ENGINEERING DEVELOPMENT STUDIES FOR MOLTEN-SALT BREEDER REACTOR PROCESSING NO. 1. (1970)

One planned objective of these experiments is the investigation of mass transfer between the salt and bismuth under different flow conditions in various contacting devices.The effective overall mass-transfer coefficient (or, equivalently, the height equivalent to a theoretical stage) will be determined in several experiments with various contactors which include packed and baffled columns.The mass-transfer performance is determined, in part, by the hydrodynamic conditions in the contactor; information on hydrodynamic conditions in packed columns will be inferred from measurements of the pressure drop through the column by analogy X to a water-mercury system being studied by Watson.The experiments should answer the following questions: (l) What is the limiting flow rate beyond which the column will flood?(2) Is the bismuth well dispersed, or does channel type flow occur?(3) How much interfacial area exists for mass transfer?(4) Is disengagement of the phases complete in the end sections, or does entrainment present a problem?(5) How severe a problem will be caused by axial backmixing, particularly in the salt phase at high metal rates?A second objective is the evaluation of the performance of auxiliary equipment necessary to perform experiments of this type.Such information will be used in designing subsequent experimental facilities.The following components will be included in the evaluation: freeze valves, filters, instrumentation, and supply systems for argon, hydrogen, and hydrogen fluoride.We plan to determine the probable lifetime for freeze valves subjected to repeated freeze-thaw cycles since we expect them to fail eventually under such stress; in addition, we will study the performance of freeze valves containing two fluid phases.The performance of filters with the possible entrainment of a second fluid is also of interest.As a part of these studies, we wish to determine whether carbon steel is a suitable structural material for short-term use in experiments of this kind, and whether graphite is a suitable material in which to hydrofluorinate the salt and metal mixture.In carrying out the experiments outlined above, we will gain operating experience and confidence in handling the process fluids.We will also uncover areas of unforeseen difficulty, where further developmental work may be needed. General Operating ProcedurePrior to an experiment, slightly more than 15 liters of salt and 15 liters of bismuth will be present in the treatment vessel.This material will be hydrofluorinated to return lithium, thorium, uranium^ etc. to the salt phase, and to remove oxides from the salt.After suitable sparging with argon to remove HF and H^, sslt (15 liters) will be transferred to the salt feed tank, leaving a heel about l/2 in.deep in the treatment vessel.Then bismuth (15 liters) will be transferred to the bismuth feed tank, leaving an additional heel of about 1 in.Finally, reductant will be added to the bismuth in the metal feed tank.Samples of salt and metal feed will be withdrawn.During an experiment, salt and metal may be transferred through the column at controlled flow rates from 0*05 to O.5 liter/min.During this transfer, the pressure drop across the column can be monitored; ?.ud samples can be taken from the salt and the metal streams exiting from the column.After an experiment, the salt and the metal may be sampled in the catch tanks before being transferred back to the treatment vessel.Hydrofluorination would be repeated to return lithium, thorium, and uranium to the salt phase prior to the next run.Thus, there will be a constant amount of each component in the system (notably uranium), except for a known amount of thorium which will be added to the system in each run.Material-balance determinations will be greatly facilitated by this fact.'1 '1! , ;'' 1 , Description of Major Processing Equipment; M All components that contact molten salt or bismuth are fabricat.ed-'^of'.Vi, carbon steel, except as noted-The major components in the system "V V'. .)i >' , ''nV 'Vv'A 1 .for handling salt and metal are described below and are shown schematically?';'Ohin Fig. 1.