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Summary: The future of nuclear energy in the energy mix faces a permanent scrutiny of safety aspects in conciliation with bridled costs, either fission‐ or fusion‐based. This affects to all the exciting milestones pursued in XXIst. To name few in the field of fission, the deployment of the IVth generation reactors is expected or the definitive solution to the radioactive wastes is sought. A mention apart is made to fusion technology, with ITER as the flagship project. It seeks a virtually infinite energy source, intrinsically safe and with reduced radioactive waste production with respect to fission the first commercial reactor. All these, and many other endeavors, share the operation of sophisticated devices in the presence of intense ionizing radiation fields. Humans and electronics must be protected to ensure safe and reliable performance, while shielding normally represents a large fraction of the budget. This involves nuclear analysis in the design phase to forecast the radiation conditions. The complexity of the simulation of 3D radiation fields that is computationally affordable nowadays is unprecedented. While sophistication in geometries and source definitions has become routine, the resulting complexity of these scalar fields makes their analysis increasingly difficult. The need of enhancement of the analysis techniques is evident today. Vector calculus is proposed following a physical interpretation of the field lines that boosts the analysis capabilities. It identifies the trajectories around which shielding is weakest in an automated errorless and effortless approach. Its power is illustrated with an example relevant to the ITER reactor. [ABSTRACT FROM AUTHOR]

The depiction of the nuclear responses of the ITER European Test Blanket Modules (TBMs), Helium Cooled Lithium Lead (HCLL) and Helium Cooled Pebbles Bed (HCPB) is presented in this work. Following important components update, and important methodological advances, the nuclear heat and the tritium production have been revisited, giving new estimations 10% higher than the previous evaluation for nuclear heat in both TBMs and to 15% higher for HCPB T production. This has an impact on the thermo-mechanical design of the TBM and the tritium handling. In addition, the Shutdown Dose Rates in the respective port interspace have been characterized in local approach. It shows a performance that could imply compatibility with planned in-situ maintenance activities when analysed in global approach, an improvement with respect to previous evaluations. [ABSTRACT FROM AUTHOR]

• The size of the gaps around the ITER equatorial and upper ports has associated a certain tolerance due to manufacturing and installation. • Gap size variability has an impact on the nuclear responses. • MCNP simulations show the extent of the impact of the gap variability. • A novel modelling approach, which was developed ad-hoc and used to manipulate the size of the port gaps via displacements of the geometry universes, is described. The size of the gaps around the ITER equatorial and upper ports has associated a certain tolerance due to manufacturing and installation. This variability has an impact on the nuclear responses at magnets and port interspace maintenance locations. This effect is not usually considered as the ITER neutronic reference models represent the nominal gaps configuration. This paper aims to estimate the effect of the gap size variability on nuclear heating in the magnets during plasma operation and shut-down dose rate at the port interspace maintenance location taking advantage of a set of MCNP simulations with different gap configurations. The effect has been shown to produce increases of up to 30% in the worst-case configurations. The novel modelling approach, which was developed ad-hoc and used to manipulate the size of the port gaps via displacements of the geometry universes, is also described here. This approach led to important time savings, and it may be used in future studies with similar requirements. [ABSTRACT FROM AUTHOR]