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Fuel assembly deformations can lead to problems during the handling of fuel assemblies during outages. Usually these problems occur at times where the work is on a critical path, causing longer outage times as well as damages to fuel assemblies.

COLOSS helps to minimize the time and risk for handling operations during outages
With the Core Loading Sequence Simulator (COLOSS) you can analyze potential critical loading steps and optimize complete loading sequences. Based on either measured or predicted fuel assembly deformations, the friction forces between fuel assemblies during each unloading and loading step are evaluated. To facilitate the creation or optimization of loading sequences, the results can be displayed graphically.

Your benefits

  • COLOSS helps you to optimize your outage and thus save time and money
  • Application of COLOSS significantly reduces the core loading and unloading times
  • The risk of damages during handling operations is minimized
  • The assessment of multiple loading sequences is possible in a short amount of time
  • The ideal region to start the unloading, respectively finish the loading of the core can be identified
  • No changes of loading or unloading sequences during the outage


The application of COLOSS within the scope of the outages 2013 and 2014 in a 16x16 plant was successful and to the complete satisfaction of our customer.

Interested in Optimization of Reactor Core Loading and Unloading?

AREVA NP Germany