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Title: AN EXPERIMENT TO STUDY PEBBLE BED LIQUID-FLUORIDE-SALT HEAT TRANSFER

AN EXPERIMENT TO STUDY PEBBLE BED LIQUID-FLUORIDE-SALT HEAT TRANSFER A forced-convection liquid-fluoride-salt loop is being constructed at Oak Ridge National Laboratory (ORNL). This loop was designed as a versatile experimental facility capable of supporting general thermal/fluid/corrosion testing of liquid fluoride salts. The initial test configuration is designed to support the Pebble Bed Advanced High-Temperature Reactor and incorporates a test section designed to examine the heat transfer behavior of FLiNaK salt in a heated pebble bed. The loop is constructed of Inconel 600 and is capable of operating at up to 700oC. It contains a total of 72 kg of FLiNaK salt and uses an overhung impeller centrifugal sump pump that can provide FLiNaK flow at 4.5 kg/s with a head of 0.125 MPa. The test section is made of silicon carbide (SiC) and contains approximately 600 graphite spheres, 3 cm in diameter. The pebble bed is heated using a unique inductive technique. A forced induction air cooler removes the heat added to the pebble bed. The salt level within the loop is maintained by controlling an argon cover gas pressure. Salt purification is performed in batch mode by transferring the salt from the loop into a specially made nickel crucible system designed to remove oxygen, moisture and other salt more » impurities. Materials selection for the loop and test section material was informed by 3 months of Inconel 600 and SiC corrosion testing as well as tests examining subcomponent performance in the salt. Several SiC-to-Inconel 600 mechanical joint designs were considered before final salt and gas seals were chosen. Structural calculations of the SiC test section were performed to arrive at a satisfactory test section configuration. Several pump vendors provided potential loop pump designs; however, because of cost, the pump was designed and fabricated in-house. The pump includes a commercial rotating dry gas shaft seal to maintain loop cover gas inventory. The primary instrumentation on the loop includes temperature, pressure, and loop flow rate measurement. Although techniques for all these measurements have improved, no commercial instrumentation was available for flow and pressure measurement that had been tested under these conditions. Instrumentation was tested and modified to meet both corrosion and temperature requirements. This paper discusses the issues encountered during the design and construction of the ORNL Liquid Salt Loop and should prove useful to those contemplating construction of similar high-temperature liquid-fluoride-salt facilities. « less
Authors: ; ; ; ; ; ; ; ;
Publication Date:
OSTI Identifier:OSTI ID: 1025835
DOE Contract Number:DE-AC05-00OR22725
Resource Type:Conference
Resource Relation:Conference: ICAPP 2011, Nice, France, 20110502, 20110505
Research Org:Oak Ridge National Laboratory (ORNL)
Sponsoring Org:USDOE
Country of Publication:United States
Language:English
Subject: 36 MATERIALS SCIENCE; ARGON; CONFIGURATION; CONSTRUCTION; CORROSION; COVER GAS; CRUCIBLES; FLOW RATE; FLUORIDES; FORCED CONVECTION; GRAPHITE; HEAT EXCHANGERS; HEAT TRANSFER; IMPURITIES; INCONEL 600; INDUCTION; MOISTURE; NICKEL; OXYGEN; PRESSURE MEASUREMENT; PURIFICATION; SILICON CARBIDES liquid salt; FLiNaK; Heat Transfer; Pebble Bed; FHR; AHTR; High Temperature Reactor; molten salt