After initially reporting that the quake - which measured 6.8 on the Richter scale and killed at least nine in the coastal Niigata area of central Japan - had not seriously damaged the Kashiwazaki Kariwa plant, the Tokyo Electric Power Co. (TEPCO) eventually admitted that multiple radioactive leaks had occurred.
TEPCO reported late Monday that about 1,200 liters of radioactive water had escaped from a reactor building. And on Tuesday it acknowledged that a damaged exhaust stack had accidentally discharged cobalt-60 and chromium-51, while barrels containing low-level radioactive waste had tipped over.
In all, the company said the plant suffered damage at 50 separate points, raising general questions regarding the safety of nuclear power plants in the earthquake-prone nation, and prompting a government order forbidding the plant from restarting until appropriate checks had been conducted.
Although the plant's emergency system automatically shut down the four power units operating when the temblor hit, a fire that ignited a short time later in the plant's third unit was not contained for three hours, with firefighters reporting inadequate water pressure to effectively combat the blaze.
Japanese experts and officials quickly raised concerns as news of the leak spread, because while it was discovered at around noon Monday, it took until about 6:00 p.m. for the company to confirm the water was radioactive.
The government was not informed until an hour later, and the public did not learn of the incident until nearly 10:00 p.m.
Japan's nuclear safety record is not entirely enviable, especially considering its heavy reliance on atomic energy to power its economy. The country has 55 working reactors, but most were built to laxer specifications, and are able to withstand earthquakes measuring just 6.5 on the Richter scale.
Coincidentally, a review had been launched last September with the aim of raising that standard to 6.9, but Monday's quake has already led some experts to demand the government set even stricter requirements.
Despite plans to rely on nuclear power for up to 40% of its energy needs by 2010, Japan's nuclear industry has been plagued by accidents and scandals involving safety cover-ups.
In 2004, a ruptured steam pipe at the Mihama Nuclear Power Plant in western Japan killed five workers and injured six, and in 1999 an accident at a reprocessing plant killed two and exposed hundreds to radioactive contamination.
