Nuclear Fuel Rod Recycling

In response to the nuclear industry’s desire for longer coping times following the
Fukushima accident in Japan in 2011, Westinghouse Electric Company’s EnCore® accident
tolerant fuel (ATF) program is developing and commercializing an advanced fuel cladding and
fuel pellet to improve safety and economic performance. Fuel rods
are metallic tubes containing nuclear reactor fuel and are bundled into fuel assemblies to be
loaded into the reactor core. Westinghouse has developed Optimized ZIRLOTM and AXIOM®
material for these fuel rods, which are advanced chromium coated zirconium alloys that can tolerate long
reactor cycles. While utilizing Cr coated zirconium has many advantages,
one of the primary challenges faced is that when a coolant solution flows
through a nuclear reactor, it causes corrosion when encountering the zirconium fuel rods at
high temperatures. The Cr coating
reduces the corrosion and consequently hydriding of the zirconium, allowing much longer fuel
cycles and greatly reducing oxidation during accident conditions.
The use of this oxidation and corrosion-resistant coating for the zirconium
alloy tubes has been a crucial development in nuclear fuel research.

Westinghouse has explored the prospect of recycling the zirconium material used in the
manufacturing of these fuel rods in conjunction with Western Zirconium Inc. To recycle
the tubes, the corrosion-resistant chromium coating must first be removed, and certain acceptance
criteria must be met to confirm that there is a minimal amount of chromium remaining. During
the summer of 2022, research was conducted at Westinghouse in Pittsburgh, Pennsylvania to
determine the most effective way to remove the chromium coating from the fuel rods.
Both mechanical and chemical removal methods of the chromium coating were explored.
The mechanical removal of the chromium involved physically
grinding off the coating using a center-less grinding method. The chemical removal
consisted of chemically stripping the rods by placing them into acid baths for a certain amount of
time until the coating had been removed. After each of these removal processes were completed,
the rods were taken back to Westinghouse for material analysis to verify that the coating had in
fact been entirely removed. At Westinghouse laboratories, metallographic, SEM, and EDS
analyses were performed to examine the composition of the outside of the rods.

After the analysis on the tubes that had undergone mechanical coating removal was
completed, Western Zirconium confirmed that the chromium was successfully removed to the
point of meeting their acceptance criteria for recycling. The post chrome removal
analysis for the tubes that had been chemically stripped is still currently being conducted, and these
results will be incorporated into the upcoming presentation to compare the two methods.