Venue to Salle des conseils
The "Salle des conseils" is easily reachable from the RER B - Orsay Ville train station by exiting the station on the "University exit" side (opposite to the city side) and walking 2 min to the 100M building entrance. See point of interest 2 on the detailed map:
https://www.ijclab.in2p3.fr/wp-content/uploads/sites/12/2021/01/map_IJCLab-A4-RectoVerso-180923.pdf
Wednesday social dinner
Everybody is welcome to the Wednesday's social dinner that will take place at Gramophone (27 boulevard Dubreuil, Orsay, near the Orsay-Ville RER train station) and the meals cost will be covered by IJCLab group.
https://www.qwant.com/maps/place/osm:way:65654421@Le_Gramophone#map=16.50/48.6979470/2.1843911
Thursday lunch
The Thursday lunch will be at the CESFO canteen (plan to bring about 15€ in cash if you'd like to join):