A novel approach to process TRISO nuclear fuel using plasma-aided chemistry

TL;DR

This paper explores plasma-assisted chemical processes for reprocessing TRISO nuclear fuel, demonstrating the feasibility of removing barrier layers using plasma etching techniques to facilitate volume reduction and potential recycling.

Contribution

It introduces a novel plasma-based method for etching TRISO fuel layers, enabling potential reprocessing and volume reduction of nuclear fuel waste.

Findings

Chemical etching of SiC and PyC layers is achievable with plasma radicals.

Complete removal of TRISO layers is demonstrated in laboratory conditions.

Further research needed on waste gases and process optimization.

Abstract

This paper provides a unique and to the best of our knowledge first-of-a-kind attempt to develop chemical processes that may contribute to the volume reduction of SMR TRISO-based fuels and aims at the eventual ability to reprocess the spent fuel. To this end, the etching behavior of two materials, silicon carbide, SiC and pyrolytic carbon, PyC, that are generally used for the different barrier layers of a TRISO particle has been investigated. Either F/NFx or O radicals were used as etching agents and were obtained from NF3 and molecular O2, respectively, using a microwave plasma generated in a remote plasma source RPS. Laser heating of the sample materials of up to 1200 {\deg}C allowed for determination of etching rates. The results of these experiments show that chemical processing of TRISO particles via plasma-assisted etching is possible and complete removal of the encapsulation and TRISO layers can be achieved. Additional research on the waste streams and off-gases, in particular the possibility of introducing intermediate steps to reduce the CO2 formed in the chemical reactions is needed.