“What’s happening now is ³more akin to the reactor accident at Three Mile Island in Pennsylvania in 1979 than Chernobyl,” blogged Aleksandr Uvarov, editor of the Moscow-based web portal AtomInfo-Center. At Three Mile Island, a coolant failure led to a partial reactor core meltdown—though like in Fukushima, the casing of the Three Mile Island reactor wasn’t breached, unlike the catastrophic explosion that blew apart Chernobyl.

Japanese Chief Cabinet Secretary Yukio Edano confirmed Sunday to reporters that a partial meltdown in Reactor 3 is “highly possible,” and the presence of radioactive cesium in leaked radiation suggests that fuel rods have already melted, according to U.S. nuclear physicist Ken Bergeron. “The containment building at this plant is certainly stronger than that at Chernobyl but a lot less strong than at Three Mile Island, so time will tell,” he said.