Asahi reports that attempts to cool the Fukushima Daiichi Unit 1 reactor with massive infusions of water -- called "water entombment" -- has failed due to large-scale leakage of the water from the primary containment structure. 3,000 tons of highly radioactively contaminated water has leaked into the reactor building's basement, threatening to overflow into the turbine building and then the ocean, as has happened previously at the Unit 2 and 3 reactors. Installing new cooling systems is very dangerous for workers, as radiation dose rates of up to 200 rem (2,000 millisieverts) per hour have been detected in the building. About 500 rem of exposure will deliver a lethal dose to 50% of people; they will die within 60 days, even with medical intervention.