A reactor system (1) having a reactor 3, at least one cooler (5) connected to the reactor (3), at least one pump (7) for circulating at least some of a liquid heat-transfer medium (9), wherein the pump (7) is connected to the reactor (3) and/or the at least one cooler (5), and a container (11) for collecting the liquid heat-transfer medium (9) is provided. The container (11) is connected to the reactor (3) and/or the at least one cooler (5) and is disposed substantially below the reactor (3) and/or the at least one cooler (5). Also provided are exothermic reactions which are conducted in the reactor system.