Modelling of Sludge Supernate Interactions

NNL has extensive experience of modelling radioactive Magnox sludges in aqueous environments such as ponds and solids settling tanks. Modelling focuses on the settling characteristics of the sludge particles and the chemical interaction between sludge and supernate. It's then used to support the safety case for the building of new sludge storage facilities at Sellafield.

Our proven track record in developing mixed chemical and process models means we produce bespoke models of existing and proposed plants. Better still, we design them to focus on the aqueous chemistry and feed/waste stream predictions.

Modelling Techniques:

Models are typically developed as a process model using gPROMS, allowing the engineering of the plant to be captured. The chemical and physical processes involved are then included and parameterised against plant, experimental and simulated data. The resulting model can then be used to make predictions about the behaviour of the plant over time. Our technologists are not tied to using a specific modelling package, so carry a wealth of experience in selecting the correct tools for every project.

Modelling applications:

We've used modelling to make predictions about a number of pond and settling tank processes and associated chemistries. Examples include:

  • pH fluctuation due to:
    • Carbonation
    • Feed pH changes
    • Chemical buffering
  • Liquor composition, in terms of:
    • Active species, such as Cs-137 and Sr-90.
    • Inactive species, such as Mg2+ and Na+
  • The release or adsorption of activity onto sludge
  • Settling characteristics of sludge, either from a plant feed or disturbance of previously settled material
  • The effect of chemical reactions on liquor chemistry and gas production, such as the corrosion of metallic sludge and associated hydrogen production