Technology issues in the design of medium-to-high power spallation targetsfor accelerator driven systems

Accelerator Driven Systems in nuclear technology will handle very high powe r of ionizing and non-ionizing radiation in a spectral energy range not cur rently prevailing in power generating facilities. Experience shows that, du e to the very sophisticated technology used in the driving accelerators, fr equent shea beam trips must be anticipated, at least in early stages of the development. This, together with the intense cooling requirements, results in severe restrictions in the allowable load parameters for solid target a nd structural materials. The situation may be further aggravated by radiati on damage and other mechanisms leading to enhanced materials degradation. S ince little is known on the details of these effects, an aggressive materia ls research and development program is necessary to provide reliable engine ering data. Using the example of medium to high power research spallation n eutron sources currently under development or in operation, design issues a re discussed and ongoing research is described.