High-temperature compatibility study of iridium (DOP-26 alloy) with graphite and plutonia

Abstract

This report outlines the materials compatibility tests conducted on DOP-26 iridium alloy and carbon. The carbon used was in the form of woven graphite as present in the impact shell used to encase plntonia in nuclear heat sources. In addition, compatibility tests of the DOP-26 alloy with plutonia are described. The reactivity observed in both systems is discussed.

Investigation of oxygen sources and subsequent thorium oxidation in the iridium DOP‐26 cladding material and PuO2 fuel system

“…For example, it has been shown that with partial pressures of oxygen on the order of at least 1.3*10 −3 Pa has a substantial influence on the grain growth of the system due to the oxidation of thorium at the surface of the iridium alloy cladding. 1,2 High quality argon gas sources have a nominal oxygen impurity <10 ppb (<10 −6 wt%). 25 This indicates that if the Ar gas at a pressure ≥260 kPa has 5 ppb oxygen impurities, it would be the equivalent to the partial pressure of oxygen used in previous experimentation.…”

“…1 Iridium was chosen because of its high temperature strength, corrosion resistance, and compatibility with plutonia and graphite. [1][2][3] Tungsten is added for increased fabricability at high temperatures. 1 Thorium is added to improve the impact ductility of the alloy to prevent cracking during an impact event.…”

“…This is an iridium‐based alloy that has 0.3, 0.006. and 0.005 wt% of tungsten, thorium, and aluminum, respectively 1 . Iridium was chosen because of its high temperature strength, corrosion resistance, and compatibility with plutonia and graphite 1‐3 . Tungsten is added for increased fabricability at high temperatures 1 .…”

Properties of Hafnium Oxide with Respect to Its Use as a Simulant for 238PuO2 in Safety Studies

“…We assumed that this diameter was 6,000 µm. ρ(hafnia) = 8.7659 g/cm 3 , 90.56% theoretical density ρ(urania) = 9.2064 g/cm 3 , 84% theoretical density ρ(plutonia) = 9.9596 g/cm 3 , 87.21% theoretical density Appendix II …”

“…This alloy was developed by Oak Ridge National Laboratory, (1) with the alloy development complemented by axial testing and hightemperature compatibility studies conducted at Los Alamos National Laboratory. (2)(3) Two capsules are held in a Fineweave-Pierced Fabric † (FWPF) graphite impact shell (GIS), and two GISs are contained within an FWPF aeroshell module.…”