We know how to store it safely though melt the radioactive material into glass ingots and store them in stainless steel barrels at the bottom of old mineshaft in geologicly stable dry areas like yukca mountain. But NIMBYs wont let us. The fear of leaking containment vessels goes back to early days of nuclear such as the Hanford site. Yes thats a horrible mess and a Superfund site. It also dates back to the Manhattan project and waste from the first nuclear pile. We have learned a bit more since the 1940's.

AFAIK it's pretty well know how long the shielding works, so you can always renew it. Also, with coal the shielding is impossible at all.