Structured Innovation: Solving the problem of Soil Contamination at Washington Hanford Closure

. . . Continuing the series on Structured Innovation . . .

A special meeting of the MEC had been called because Dwain McMullin was in town and Henrietta had arranged for him to share a case study with them.  Dwain was one of the TRIZ Coaches at the Hanford Site, a center of radiological research and nuclear fuel fabrication for the past 60 years.  The work performed at this location had resulted in highly contaminated facilities and waste sites as well as a large inventory of radioactive material.  Mr. McMullin agreed to share his team’s process in coming up with an inventive solution to resolve the problems encountered in the clean-up project.  At the outset Henrietta told the MEC that Dwain was not prepared to share the outcome of the project at this short notice, but the important thing for them was to understand how they got to the recommendation stage.

Dwain explained that a significant spill had occurred in the building in the mid-1980’s.  The spill was cleaned up and there was no knowledge that any of the contamination had breached the floor until grout was removed from the area in November 2009 and they uncovered a breach in the liner.  Readings taken through April 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 clean up process:

  • Eliminate/minimize radiation exposure and contamination
  • Eliminate/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 very heavy monoliths of grouted contaminated soil
  • Cut large monoliths, if necessary, while still preventing radiation exposure
  • Penetrate very 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 a plethora of contradictions and decided to use the TRIZ approach.  They agreed on the following criteria for their Ideal Final Result:

  1. Remove the contaminated soil and handle it in one go in the final disposal package.
  2. Make the disposal package as big as possible
  3. Have zero industrial (safety) injuries and environmental releases
  4. Keep radiation dose to workers as close to zero as possible
  5. Perform the remediation work with the existing facility
  6. Maintain the structural integrity of the building.

Following the TRIZ methodology, these were restated as generic desired functions:

  1. Move solids (soil)
  2. Shield personnel
  3. Lift heavy loads
  4. Stabilize solids (soil)
  5. Move monoliths
  6. Provide structural support

Lots of contradictions presented themselves as they examined the desired functions/results, e.g.,

  • Removing soil with high levels of contamination cleans the area BUT creates the need for significant shielding and short duration work times to prevent exposure to elevated dose levels
  • Removing soil with high levels of contamination cleans the area BUT is likely to weaken structural support
  • Solidifying 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 & moving 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 container requirements.
  • Stabilizing contaminated soil would allow packaging in shielded containers BUT also has the potential for multiple handling, additional waste and increased dosage exposure.
  • Demolishing the facility/building gives clear access to contaminated soil BUT removes all shielding and confinement that the building (with its ventilation) 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 on areas to work on and to ensure that the team’s effort is directed to removing the unwanted ‘effect.’  Fig 1 created by the team clearly indicates that the primary unwanted effect is the ‘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.

Fig. 1 Cause & Effect DiagramAs a reminder, TRIZ emphasizes the use of existing resources, to solve the 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 not be ignored.  Dwain’s project team made a long list of available resources, including but not limited to

  • 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 functional interactions (Fig 2).   Once again, the majority of the harmful effects were associated with the radioactive contamination and the challenge was to stabilize and remove the contaminated soil while eliminating personnel exposure.

Fig 2 Soil Contamination Project DiagramFocusing on generic solutions to the generic problems identified (noted earlier) 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 our specific cleanup project.  The team searched for solutions on topics such as

  • Remote excavation
  • Soil stabilization
  • Soil solidification
  • Remote mining
  • Under building soil removal
  • Subsurface / soil vitrification

Once current methods were identified, information collected and analyzed for viability; patents searches were also conducted and identified for their relevancy.  Various concepts were generated and informal screenings performed subsequently evaluated by the project team.  Various concepts were generated and informal screening performed (using the IFR elements as success criteria) and a top recommendations list was created, listed here in random order:

  • Create monoliths our 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
  • Multi-use grout as a drilling fluid and for pretreatment
  • Use limited canister shielding
  • Leave canister in place
  • Challenge regulations

Fig 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.  Dwain promised Henrietta and the MEC team that he’ll tell them about the implementation when the information release is approved, and he said that he was sure that TRIZ would be used multiple times during the implementation to solve the problems as they arose.

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