For sub-sized fatigue specimens made of EUROFER97 in unconstrained contact to ceramic breeder pebbles, exposed to purge gas conditions for different durations in an oven, a chemical surface attack ...was observed which led to a significant reduction of fatigue lifetime Aktaa et al., 2020. To better reproduce the flow of the purge gas in the breeding zone of a Helium-Cooled Pebble Bed Breeding Blanket, the experiment was now repeated by placing the same kind of samples in the helium loop HELOKA HEMAT, where the gas is permanently circulated in a closed circuit, and its water content is controllable. The composition of the gas was monitored with a mass spectrometer and humidity sensors. The samples were exposed to a mixture of helium and 0.1vol% hydrogen at DEMO relevant operating conditions (550 °C, 1.2 bars abs.) for a duration of 8, 16, 32, and 64 days, respectively. New sample holders were designed which allow direct contact of the samples with the gas mixture. A special procedure for the handling of the test section was implemented to avoid contact of the hygroscopic pebbles with air humidity during the preparation phase and during the extraction of the samples from the test rig.
The present contribution discusses the various considerations on which the test rig design was based, followed by a description of the experimental setup and preliminary results of the testing campaign. These are similar to the results achieved in the oven experiment. In the future, the loop will be used for tests with up to 200 Pa partial pressure of steam in helium; a mixture that is considered relevant for the DEMO purge gas composition.
Recent analysis result in significant impact on the design of the Helium Cooled Pebble Bed (HCPB) Breeding Blanket (BB). Especially the main demanding sub-component of the BB in terms of fabrication, ...the First Wall (FW) is highly affected. As a matter of fact, the relevance of the developments made for the industrial fabrication of the FW used e.g. in the EU HCPB Test Blanket Module (TBM) for ITER is limited: On one hand in terms of the overall dimensions, but also in terms of geometry and cooling channel configuration. Thus, a fabrication strategy for the FW was proposed as an option in 2018 based on Additive Manufacturing (AM) offering a solution to cover the new aspects. The dedicated fabrication routine is based on Cold Spray (CS) in alternation with machining. In terms of manufacturing of non-plasma facing complex shaped thin- or double wall BB structures (e.g. Fuel Pins proposed for the HCPB BB) the use of AM also provides benefits compared to conventional technologies. Therefore, the AM process of Selective Laser Melting (SLM) is also investigated in terms of applicability for BBs. This paper gives an overview about the advances in different AM options applied for nuclear fusion structural low activation steels. Possibilities for spin-offs to other technological fields are discussed and conclusions are drawn reflecting licensing aspects and technological limits.
•This paper analyzes the open issues of the current reference IFMIF-DONES test cell design. The open issues include the lithium cavitation in the long chute, activation of the quench tank, ...maintenance procedures, and etc.•An optimized test cell configuration which features installing the quench tank half-buried in the test cell floor is proposed to solve the open issues of the reference design.•Two options have been compared side by side from the aspects of tritium generation rate, neutron streaming, lithium flow stability, maintenance scenarios, and etc.
The test cell (TC) in IFMIF-DONES (International Fusion Material Irradiation Facility – Demo Oriented NEutron Source) is the meeting area of the three major systems (test systems, lithium systems, and accelerator systems) to host the irradiation test module, lithium target assembly and the end section of the accelerator line. Although the design of the TC, to a large extent, inherits that of the reference IFMIF-EVEDA (Engineering Validation and Engineering Design Activities) TC, design justifications are required to solve the existing major open issues such as cavitation of the lithium flow, activation and maintainability of key components, and etc. In this paper, these major open issues of the reference TC layout are addressed and a TC reconfiguration proposal, featuring arranging the lithium quench tank inside the TC, is introduced. The two concepts are investigated, analyzed, and compared on the aspects of lithium flow stability, tritium generation rate, key component maintenance scenarios, irradiation shielding, and in-TC components arrangement.
The Q-PETE (Hydrogen Permeation and Transport Experiment) at KIT is set up to investigate hydrogen isotopes permeation through structural materials with specific relevance to the HCPB (helium cooled ...pebble bed) DEMO blanket breeder zone. The results are intended to provide validation data for simulation codes. A second objective is the direct determination of material data. In the first stage deuterium permeation through a Eurofer membrane will be studied using a mass spectrometry method.
This paper describes the definition, the design development, the experimental setup and the characterization of the mass spectroscopy method foreseen for the Q-PETE experiment. The permeator setup was designed taking into account results from uncertainty optimization efforts and manufacturing aspects. Based on the decided geometry, engineering analyses concerning thermal responses and tritium transport were performed. The aim of the characterization of the mass spectroscopy method is to provide a proper foundation for the uncertainty analyses, as well as to optimize the technique. The noise level was related to relevant spectrometer operation parameters. On this basis measures to reduce the background level for the deuterium concentration by a factor of 5 could be found and implemented to the spectrometer analysis procedure.
Heat transfer and pressure drop measurements were conducted to study the thermal-hydraulics in a square, round-edged channel roughened by ribs (e/Dh = 0.0638, p/e = 10) on one wall at Reynolds ...numbers ranging from 5.0 × 104 to 2.5 × 105. Three variously shaped ribs were investigated: Transverse ribs with square cross sections, transverse ribs, and upstream directed 60° V-shaped ribs with round-edged rib front and rear surfaces. Friction factors, Nusselt number ratios, roughness functions, and the thermal performance were presented. The highest heat transfer and best thermal performance is reached by the upstream directed V-shaped ribs.
► Helium Loop Karlsruhe-Low Pressure (HELOKA-LP) succesfully taken to operation at the end of 2009. ► Verified that HELOKA-LP fulfils all requirements to test the High Flux Test Module (HFTM). ► Some ...improvements could be done (e.g. reduction of power consumption, enhancement of control path parameters). ► We obtained a chronological sequence of the helium gas impurity which is important for the International Fusion Irradiation Facility (IFMIF).
As part of the Engineering Validation and Engineering Design Activities (EVEDA) for the International Fusion Materials Irradiation Facility (IFMIF) 1, it is foreseen to design and test a 1:1 scale prototype of the IFMIF High Flux Test Module (HFTM) 2. The module has been designed to be cooled by a low pressure helium gas flowing through minichannels to remove the nuclear heat.
The Helium Loop Karlsruhe-Low Pressure (HELOKA-LP) has been designed to provide coolant at 1:1 HFTM operational conditions: massflow 12–120g/s, inlet pressure 0.3–0.6MPa, inlet temperature RT – 250°C. A secondary objective is to use the experience gained with HELOKA-LP for the planning of the IFMIF helium cooling system.
The facility has been put into operation in 2009, and has since then been in a test and optimization phase. It was proven, that the above mentioned requirements for the facility are achieved. The paper describes the process layout and components of the facility. The performance is characterized by the results of several steady state and transient benchmark tests. Typical start-up and transition times relevant for the operation mode in the IFMIF irradiation campaigns are obtained. Additionally first results on the impurity ingress and the cooling gas chemistry are described.
•Quench tank design optimization for DONES liquid-lithium target.•Comparison of two design options of the quench tank.•Thermal-hydraulic analysis of lithium flow conditions in the quench ...tank.•Thermal-structural analysis of quench tank structure.
In the DONES (DEMO-Oriented Neutron Source) neutron source a single accelerator line delivers 125 mA of deuterons at 40 MeV to a flowing liquid lithium target with a free (vacuum) surface facing the deuteron beam. Neutrons with fusion-relevant spectrum are generated by a stripping reaction and used for material samples irradiation. The Quench Tank (QT) system has the function to collect the open-surface high-speed (15 m/s) lithium-flow emerging from the target assembly and deliver it to the lithium piping system under controlled conditions. Several detailed studies on specific QT design features have been performed. The following design aspects have been analysed:
-Influence of the shape and orientation of the QT on the flow behaviour;-Influence of QT internal elements on the control and enhancement of the mixing of the jet with the stagnant lithium;-Transient mixing of lithium with temperature step-change due to beam on/off events;-Structural analysis of the QT.
As result an optimized design of the QT with enhanced flow conditions is proposed.
An experiment termed “Q-PETE” representative for the situation in the Helium Cooled Pebble Bed (HCPB) breeding zone and suitable for the validation of relevant tritium transport codes has been ...devised. In a temperature controlled setup a hydrogen loaded gas is directed over a steel membrane (several millimeter thickness) into which it can permeate. On the other side of the membrane a sweep gas flow collects the permeated hydrogen and transports it to a quadrupole mass spectrometer for quantitative time resolved detection. This paper introduces methods to handle time resolved permeation experiments with sweep gas, considering the residence time distribution of the sweep gas. The methods are used to quantitatively simulate the planned experiments and expected signal distortion effects. Additionally, an uncertainty model is applied to find optimized process- and geometry parameters for the experiments.
A maintainable test cell (TC) concept, which targets replacing TC key components in case of damages, for the IFMIF-DONES (International Fusion Materials Irradiation Facility – Demo Oriented NEutron ...Source) facility is proposed to facilitate the maintenance of key containment and biological shielding components, i.e. the liner and the surrounding concrete walls. Unlike the current TC reference design which features permanent liner and concrete shielding walls, the new proposal decouples the components which suffer relative high failure possibilities from the ones which can stay as permanent construction structures. The former ones, that are expected to be replaced in case of damage, include removable sections of the liner and part of the biological shielding materials. Fundamental mechanical solution of this configuration is briefly described, and technical feasibilities are preliminarily analyzed for the aspects of independent liner enclosure structure, maintenance scenarios using remote handling systems, etc.
•A comparative neutronics assessment of two QT location options provides key information for the IFMIF-DONES TC design.•A parametric study of the neutron streaming effect in the lithium chute has ...been conducted.•Shutdown dose analysis of DONES test cell shows that the dose rate in the lithium facility room is too high to be hands-on accessed.
The quench tank (QT) location in the test cell is an open issue for IFMIF-DONES (International Fusion Material Irradiation Facility- DEMO Oriented NEutron Source) design. Neutronics assessments have been carried out on two QT location options. A parametric study of the neutron streaming in the lithium chute shows a quasi-linear dependence of the neutron flux on the void thickness. For both options, activation calculations at key locations of the QT system indicate that the contact dose rate is higher than the hands-on dose limit over the whole maintenance period. In addition, the shutdown dose rates in the lithium facility room after 1-day shutdown exceed the hands-on dose limit in different levels. Therefore, remote handling is required for the maintenances of the QT in both considered locations.
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