European DEMO divertor target: Operational requirements and material-design interface

Recently, an integrated program of conceptual design activities for the European DEMO reactor was launched in the framework of the EUROfusion Consortium, where reliable power handling capability was identified as one of the most critical scientific as well as technological challenges for a DEMO reactor. The divertor is the key in-vessel plasma-facing component being in charge of power exhaust and removal of impurity particles. The DEMO divertor target will have to withstand extreme thermal loads where the local peak heat flux is expected to reach up to 20 MW/m2 during slow transient events in DEMO. To assure sufficient heat removal capability of the divertor target against normal and transient operational scenarios under expected cumulative neutron dose of up to 13 dpa is one of the fundamental engineering challenges imposed on target design. To develop the design of the DEMO divertor and related technologies, an R&D work package 'Divertor' has been set up in this consortium. The subproject 'Target Development' is devoted to the development of the conceptual design and the core technologies of the plasma-facing target. Devising and implementing novel structural heat sink materials (e.g. W/Cu composites) to advanced target design concepts is one of the major objectives of this subproject. In this paper, the underlying design requirements imposed by the envisaged power exhaust goal and the prominent material-design interface issues are discussed. In addition, the candidate design concepts being currently considered are presented together with the related material issues. Finally, the first results achieved so far are presented

Divertor of the European DEMO: Engineering and technologies for power exhaust

In a power plant scale fusion reactor, a huge amount of thermal power produced by the fusion reaction and external heating must be exhausted through the narrow area of the divertor targets. The targets must withstand the intense bombardment of the diverted particles where high heat fluxes are generated and erosion takes place on the surface. A considerable amount of volumetric nuclear heating power must also be exhausted. To cope with such an unprecedented power exhaust challenge, a highly efficient cooling capacity is required. Furthermore, the divertor must fulfill other critical functions such as nuclear shielding and channeling (and compression) of exhaust gas for pumping. Assuring the structural integrity of the neutron-irradiated (thus embrittled) components is a crucial prerequisite for a reliable operation over the lifetime. Safety, maintainability, availability, waste and costs are another points of consideration. In late 2020, the Pre-Conceptual Design activities to develop the divertor of the European demonstration fusion reactor were officially concluded. On this occasion, the baseline design and the key technology options were identified and verified by the project team (EUROfusion Work Package Divertor) based on seven years of R&D efforts and endorsed by Gate Review Panel. In this paper, an overview of the load specifications, brief descriptions of the design and the highlights of the technology R&D work are presented together with the further work still needed

Conceptual design studies for the European DEMO divertor: Rationale and first results

In the European fusion roadmap, reliable power handling has been defined as one of the most criticalchallenges for realizing a commercially viable fusion power. In this context, the divertor is the key in-vessel component, as it is responsible for power exhaust and impurity removal for which divertor targetis subjected to very high heat flux loads. To this end, an integrated R&D project was launched in theEUROfusion Consortium in order to deliver a holistic conceptual design solution together with the coretechnologies for the entire divertor system of a DEMO reactor. The work package \u2018Divertor\u2019 consistsof two project areas: \u2018Cassette design and integration\u2019 and \u2018Target development\u2019. The essential missionof the project is to develop and verify advanced design concepts and the required technologies for adivertor system being capable of meeting the physical and system requirements defined for the next-generation European DEMO reactor. In this contribution, a brief overview is presented of the works fromthe first project year (2014). Focus is put on the loads specification, design boundary conditions, materialsrequirements, design approaches, and R&D strategy. Initial ideas and first estimates are presented

Uneven Power and the Pursuit of Peace: How Regional Power Transitions Motivate Integration. CES Working Paper, no. 150, 2007

This paper addresses two related puzzles confronting students of regional and international integration: Why do states willingly pool and delegate sovereignty within international institutions? What accounts for the timing and content of regional integration agreements? Most theories of integration suggest that states integrate in order to solve problems of incomplete information and reduce transaction costs and other barriers to economic growth. In contrast I argue that integration can serve to establish a credible commitment that rules out the risk of future conflict among states of unequal power. Specifically, I suggest that integration presents an alternative to preventive war as a means to preclude a rising revisionist power from establishing a regional hegemony. The implication is that it is not countries enjoying stable and peaceful relations that are most likely to pursue integration, but rather countries that find themselves caught in a regional security dilemma, which they hope to break out of by means of institutionalized cooperation. I evaluate this proposition against evidence from two historical cases of regional integration: the German Zollverein and the European Communities