Mechanical engineering services

Tender description

The STEP Work Package 5 (resilient nuclear components) wishes to harness industrial expertise in heat exchanger design outside fusion and to identify whether this expertise can be applied to developing a candidate concept design for the STEP divertor. More in-depth design and testing, to be carried out during the STEP programme conceptual design phase (2020-2025), is contingent on an initial feasibility study or studies to be carried out in 2019; the nature of which will be described in calls for proposals in the form of a design challenge to be issued for tender in September 2019. Concept design requirements: — a divertor target must remove at least 10-20 MWm-2 of steady state planar surface heat flux. A higher heat flux handling is desirable, as loads of up to 200 MWm2 have been suggested for the most ambitious power plant designs, — the total heated area in a fusion power plant divertor will be approximately 50-100 m2, but a concept can be initially demonstrated on an area of order 10 cm2, provided some indication of scalability and/or modularity is included, — for a final design, at least 3 mm thickness of Tungsten armour must be included between the heated face and the working fluid (5 mm preferred). For concept design purposes, this can be neglected, provided indication is made of how such armour would subsequently be incorporated, — heatsink and structural material and working fluid choice for a divertor design is constrained by the effects of neutron irradiation (activation, transmutation, and radiation-induced material property degradation), by compatibility with the tokamak environment (most notably vacuum, hydrogen isotopes, and helium), and by the need to join to tungsten armour, as well as more obvious thermomechanical limitations of cyclical loading and operation at elevated temperature for extended periods. Concept designs do not necessarily need to consider all these factors, but a clear route to their inclusion in subsequent development must be evident, — current baseline designs employ pressurised water as the cooling fluid at approximately 150 ºC. In order to increase overall balance of plant efficiency or to rationalise the cooling system with others within the tokamak, higher temperature options including the use of advanced coolants including high temperature gas, liquid metals, or molten salts are welcome, within the bounds of material limits, but heat flux handling capability is the primary requirement. Scope: — the proposed work must include the production of a concept high heat flux handling device suitable for use in the STEP fusion reactor, — proposed work may include modelling, manufacturing trials, prototype fabrication, and/or representative testing, and must include indications of proposed follow-on activities, — suggestions of testing making use of UKAEA capability such as the HIVE high heat flux facility are welcome, — the total duration of these activities will not exceed three months and must be complete by February 2020, with proposed follow-on activities to be carried out over the next 2-5 years, — if more than one proposal is received and if these seek to address sufficiently different aspects of the challenge, multiple contracts may be placed. Additional reading: [1] EUROfusion Roadmap 2018 (https://www.euro-fusion.org/eurofusion/roadmap/). [2] J. H. You et al., ‘European DEMO divertor target: Operational requirements and material-design interface’, Nucl. Mater. Energy, vol. 9, pp. 171-176, Dec. 2016. [3] J. H. You et al., ‘European divertor target concepts for DEMO: Design rationales and high heat flux performance’, Nucl. Mater. Energy, vol. 16, pp. 1-11, Aug. 2018. [4] R. A. Pitts et al., ‘A full tungsten divertor for ITER: Physics issues and design status’, J. Nucl. Mater., vol. 438, No SUPPL, pp. S48–S56, Jul. 2013. [5] T. Hirai et al., ‘ITER divertor materials and manufacturing challenges’, fusion engineering and design, North-Holland, 19.7.2017.