Research Needs for High-Level Waste Stored in Tanks and Bins at U.S. Department of Energy Sites Environmental Management Science Program (2001) / Chapter Skim
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6. Tank Closure and Other Long-Term Issues
6. Tank Closure and Other Long-Term Issues
Pages 65-76
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From page 65... ...
The area surrounding the tanks (the near field) must be monitored in the long term after tank closure to allow immediate remedial action in case residual waste releases threaten plants, animals, or humans.
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From page 66... ...
* Title 10 CFR Part 61 describes licensing requirements for classification of LLW sent to land disposal facilities.
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From page 67... ...
New techniques should reduce the risk of secondary waste leakage and could use semiautonomous retrieval methods. The use of untethered robots is an example of a highly desirable basic research field that cou Id lead to effective sol utions where conventional engi neeri ng approaches often involve prohibitive costs (see Sidebar 6.2~.
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From page 68... ...
The distance between the primary liner and the secondary pan in this type of tank (type 11) varies between 2 and 6 feet.
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From page 69... ...
For instance, such movement could be accomplished through innovative propulsion means on the robot or through manipulation of a surrounding magnetic field; 4) novel power supplies, including possibly exterior power supplied remotely to the robot via magnetic or electric fields without any wire link; and 5)
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From page 70... ...
Then, the blockage must be removed without damaging the pipeline. Current methods to remove waste plugs involve chemical, pressure cycling, and vibration methods (DOE-TFA, 2000b)
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From page 71... ...
Consideration should also be given to research on untethered semiautonomous characterization tools. Immobilization of Residual Waste within the Tank Grouting is the current baseline technique to fill the volume before closure.
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From page 72... ...
In the two closed tanks at the SRS, the three-layered backfill system used consists of a chemically reducing grout at the bottom of the tank, a controlled ~owstrength material occupying most of the empty space, and a highstrength grout at the top of the tank. The primary function of the chemically reducing grout is to reduce the mobility oftechnetium-99, the main environmental risk contributor at the SRS.
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From page 73... ...
Research in imaging techniques is desirable in order to develop methods that penetrate soil in depth and can identify contaminants. For example, prompt gamma neutron activation is a promising technique but has a penetration range of only one meter or less, depending on the sensitivity required.
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From page 74... ...
In this black and white reproduction of the original color figure, the velocity and attenuation scales do not fully show the complete range of values (for example, black may indicate either high or low velocity/attenuation, while white represents the intermediate values)
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From page 75... ...
Subsurface engineered barriers are under consideration at Hanford to reduce the impact to the environment of leaked waste by containing subsurface contamination within the near-field. The major drawback of current barrier technologies is that engineered barriers tend to leak even after short times.
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From page 76... ...
Basic research on innovative horizontal drilling methods that do not create new pathways for flow of contaminants and new injection material to create an impermeable barrier beneath the tank is also desirable.
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