Thorium Nuclear Power generators scale beautifully from small portable generators to full size power plants. One of the first applications was as an airborne nuclear reactor.
Granted this was not a Thorium breeder reactor, but it proves nuclear reactors can be made lightweight. Thorium reactors can be made even lighter as long as they are not of the breeder type.
Lawrence Livermore, Los Alamos, and Argonne national laboratories are designing a self-contained nuclear reactor with tamper-resistant features. Called SSTAR (small, sealed, transportable, autonomous reactor), this next-generation reactor will produce 10 to 100 megawatts electric and can be safely transported on ship or by a heavy-haul transport truck.
This type of reactor can be transported to disaster areas, and provide emergency power, during rescue and rebuilding efforts. This particular reactor still uses solid fuel and steam heat exchanger. A LFTR reactor with a supercritical CO2 gas heat exchanger would be even more compact and efficient.
From these compact designs, Thorium power can be scaled up to any size.
Len Bilén's blog, a blog about faith, politics and the environment. 