High-density UO2 fuel pellets in blanket rods of the first Shippingport core show no structural change after depletions to 6.4 × 1020 fissions/cm3. After 1885 days in hot water, corresponding to post-transition corrosion conditions, the Zircaloy-2 tubing shows a mottled appearance and an oxide thickness averaging 2.4µm, predictable from out-of-pile autoclave testing. The hydrogen content of the tubing agrees reasonably well with similar predictions.