Update (March 15): Shortly after this post was originally published, the situation at the Fukushima Daiichi facility worsened dramatically: there was an explosion at a third reactor, which may have damaged the containment unit there, along with a new fire. Reports elsewhere now suggests that more radioactive material escaped, but the extent of the risk of further release of radioactivity is not yet clear. The title of the post has been edited to reflect the changing situation. (Original title: "Relax: Fears Of Japan's Radioactive Leakage Are Overblown")
A second explosion hit Japan's Fukushima Daiichi nuclear power plant today and authorities are preparing to pump seawater into a third imperiled reactor. But considering that Friday's earthquake was seven times more powerful than the maximum limit they were designed to withstand, we're lucky the situation isn't much worse. Japan's scenario is a far cry from Chernobyl: Any radioactive leakage that has occurred is low, and unlikely to affect anyone outside the local area (if that). What Happened Both today's explosion (in reactor No. 3) and the one on Saturday (reactor No. 1) have the same cause: a breakdown in the cooling system as tsunami waters swamped generators. Specifically, today's explosion was caused by hydrogen gas, which builds up as the seawater that's pumped in to cool the reactor also heats up. From video footage, the explosion looks devastating, and while 11 people were injured, the steel and concrete containment shell around the nuclear reactor was not damaged---which is the main reason why authorities say the situation is mostly under control. "There is no massive radioactive leakage," Cabinet Chief Cabinet Secretary Yukio Edano told the New York Times. Here's a rundown on the risks in the leakage that has occurred: What Is Escaping (and How)? The root problem is heat: Even though the nuclear chain reaction is safely stopped in all of Japan's nuclear reactors, that doesn't stop heat from building up.
