I have heard recently that a new plant could be built in 5 years at a cost of $1.5 billion.  The advanced reactor designs are simpler than the old dinosaurs and therefore more efficient and quicker to put together.  Standardization would also make everything cheaper and faster.

Utilities are considering six new plants for the US.  In the long run, once they earn out construction costs, they are profitable--even though, unlike other electricity sources, nuclear plants have to pay for security and to be responsible for their waste.

Here's what the Energy Information Agency, usually a reliable source, has to say about new construction:

A primary source of doubt regarding the potential of nuclear power, at least in the U.S., has been whether the recent nuclear technology has been too expensive to compete in the commercial marketplace. There have been no orders for new nuclear power plants during the last three decades in the United States and Canada. Finland's order for a new reactor in 2003 broke a similar extended hiatus in Western Europe, excepting France where orders tailed off later. France now looks likely to follow. Reactor vendors have not ignored the message that their product has recently involved high investment costs and long construction periods. Vendors now seek to position their product with promises of lower prices, shorter construction times, and specified financial arrangements. Most competitors are now offering fixed and historically low prices for at least the nuclear components of their designs.  These promises vary with the price of basic materials such as steel and concrete and as first of a kind engineering costs are allocated or eliminated.  Location, buyer specifications, and regulatory requirements can also alter anticipated costs.

Concerns regarding construction costs for new nuclear power plants contrast sharply with the comparatively low cost of operating commercial reactor designs. Overall operating costs for nuclear power plants, as reported to the Federal Energy Regulatory Commission (FERC), have been roughly the same as (most recently slightly less than) operating costs for coal-fired plants for about two decades. Such operating costs are considerably below the costs of operating most natural gas-fired generation units even when natural gas prices are relatively low. Moreover, the fuel cost component of operating a nuclear power plant is particularly low. This operating cost advantage has given existing nuclear power units a favored position in the provision of base load electric power. Nuclear plant designers hope to take advantage of such low operating costs in positioning their new designs.  Whether they will succeed has not yet been demonstrated.  http://www.eia.doe.gov/cneaf/nuclear/page/analysis/nucenviss2.html