The biggest reason for the cost overruns at Vogtle/Summer is an inexperienced construction workforce, especially management. Costs for the last round of nuke construction were high because we tried to build way too many at the same time, diluting the workforce. Then after an almost 30 year layoff, we tried again, but this time almost all the experienced nuclear construction folks had retired or died with no replacements. Watts Bar 2 ran over because of stupid management decision at the re-start of the construction, and then the same happened for Vogtle and Summer.
I am among the youngest of the engineers who built and started up the last batch of plants, and I am 61. The guys who were our managers back then, especially the good ones, were at least 10 years older, most were 20 years older. I hope we can keep an small cadre of experienced nuclear construction managers/engineers/craft active when Vogtle and Summer go online. Maybe, if all goes well, someone will order another one.