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

Accelerator Driven Systems in nuclear technology will handle very high power of ionizing and non-ionizing radiation in a spectral energy range not currently prevailing in power generating facilities. Experience shows that, due to the very sophisticated technology used in the driving accelerators, frequent 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 and structural materials. The situation may be further aggravated by radiation damage and other mechanisms leading to enhanced materials degradation. Since little is known on the details of these effects, an aggressive materials research and development program is necessary to provide reliable engineering data. Using the example of medium to high power research spallation neutron sources currently under development or in operation, design issues are discussed and ongoing research is described.