Indentation Creep of UO₂ before and after Irradiation

Abstract

Measurements of creep by the indentation with Knoop indenter were performed for sintered UO₂ pellets before and after irradiation and a non-irradiated single crystal with an applied load of 50 g. Room temperature creep of non-irradiated sinters included grain boundary sliding. The creep at the lowest dose (7.8×10¹⁴ fiss./cm³) also involved the grain boundary sliding, while no creep was observed after irradiation of 2.9×10¹⁶ fiss./cm³. Irradiated sinters at a dose between 1.4×10¹⁶ and 1×10¹⁸ fiss./cm³ yielded not only primary creep without the grain boundary sliding but also secondary creep, in which cracks were formed when a dose was less than 4.8×10¹⁷ fiss./cm³. At a dose of 1×10¹⁸ fiss./cm³ the enhanced secondary creep independent of the temperature between 100 and 150°C was observed.

KEYWORDS:

• creep
• indentation
• Knoop indenter
• uranium dioxide
• radiation effects
• fission damage
• grain boundary
• dose rates
• temperature dependence