In order to get TGV Sud Est engine, you have to finish the following achievement:
You need to sell 200 000 uranium units.
This means that you need to click on your Materials and the Sell button as this screenshot shows:
Use slider to select at least 200 000 units of U-235 and hit Sell:
Afterwards the achievement will be finished, you can collect your TGV Sud-Est locomotive, add all 9 TGV Sud-Est wagons and send the complete set to Lucy to finish her objective #17