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Tensions are rising in Japan over radioactive water leaking into the Pacific Ocean from Japan's crippled Fukushima Daiichi nuclear plant, a breach that has defied the plant operator's effort to gain control.

Prime Minister Shinzo Abe on Wednesday called the matter “an urgent issue” and ordered the government to step in and help in the clean-up, following an admission by Tokyo Electric Power Company that water is seeping past an underground barrier it attempted to create in the soil. The head of a Nuclear Regulatory Authority task force told Reuters the situation was an "emergency." (See Pictures: The Nuclear Cleanup Struggle at Fukushima.”)

It marked a significant escalation in pressure for TEPCO, which has come under severe criticism since what many view as its belated acknowledgement July 22 that contaminated water has been leaking for some time. The government now says it is clear that 300 tons (71,895 gallons/272,152 liters) are pouring into the sea each day, enough to fill an Olympic-size swimming pool every eight days. (See related, “One Year After Fukushima, Japan Faces Shortages of Energy, Trust.”) While Japan grapples with the problem, here are some answers to basic questions about the leaks

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A more recent update

Japan's Nuclear Regulation Authority announced Wednesday that it officially is reclassifying the radioactive water leak at the troubled Fukushima Daiichi nuclear power plant from Level 1 to Level 3 on the International Nuclear and Radiological Event Scale (INES), denoting it as a "serious incident."

That rating sounds ominous, to be sure. But its real meaning—and the significance of Japanese officials' decision to make a more dire assessment of the crisis—are, like many other ramifications of the ongoing crisis at Fukushima, frustratingly unclear.

"In some respects, it's not that big of an issue what they call it," explained David Lochbaum, a veteran nuclear engineer who works as a safety advocate for the Union of Concerned Scientists. "It's still the same mess." (See related: "Latest Radioactive Leak at Fukushima: How Is It Different?")

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