What We Are Doing
Safely Managing Waste
Evaporator upgrades set stage for waste reduction
The 242-A Evaporator is undergoing major upgrades in preparation for liquid waste volume reduction campaigns beginning in spring 2009. Workers have finished upgrading the ventilation and monitoring and control systems and rebuilding one of two main pumps and have removed nearly all of the radioactive contamination in the condenser room.
The condenser room is the operating heart of the evaporator, containing most of the operating instrumentation and transmitters.
As the last operating nuclear facility at Hanford, the 242-A Evaporator is critical to the cleanup mission. The evaporator creates storage space in double-shell tanks by removing water and concentrating the liquid waste, making it possible to empty the waste from Hanford’s aging single-shell tanks.
Independent panel to review single-shell tank integrity
With the support and direction of DOE’s Office of River Protection, Washington River Protection Solutions has convened an independent panel of experts to review all pertinent information and programs regarding construction and operation of the single-shell tanks. The panel has met twice, so far, and has reviewed an extensive amount of information, leading it to recommend a number of actions to enhance the existing program of monitoring the integrity of the tanks. They have also proposed methods to better inspect and assess them. The panel is made up of nationally recognized experts in numerous engineering and scientific disciplines associated with single-shell tank integrity.
The expert panel was asked to assist with defining the scope of the structural and seismic analyses, review the design and specifications for the tanks at the time they were constructed, review thermal and waste storage histories and assist in selecting non-destructive evaluation (NDE) techniques of the concrete domes, reinforcing bars, and the steel tank liners.
Based on information presented to them in their first series of meetings they said they consider the single-shell tanks to be structurally sound. Barring a major seismic event they said they believe a catastrophic failure of a tank is not credible. They went on to say, however, that a lot of analysis work and tank inspection still needs to be done to ensure tank integrity is maintained into the future.
Because the single-shell tanks will hold waste far longer than original tank designers expected, WRPS wants to be sure they will remain as sound as possible until the waste in these tanks can be removed. The panel gave us a very good start on a roadmap which we can use to enhance our tank structural integrity program to ensure we can continue to safely store the waste until all are emptied.
As part of their preliminary recommendations, the panel has identified the need for assessments of the rebar and the concrete conditions in the tanks, a series of analyses using waste simulant to show the impacts of waste on rebar and concrete, and taking vertical core samples of selected concrete tank walls. Other recommendations included continued dome deflection surveys, and corrosion studies to assess the ability to prevent the development of any new tank leaks.
A similar expert panel process was used several years ago for Hanford’s 28 double-shell tanks, resulting in a very effective integrity assessment program.
Hanford’s 149 single-shell tanks, many of which date back to the early days of the Manhattan Project during World War II, have long since passed their original design life. While most are still sound, their long term integrity is critical as they will need to continue to hold solids and sludges until the waste can be removed and prepared for disposal.
