DTT Divertor Tokamak Test facility Project Proposal: an opportunity for facing one of the major challenges along the roadmap to the realisation of fusion energy

The recent formation 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 to optimise the operation with a conventional divertor based on detached conditions to be tested on ITER, EUROfusion has launched a dedicated project to investigate alternative power exhaust solutions for DEMO, and the design of a new machine named "Divertor Tokamak Test facility" (DTT), capable of eventually integrating all relevant physics and technology issues. The set of possible alternative solutions to be assessed includes advanced magnetic configurations and liquid metal divertors. 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, at least in terms of dimensionless parameters. An optimal balance between these requirements and the need to realize the new experiment accomplishing the DEMO timescale, leads to the choice of the following machine parameters: major radius R=2.15 m, aspect ratio A=3.1 (A=R/a, where ‘a’ is the tokamak minor radius), toroidal field BT=6 T, plasma current Ip=6 MA, additional power PTot=45 MW. The machine will have the possibility to test several different magnetic divertor topologies, in reactor relevant regimes. Different plasma facing materials will be tested (tungsten, liquid metals) up to a power flow of the order of 20MW/m2. The final target of this 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 2022. 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 2016) up to full commissioning and the first plasma (during 2022). 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 150 people involved for the operation (50% professionals, 50 % support personnel). In addition, a significant amount of on-site workers are expected during the construction, not to mention the indirect and spin-off opportunities. The expected economic impact on the hosting territory is also significant. Some financial fall-out for both the construction and the operation should be addressed to the territory (buildings, electrical grid, maintenance, etc.). 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 ... While the European Programme allocated about 60 MEUR in Horizon 2020, the expected total cost for realizing this DTT proposal is estimated to be about 500 MEUR. DTT is a strategic investment in the key areas of research and innovation, with significant implications on the energetic problem, offering a stimulus on higher education and training in the fields of science and engineering. Recently, the Italian Government has offered to the European fusion system the opportunity to get complementary funding for a dedicated exhaust facility located in Italy. The proposal is among the projects submitted to the 315 billion Euro of Juncker's plan (EFSI: European Fund for Strategic investments). This report presents the DTT proposal worked out by an International European Team of experts. Its contents has been independently revised and recommended by Chinese experts. It demonstrates the possibility to set up a facility able to bridge the power handling gaps between the present day devices, ITER and DEMO within the European fusion development roadmap, which plays a crucial role for the development of one of the most promising technologies for an alternative, safe and sustainable energy source.

Una delle principali sfide nella Road Map verso la Fusione è costituita dal problema dei carichi termici. A tal fine EUROfusion ha fatto partire un programma per studiare soluzioni alternative al problema dei carichi termici in DEMO, con il progetto di una macchina denominata "Divertor Tokamak Test facility" (DTT), in grado di fornire soluzioni integrate con tutti gli aspetti fisici e tecnologici. DTT dovrà operare in scenari integrati, con carichi termici rilevanti, divertori flessibili, condizioni di plasma simili a quelle previste per DEMO. Il compromesso tra prestazioni richieste e la necessità di rispettare la scala dei tempi dettata dalla Road Map ha portato alla scelta dei seguenti parametri: raggio maggiore R=2.15 m, rapporto di aspetto A=3.1 (A=R/a, dove ‘a’ è il raggio minore del tokamak), campo magnetico toroidale BT=6 T, corrente di plasma Ip=6 MA, potenza addizionale PTot=45 MW. La macchina potrà provare differenti concetti e topologie di divertore. Saranno testati diversi materiali con flussi termici fino a 20MW/m2. Le attività di ricerca correlate costituiranno una notevole spinta per lo sviluppo di tecnologie innovative in vari settori, con rilevanti ricadute per le industrie europee. DTT sarà operativo nel 2022. Pertanto, la realizzazione durerà circa 7 anni a partire dalla prima gara (2016) fino alla messa in servizio. Le operazioni ed il programma sperimentale dovrebbero poi coprire un periodo di oltre venti anni, fino all'inizio della costruzione di DEMO ed oltre. L’impatto occupazionale previsto è rilevante, almeno 150 persone coinvolte nella sperimentazione. E' inoltre previsto un notevole numero di lavoratori coinvolti nelle fasi di costruzione ed operazione, senza contare le opportunità per spin-off e sub-appalti. L'impatto economico previsto sul territorio è significativo nelle fasi di costruzione ed in quelle successive (edifici, rete elettrica, manutenzione, ecc.). La presenza permanente di un team internazionale darà luogo a ricadute sul territorio legate al soggiorno del personale e delle relative famiglie. EUROfusion ha stanziato circa 60 M€ in Horizon 2020, ma il costo previsto per la realizzazione di DTT è valutato intorno alla cifra di 500 M€. Vedendo nel progetto DTT un'occasione per dare un contributo al problema energetico ed al tempo stesso investire nella ricerca europea con prospettiva di elevatissimo ritorno economico, il governo italiano ha offerto l'opportunità di ottenere i finanziamenti necessari a costruire DTT in Italia. La proposta è fra i progetti presentati per il finanziamento tramite i 315 miliardi di Euro previsti dall'Agenda Juncker (EFSI: European Fund for Strategic Investments).