Nuclear waste literally comes from power plants. If their residual heat could be used to generate electrical power, it would be done already.
It can be (and is, although not everywhere) used, for cogeneration - residual heat from any thermal plant used for district heating/industrial heating processes.
Nuclear waste also comes from plutonium production. And it could be used to generate power, but this leads to fuel reprocessing, which runs afoul of nonproliferation treaties, as it produces weapons-grade fissile material.
It can be (and is, although not everywhere) used, for cogeneration - residual heat from any thermal plant used for district heating/industrial heating processes.