Why did we ever not use the nuclear waste as a power source?
No. Seriously. It's still radioactive. Thus release energy.
Right now those sticks are just submerged in water that are constantly replaced.
I can think of the top of my head of at least three way to add a turbine to that. Without reshaping the the Rods themselves. Nor Endangering the environment.
Option A
Each rod is in a tube. The water around it warm and rise. As the water go through it, the tube, which is made of an Electro-Thermal coupling system. Uses the heat differential to generate power.
Option B
The rods are around a cone, from the wide-Face-down cone cold water flow out, and are wormed by the rods.
The Tank walls also lean in.
At the top of the cone, instead of a point, a tube rises a few feet. with a turbine at the line between cone and tube.
Rational - The Rods heat the water. that rise. this draws more from the cone.
The leaning walls of the chamber meant they don't cool too fast. Thus the tube draws more water at the top.
A much wider surface area at the top will allow a sufficient cooling so the cycle is maintained with less resources invested than gained.
Option C
Honestly - a combination of the other two.