Update: Nuclear Fuel Rods Exposed; Nuclear Plant Rocked by Second Blast in Japan

Editor's update: Efforts to cool down the Fukushima Daiichi Nuclear Power Station with seawater appear to have failed. The NYT reports:

Japan’s struggle to contain the crisis at a stricken nuclear power plant worsened sharply early Tuesday morning, as emergency operations to pump seawater into one crippled reactor failed at least temporarily, increasing the risk of an uncontrolled release of radioactive material, officials said.

With the cooling systems malfunctioning simultaneously at three separate reactors at the Fukushima Daiichi Nuclear Power Station after the powerful earthquake and tsunami, the acute crisis developed late Monday at reactor No. 2 of the plant, where a series of problems thwarted efforts to keep the core of the reactor covered with water — a step considered crucial to preventing the reactor’s containment vessel from exploding and preventing the fuel inside it from melting down.

The plant’s operator, Tokyo Electric Power, said late Monday that repeated efforts to inject seawater into the reactor had failed, causing water levels inside the reactor’s containment vessel to fall and exposing its fuel rods. After what at first appeared to be a successful bid to refill the vessel, water levels again dwindled, this time to critical levels, exposing the rods almost completely, company executives said.

The AP is reporting that nuclear fuel rods were exposed at Unit 2 of the Fukushima Dai-ichi, as authorities scrambled to prevent a nuclear meltdown. 

SENDAI, Japan (AFP) - An explosion rocked an earthquake-hit nuclear plant Monday, as Japan struggled to avert a catastrophic reactor meltdown caused by a quake and tsunami feared to have killed more than 10,000.

A new tsunami scare triggered evacuations on the devastated northeast coast after a large wave was spotted rolling in to shore, but authorities said they had detected no sign of a tsunami or a quake that would have caused it.

Japan has been battling to control two overheating reactors at the ageing Fukushima plant after the cooling systems were knocked out by Friday's 8.9-magnitude quake and the resulting tsunami that swallowed up whole towns. Scene: Japanese towns become wastelands

Shortly after Prime Minister Naoto Kan said the plant was still in an "alarming" state, a blast at its number-three reactor shook the facility and sent plumes of smoke billowing into the sky.

The plant's operator TEPCO said that nine people were injured in the blast, which authorities said was probably a hydrogen explosion.

The chief government spokesman Yukio Edano said TEPCO reported that the reactor was probably undamaged and there was a low possibility of a major radiation leak at the plant, 250 kilometres (160 miles) northeast of Tokyo.

Another explosion blew apart the building surrounding the plant's number-one reactor on Saturday but the seal around the reactor itself remained intact. Nuclear contamination: The options

With ports, airports, highways and manufacturing plants shut down, the government has predicted "considerable impact on a wide range of our country's economic activities".

Tokyo's stock market plunged more than six percent in afternoon trade as investors absorbed the impact, including power outages and plant shutdowns, after the biggest quake in Japan's history.

The yen surged to a four-month high after the central bank pumped a record amount of money into financial markets while shares in auto makers were hammered more than 10 percent after they were forced to close factories.

Leading risk analysis firm AIR Worldwide said the quake alone would exact an economic toll estimated at between $14.5 billion and $34.6 billion (10 billion to 25 billion euros), without taking into account the effects of the tsunami.