The portion of tube 12 near its external walls is maintained at a temperature at least 100 degrees C. below that of the alkali metal in tube 14 by means such as {HEAD ~ thermal exchange} with ambient temperature air or {TAIL ~ other coolant fluids} 
with
The portion of tube 12 near its external walls is maintained at a temperature at least 100 degrees C. below that of the alkali metal in tube 14 by means such as { HEAD ~ thermal exchange } with ambient temperature air or { TAIL ~ other coolant fluids }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL