Postirradiation Dimensional Stability and Fission Product Behavior of Deliberately Defected UO₂ Fuel at 200 and 400°C

Twenty-four-hour sweep tests have been carried out in flowing air at 200 and 400°C on deliberately defected UO₂ fuel elements with 2.5-yr discharge times. At 200 C there was no diametral change, but at 400 °C, swelling and severe sheath cracking were observed. Neither short-lived fission products nor ¹³⁴Cs, ^I37Cs, or ¹⁰⁶Ru were detected above background. Maximum ⁸⁵Kr release was ≤7.4 × 10⁴ Bq (≤2 × 10^-6 Ci).