Heißdampfreaktor (superheated steam System used to initiate, maintain and control a fission chai...) Großwelzheim/Main, Nuclear reactor with water as a coolant and as a moderator, ... with integrated nuclear superheating with an electric gross output of 25 Megawatt, million times the power unit of watt (W). 1 MW = 1..., nuclear commissioning on 14thOct. 1969. Shut down since April 1971. The plant was used for many years following the shutdown for research projects relating to System used to initiate, maintain and control a fission chai... safety. The dismantling of the plant has been completed and the “green meadow” condition restored.