There are “significant construction flaws” in some newer, double-walled storage tanks at Washington state’s Hanford nuclear waste complex, which could lead to additional leaks, according to documents obtained by The Associated Press.  Those tanks hold some of the worst radioactive waste at the nation’s most contaminated nuclear site.

One of the 28 giant underground tanks was found to be leaking in 2013. But subsequent surveys of other double-walled tanks performed for the U.S. Department of Energy by one of its Hanford contractors found at least six shared defects with the leaking tank that could lead to future leaks, the documents said. Thirteen additional tanks also might be compromised, according to the documents.  Questions about the storage tanks jeopardize efforts to clean up radioactive waste at the southeastern Washington site. Those efforts already cost taxpayers about $2 billion a year.  “It is time for the Department (of Energy) to stop hiding the ball and pretending that the situation at Hanford is being effectively managed,” Sen. Ron Wyden, D-Ore., wrote this week in a letter to Energy Secretary Ernest Moniz…

Hanford contains some 53 million gallons of high-level radioactive wastes from the production of plutonium for nuclear weapons. They are stored in 177 underground storage tanks, many of which date back to World War II and are single-walled models that have leaked. The 28 double-walled tanks were built from the 1960s to the 1980s.

Current plans call for transferring wastes from leaking single-walled tanks to the newer and bigger double-walled tanks, where the waste will be stored while a $13 billion plant for treating the waste is constructed. But the treatment plant is plagued with design problems and construction has stalled.  The situation did not appear dire until the news in October 2012 that the oldest of the double-walled tanks, called AY-102, had leaked, becoming the first of those 28 tanks to do so.

At the time, the Energy Department blamed construction problems with this particular tank for the leak and said it “seems unlikely” that the other double-walled tanks would leak.  However, Wyden said engineering reviews of six other double-walled tanks “found significant construction flaws in those six tanks essentially similar to those at the leaking tank.” Those six tanks contain about 5 million gallons of radioactive wastes, wrote Wyden, who is chairman of the Senate Energy and Natural Resources Committee….

Hanford, located near the city of Richland, stores about two-thirds of the nation’s high-level radioactive waste.  Officials have said the leaking materials pose no immediate risk to public safety or the environment because it would take perhaps years for the chemicals to reach groundwater.  The federal government built Hanford at the height of World War II as part of the Manhattan Project to build the atomic bomb.

Excerpts from Drew Vattiat, Hanford’s worst radioactive waste vulnerable to leaks from flaws in newer storage tanks, Associated Press, Feb. 28, 2014