On the use of flat tile armour in high heat flux components

The possibility to have a flat the geometry for those high heat flux components subjected to a convective heat nux (namely the divertor dump target, lower vertical target, and the limiter) has been investigated. Because of the glancing incidence of the power load, if an armour tile falls off an extremely high heat flux hits the leading edge of the adjacent tile. As a result a rapid temperature increase occurs in the armour-heat sink joint. The heat flux to the water coolant also increases rapidly up to a factor of 1.7 and 2.3 for a beryllium and CFC armour, respectively, thus causing possible critical heat nux problems. Thermal stresses in the armour-heat sink joint double in less than 0.4 a and triplicate after I s thus leading to a possible cascade failure. Therefore the use of a flat tile geometry for these components does not seem to be appropriate. In this case a monoblock geometry gives a much more robust solution. (C) 1998 Elsevier Science B.V. All rights reserved.