The Effect of Element Bow on Dryout Power and PDO Heat Transfer in CANDU Fuel Bundles

Abstract

Dryout and post-dryout tests were performed in a modified 37-element simulated CANDU fuel bundle, with one outer element of the last bundle bowed at gradual but controlled steps toward the pressure-tube wall. The dryout power decreased moderately as the gap size was reduced from nominal to about 40%. For smaller-than-40%-gap sizes, however, the dryout power increased in most cases; this resulted in almost equal dryout powers at the nominal and zero gap sizes. The maximum surface temperature of the bowed element at up to 20% overpower increased with decreasing gap sizes; however, for gap sizes smaller than 35% of the nominal gap, the surface temperature fluctuated moderately.