sentences:  Construction on site began in 1961.Oldbury was the first nuclear power station in the UK to use prestressed concrete pressure vessels, earlier Magnox reactors having used steel pressure vessels more suited to smaller reactors.The design net power output of the station was 626 MWe, but due to steel corrosion problems from the hot carbon dioxide coolant within the reactor, operating temperature had to be reduced soon after operation started causing a large drop in power output.