The nuke people I've been talking with discounted nuclear in the district heating role, because they can make power instead, and that's more valuable. Sure, if you reduce power generation a bit you will get far more energy back in the form of 100 degree water, but you can only sell that at capacity during a few winter months. During the rest of the year you'll have an oversized nuke. That costs money. What if you instead build a small reserve turbine that you shut down during the winter? Well, these turbines are pricy. They might well cost hundreds of millions of euros. It's hard to make that work economically when you by definition need to keep this reserve turbine offline as long as the district heating system is online.

Of course, a week after they've explained that it was an economic impossibility Fortum went out and said they'd like to incorporate district heating for Helsingfors (Helsinki) when they build their new nuke at Lovisa...

Peak oil is not an energy crisis. It is a liquid fuel crisis.