Fig 178. Top of rareearth Stripper vessel showing the nozzles.
electrically insulated from the other equipment to minimize the rate of transfer of lithium between the two bismuth pools (which have different lithium concentrations) in the experiment. The LiCl transfer line is constructed of 'h-in. sched 80 pipe and is insulated from the rareearth stripper vessel by the water-cooled, Teflon-gasketed flange assembly shown on the right side of the figure. The portion of the carbon-steel pipe located adjacent to the cooled flanges is heated by a nickel-jacketed copper sleeve on which a Calrod heater will be mounted. The method used for mounting the heater will facilitate replacement of the heater in the event that this becomes necessary. The heater will be wound in the grooves in the enlarged threaded part of the nickel-clad copper sleeve. This figure also shows the flame-sprayed, oxidation-resistant
nickel aluminide coating that was applied to the carbon-steel parts of the vessel. We are still testing the agitator drive unit and the nonlubricated shaft seal assembly, which is watercooled and buffered with inert gas. The assembly contains two standard graphite-impregnated Teflon Bal-Seals (product of Bal-Seal Engineering Co.). Figure 17.9 shows the test equipment prior to completion of the piping and installation of the electrical heaters and thermal insulation. Two seals were tested initially for 820 hr at shaft speeds of 150 to 750 rpm while salt and bismuth were agitated at 650째C in the 3-in.-diam test vessel. The seals were buffered with argon at 16 psig. After an initial run-in period, the seal leak rate was about 8.6 cm3 of gas per hour. After 700 hr of operation, the leak rate increased rapidly up to the time