JUDY WOODRUFF: Now, the latest on the struggle to stabilize a Japanese nuclear plant hit by earthquakes and the tsunami.
Japan's prime minister acknowledged again today that his country faces its gravest problems in decades.
Tom Clarke of Independent Television News narrates our report.
TOM CLARKE: It's still not clear what's going on within the mangled remains of Fukushima. Steam continues to carry some radioactivity away from the plant. A haze of fumes remains above this storage pond, obscuring, as it has for days, the extent of damage to hundreds of tons of highly radioactive fuel beneath.
So little is certain, even Japan's embattled prime minister couldn't put a positive gloss on it at his first parliamentary questions since the disaster.
NAOTO KAN, Japanese prime minister (through translator): This is a situation in which we cannot have any optimism. We continue to deal with the situation with the utmost alertness.
TOM CLARKE: There are new details about the extent of contamination at the plant, particularly highly radioactive water beneath the reactors. But Japanese health officials are struggling to balance the very real risks for people living around the Fukushima plant with the harm that evacuation and relocation so brings.
REIKO SATOU (through translator): My biggest concern is whether I will be able to go back home or not, and if I go back home, whether I will be able to return to my life. I'm also worried about the stresses my family and evacuees close to me are going through.
TOM CLARKE: Given the levels of radiation, this kind of anxiety could be more harmful than the fallout.
Here in Yamamoto, 1,000 people are thought to have died. Japan is being forced by sheer numbers to break the tradition of cremation and bury its tsunami dead in mass graves -- 18,000 may have died, yet confirmed fatalities due to radiation from Fukushima are zero. Even though it still dominates the headlines in Japan and abroad, the nuclear crisis here bears no relation to the enormity of the humanitarian one.