Abstract
As the means for decreasing the maximum fuel cladding surface temperature which was an issue on the reactor core thermal design of SCWR, promoting heat transfer was proposed by using a spacer with a small wing-shape rib installed in fuel bundles. Preliminary analyses were performed to investigate numerically the heat transfer performance of the spacer with a small wing-shape rib. As the result, it was found that the average heat transfer coefficient in subchannels including the small ribbed spacer with an attach angle of thirty degree becomes more than 20% higher than that in subchannels including the small spacer without the ribs.
