Forty-two instrumented burnout points are reported for the second l2-rod test section which had 0.440-in diameter rods with a minimum spacing of 0.022 in. be een rods. Each rod was wrapped with a 0.022-in. wire. The rods were arranged in a 3 x 4 array to form a 60 deg parallelogram. A contoured housing maintained the minimum spacing between the outer rods andd the housing wall. The tests were performed with vertical upflow at 1200 psia. The ranges of variables studied were: mass velocities from 0. plus or minus to 4.1 x 10/sup 6/ lb/hr-ft/sup 2/, exit steam qualities between 2 and plus or minus 2%, and instrumented burnout heat fluxes as high as 1.28 x 10/sup 6/ Btu/hr-ft/sup 2/. The burnout results showed a strong direct mass velocity effect at exit qualities below 10%. Above 10%, and inverse mass velocity effect was seen to develop particularly at high mass velocities. All the burnouts were observed to take place on outer rods facing the unheated housing walls. Hence, these results provide and estimate of the burnout performance of only the outer rods since the irterior rod surfaces have higher burnout heat flux limits in this geometry. A qualitative analysis ismore » made for predicting the burnout location in a rod bundle. Two phase pressure drop measurements were made to show that the flow was inherentiy stable in the area of interest for the Snap 4 reactor. Rod surface temperatures were measured and heat trandsfer coefficients were calculated. (auth) « less