Speaker
Description
The decay of radioactive nuclides activated during the operation of nuclear fusion reactors represents one of the main safety concerns, leading to worker exposure during shutdown and maintenance phases as well as damage to critical electronics. For this, safety demonstrations of fusion reactors like ITER require a precise assessment of the Shut Down Dose Rate (SDDR). In recent years, the Direct-1-Step (D1S) methodology has been the most used due to its much greater computational speed compared to the Rigorous-2-Step (R2S) approach. However, when the assumptions underlying the D1S methodology no longer hold, e.g. when multi-step decay reactions occur in materials like tungsten, alternative approaches must be investigated. This work aims to explore and develop possible adaptations of the D1S methodology for the specific case of the ITER reactor, where tungsten (W) has been introduced as the First Wall (FW) material. The activation of tungsten triggers multi-step decays that make the standard D1S unusable for accurate In-Vessel SDDR calculations. The objective is to propose a modified methodology that maintains the advantages of D1S while ensuring the necessary accuracy for ITER's radiological safety, and to evaluate and understand the impact of FW material replacement on In-Vessel SDDR.
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