What is "massive contamination"?
Who says we will have "massive contamination"?
Depending on what your definition of "massive contamination" is, it may or may not be possible to build the perfect plant. There is always "something else" that could go wrong.
Sure. My idea of "massive contamination" is somewhere way below what was released at Chernobyl.
As a starting point for safe reactor designs, consider the Voyager probes. :)