For the nukes there are a few so called SMR (small modular reactors) being worked on, and some of the are in process of licensing with NRC. The main selling pint is that these units with a capacity of about 200MWe can be deployed under 1bil dollars when compared to 15bil dollars for a large plant (>1000MWe). Most of these small plants can operate in a load follow mode, similar to gas plants. Also their footprint is similar to that of a gas plant rather than to that of a large nuke.

See for example:

BW mPower http://en.wikipedia.org/wiki/B%26W_mPower

Nuscale http://en.wikipedia.org/wiki/NuScale

SMR-160 http://en.wikipedia.org/wiki/SMR-160

Westinghouse SMR http://en.wikipedia.org/wiki/Small_modular_reactor#Westingho...