RICHLAND, Wash. — Inspectors at the Hanford Nuclear Reservation in south-central Washington state have found at least seven leaks in the site’s oldest double-walled radioactive waste storage tank.

Tank AY-102 was known since 2012 to have a slow leak from its inner shell into the space between its inner and outer walls.

The Tri-City Herald reports that the tank, which was built in the 1960s and once held 744,000 gallons of waste, had been emptied of all but 19,000 gallons by February.

Then an inspection was done with video cameras.

Glyn Trenchard, a tank manager for the U.S. Department of Energy, told the Hanford Advisory Board on Wednesday that a total of seven leaks were found.

The Energy Department said no waste is believed to have breached the outer shell to contaminate the environment.

Hanford for decades made plutonium for nuclear weapons and the wastes are left over from that work. The most toxic wastes are stored in 177 giant underground tanks. There are 28 newer double-walled tanks and 149 single-walled tanks, some of which date back to the dawn of the Cold War. Many of the single-walled tanks have leaked over the years.

The tanks are made of carbon steel and contain more than 56 million gallons of the wastes that are the most difficult to treat for permanent disposal. Efforts to dispose of those wastes are expected to take decades and cost tens of billions of dollars.

When Tank AY-102 was emptied, leaks were revealed in two welds on the bottom of the inner wall, Trenchard said.

In addition, corrosion appeared to have left pits in the floor of the inner wall, he said.

To determine if any of the pits went all the way through the steel, a small amount of liquid was pumped into the space. The liquid drained through the pits in five places, bringing the total number of known leaks to at least seven, Trenchard said.

The inspection data will be used as the Department of Energy and state Department of Ecology negotiate on whether the tank can be repaired and returned to service.


Information from: Tri-City Herald, http://www.tri-cityherald.com