The Department of Energy is considering building a new facility between the Hanford tank farms and the vitrification plant to blend, sample and stage waste and do some pretreatment of waste before it is sent to the vitrification plant.
It's the second of two possible new facilities DOE has discussed this year to help get 56 million gallons of radioactive and hazardous chemical waste treated for disposal.
Both were possible solutions discussed in what DOE called a "framework" document released in September after a year of studying technical issues.
The Hanford underground, double-shell waste tanks were not built with feeding waste to a treatment plant in mind, said Isabelle Wheeler, DOE program manager of the waste feed delivery systems for the Hanford tank farms. She spoke at a Wednesday committee meeting of the Hanford Advisory Board in Richland.
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The proposed facility would mix waste so the solids are suspended in the liquids. It would blend the waste so not too much or too little is included in batches sent to the vitrification plant for glassification. And it also would have capabilities to allow good samples of waste to be collected to make sure the waste falls within the parameters the vitrification plant is prepared to handle and treat.
But it also could do some work to address concerns about whether the vitrification plant can safely handle certain waste.
The proposed new facility would have capabilities to "precondition" some of the waste that could be problematic for the vitrification plant's Pretreatment Facility, including large particles, dense particles and specific isotopes. Various options are being considered to reduce the size of particles and it also could make sure that not too much of a specific isotope is sent to the vitrification plant, according to DOE.
"Basically we would keep the problem in-house and manage it in-house on the tank farm side," Wheeler said.
Concerns have been raised about keeping high-level radioactive waste adequately mixed and preventing a buildup of plutonium that could lead to an unplanned nuclear reaction at the vitrification plant.
Managing the problematic waste could allow some waste to be sent directly to the High Level Waste Facility for treatment, bypassing the Pretreatment Facility at the vitrification plant if needed, Wheeler said. Construction has stopped at the Pretreatment Facility until technical issues are addressed.
The other new facility discussed in the framework document would be an underground plant to pretreat liquid tank waste, which is primarily low-activity radioactive waste, and allow it to bypass the Pretreatment Facility and go directly to the Low-Activity Waste Facility.
The new waste sampling and staging facility would reduce risks of upgrading aging waste tanks, Wheeler said. Some of the work proposed for the new facility, such as mixing waste, could be done in existing double-shell tanks, but that would require putting multiple powerful mixers in aging tanks past their design life, she said.
Double-shell Tank AY-102 was expected to be the feed tank for the vitrification plant before a leak between its shells was discovered last year.
Building a new facility in a location without previous contamination would be easier than retrofitting a radioactive facility, and it would have up-to-date safety and radiation-control systems to reduce risks to workers, Wheeler said.
The proposed facility also could have some waste storage capacity benefits. It would have some storage as waste is staged there before being transferred to the vitrification plant and also might allow some high-level radioactive waste to be treated sooner, freeing up space in Hanford's double-shell tanks.
DOE has 28 double-shell tanks, including Tank AY-102, that are used to hold waste pumped from leak-prone single-shell tanks, but they are nearing capacity.
The proposed new facility to prepare waste still is in the conceptual phase and there are no schematics to show what it might look like and no estimates of its cost or its capacity, Wheeler said.
She would not anticipate the facility being commissioned until 2020, but that could change if the project is fast-tracked, she said. The vitrification plant is required to begin treating waste in 2019, but DOE has notified the state of Washington that deadline is at risk of being missed.
w Annette Cary: 582-1533; email@example.com; Twitter: @HanfordNews