Distinguished Merit Award: Computational Fluid Dynamics Study and Calculations

Large inventories of tritium have accumulated in Canada in the past few decades, from the activation of heavy water in CANDU® reactors. Through the lifetime of these reactors, as well as associated processing or research facilities, tritium has migrated throughout the buildings in which it was used; this also includes the uptake of tritium deep into the concrete of these buildings. As traditional remediation techniques that rely on surface contamination treatment would not be effective, and deep tritium remediation prior to demolition is difficult and still an area of active research, alternative solutions that rely on leaving the tritium in-situ are being pursued.

This project documented the completion of the milestone for conducting a Computational Fluid Dynamics (CFD) study to support decision-making for decommissioning strategies for nuclear facilities. The study centred around B250 at the Chalk River Laboratories site and aimed to inform how much tritium can be left in-situ without compromising safety during open-air demolition.

“Open air demolition” approach results in material with active contamination being released into the atmosphere during the demolition activities, a risk that needs to be quantified. One of the challenges with this process, is that the dispersion around the buildings is often quite difficult to characterize, given the complex emission source and buildings nearby that result in convoluted wind field profiles. It is largely beyond the capabilities of classical modeling tools, but it is something that can be accomplished with higher fidelity modeling tools like Computational Fluid Dynamics (CFD). With many legacy buildings that have contained tritium in the past slated for decommissioning, if open air demolition is to remain an option while leaving tritium contamination insitu, advanced tools that can help quantify the worker dose should be evaluated as part of the tool set.

This study focused on demonstrating the methodology of applying CFD to decommissioning applications for worker dose evaluation, with the aim to use this knowledge for future projects as part of a decommissioning safety analysis tool set.The team demonstrated exceptional initiative by going beyond traditional modeling approaches, exploring high-fidelity simulations to address complex tritium dispersion challenges, and the effective application of CFD to this context represents a novel approach in decommissioning strategy development, especially in the context of radiological safety.