Shutdown dose rate measurements with Ionization Chambers during and at the end of DT operations at JET

Within the framework of EUROfusion’s technological exploitation of deuterium–tritium (DT) operation at JET—initiated under work package JET3 and continued under PrIO—the NEXP subproject was conceived to exploit the substantial neutron yield expected during the DT campaigns (DTE2 and DTE3) to validate the numerical tools employed for neutron streaming and shutdown dose rate (SDDR) prediction in ITER. This validation, grounded in direct comparison between computational predictions and experimental measurements, constitutes a critical step in demonstrating the reliability of the SDDR methodology that underpins ITER’s radiation safety case. As part of this activity, a dedicated dosimetry system based on spherical air-vented ionization chambers was installed in the JET Torus Hall in 2015 and has since undergone successive hardware and software upgrades to address operational challenges identified across DT experimental campaigns. This work traces the evolution of the SDDR dosimetry system and presents the analysis of the measurements acquired during the DT operation of JET, in particular the third DT campaign (DTE3) and, uniquely, throughout the ongoing final shutdown, a phase offering measurement conditions unlikely to be replicated elsewhere. SDDR predictions with the Advanced D1S tool by ENEA are described as well.