nuclear plant[0] was built right next to a newly constructed suburb precisely so that it could be used for district heating too. And also for producing small quantities of weapons grade plutonium, for... research purposes. Waste not, want not!

(It didn't last very long and was shut down in the mid 1970's, for somewhat obvious reasons.)

[0]: https://en.wikipedia.org/wiki/%C3%85gesta_Nuclear_Plant