The GDR Meeting site can be accessed by CEA shuttle or public transportation from the station Le Guichet of the RER-B line. Indications about the location of shuttle, buses, and GDR Meeting building can be found at the link :
The CEA shuttle is free and departs every quarter of an hour between 8:00am and 9:30am. L'Orme des Merisiers is the first stop.
Additionnaly the commercial line 9 is available from the Le Guichet station, following the schedule :
Other commercial lines (91.06B, 91.06C, 91.10) are available from Massy station. Maps and schedules can be found at :