3 MW solid rotating target design

A rotating solid target design concept is being developed for potential use at the second SNS target station (STS). A long pulse beam (∼1 ms) at 1.3 GeV and 20 Hz is planned with power levels at or above 1 MW. Since the long pulse may give future opportunities for higher power, this study is looking at 3 MW to compare the performance of a solid rotating target to a mercury target. Unlike the case for stationary solid targets at such powers this study indicates that a rotating solid target, when used with large coupled hydrogen moderators, has neutronic performance equal to or better than that with a mercury target, and the solid target has a greatly increased lifetime. Design studies have investigated water cooled tungsten targets with tantalum cladding approximately 1.2 m in diameter, and 70 mm thick. Operating temperatures are low (<150 deg. C) with mid-plane, top and bottom surface cooling. In case of cooling system failure, the diameter gives enough surface area to remove the decay heat by radiation to the surrounding reflector assemblies while keeping the peak temperatures below approximately 700 deg. C. This temperature should mitigate potential loss of coolant accidents and subsequent steam, tungsten interaction which has a threshold of approximately 800 deg. C. Design layouts for the sealing systems and potential target station concepts have been developed.