Further tests to determine whether the first Hanford double-shell tank is leaking waste into the soil have been inconclusive, the Department of Energy said Friday.
DOE has known since at least October that underground Tank AY-102, which holds 857,000 gallons of radioactive and hazardous chemical waste, has an apparently slow leak from its interior shell. But until a month ago, DOE was confident that the leaked waste was being contained by the outer shell.
On June 20 it began to suspect that the outer shell also might be leaking based on results of routine testing related to the tanks leak detection pit.
Since then more water collected in the leak detection pit has been tested, a video inspection has been conducted and the pump used to remove water from the pit has be taken apart and analyzed.
Based on this testing, there is no conclusive indication of a leak from the secondary tank at this time, DOE said in a statement released Friday.
But because of radiation readings taken in June, the Washington State Department of Ecology wants liquid waste removed from the tank.
Our position is despite the statement the tests are not conclusive the state has serious concerns about the high radiation reading June 20 and we believe work needs to begin immediately to pump liquids from this tank, said John Price of the Department of Ecology.
The state believes that removing liquid from the tank would reduce pressure that may be contributing to the leak. The deeper the liquid, the greater the pressure is in the part of the tank that is leaking.
The waste in the tank includes 706,000 gallons of liquid and 151,000 gallons of sludge. Although some of the liquid must remain because the radioactive waste in the tank generates heat, possibly 650,000 gallons or more could be safely removed.
DOE has taken actions needed to prepare to immediately begin pumping the liquid from this tank if warranted, DOE said.
State law is clear on the matter, Price said.
If a leak is discovered in the inner shell of the tank, DOE must remove as much of the waste as necessary to prevent dangerous releases of waste within 24 hours or at the earliest practicable time, he said.
Hanford has 177 underground tanks to hold 56 million gallons of radioactive and hazardous chemical waste left from the past production of plutonium for the nations nuclear weapons program. The tanks include 28 newer double-shell tanks to hold waste emptied from 149 leak-prone single-shell tanks until it can be treated for disposal.
The 28 double-shell tanks are nearing capacity with the vitrification plant being built to treat the waste not scheduled to be operating until 2019. With Tank AY-102, which has held waste for more than 40 years deteriorating, DOEs options for safely holding waste emptied from single shell tanks are further limited. Pumpable liquid has been removed from all the single shell tanks to leave primarily sludge remaining, but six of them still are believed to be leaking into the ground.
If liquid waste is pumped from Tank AY-102, it would be divided among three other double-shell tanks. Checks of Hanfords other double-shell tanks have not found leaks within them.
The volume of the liquid waste removed from Tank AY-102 then could be reduced by running it through Hanfords evaporation plant.
A pump already is installed in Tank AY-102 that could remove liquid. However, DOE has estimated that it would take 19 months to plan, buy and stall equipment that could pump the sludge from the tank, if thats determined to be necessary.
Testing for leaks at the tank is continuing to be conducted, including preparations to test more of the water in the leak detection pit as it collects. Water in the leak detection pit comes from a concrete pad beneath the underground tank and can be from precipitation that runs through the soil or a possible leak from the tank.
On June 20, enough water in the pit had been collected to lower a pump into the pit and remove the water, a routine process. There was no unusual reading from the water, but when the pump was pulled out, radiation was detected. However, the high pH level thats typically linked to the caustic used in the tank was not evident.
The additional testing over the last month has included taking the pump apart to try to determine more about the source of the radiation. A video camera had been lowered into the pit to look into the drain pipe and more of the remaining water in the pit as been tested, both reportedly without unusual results.