Synthesis, characterisation and corrosion behaviour of simulant Chernobyl nuclear meltdown materials

Abstract

Understanding the physical and chemical properties of materials arising from nuclear meltdowns, such as the Chernobyl and Fukushima accidents, is critical to supporting decommissioning operations and reducing the hazard to personnel and the environment surrounding the stricken reactors. Relatively few samples of meltdown materials are available for study, and their analysis is made challenging due to the radiation hazard associated with handling them. In this study, small-scale batches of low radioactivity (i.e., containing depleted uranium only) simulants for Chernobyl lava-like fuel-containing materials (LFCMs) have been prepared, and were found to closely approximate the microstructure and mineralogy of real LFCM. The addition of excess of ZrO 2 to the composition resulted in the first successful synthesis of high uranium-zircon (chernobylite) by crystallisation from a glass melt. Use of these simulant materials allowed further analysis of the thermal characteristics of LFCM and the corrosion kinetics, giving results that are in good agreement with the limited available literature on real samples. It should, therefore, be possible to use these new simulant materials to support decommissioning operations of nuclear reactors post-accident.

Safely probing the chemistry of Chernobyl nuclear fuel using micro-focus X-ray analysis

“…13 Furthermore, the corrosion rates of U from the simulant LFCMs were found to be similar to those determined from limited studies of real LFCM. 13 Micro-focus X-ray analysis Samples were prepared for m-focus measurements (m-XRF, m-XANES and m-XRD) by sectioning mounting on a 250 mm thick Spectrosil fused quartz slide. The sample was then thinned and polished to a thickness of 50 mm by standard metallographic procedures.…”

“…This has resulted in the formation of secondary uranium phases at the surface of LFCM 35 that can be released into the air as aerosol particles, which are a respirable hazard during decommissioning processes. 36 Given that the local coordination of U in the glass matrix of brown and black LFCM was different, and that in our previous work we showed that LFCM corrosion by water proceeded in a similar mechanism to glass corrosion, 13 it is possible that the U released during glass corrosion, and hence the formation of secondary uranium phases may be different for the brown and black LFCM. Further work is required to determine the corrosion mechanisms and verify this hypothesis.…”

“…Analysis by X-Ray Diffraction (XRD) and Scanning Electron Microscopy, coupled with Energy Dispersive X-ray Spectroscopy (SEM/EDS), demonstrated that the simulant LFCMs accurately reected the phase assemblage, microstructure and mechanical properties of real brown and black LFCM. [12][13][14] Thermal characterisation of the simulants conrmed that the crystallisation temperatures were consistent with those of naturally-occurring versions of the LFCM minerals. 13 Furthermore, the corrosion rates of U from the simulant LFCMs were found to be similar to those determined from limited studies of real LFCM.…”

“…[12][13][14] Thermal characterisation of the simulants conrmed that the crystallisation temperatures were consistent with those of naturally-occurring versions of the LFCM minerals. 13 Furthermore, the corrosion rates of U from the simulant LFCMs were found to be similar to those determined from limited studies of real LFCM. 13 Micro-focus X-ray analysis Samples were prepared for m-focus measurements (m-XRF, m-XANES and m-XRD) by sectioning mounting on a 250 mm thick Spectrosil fused quartz slide.…”

“…excluding ssion products, were synthesised and characterised. [12][13][14] Detailed bulk analysis of these simulant materials was reported and the morphology and mineralogy were found to closely approximate those of real LFCMs. In the present study, micro-focus synchrotron X-ray analysis was used to investigate several representative regions of these materials.…”