Forced-circulation loop tests

Te.sts have also been made in which the fissioning fuel is pumped through a system in which a thermal gradient is maintained in the fluid. These tests included the Aircraft Reactor Experiment (described in Chapter 16) and three types of forced-circulation loop tests. A large loop, in which the pump was outside the reactor shield, was operated in a horizontal beam hole of the LITR, A smaller loop was operated in a vertical position in the LITR lattice with the pump just outside the lattice. A third loop was operated completely within a beam-hole of the MTR. f The operating conditions for these three loops are given in Table 12-8. 

Dynamic tests of the reaction between Bi and steel in the presence of a radiation field must be completed before a final selection can be made of materials for the LMFR. The effect of velocity on corrosion is not certain from the out-of-pile studies, so that no exact analogy can be made between out-of-pile forced circulation loops and in-pile capsules. There has been limited work done at Harwell [6] with thermal convection loops in and out of a radiation field. These loops had no U but did contain Ca and Zr inhibitors. The data suggest that pile radiation may have induced some acceleration of mass transfer. 

An in-pile, forced-circulation loop has been built at BNL and two others at Babcock Wilcox Research Laboratory to test the corrosion stability of LMFR materials under conditions to be expected in the reactor experiment. In this loop, Bi containiiif approximately 1500 ppm of 180 ppm Zr, and 850 ppm Mg will be pumped at a rate of 5 to 7 gpm. The bulk A2 will be approximately 75°C, with a maximum temperature of 500°C. There are three sample sections in the loop one, containing samples of 1 % Cr-1/2% Mo steel, 2 % Cr-1% Mo steel. Be, and graphite, will be at the center of the reactor and will be in a flux of approximately 3 X lO " thermal neutrons one within the shield will see delayed neutrons at a temperature of 500°C and the third section will be outside the reactor at a temperature of 425°C. This test is presently being assembled, and will be operating late in 1958. 

Fuller, C. J. and MaePherson, R. E., "Design and Operation of Stainless Steel Forced-Circulation Boiling-Potassium Corrosion-Testing Loops, Oak Ridge National Laboratory Report, ORNL-TM-2595, 1967. 

For testing the scaling laws, a two-phase natural circulation loop as shown in Fig. 11 was constructed. The loop was made of 50 mm NB (2 Sch 80) pipes except for the separator which is 150 mm NB (6 Sch 120) pipe. The separated steam is condensed and the condensate is returned to the separator. The vertical heater is direct electrically heated with a high current source. The loop was extensively instrumented to measure temperature, pressure, differential pressure, level and flow rate. Further details of the loop are available in Naveen et al. (2000). Prior to the actual experiments, pressure drop across one pipe segment was measured under forced flow conditions. This gave the following equation for the friction factor... 

Membrane Testing. The membranes were characterized on an RO test loop. Hollow-fiber modules were equipped with fittings as shown in Figure 4 to allow circulation on both sides of the membrane. Flat-sheet membranes were tested in special cells of the type shown in Figure 5 recirculation solution could be pumped into a port in the center of the cell and forced to flow through a sintered stainless steel support plate to reach the permeate side of the membrane. 

A small re-circulation pipeline loop was used for measuring the slurry flow parameters. A test section consists of three stainless steel pipes of inner diameter D = 10.5, 17.5 and 26.8 mm. The length/diameter ratio of the test section for each pipe diameter was 300, 400 and 260, respectively. The slurry was forced to pipe by a screw pump with speed regulator from an open storage tank, equipped with an agitator to prevent slurry settlement. All pipes used in the test section could be considered as smooth pipes. Measuring section of the loop was equipped with three pressure tapings connected to differential pressure transducers. Box divider at the pipe outlet allowed direct volumetric measurement of the flow rate, slurry density and concentration, Chara et al [5]. 

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