Few industrial accidents present as many repair and cleanup challenges as dealing with a melted reactor core. When a large power plant reactor melts, like at Chernobyl, immediate decontamination is not feasible-the building itself becomes a long-term waste site. Within a year at Chernobyl, engineers had used three hundred thousand tons of steel and concrete to enclose the entire ruined reactor in a twenty-four-story tomb. This sarcophagus had to be built using so called "arms length" methods since workers were limited in how long they could stay near the highly contaminated site.

The radioactivity is so intense coming off the melted core of unit number four that even today this massive building does not stop it all. The hastily built structure is now showing signs of cracking, so Russian engineers have begun to build yet another containment building...