Beam to Shell Temperature Differencees for the CC Cryostat

Abstract

This note documents the calculation of stresses resulting from temperature differences between the CC cryostat shell and the module array support beams, and the calculation of corresponding maximum allowable temperature differences to be monitored during the cooldown of the cryostat. A finite element model of a portion of the inner vessel shell was analyzed for a uniform temperature change. The shell was assumed to be completely restrained by the support beams. A maximum allowable temperature difference was determined based on limits on secondary stress ranges prescribed by the ASME Code (Section VID, Division 2). The maximum allowable difference between the cryostat shell and the support beams was found to vary from about 18K near room temperature to about 30K as the shell temperature approaches liquid argon temperature. The allowable values are tabulated below and plotted in Figure 1. The variation results from the decrease in the coefficient of thermal expansion of stainless steels at lower temperatures. As shown in the plot, the variation is roughly linear. Note that although the shell is assumed to be at the lower temperature in Fig. 1, the limitation on temperature difference will also apply during warmup, when the shell will likely be warmer thanmore » the beams.« less