Sicherheitstechnische Auslegung der Betriebsumgebung eines Hochleistungs-Spallationstargetsystemes der Megawattklasse mit Quecksilber als Targetmaterial

This thesis is concerning the safety relevant layout of the environment of a mercury based 5-Megawatt-spallation target. All safety relevant aspects related to construction, operation and dismantling as well economical issues were taken into account. Safety concerns are basically driven by the toxic and radioactive inventory as well as the kind and intensity of radiation produced by the spallation process. Due to significant differences in inventory and radiation between a spallation source and a fission reactor, for the design of the spallation source mentioned above the safety philosophy of a fission reactor must not be used unchanged. Rather than this a systematic study of all safety related boundary conditions is necessary. Within this thesis all safety relevant boundary conditions for this specific type of machine are given. Beside the spatial distribution of different areas inside the target station, influence of medias to be used as well as arising radiation and handling requirements are discussed in detail. A general layout of the target station is presented, serving as a basis for all further component and system development. An enclosure concept for the target station was developed, taking into account the safety relevant issues concerning the mercury used as target materials, the water cooling loops containing massive amounts of tritium as well as the materials used for the moderators potentially forming explosive mixtures. Concept and detailed technical layout of the enclosure system was chosen to guarantee safe operation of the source as well as taking care of requirement arising for handling needs. For design of the shielding different suitable materials have been discussed. A design for assembling the shielding is shown taking into account the safety relevant equirements during operation as well as during dismantling. The neutron beam shutters, buried inside the shielding were designed to optimize handling and positioning issued of the inner part of the neutron guide system. Due to the high amount of safety relevant handling procedures, concepts for time efficient and safe handling of the major components have been developed. Based on the concepts shown is this thesis, construction an operation of a high power spallation source of the described kind seem to be feasible considering safety and costs

Design and manufacturing of permanent magnet bearing rings for high speed applications

We provide an overview of the challenges for the design of magnet rings for high-speed permanent magnet bearings focusing on manufacturing aspects. We analyze an assembly of a NdFeB magnet ring with a hub and a bandage, both made of Ti-6Al-4V (titanium grade 5). Thereby, we consider bandage thicknesses, tolerances and assembling processes. This is supported by simulations using Finite Element Method (FEM) analysis in ANSYS workbench 2020. We analyze the stresses during a press-fit joining process between the magnet and the bandage and subsequent consequences for the stresses on the system for rotation speeds up to 120,000 RPM. Finally, we consider safety aspects by implementing a cracking of the magnet at high rotation speed. The results of the simulations show that the stresses on the magnet are the limiting factor of the rotation speed in all cases analyzed here. For an idealized system, mainly the bandage thickness and the required rotation speed define suitable tolerancesfor the fitting of the bandages and magnets. For a real system, residual stresses of the joining process and ovalization effects of the bandage decrease either the allowable speed or the allowable tolerances, thereby considerably influencing the required manufacturing precision. A safety analysis shows that the hub-magnet-bandage assemblies analyzed here are safe with respect to magnet cracking even at high speed

Thermal Hydraulic and Thermo-Mechanical Design of the Proton Beam Window for ESS

The proton beam window for the European Spallation Source ESS will separate the 1 bar monolith helium atmosphere and the accelerator vacuum. In medium power spallation sources like ISIS, SINQ or the SNS source in Oak Ridge, cylindrical or spherical double walled water cooled windows are used, but during the design of the beam window for the spallation source SNS it became obvious, that this concept is already pushed to its limits at a beam power of 1.4 MW. A novel design concept called pan-pipe design was proposed for the ESS-PBW, which is optimized for high coolant pressures – as helium is the designated coolant for the PBW at ESS - and the typical pressure difference of 1 bar over the window. In the present study the detailed thermo-mechanical design of the PBW made of aluminium is shown. The main focus of the investigations was set on fatigue loading due to mechanical and cyclic thermal loads and on an optimized flexible interface between the PBW and its massive frame

Lightweight fast rotating Fermi-chopper, proof of principle for a scalable array chopper

The concept of the Fermi chopper array based on small Fermi rotors is explored. The advantages of such an array would be very low stored kinetic energy even for very fast running large area choppers and emerging possibilities for new and very flexible focussing schemes. The work comprises the investigation of a drive concept with a small motor and the design of a precise phase control. Further the rotor mechanics (stress and deformation) at high rotation frequencies has been optimised by FE-calculations. A chopper concept is studied with a small high speed motor connected to the rotor by means of an elastic shaft. This concept is comparable to the model of the “de Laval” or “Jeffcott” rotor.The development from a first layout of the Fermi rotor to a prototype aiming at high running speeds up to 1000 Hz is described and results for transmission, blocking and pulse shapes obtained at the ESS test beamline are reported