cool, wonder what the down side is?
The simple fact it is nuclear energy will doom it's implementation in the U.S. The average citizen doesn't understand the advances in reactor design and fundamental shifts a pebble bed reactor has with respect to efficientcy and safety. The envirowackos will use that ignorance against the better interests of this country and continue their massive no nuclear power for any reason at any time attitude. Even if the go ahead was given, it would be tied up in state and federal courts for decades before the first shovelful of dirt is turned in the construction.
Possible drawbacks:
1. Since they are inherently safe, there may not be a need for a containment structure to contain the results of an accident. This may make these reactors more attractive as a terrorist target. Solution: require a missle shield.
2. There will be a greater volume of radioactive waste (not more radioactivity), simply because of the size of the pebble. Offsetting aspects of a PBMR include the ability to use non-enriched uranium, and the used pebbles are inherently safer to handle...and some argue are safe enough to dispose of as is.
Unknowns.
1st, these are just designs. None has ever been built. 2nd, fuel handling is extremely complex. 3rd, it's gas cooled and past experience with gas cooled reactors has not been encouraging from a reliability standpoint. There are just too many unknowns at this point to start jumping up and down.
All that said, I'd like to see research continue and see if these can be commercially viable, but I wouldn't dump all of my eggs in that basket right now. We know that light water reactors work well and we need to start building more of them now.