Corrosion resistance of pyrolytic graphite in LiCl-KCl-UCl₃ molten salt for pyrochemical reprocessing application

ABSTRACT

Pyrolytic graphite (PyG) is a highly oriented, dense and crystalline form of graphite, which exhibits superior air oxidation resistance, corrosion resistance, and favourable mechanical, thermal, and electrical properties compared to conventional graphite materials. It is proposed as the material of construction for high-temperature molten LiCl-KCl for pyrochemical reprocessing of metallic fuel. In the present study, long-term corrosion behaviour of PyG in LiCl-KCl molten salt with 5 wt-% UCl₃ was evaluated by immersion studies at 873 K for 2000 h, under inert argon atmosphere. Characterisation of PyG before and after molten salt exposure was carried out using X-ray diffraction technique, scanning electron microscope with energy dispersive spectroscopy, laser Raman spectroscopy and X-ray photo-electron spectroscopy. The results revealed the superior corrosion resistance and excellent phase stability of PyG with negligible weight change and no appreciable change in the surface chemistry and morphology up to the exposure time of 2000 h.

KEYWORDS:

• Pyrolytic graphite
• corrosion
• molten salt
• uranium chloride
• surface analysis

Acknowledgements

The authors are indebted to Shri P. Venkatesh, MC&MFCG, IGCAR for his support in the preparation of molten salt, Dr S. Ramya, CSTD and Shri. K. G. Raghavendra, PMD, IGCAR for providing LRS data and SEM images, respectively. The authors acknowledge Mr Yogesh Kumar and Mr Kaliraj of CSTD for assistance in molten salt corrosion test. This work forms a part of the thesis to be submitted by Ms Madhura to HBNI, Mumbai for the award of MSc degree in Engineering Sciences. She also expresses her gratitude to DAE for providing Fellowship to carry out this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

S. Ningshen http://orcid.org/0000-0002-2078-7870