If a system is poorly understood, then by definition it cannot be factored into predictions. When we say something is “unlikely” we mean “it is unlikely based on what we understand”. I don’t think it’s very useful to ask, “Well, is it unlikely based on what we don’t understand?”, because that’s not a question that can be answered.
All sources of power require some amount of mined materials, even if its just in construction. Nuclear waste is much less problematic than CO2 emissions, and nuclear power has the advantage of providing a consistent base load.