Progress report No. 31 for a program of thermoelectric generator testing and RTG degradation mechanisms evaluation

Thermal conductivity measurements of the p-type and n-type selenide alloys after 19,800 hours and 6,500 hours, respectively, continue to show good agreement with the 3M Co. published data. Ingradient testing of n-legs after 8900 hours show comparable performance to the reported 3M data. Ingradient testing of p-legs at accelerated test conditions has completed 5432 hours and performance shows reasonable correlation with accelerated temperature and current gradients. This test has been discontinued to accommodate ingradient performance testing of the new design p-type legs with the Astroquartz/slurry wrap. Weight loss testing of the new design p-type TPM217 (no partition) with the Astroquartz/slurry wrap has been continued at both ingradient and isothermal test conditions. A check of one sample after 1000 hours at T/sub H/900/sup 0/C and T/sub C/150/sup 0/C shows a very low weight loss rate, comparable to that reported by the 3M Co. and these tests are continuing. A post-mortem examination of the RCA Reference Generator, which operated for 62,339 hours prior to failure, has been initiated and the metalligraphic analysis was completed during this report period. The remaining MHW generator, Q1-A, on test has accumulated 14,191 hours and performance remains stable. An evaluation of the performance of the Voyager 1more » and 2 RTGs after 14,661 hours and 15,160 hours of operation, respectively, versus the DEGRA prediction code, continues to show good agreement.« less