Atr Extended Burnup Program.

Review and Summary of Oxide Thickness Data for Aluminum-Clad Spent Nuclear Fuel

“…Two data points at relatively high temperature fell significantly below the curve and were noted to possibly reflect spalling of oxide [25].…”

“…Oxide thicknesses on the convex surfaces of many fuel plates were measured using the eddy current technique. Reported per-plate maximum oxide thicknesses ranged from 0.49-1.75 mils (12-44 µm) for different plates [25]. Metallographic characterization found thicknesses consistent with the eddy current technique, and indicated that thicknesses on the convex and concave surfaces were comparable [25].…”

“…Griebenow [25] reported oxide measurements obtained during post-irradiation destructive examination of ATR fuel elements operated during two phases of the ATR startup program. The fuel was operated at power for either 35 or 27 days depending on the fuel element and was stored underwater in the ATR canal for >6 months prior to examination.…”

“…Reported per-plate maximum oxide thicknesses ranged from 0.49-1.75 mils (12-44 µm) for different plates [25]. Metallographic characterization found thicknesses consistent with the eddy current technique, and indicated that thicknesses on the convex and concave surfaces were comparable [25]. The convex surface of plate 19, which is exposed to the outside coolant channel and is the most accessible plate surface without disassembly, tended to have lower oxide loading than the surfaces facing inner water channels [25].…”

“…Full sets of oxide thickness measurements (not just the maximum) were plotted for a few fuel plates. Sixteen measurements from (interior) fuel plate 5 from an element operated for 35 days and stored wet for >6 months were plotted as a function of the initial fuel plate surface temperature (~120-240°F / ~49-116°C), showing measured oxide thicknesses ranging from ~0.1-1.5 mil (3-39 µm) with the majority of measurements in the upper end of the range [25]. The average of the measured values is ~1 mil (25 µm) (note that the spacing of the measurements is unspecified), and 10 of 16 data points measured >1 mil (25 µm).…”