Long-term stability of Alnico 5 and 8 magnets at 700 to 1200$sup 0$F

Tests performed to determine the long-term stability of Alnico 5 and 8 magnets for use in permanent magnet in-core sodium flowmeters are described. The results of this experiment showed that two processes combine to affect magnetic stability of these magnets at temperatures above 700 deg F: loss of field strength with time, the rate of loss increasing with temperature, and partial recovery of the loss caused by a high-temperature stabilization. The conclusion is that for a given temperature the most stable performance will be obtained by balancing these iwo processes with an optimum stabilization procedure. This procedure has yet to be established. For 12,000-hr operation, the recommended maximum temperatures are 1000 deg F for Alnico 5 (< plus or minus 10% drift), and 1100 deg F for Alnico 8 (< plus or minus 15% drift). (auth