We covered Hyperion's trailer sized nukes, last we heard, the Department of Energy was installing one at Savannah River.*Here's another contender, from the Al Fin blog:
After the doomsday bell tolls, you will want to have a safe hideaway, packed with your favourite foods, beverages, people, and prescription drugs. But no matter how safely your bunker is designed, you cannot survive long without a source of heating and electrical power.
Issues of energy density dictate the need for a nuclear power and heat source -- either fission or fusion. The choice seems to come down to either a small modular nuclear fission reactor -- such as the NuScale or Wilcox and Babcock models, vs one of the new scalable fusion reactor models. The Lawrenceville Plasma Physics focus fusion device pictured below, appears to be the leader of the pack in terms of timeline for proof of concept, prototype, commercial demo, and mass production.
All images below taken from Lawrenceville Plasma Physics Inc (PDF) (via) NBF
Five megawatts baseload power should be enough to supply the power and heat needs of most medium-sized doomsday communities. When living in an underground environment, it is easy to underestimate needs for space lighting and grow-lighting, as well as power for supplying pumps, compressors, blowers, fans, filtration devices, and various electronic devices.
The diagram above attempts to illustrate energy flows and losses in the focus fusion system. Operation of the reactor will be highly automated, but a certain amount of oversight will be necessary, to assure smooth function and to limit the need for unscheduled maintenance shutdowns....MOREPreviously:
First Order for "small, compact, transportable, nuclear power reactor"?
Lloyds List, Hyperion Power, Enterprise Shipping to Explore Nuclear Propulsion for Commercial Shipping
Hyperion to Build Demonstration Nuke the Size of two Hot Tubs for DOE Savannah River Site