Following reports of a third explosion and a fire, with radiation levels as much as 400 times above normal, the situation at Japan’s Fukushima Daiichi nuclear plant had become so dire it seemed the country was on the verge of a complete nuclear meltdown. However, some positive developments occurred late Tuesday. The higher radiation levels recorded earlier, possibly from a fire in the No. 4 reactor, stabilized and then dropped toward evening, Japanese authorities said. Also, engineers at the plant are continuing efforts to cool down the most heavily damaged reactor, No. 2, by pumping in seawater with firefighting equipment. Most of the 800 workers at the plant had to leave due to threat of dangerous radiation exposure, but some 50 remained in a heroic attempt to prevent the cores of three reactors from leaking more radiation. The crisis at the Fukushima Daiichi Nuclear Power Station is still the worst nuclear accident since the Chernobyl disaster a quarter century ago, and Japanese Prime Minister Naoto Kan, in a brief morning address to the nation, warned there was “a very high risk” of further radiation leakage.