The Dow Jones Industrial Average fell 0.71 percent in opening trades, down 88.17 points to 12,293.47.
"In Asia, news that the Fukushima nuclear crisis was elevated on par with Chernobyl rocked equities," said Kimberly DuBord of Briefing.com.
The Nikkei had earlier lost 1.7 percent.
The malaise carried over into US markets, with traders also eying aluminum giant Alcoa, which posted a strong profit for the first quarter, but with lower revenues.
Alcoa shares fell more than five percent on the news.
The firm recorded $308 million in net earnings for the three months to March 31, compared with $258 million the previous quarter and a loss of $172 million a year earlier.
Meanwhile news that Cisco was slashing 550 jobs and closing Flip video camera business, which it bought in March 2009 for 590 million dollars, sent its shares down slightly.
The tech-rich Nasdaq Composite lost 17.01 points (0.61 percent) to 2,754.50.
The S&P 500-stock index, a broad measure of the markets, fell 9.10 points (0.69 percent) to 1,315.36.
The bond market rose. The yield on the 10-year Treasury was 3.52 percent, down from 3.57 percent on Monday, while that on the 30-year bond stood at 4.60 percent, down from 4.63 percent.
Bond prices and yields move in opposite directions.