K. Nishida et al., SPACER EFFECT ON LIQUID-FILM FLOW AND CRITICAL POWER IN BWR FUEL BUNDLES, Journal of Nuclear Science and Technology, 31(3), 1994, pp. 213-221
Liquid film thickness measurements and flow pattern observations near
a spacer have been carried out using 4x4 and 9x9 mock-up fuel bundles
with air-water co-current flow. The spacer had two different effects o
n the liquid film flow in the downstream region : (a) liquid droplet e
ntrainment and deposition induced by turbulence enhancement in gas cor
e flow; and (b) liquid droplet entrainment and deposition induced by a
direct interaction of liquid film flow and spacer elements. The forme
r effect was taken into account for development of a new spacer model
to estimate dependence of critical power on spacer pitch. The liquid f
ilm model, including the spacer model, was confirmed to predict the cr
itical power with high accuracy.