Rise in Temperature of Uranium Dioxide during Swaging

Abstract

As a part of studies on the development of the swaging process for fabrication of the UO₂ fuel rod, UO₂ compaction and energetics in swaging were dealt with mainly by investigation of the rise in temperature during the process. The temperature was measured by means of a thermocouple of Chromel-Alumel or Pt-PtRh inserted into UO₂ powder in a container of the stainless steel tube. The rise in temperature of UO₂ compact during swaging was as high as 1680°C for hot swaging at 720°C, whereas only a temperature rise of 170°C was observed for cold swaging. The main causes for the heat generation were plastic deformation and friction between UO₂ particles, The former was dominant in hot swaging, and the latter in cold swaging. Optical and electron micro-scopies also revealed the plastic deformation and temperature rise of UO₂ compact. The internal energy stored in cold swaged UO₂ compact was detected by specific heat measurement.