Radioactive Cleanup: A Job for TRIZ

Solving the problem of soil contamination at Washington Hanford Closure

Published: Monday, July 7, 2014 - 11:55

Editor’s note: This article continues the series exploring structured innovation using the TRIZ methodology, a problem solving, analysis, and forecasting tool derived from studying patterns of invention found in global patent data.

A special meeting of the TRIZ executive committee had been called because Dwain McMullin was in town, and Henrietta, the committee facilitator, had arranged for him to share a case study with the group.

McMullin was one of the TRIZ coaches at a center of radiological research and nuclear fuel fabrication called Washington Hanford Closure in Richland, Washington. The work performed there had created highly contaminated facilities and waste sites as well as a large inventory of radioactive material. McMullin agreed to share his team’s process in coming up with an inventive solution to resolve the problems encountered during the cleanup project.

At the outset Henrietta told the committee that McMullin was not prepared to share the project outcome at this short notice, but the important thing for them was to understand how the Hanford team got to the recommendation stage.

McMullin explained that a significant spill had occurred in the building during the mid-1980s. The spill was cleaned up, and there was no indication that any of the contamination had breached the floor until grout was removed from the area in 2009, and a breach in the liner was discovered. Readings taken through spring of 2011 indicated that the contamination had not spread beyond the building’s footprint, and it was above groundwater and not mobile. However, challenges included building deactivation, decommissioning, decontamination, and demolition of the building. A team was formed to help identify and solve problems associated with these challenges.

The problem-solving team identified a long list of specific challenges with the cleanup process:
• Eliminate or minimize radiation exposure and contamination
• Eliminate or minimize airborne releases
• Stabilize the contaminated soil
• Determine the boundaries of soil contamination
• Minimize the number of shipping containers for the contaminated soil
• Minimize handling and personnel exposure to the shipping containers
• Contain the soil-excavation process to the facility
• Excavate the contaminated soil with remote equipment
• Shield workers from radiation
• Maintain structural support for the building and cell when the soil is removed from underneath it
• Find a final disposal location for the contaminated soil that meets all regulatory requirements
• Lift potentially heavy monoliths of grouted contaminated soil
• Cut large monoliths, if necessary, while still preventing radiation exposure
• Penetrate hard layers of cobble soil to take contamination samples and radiation readings
• Evaluate how to remove shipping containers through the narrow airlock corridor if the soil is removed internally through the cells

The project team noted many contradictions and decided to use the TRIZ approach. They agreed on the following criteria for their ideal final result (IFR):
• Remove the contaminated soil and handle it at one time in the final disposal package
• Make the disposal package as large as possible
• Have zero industrial (i.e., safety) injuries and/or environmental releases
• Keep radiation exposure to workers as close to zero as possible
• Perform the remediation work with the existing facility
• Maintain the building’s structural integrity

Following the TRIZ methodology, these were restated as generic desired functions:
• Move solids (soil)
• Shield personnel
• Lift heavy loads
• Stabilize solids (soil)
• Move monoliths
• Provide structural support

Many contradictions presented themselves as the team examined the desired functions and results:
• Removing radioactive soil with high levels of contamination cleans the area but creates the need for significant shielding and short work times to prevent exposure to radiation.
• Removing radioactive soil with high levels of contamination cleans the area but is likely to weaken structural support.
• Solidifying radioactive soil in monoliths reduces the number of units to be handled but requires special lifting capabilities, and size reduction later presents its own difficulties.
• Packaging and moving the material in smaller containers would be safer and easier but it would increase the number of containers to be handled and the likelihood of exposure to contaminated soil.
• Moving monoliths removes large volumes but would not meet transportation limitations and disposal-path requirements.
• Stabilizing contaminated soil would allow packaging in shielded containers but also has the potential for multiple handling, additional waste, and increased radiation exposure for workers.
• Demolishing the building gives clear access to contaminated soil but removes all shielding and confinement that the building could provide.
• Washing the soil would concentrate the contaminants but make the shielding, handling, and disposal issues worse.

A cause-and-effect diagram was created to help narrow the focus of areas on which to work, and to ensure that the team’s effort was directed toward removing the unwanted “effect.” Figure 1 clearly indicates that the primary unwanted effect is that “very high radiation sources present dangerous work conditions.” All the boxes around the highlighted box are the causes that were then analyzed to see how they could be eliminated.

Figure 1: Cause-and-effect diagram of primary unwanted effect

As a reminder, TRIZ emphasizes the use of existing resources to solve a problem, especially resources that are free (e.g., air, water, sunshine), previously unused, and easily available. Natural bioremediation sources such as photosynthesis transform hazardous waste or contamination into a harmless substance and should be considered. McMullin’s team made a list of available resources, including:
• Clean soil
• Heat from contaminated soil
• Airborne activity
• Adjacent cells
• Cell floors
• Cell ventilation
• Air-lock corridor
• Workers
• Shielding
• Sunlight
• Humidity
• Barometric pressure

These were all analyzed to see how they could be used to solve the problem.

A functional interaction diagram was also created to display all relevant components in the system and show the interactions (see figure 2). Once again, the majority of harmful effects were associated with the radioactive contamination, and the challenge was to stabilize and remove the contaminated soil while eliminating personnel exposure.

Figure 2: Functional Interaction diagram

Focusing on generic solutions to the generic problems identified opened up the solution set beyond the nuclear realm to find cases where “someone somewhere has solved this problem.” Once those solutions were found, the team figured out how to adapt them to their cleanup project. The team searched for solutions on topics such as:
• Remote excavation
• Soil stabilization
• Soil solidification
• Remote mining
• Under-building soil removal
• Subsurface and soil vitrification

Once current methods were identified, and information was collected and analyzed for viability, patents searches were conducted and identified for their relevancy. Various concepts were generated, and informal screening performed using the IFR elements as success criteria. A top recommendations list was created, listed here in random order:
• Create monoliths out of grout and contaminated soil in other cells
• Underpin the cell for monolith removal prior to soil excavation
• Magnetically remove strontium-90
• Vapor extract cesium-137
• Expand expansion joint to introduce stabilization media
• Multiuse grout as a drilling fluid and for pretreatment
• Use limited canister shielding
• Leave canister in place
• Challenge regulations

Figure 2 also shows the underpinning of the cell prior to soil excavation as part of the solution for ensuring structural integrity.

These were all evaluated and solution concepts developed. McMullin promised Henrietta and the TRIZ executive team that he would tell them about how the recommendations were implemented when they were approved for release. He said TRIZ would be used multiple times during the implementation to solve other problems as they arose.

About The Author

Akhilesh Gulati

Akhilesh Gulati has 25 years of experience in operational excellence, process redesign, lean, Six Sigma, strategic planning, and TRIZ (structured innovation) training and consulting in a variety of industries. Gulati is the principal consultant at PIVOT Management Consultants and CEO of the analytics firm Pivot Adapt Inc. in Southern California. He holds a master’s degree from the University of Michigan-Ann Arbor, an MBA from UCLA, and is a Six Sigma Master Black Belt and a Balanced Scorecard Professional.