An explosion at an earthquake-damaged nuclear plant was not caused by damage to the nuclear reactor but by a pumping system that failed as crews tried to bring the reactor's temperature down, Chief Cabinet Secretary Yukio Edano said Saturday.
The next step for workers at the Fukushima Daiichi plant will be to flood the reactor containment structure with sea water to bring the reactor's temperature down to safe levels, he said. The effort is expected to take two days.
Radiation levels have fallen since the explosion and there is no immediate danger, Edano said. But authorities were nevertheless expanding the evacuation to include a radius of 20 kilometers (about 12.5 miles) around the plant. The evacuation previously reached out to 10 kilometers.
The explosion about 3:30 p.m. Saturday sent white smoke rising above the plant a day after a massive earthquake and tsunami crippled cooling systems at the plant in northeastern Japan. Four workers were injured in the blast.
The walls of a concrete building surrounding the reactor container collapsed, but the reactor and its containment system were not damaged in the explosion, Edano said.
