I wasn't speaking of a specific project, just the average times it takes for the stages (deciding on the site, construction, testing). I am sure depending on circumstance, you can trim some time off on the deciding site part as it's the most time consuming. U.S. Nuclear Regulatory Commission has to grant a license to the companies before even talking about building a plant. Then the site has to be chosen and the type of plant agreed on. Once decided the company then has to get a "combined license" (COL) application going and this is where the public is introduced. Every single regulatory plan has to be gone through by all parties and agreed upon. On average, the approval process alone is 5ish years. Once all that is agreed to, the NRC issues the combined license and construction can begin. For a large plant it's at minimum 5 years to build...smaller ones can be 3-5. They alot a year to two years for testing once construction is complete.
Full Disclosure...these were the timeframes in the 2014-2016 timeframe, so things may have changed. However, I am unaware of a plant that's been built in the last 25ish years so. To me, it feels like people have been convinced that the amount of time to go through these steps are what make us safe. The government has convinced us it's a safety feature, not inefficiency on their part...similar to how some view vaccines these days.