Neutronic considerations in nonlinear dynamic multibody systems: Enhanced analysis of the absorbed dose in remote handling equipment Daniel Iglesias * , Tim Eade * , Juan C. García Orden # , Zamir Ghani * , Lee Packer * , Zsolt Vizvary * , Antony Loving * * Culham Centre for Fusion Energy UK Atomic Energy Authority Culham Science Centre, Abingdon OX14, United Kingdom daniel.iglesias@ccfe.ac.uk # ETSI Caminos, Canales y Puertos, Universidad Politécnica de Madrid C/ Profesor Aranguren s/n, 28042 Madrid, Spain, juancarlos.garcia@upm.es Abstract Fusion reactors are an excellent carbon-free alternative to help meet our future energy demands. Zero emissions, no long-lived radiation waste, abundant fuel supplies, and inherent safety are the most important advantages of magnetic confinement fusion reactors. On the downside, developing a fusion power plant represents an extremely challenging task from the physics, material technology, and engineering perspectives. The damage caused by highly energetic neutrons to the in-vessel components requires regular maintenance operations for their replacement. During shutdown, the activated materials decay, emitting gamma radiation. This ionizing field, along with the risk of contamination from activated dust, makes the use of remote handling equipment for all the in-vessel maintenance operations mandatory. Even for these mechatronic devices, the extremely high radiation fields in the range of kGy/h—as shown in Figure 1—represents a huge constraint on their design. The survival of their components is usually estimated by a simplistic approach. The maximum level of absorbed dose, along with the intervention time, gives an upper bound to the total damage. This has been sufficient for present experimental reactors, such as JET, as the radiation levels are orders of magnitude below those expected for future power plants [1]. What is more, heavily radiated assemblies need to cope also with the thermal effects arising from the surface and volumetric heat generation. Figure 1: Active blanket segment handling (left) with remote handling equipment in yellow. Radiation environment (centre) and model (right); max. absorbed dose is 2 kGy/h. The effects on fixed equipment by moving activated components during maintenance scenarios have been previously studied [2,3] and applied to ITER-related scenarios. These approaches use component activation sources generated using the FISPACT-II inventory code [4]. Monte Carlo-based radiation transport codes such as MCNP, together with a range of custom source routines are then used to simulate the radiation fields from both activated static and moving components. The results from the static and moving components can be combined to determine the full radiation field impinging on a component.