The USSR built a nuclear district heating system in Gorky (now Nizhny Novgorod) but never commissioned it because of the general anti-nuclear sentiment at that time.
It's certainly possible and not even very hard (by nuclear standards) because the reactor can operate at ambient pressure.
The biggest issue is inefficiency and cost of district heating except for places like Finland. It's now cheaper to install heatpumps instead.
Bohunice Nuclear Power Plant is used for nuclear district heating.
"Upon development of a district heating supply network in the town of Trnava near Bohunice NPP, V2 switched to co-generation. Part of this system is a heat feeder line commissioned in 1987. In 1997, a heat feeder line to Leopoldov and Hlohovec was created, branching off from the Trnava line."
https://www.world-nuclear-news.org/articles/fourth-finnish-m...
"Feasibility of small modular reactors for decarbonizing district heating systems: a case study of the Helsinki metropolitan area"
https://www.sciencedirect.com/science/article/pii/S002954932...
Haiyang’s District Heating Project in China
https://www.iaea.org/newscenter/news/carbon-free-heating-kee...