Safe (er) Nuclear Energy?

MIT has released a study by the Nuclear Science and Energy Department on a concept to build modular and relatively cheap nuclear reactors to generate electricity or hydrogen. The Pebble Bed reactor described in the study It relies on hundreds or thousands of self-contained, tennis-ball sized graphite "pebbles" encasing small uranium pellets. These pebbles when piled together within a reaction vessel undergo nuclear fission, heating gas to turn a turbine.Has a number of advantages over current nuclear reactor technology: It cannot undergo runaway nuclear fission, damaging or destroying the reactor. The cooling system is dramatically less complicated and more robust than that of current reactor technology, leading to lower construction costs. The design is modular, so components can be constructed in assembly-line fashion and transported into place, again reducing costs of building them. Because the reactor itself is small, multiple reactors can be built in high-demand areas. Disadvantages include the fact that depleted pellets may be difficult to contain over long periods of time. Interestingly, the authors notes that this technology may be small enough to power some vehicles (though likely airship, aircraft, or naval-vessel sized, as opposed to personal-vehicle side). Military implications can include reduced dependence on imported oil, and (with transportable, ship or airship-mounted designs), high-power generation in remote, expeditionary environments.