"TOKYO — Emergency vents that American officials have said would prevent devastating hydrogen explosions at nuclear plants in the United States were put to the test in Japan — and failed to work, according to experts and officials with the company that operates the crippled Fukushima Daiichi plant.
The failure of the vents calls into question the safety of similar nuclear power plants in the United States and Japan. After the venting failed at the Fukushima plant, the hydrogen gas fueled explosions that spewed radioactive materials into the atmosphere, reaching levels about 10 percent of estimated emissions at Chernobyl, according to Japan’s nuclear regulatory agency.
Venting was critical to relieving pressure that was building up inside several reactors after the March 11 tsunami knocked out the plant’s crucial cooling systems. Without flowing water to cool the reactors’ cores, they had begun to dangerously overheat."
Hiroko Tabuchi, Keith Bradsher and Matthew L. Wald report for the New York Times May 17, 2011.