The tightness of the bell-jar–to–base plate seal is confirmed as the final step in this step. To conduct the leak test, the reactor is evacuated by one of the three mobile Process Vacuum Carts (VC-1401, VC-1402, or VC-1403). The vacuum cart is attached to the reactor via quick disconnect couplings. The leak test is conducted in four steps: initial evacuation, pressure test, depressurization, and vacuum test.