SNS Tube Moderator manufacturing feasibility study
The scope of the tube moderator manufacturing feasibility study was to develop all processes, including design optimization, machining, welding, assembling, NDT and DT testing, of a Second Target Station (STS) tube moderator unit for the spallation neutron source SNS of the Oak Ridge National Laboratory necessary to ensure that the complex design can be manufactured under the given high-quality requirements.
The unit consists of an inner triangular cold moderator, which is filled with liquid hydrogen at -253°C and an outer vacuum vessel. The vacuum vessel itself has six neutron beam extraction channels, which are located laterally around the cold moderator. The entire unit is embedded in a beryllium reflector assembly (not shown in the picture) and positioned just above the spallation target.
Technical Challenge
A particular challenge in the project was the joining of the individual components. The high-strength aluminum alloy Al6061-T6 used is generally considered to be difficult to weld, which is why extensive preliminary tests were carried out by our special joining laboratory staff before the actual component was manufactured.
Another important step in the development was to determine the limits of the system under the most realistic possible load conditions. For this purpose, a liquid nitrogen burst test and a cryogenic thermal shock cycling test was performed.
The result of the destructive testing under realistic load conditions was a burst pressure of the moderator vessel of 263.38±1.32bar, which is about ten times higher than the operation pressure.
The project was successfully completed in late summer 2022 with the delivered prototype to the Spallation Neutron Source SNS of the Oak Ridge National Laboratory, USA.