They started building it before detailed design was done which is always the case with construction projects but they really misjudged how early they could star

They started building it before detailed design was done which is always the case with construction projects but they really misjudged how early they could start. As a result, whenever they had to stop to review an element of the construction plan or detailed design, they had to idle the entire trained workforce. Since you can't just hire nuclear trained welders etc off the street in Finland, these people were paid but doing nothing during that time. Contrast with China where this happened with their EPRs, they are building lots of other nuclear plants to they just put the labour force on buses and moved them to other projects for a few months. Obviously that makes a big difference.