Taking the train from Paris:
You can take the TGV train from Paris airport (Charles De Gaulle) to Saint Pierre des Corps, (8Km from the Château). You may have to switch trains on Montparnasse station in Paris.
We haven't tried this route.
Click here to go to the TGV web site
Driving from Paris:
An alternative to train is to rent a car in Paris and drive. The drive is about 2 hours. If you make reservations from the US make sure that you get a confirmed quote in US dollars (the car company in France will charge in Euro's).