One of the waste products of many nuclear power plants is heat. They send it towers in the form of steam and some have dumped heat into nearby rivers. The basic problem is that when you use steam heated by a nuclear reactor to power a turbine, the steam says fairly hot while no longer being very useful for spinning the turbine and generating electricity. One solution to this is co-generation, i.e. using steam generated by a reactor first to power a turbine and generate electricity, and then using the waste heat to, for example, heat buildings. At its best, it is highly efficient. Does anyone know if any nuclear co-generation plants exist on a commercial basis, and if so where and how their track record has been? Are any in the U.S.? Why hasn't this approach been pursued more often? Are there technological barriers?