An unusual radiation reading in Hanford’s second-oldest double-shell tank has officials investigating to see if it may have an interior leak.
However, an inspection with a video camera lowered into the space between the inner and outer shells has shown no sign of a radioactive waste leak.
The camera looked at all areas except those under some piping without finding any visual changes since inspections in 2012, 2013 and 2014, said Tom Fletcher, the Department of Energy assistant manager of the Hanford tank farms.
DOE received results of the visual inspection Monday.
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“Thus far all the evidence we have seen does not indicate any interior leak,” said Alex Smith, the new director for the Washington State Department of Ecology Nuclear Waste Program. The ecology department regulates Hanford tanks.
Hanford’s single- and double-shell tanks store 56 million gallons of waste left from the past production of plutonium for the nation’s nuclear weapons program.
Hanford has 28 double-shell tanks and the oldest tank, Tank AY-102, which had extensive construction issues when it was built in 1969, is being emptied because it is leaking waste from the primary shell into the space between its shells. That gap is called the annulus.
Concerns were raised about a second tank, Tank AY-101, when routine checks done every two weeks for radiation in the ventilation system for the annulus found levels above the normal background level. The radiation levels were not high enough for an alarm to sound, Fletcher said.
Laboratory tests showed that the sample had cesium, americium and plutonium, which are consistent with waste in the tank.
We can’t make a judgment one way or another.
Tom Fletcher, DOE assistant tank farms manager
The underground double-shell tanks each can hold up to one million gallons of waste and Tank AY-101, which started storing waste in 1971, is almost at capacity with 995,000 gallons of waste.
Hanford officials are considering possible causes and have not ruled out an interior leak.
“There is a potential there is something that you can’t see that is causing the change,” Fletcher said.
But engineers also are investigating possible other causes, such as cross contamination of the annulus ventilation system from the main waste storage tank’s ventilation system. Americium and plutonium are flighty and can spread easily, Fletcher said.
There also is a possibility that the contamination is “historical,” and has been there for a significant period of time and just found recently by chance, Fletcher said. It could have spread through some cross connection between the primary tank and annulus or their ventilation systems.
“We can’t make a judgment one way or another,” Fletcher said.
Officials also are discussing when another visual inspection of the space between the tank’s shells should be conducted.
The state is considering whether it will need to play a role in requesting additional visual monitoring, Smith said.
I will also be asking the U.S. Government Accountability Office to examine what and when DOE knew about the leaks in these tanks.
U.S. Sen. Ron Wyden, D-Ore.
In Tank AY-102 an estimated 70 gallons of waste leaked over a period of several years, drying in three patches on the floor that were clearly visible in videos taken at the bottom of the 30-foot-high annulus. With pumping underway this spring to remove waste from the tank because of the interior leak, the rate of leakage has increased dramatically.
Sen. Ron Wyden, D-Ore., said he would be asking the Government Accountability Office to look into what and when DOE knew about possible leaks its double-shell tanks, the adequacy of DOE’s tank safety efforts and “the deteriorating condition of all of the high-level waste tanks.”
DOE has 149 single-shell tanks, with one known to be leaking waste into the soil beneath it at a rate estimated to be comparable to a dripping faucet.
Some of the single-shell tanks have held waste since World War II and other tanks are believed to have leaked in the past before most liquid waste was removed from them.
DOE has been transferring the waste in the leak-prone single-shell tanks into newer double-shell tanks built between 1968 and 1986 until the waste can be treated for disposal at the vitrification plant being built to glassify the waste.
Wyden also renewed his request on Tuesday for Energy Secretary Ernest Moniz to appoint an independent panel to oversee the response to the leak in Tank AY-102 and analyze the safety of the 27 other double-shell tanks. An independent panel appointed by local Hanford officials has been meeting to consider tank integrity.
Tom Carpenter, the executive director of Hanford Challenge, a Seattle-based watchdog group, said Hanford is nearly out of double-shell tank space, particularly since the contents of Tank AY-102 are being emptied into other double-shell tanks.
“There is no other realistic option but to begin building new tanks immediately,” he said in a statement.
The state of Washington also has wanted more waste storage tanks built as DOE has failed to meet deadlines at the vitrification plant, most recently because of technical issues.
However, a federal judge ruled last month that DOE does not have to build more double-shell storage tanks. But she said she would consider revisiting that decision if DOE cannot meet certain deadlines to empty its single-shell tanks because of a lack of double-shell tank space.
DOE has opposed building more waste storage tanks, saying the Hanford budget would better be spent on advancing environmental cleanup and getting waste disposed of rather than storing it.