The Hanford Advisory Board is recommending the Department of Energy start work immediately to build new storage tanks for high-level radioactive waste.
The board acknowledged the recommendation was a significant shift in the board's thinking.
In the past some board members have emphasized that attention and available money should be concentrated on getting the waste treated for disposal, rather than building more tanks to store it.
But now members are concerned about the recent discovery of a leak of waste from an inner shell of one of Hanford's 28 double-shell tanks. Although waste has been contained between the shells, as the double-shell tanks were designed to do, the slow leak is a possible indication that the double-shell tanks may be deteriorating.
DOE has 56 million gallons of radioactive and hazardous chemical waste stored in underground tanks from World War II and Cold War production of weapons plutonium.
It is working to empty waste from 149 single-shell tanks, many of which leaked in the past, into the newer double-shell tanks to be stored until it can be treated for disposal.
The board should have recommended new tanks be built a decade ago, said board member Jerry Peltier.
"This is long overdue," he said. "That the tanks will not last until all the waste is vitrified has finally been recognized."
Last month DOE confirmed that its oldest double-shell tank, Tank AY-102, has a slow leak of waste from its inner shell into the space between its inner and outer shells. The tank was designed to last 40 years and started accepting waste in about 1971.
"A number of the DSTs (double-shell tanks) are nearing the end of their design lives and yet there is no plan for the complete retrieval of them for decades," the board said in written advice to DOE and its regulator, the Washington State Department of Ecology.
The Tank AY-102 leak points out the need to develop additional contingency measures, and sufficient budget should be requested for that, the board said.
Hanford already is short on double-shell tank space, but needs to have tank space that would be immediately available to empty a leaking double-shell tank and prevent further spread of waste in the environment, the board said.
Now, in an emergency, waste would have to be distributed among many double-shell tanks that have some available space and in some cases that would require testing to make sure waste from different tanks is compatible before it is transferred.
"DOE indicated in the latest briefing that such testing could take weeks, if not months, to draw down the waste in one tank," the board said. That lack of agility could allow large amounts of waste to leak from an inner shell of a tank before it is emptied, it said.
At times chemistry in the waste tanks has not met limits set for corrosion control, and the board questioned whether enough was known about what was in the tanks to protect against corrosion.
There also is concern that Tank AY-102 was planned to be used to demonstrate how waste would be mixed and sampled to meet acceptance criteria for treatment at the vitrification plant, which could begin accepting waste in 2019.
As waste now in Tank AY-102 is fed to the plant for treatment, the tank likely would have been refilled, possibly multiple times.
As DOE develops additional tank capacity, it should consider the requirements of the vitrification plant and allow for maximum flexibility for blending, transferring and segregating waste, the board said.
But the board also warned that even though it appears more tanks are needed as an interim measure to protect the environment, building more tanks at Hanford will not delay the urgent need for waste treatment.
A team is being put together with representatives from DOE, its tank waste contractor, the Department of Ecology and the Washington State Department of Health to evaluate a path forward for Tank AY-102, said Jeremy Johnson, DOE's Hanford tank integrity program manager.
DOE values the Hanford Advisory Board's input and the team will take it into consideration, he said. Tank AY-102's role as a mixing demonstration tank is being re-evaluated, he said.
Along with recommending the addition of tank storage space, the board also recommended ensuring emergency tank space is available at all times, maintaining the chemistry of the tanks, increasing the frequency of tank inspections and looking at potential ways to repair Tank AY-102.