http://www.youtube.com/watch?v=gnVV9sq78Yg
Tokyo Electric Power Company, or TEPCO, says its workers detected radioactivity of 900 millisieverts per hour being emitted from a 30-by-30 centimeter concrete fragment, 5 centimeters thick, on Wednesday
Source: http://www3.nhk.or.jp/daily/english/24_01.html
For conversion purposes, 0.9 Sieverts = 900 Millisieverts = 900,000 Microsieverts. Radiation levels of 4 sieverts per hour will cause fatality in 50% of people and at 6 sieverts per hour death is almost certain.