D:EEP

Contamination Depth Profiling to provide intelligence lead decommissioning

Overview

Correctly classifying waste from nuclear decommissioning is a challenging job. Currently, depth of contamination is usually estimated with a sparse grid of core samples removed with a coring drill from the surface under examination. Drilling cores is hazardous manual work that generates significant airborne contamination and in the process damages the fabric of the facility. The time to obtain data is also very slow.

Today a significant amount of waste is pessimistically classified into higher more expensive waste streams leading to greater costs. The challenge of this project was to better classify nuclear waste so that it could be more accurately disposed of driving costs down.

Approach

We collaborated with Costain to develop a non-invasive measurement technique to profile the depth of entrained radioactive contaminants. This allows a more precise segregation of contaminated material during decommissioning, significant waste storage savings and more complete characterisation of structures.

The D:EEP technology is a spectral analysis technique combining specially designed hardware and software to interrogate the concrete structure of a nuclear sites. It provides a non-intrusive picture of the penetration contamination within a concrete surface. This allows users to ascertain the depth of contamination of multiple gamma emitting isotopes within 1mm accuracy up to at least 50mm and work up to a maximum depth of 150mm. Measurements from s single point or a picture of an entire surface are possible.

Solution

Through a series of deployments we have shown that contamination is usually very shallow within the material, but not always.

The small sensor head has been deployed by hand, and on various different robots. In 2018 we worked with Sellafield to deploy D:EEP underwater in one their ponds. A watertight casing was implemented to protect the unit and keep it close to the wall. This successful deployment led to us winning a SL Business excellence Gold Award.

Conclusion

The ability to measure the depth of contamination leads to an intelligence lead decommissioning strategy. Using the information it is possible to tailor the removal of the contaminated surface to a higher level of efficiency showing significant reduction in waste generation. The benefits stretch much wider, but can be summarised as:  

 

Waste Production 

  • ILW ~30x more expensive than LLW for lifetime storage (~£60,000m-3)
  • 2013 UK Radioactive Waste Inventory estimates 190,000m3
  • 63% is from forecasted decommissioning
  • If 10% can be reclassified it would save ~£1Bn

 

Project Management 

  • Smarter working, many more reference points
  • Faster working, fast analysis turnaround
  • Less expensive to carryout full survey
  • Optimise the site operations

 

Operations 

  • Much safer than coring
  • Non-destructive data gathering
  • Fabric of facility not compromised
  • No airborne contaminants produced