Progress in materials test loop fabrication and lithium testing for the SP-100 space reactor

The last of three Materials Test Loops will have been completed by the time this paper is presented in January, 1993. This report describes the successful fabrication, operation and evaluation of this series of niobium alloy (Nb-1Zr and PWC-11) thermal convection loops designed to contain and circulate molten lithium at temperatures up to 1400 K. In the SP-100 program at San Jose, approximately 500 weldments will have been exposed to lithium at 1350 K; 300 GTA welds forming lithium pressure boundaries in either convection loops or test capsules, 150 weld specimens produced in deliberately contaminated atmospheres and 20 electron beam welds. It has been observed that no attack occurred for any pure weldment either with of without PWHT and that no welds were made which accidently deviated from purity. The bulk oxygen threshold for weldment attack is 170--200 ppm oxygen with nitrogen content being directly related to attack