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 {TAIL ~ ambient temperature air} or other coolant fluids 
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 { TAIL ~ ambient temperature air } or 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 TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH