Radiation spreading from the Fukushima No. 1 plant threatens to derail Prime Minister Shinzo Abe's efforts to revive nuclear power and deliver the lower energy prices needed to power his economic reforms.

As Abe prepares for a trip Saturday to the Middle East, where he will promote sales of nuclear technology, the atomic industry at home is reeling. The Nuclear Regulator Authority said this week that a new radioactive water leak was the most serious incident at the Fukushima No. 1 complex since the March 2011 meltdowns that devastated the site.

The latest setback may stoke public anger over the Fukushima disaster, undermining Abe's efforts to restart some of Japan's 48 idled reactors and boost nuclear exports — key elements of his plan to drive an economic revival. Abe, who must decide whether to proceed with a sales tax hike, is counting on restarting reactors to help reduce energy imports and fuel growth in consumer confidence and corporate earnings.