Japanese official says pumping system caused nuclear plant blast
- NEW: The walls of a concrete building surrounding the reactor collapsed, a cabinet official says
- NEW: A wider evacuation is ordered at a second plant, Fukushima Daini, IAEA says
- The explosion at the quake-damaged nuclear plant was not caused by the reactor
- Japan's nuclear agency says radioactive cesium is detected in the air near one plant
(CNN) -- 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.
Before Edano's announcement, Malcolm Grimston, associate fellow for energy, environment and development at London's Chatham House, said the explosion indicated that "it's clearly a serious situation, but that in itself does not necessarily mean major (nuclear) contamination."
Japanese public broadcaster NHK said the injured workers were in the process of cooling a nuclear reactor at the plant by injecting water into its core.
The Fukushima prefecture government said hourly radiation levels at the plant had reached levels allowable for ordinary people over the course of a year, Kyodo reported.
Skipping on down...
Agency earlier said atomic material had seeped out of one of the five nuclear reactors at the Daiichi plant, located about 160 miles (260 kilometers) north of Tokyo.
"This is a situation that has the potential for a nuclear catastrophe. It's basically a race against time, because what has happened is that plant operators have not been able to cool down the core of at least two reactors," said Robert Alvarez, a senior scholar at the Institute for Policy Studies in Washington.Read More and See Videos...