Why don't we build these reactors deep underground? Doesn't the United States use an old abandoned mine to store spent nuclear rods while they decay?<p>Is it extremely cost prohibitive to dig down into existing abandoned mines (or even quarries)? and retrofit them with nuclear reactors?<p>Even if something catastrophic happens, if it's geologically separated by thousands of tons of rocks/dirt/sediment and is away from a water table, it wouldn't be a problem, no?