There are fears of a third potential explosion at a nuclear plant in northeast Japan following Friday's earthquake and tsunami.
Officials say the fuel rods in one reactor were fully exposed after it lost its ability to cool down. Sea water is being pumped on the rods to cool them down and prevent another explosion.
Earlier Monday, a hydrogen explosion at another reactor at the same plant sent a massive cloud of smoke into the air. Eleven workers were injured. On Saturday, a third nuclear reactor at the plant exploded, injuring four workers and causing mass evacuations. Much of the reactor's outer building was destroyed.
Seventeen U.S. military personnel involved in helicopter relief missions were found to have been exposed to low levels of radiation upon returning to the USS Ronald Reagan, an aircraft carrier about 100 miles offshore.
U.S. officials say the exposure level was roughly equal to one month's normal exposure in the environment. The 17 were scrubbed with soap and water, and were declared contamination-free. But as a precaution, the carrier and other U.S. 7th Fleet ships have shifted to another area.
Meanwhile, stocks are headed for a lower opening as investors assess the economic fallout of a massive earthquake in Japan. The devastating earthquake and tsunami along Japan's northeast coast killed thousands of people and led to what is expected to be billions in dollars of damage. That raised fears of an economic slowdown in the world's third-largest economy.
Oil prices fell $1.59 to $99.57 a barrel Monday, and Japan's central bank pumped a record $184 billion into money market accounts to encourage bank lending.
In the U.S., Warren Buffett's Berkshire Hathaway Inc. said it would purchase chemical company Lubrizol for $9 billion in cash.