Image of the U.S. rescue effort in Japan following the earthquake and tsunami (Photo courtesy of the U.S. Navy).

Japan’s nuclear crisis entered its fifth day on Tuesday as the Japanese government ordered 140,000 people to seal themselves indoors to avoid radiation exposure. 

As aftershocks continued to rock Japan, nuclear experts continued their struggle to contain the aftermath of explosions, fires and nuclear fuel-rod exposure at the Fukushima Nuclear Power Plant – a six-reactor nuclear power complex north of Tokyo. Fukushima took the brunt of Friday’s devastating 9.0 magnitude earthquake and subsequent tsunami. 

Although officials conceded Tuesday that the radiation levels for Fukushima and the surrounding area were high enough to affect human health, those outside the evacuated 12-mile radius from the plant face little danger.

But Japanese officials fear that the worst is still to come from what’s being called the worst nuclear disaster since the U.S. bombing of Hiroshima and Nagasaki during the Second World War.

"There is a danger of even higher radiation levels," said Japanese Prime Minister Naoto Kan, in a nationwide address. He reassured Japan that authorities were doing “everything they can" to contain the leakage.

Elevated radiation levels were detected in Tokyo on Tuesday, but officials said that the readings would not affect health levels.

Tuesday’s most serious blast at the Fukushima Nuclear Power Plant came just before 7 a.m. in the plant’s No. 2 reactor. Later, officials reported that spent nuclear fuel in reactor No. 4 heated up, sparking a fire that was quickly put out.

A timeline of Tuesday’s events from the Christian Science Monitor:

• An explosion hits Fukushima Daiichi's No. 2 reactor in the morning. Readings indicate some damage to the No. 2 reactor's suppression pool, a donut-shaped reservoir at the base of the reactor's containment vessel.
• A fire is ignited in the No. 4 reactor building Tuesday, but is later put out.
• The plant is emitting as much radiation in one hour as it normally would in six months, but government spokesman Yukio Edano says: "The possibility that a large amount of radiation has been released is low."
• The head of France's Nuclear Safety Authority, says the international alert should be from a level 4 disaster to a level 6 incident.
• Foreign companies begin to order evacuations of their employees.

--

To reach Benjamin Gottlieb, click here.

Follow him on Twitter @benjamin_max.