What is DTT
The establishment of the EUROfusion Consortium marks a big step in the roadmap toward the realisation of fusion energy with a demonstration plant DEMO by 2050.
One of the main challenges in the roadmap is to develop a heat and power exhaust system able to withstand the large loads expected in the divertor of a fusion power plant. Therefore, in parallel with the programme aimed to optimise the operation with a conventional divertor based on detached conditions to be tested in ITER, EUROfusion has launched a dedicated project to investigate alternative power exhaust solutions for DEMO. In this regard, the design of a new machine named "Divertor Tokamak Test facility" (DTT), to be able of integrating all relevant physics and technology issues has been considered very crucial to assess possible alternative solutions, including advanced magnetic configurations and liquid metal divertors.
The original DTT project proposal has been carried out by more than one hundred scientists from ENEA, CNR and Universities, with the support of some European Labs and the contribution of scientists from several European Labs. The results are collected in “DTT-Divertor Tokamak Test facility. Project Proposal”, ISBN 978-88-8286-318-0, published in 2015 (DTT “Blue Book”) and published in several papers, including the Special Issue in Fusion Engineering and Design, November 2017 (Special Section: DTT, Fusion Engineering and Design, Vol. 122, 2017).
After the Blue Book was published, the DTT team continued its intense activity in order to finalize the project and the organization; the main aims were organizational and financial objectives (site selection, organizational structure, cost revision, etc.) and, in addition, technical and design insights (up-down symmetry, parameter settling, review of critical subsystems, etc.).
The new version of the project is described in a new report (titled: “DTT-Divertor Tokamak Test facility. Interim Design Report”, Green Book) to be published by the end of the year; this note summarizes and anticipates the main elements of the new report.
DTT should operate integrating various aspects, with significant power loads, flexible divertors, plasma edge and bulk conditions approaching, as much as possible, those planned for DEMO, in terms of dimensionless parameters. An optimal balance between such requirements and the need to realize the new experiment accomplishing the DEMO timescale has been carried out by means of suitable scoping studies. The outcome of these studies led to the choice of the following parameters: major radius R=2.10 m, aspect ratio A=3.23 (A=R/a, where ‘a’ is the tokamak minor radius), toroidal field BT=6 T, plasma current Ip=5.5 MA, additional power PTot=45 MW. The machine will have the possibility to test several different magnetic divertor topologies, in relevant reactor regimes. Different plasma facing materials will be tested (tungsten, liquid metals) up to a power flow in excess of 20 MW/m2. The final target of the experiment is the realization of an integrated solution (bulk and edge plasma) for the power exhaust in view of DEMO. The related studies and experiments will allow a valuable development of innovative technologies in several different fields, with relevant spin off for the industries of all European Countries.
According to the European Road Map, the DTT experiment should start its operation in 2025. To be coherent with this plan, the realization of the device will cover a time of around 7 years, starting from the first tender (during 2018) up to full commissioning and the first plasma (during 2025). The operations should then cover a period of more than 20 years, up to the initial phases of the DEMO realization.
The occupational impact is expected to be significant, with at least 250 people involved for the operation (50 % professionals, 50 % support personnel). In addition, a substantial amount of on-site workers is expected during the construction, as well as large indirect occupational benefits and spin-off opportunities.
All the financial implications for both the construction and the operation have been addressed for the selected site (buildings, electrical grid, maintenance, etc.).
The expected economic impact on the hosting territory is also significant. In addition, the continuous presence of an international scientific staff will cause on the host territory a spin-off linked to the guest family life and activities like lodging, transport, restaurants, schools and so on.
While the European Programme allocated about 60 MEUR in next framework program, the expected total cost for realizing this DTT proposal is estimated to be about 500 MEUR. Half of the amount is covered by a European loan, granted to the Italian Government.
DTT is a strategic investment in several key areas of research and innovation, with significant implications on the energy problem, offering a stimulus on higher education and training in many fields of science and engineering. TheItalian Government has offered to the European fusion system the opportunity to get complementary funding for a dedicated exhaust facility located in Italy.
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