Martin Mittwollen

Pre-conceptual design assessment of DEMO remote maintenance

Abstract EDFA, as part of the Power Plant Physics and Technology programme, has been working on the pre-conceptual design of a Demonstration Power Plant (DEMO). As part of this programme, a review of the remote maintenance strategy considered maintenance solutions compatible with expected environmental conditions, whilst showing potential for meeting the plant availability targets. A key finding was that, for practical purposes, the expected radiation levels prohibit the use of complex remote handling operations to replace the first wall. In 2012/2013, these remote maintenance activities were further extended, providing an insight into the requirements, constraints and challenges. In particular, the assessment of blanket and divertor maintenance, in light of the expected radiation conditions and availability, has elaborated the need for a very different approach from that of ITER. This activity has produced some very informative virtual reality simulations of the blanket segments and pipe removal that are exceptionally valuable in communicating the complexity and scale of the required operations. Through these simulations, estimates of the maintenance task durations have been possible demonstrating that a full replacement of the blankets within 6 months could be achieved. The design of the first wall, including the need to use sacrificial limiters must still be investigated. In support of the maintenance operations, a first indication of the requirements of an Active Maintenance Facility (AMF) has been elaborated.

Overview of Material Challenges in IFMIF Test Cell Design

Abstract As the core region of IFMIF, the test cell (TC) suffers intense neutron and gamma irradiations. Major material challenges of the TC faced during engineering design phase are outlined and the current key material allocations are described. Actively cooled magnetite concrete is selected as the major biological shielding material for the TC, and actively cooled closed liner made of 316L stainless steel is selected to cover the complete TC internal surfaces. Material selections for sealing gaskets and electric insulations inside the TC are preliminarily defined based on dose rate maps at different locations. Metal based sealing gaskets and glass/ceramic electric insulations are applied in the areas with high dose rate, while organic based gaskets and conventional insulation materials can only be arranged behind sufficient biological shielding. Leak tight welding seams between removable interface shielding plugs and the TC liner are located in the region with very low helium generation rate (<0.01 appm/fpy) in steel so that cutting and re-welding during the complete IFMIF life span is guaranteed.

DEMO — Initiation of remote maintenance requirements

A preliminary assessment on remote maintenance for DEMO (DEMOnstration Power Plant) has been launched in 2011, mainly to revisit the rationale and technology development assumptions that have led to the selection of some design choices in the past. A more detailed assessment of the proposed schemes was required. The development of remote maintenance concepts for DEMO and future fusion power plants is driven by a couple of key requirements to maximize the overall plant availability. That includes heading for feasibility and high reliability of the plant maintenance system. This work is particularly important within the PPPT work programme as novel maintenance concepts must be developed and validated for use in DEMO. Thus one of the objectives for the European Fusion Development Agreement in Power Plant Physics and Technology (EFDA PPPT) 2012 work programme was to establish an initial set of system requirements that the DEMO fusion power plant will place on its Remote Maintenance System (RMS). Based on a preliminary DEMO model, developers of Remote Handling Equipment (RHE) should be provided with a set of comprehensive available information about the working area of RHE for in-vessel and ex-vessel maintenance. The task was not dedicated to repeat a row of top level requirements but to give technical information about different items. Work progress and results are shown in this paper. Being in a pre-conceptual phase, one of the results was that at present there are only few “real” requirements but lots of assumptions. All information was collected, further investigated and brought out as a valuable set of primary boundary conditions for the RHE developers.

New Progresses in the IFMIF Target and Test Cell Design and a Proposal for the Specimen Flow

The development of the conceptual design of the IFMIF Target and Test Cell (TTC) is briefly summarized by outlining the previous reference TTC design and the current Modular TTC (MTC) concept. Based on the MTC concept, the latest progresses of the preliminary engineering design of the key TTC components, including the TTC vessel, the Top Shielding Plugs (TSPs), the Removable Intermediate Ring (RIR), and the Test Module Interface Head (TMIH), are described. A specimen flow, based on handling requirements of the High Flux Test Module (HFTM), between the TTC, Access Cell (AC), Test Module Handling Cell (TMHC) and the Post Irradiation Examination (PIE) facilities is proposed as well as the function of the AC and TMHC is preliminary defined. The TMHC is proposed to be divided into a Component Handling Cell (CHC) and a Rig Handling Cell (RHC) regarding the dimension differences of the components to be handled inside of the cells. The recycling of the irradiated specimens for another campaign of irradiation is also considered in this specimen flow.Copyright