The first ASME code stamped cryomodule at SNS

The first spare cryomodule for the Spallation Neutron Source (SNS) has been designed,fabricated, and tested by SNS personnel. The approach to the engineering design for thiscryomodule was to maintain critical features of the original design such as bayonetpositions, coupler positions, cold mass assembly, and overall footprint. However, this newcryomodule design was required to meet the pressure requirements put forth in 10 CFR 851:Worker Safety and Health Program. The most significant engineering change was applyingSection VIII of the ASME Boiler and Pressure Vessel Code to the vacuum vessel of thiscryomodule instead of the traditional designs where the helium circuit is the pressureboundary. Applying the pressure code to the helium circuit within the cryomodule wasconsidered. However, it was determined to be schedule prohibitive because it required acode case for the niobium materials which are not currently covered by the code. Goodengineering practice however, was applied to the internal components to verify the qualityand integrity of the entire cryomodule. The design of the cryomodule, fabrication effort,cryogenic and high power RF test results will be reported in this paper.