The nuclear crisis at the Fukushima Daiichi nuclear station continues as problems multiply for the workers tasked with controlling the crisis. Japan’s nuclear safety agency raised the severity of the crisis from 4 to 5 on a 7-level international scale (Three Mile Island was also rated 5, and Chernobyl was rated 7). Radioactive steam has been exiting the plant’s second reactor, which was hit by an explosion on Tuesday. Additionally, a crack in the stainless steel lining of the fourth reactor’s storage pool, making it very difficult to refill the pool with cooling seawater. Meanwhile, workers have been focusing their efforts on containing the situation in the plant’s third reactor, where spent fuel rods threaten to melt, thereby accelerating nuclear fission. A U.S. drone has collected visual data from the site that showed that contamination had not spread beyond the 30-km exclusion zone established around the plant.