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The purpose of the study is to consider the reactor relevance of the NET design concept. Therefore the NET design, as described in 1986 at the beginning of the pre- design phase and employing a double-null poloidal divertor and a water-cooled liquid lithium-lead blanket (NET-DN), is taken as the basis for the development of a demonstration tokamak reactor concept with a fusion power rating of 2500 MW (DEMO-DN). The main areas of study are those relating to the highly stressed components near to the plasma viz., the first wall, divertor and tritium breeding blanket for which the design principles of NET- DN have been retained as far as possible. The overall conclusion of the study is that the NET-DN concept is only partly relevant to the design requirements of a DEMO-DN mainly because the double-null configuration does not permit sufficient tritium breeding using a lithium- lead blanket to close the fuel cycle (the single-null configuration, on the other hand, is expected to be adequate in this respect). Furthermore, substantial modifications are required in order to accommodate the increased power loadings on components, to enable electricity to be generated at high efficiency and to optimise the global tritium breeding ratio. More complex cooling arrangements are required for the first wall and divertors and beryllium has to be included as a neutron multiplier in the blanket. The possible effects of steam leaking from the blanket coolant pipes into the lithium- lead and causing severe damage are discussed and an alternative design of blanket employing helium as a coolant is proposed. The permeation and extraction of tritium, the magnetic forces arising during a plasma disruption, afterheat in the first wall and blanket and the maintenance procedure are also discussed.

Additional information

Bibliographic Reference: REPORT CLM-R278, 1987, AVAILABILITY: UKAEA, ABINGDON, UK
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