And then there were 40 ...
The second interview week contains of a series in-depth medical exams such as a colonoscopy, MRI, and full blood work. Since this year's candidates are likely to serve long-duration missions on the ISS, there may be more medical tests this year compared to past selections.
I don't know exactly what else transpires during the second interview week, but I'm sure there is further psychological testing and a second sit-down "interview" with the selection board.
Good luck to the finalists who made it this far!