Control of Impurities in Forced-Circulation Lithium Loop Systems^*

The potential utility¹  of liquid lithium as a blanket and possibly a coolant material for deuterium-tritium fueled fusion power reactors has generated considerable interest^1-12  in the technological problems associated with lithium handling and containment. A program of studies²  presently underway at the Argonne National Laboratory (ANL) is focusing on the development of processing and monitoring methods for large, circulating liquid lithium systems. The principal apparatus in this program is a 50-gallon capacity, forced circulation lithium loop. This facility, the Lithium Processing Test Loop (LPTL), was described in some detail in a recent publication.²  In brief summary, the LPTL is constructed almost exclusively from 304L stainless steel and contains experimental assemblies to study (1) thermally regenerative cold trapping, (2) high-temperature getter trapping (using zirconium foil as the impurity getter), (3) on-line permeation-type hydrogen isotope monitoring, and (4) molten salt extraction¹²  as an impurity removal method. In another series of experiments paralleling the LPTL studies, an attempt is being made to examine impurity element interactions in liquid lithium by electrical resistance methods. This paper presents the results of recent studies of the effectiveness of cold trapping and getter trapping as approaches to impurity control in large lithium systems. The results are based on work done with the cold trap and getter trap presently installed on the LPTL and with a specially designed flushable resistivity apparatus. The specific impurities monitored in these initial experiments were oxygen, nitrogen, carbon, and to some extent hydrogen and deuterium. The sampling and analytical methods are summarized briefly in this paper with appropriate references to earlier, more descriptive publications of their details.