Independent double failures

Independent double failures Inner and outer tube failure coincidently happen at the same tube. 

The failure of the vacuum jacket would be less serious, without a plugged neck tube. In this case, two relief valves would function independently, doubling the capacity provided in the test. 

Figure 14 Photographs showing the loci of crack growth for different double cantilever beam adhesive joint specimens pulled to failure, (a) The ERR calculated by FEM for this specimen was largest down the center of the adhesive, (b) the ERR calculated by FEM for this specimen was largest near the lower edge of the adhesive, and (c) the ERR calculated by FEM for this specimen was essentially independent of position across the adhesive thickness.

These breakers are provided for abnormal scenarios such as Loss-Of-Offsite Power and Station Blackout when it is necessary to isolate the Division I II 4160 VAC buses from the Permanent Non-safety buses. Double breakers (normally open) are also provided for the 4160 VAC standby transformer which feeds each of the Class IE buses to maintain independence when they are not being used during maintenance. No single failure can prevent operation of the minimum number of required safety loads. See CESSAR-DC, Sections 8.3.1.2.1, 8.3.1.2.3 and 8.3.1.2.5 for a... 

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