Why did the valve allow the reactor to permit radioactive steam to escape in Pretoria West, South Africa 2006?

kofex (PTY)LTD built a nuclear reactor in 2000|||Rubbish! There are only three nuclear reactors in SA. Two full scale units at Koeberg near Cape Town and a small experimental unit at Pelindaba. They all date from the early 1980s. No other reactor was built in 2000 or any other time.