The Greifswald Nuclear Power Plant at the Lubmin nuclear power generation complex on the Baltic coast in the former East Germany.
The 1975 accident
A short-circuit caused by an electrician's technical error started a brief fire in the main trough destroyed the electric supply and the control lines of five main coolant pumps. Some news reports said there was almost a meltdown of the then 1 year old reactor core according to some technical reports at the time.
It was covered up until 1989. It was initially categorised as Level 4 INES Scale event, hence the cover up by the government of the GDR, but it has subsequently listed as only level 3 and the melt down was considered not to have happened now.
The lesser 1989 accident
3 of the 6 cooling water pumps were switched off for part of a test. A 4th pump then broke down, leading to the loss of control of the reactor, 10 fuel elements being damaged and a near melt down subsequently occurred.
The accident was reportedly attributed to sticky relay contacts, not human error by the electricians as in the earlier incident.
It was categorised as only a Level 3 INES Scale event.