Advanced Monte Carlo simulations and benchmark of residual dose rate assessments in the ATLAS detector at CERN LHC

<ns3:p>Background The European Organization for Nuclear Research (CERN) pushes the frontiers of physics through the Large Hadron Collider (LHC), a 27-kilometre hadron accelerator capable of producing proton-proton collisions at a center-of-mass energy of up to 13.6 TeV. Its four main detectors (ALICE, ATLAS, CMS, LHCb) are unique examples of advanced particle detection technology and complexity. Ensuring radiological safety throughout the LHC’s environments and lifecycle is a critical task managed by the CERN Radiation Protection group. In this context, assessing residual dose rates is crucial for planning exposure situations, such as maintenance and upgrade projects during LHC shutdowns. Methods This work presents advanced Monte Carlo techniques developed at CERN to predict residual dose rates in the LHC experimental caverns, focusing on the ATLAS detector. Predictions are made using the FLUKA Monte Carlo code and the SESAME toolkit for two-step simulations. The simulation results are benchmarked against experimental residual dose rate measurements collected during LHC Long Shutdown 2 at ATLAS. Additionally, forecasts for Long Shutdown 3 are also presented. Results The FLUKA benchmark for the ATLAS detector demonstrates a general agreement within a factor of 1.5. This consistency validates both the FLUKA geometry model of the ATLAS detector and the reliability of the Monte Carlo techniques used to predict residual dose rates in such complex environments. Conclusions The study highlights the predictive capabilities of the FLUKA and SESAME coupling for simulating residual dose rates in large LHC experiments. This method plays a crucial role in ensuring radiological safety, primarily for dose prediction and optimization. The reliability of this approach is significantly supported by the benchmark results obtained at ATLAS and presented in this paper.</ns3:p>