The Hanford site in southeast Washington state once played a major part in U.S. plutonium production.

Story highlights

Last week, Washington's governor said 1 tank at the Hanford nuclear site was leaking

He now says 6 tanks are leaking radioactive waste, calling the news "disturbing"

The leaks pose "no immediate health risks," but do pose concerns, the governor says

Hanford site is home to one of the world's largest nuclear cleanup efforts

Six tanks at the Hanford Nuclear Reservation in southeast Washington state are leaking radioactive waste, the governor said Friday, calling the news “disturbing” even as he insisted there are “no immediate health risks.”

“News of six leaking tanks at Hanford raises serious questions about integrity of all single tanks,” Gov. Jay Inslee said Friday afternoon on Twitter.

Inslee said that he got the latest information about the site during a meeting in Washington with U.S. Energy Secretary Steven Chu.

One week earlier, Chu called the governor to tell him that a single-shell tank in the same location was leaking liquids at a rate of 150 to 300 gallons per year. Believed to be the first to lose liquids since 2005, that tank was built in the 1940s and can hold roughly 447,000 gallons of sludge, according to the governor’s office.

“(Chu) told me today that his department did not adequately analyze data it had that would have shown the other tanks that are leaking,” Inslee said.

The sprawling, 586-square mile Hanford site houses a total of 177 underground tanks full of radioactive sludge, of which 149 are single-shell tanks.

On Friday, Inslee said there is “still no current health risk” tied to the leaks.

He made similar comments a week earlier, saying “it would be quite some time before these leaks could breach groundwater or the Columbia River.” At the same time, the governor stressed that the problem must be addressed.

“This certainly raises serious questions about the integrity of all 149 single-shell tanks with radioactive liquid and sludge at Hanford,” he said Friday.

Hard lessons for U.S. nuclear safety from Fukushima meltdown

Hanford became a focal point of U.S. nuclear efforts beginning in 1943, when aspects of the Manhattan Project were moved there. As local residents moved out, thousands of workers moved into the site where plutonium for use in atomic bombs was produced. Two bombs were dropped on Japan during the final days of World War II.

The site – about half the size of Rhode Island, in an area centered roughly 75 miles east of Yakima – continued to buzz during the Cold War, with more plutonium production as well as the construction of several nuclear reactors.

The last reactor shut down in 1987, though a mammoth cleanup effort remained to address what state and federal authorities deemed the most contaminated site in the Western Hemisphere.

Those efforts were bolstered by about $2 billion in federal stimulus funds authorized in several years ago. But decades of more work remain, which is why Washington’s governor said he feared that across-the-board budget cuts called the sequester – which could take effect March 1, unless Congress passes and President Barack Obama signs an alternative – could negatively affect activity at the site.

“We need to be sure the federal government maintains its commitment and legal obligation to the cleanup of Hanford,” Inslee said. “To see Hanford workers furloughed at the exact moment we have additional leakers out there is completely unacceptable.”

CNN’s Carma Hassan contributed to this report.