DOE announces grants for SiC cladding research and testing

On October 5, the Department of Energy announced that it plans to award up to $50 million in grants over three years to support research on the use of silicon carbide (SiC) as fuel cladding material.

The DOE touts SiC for what it says is the material's potential to improve the safety and cost efficiency of light water reactors currently operating in the United States and said that research into SiC cladding could further the development of fuels for forthcoming reactors.

The Silicon Carbide Cladding Lead Test Rod Development-Phase 1 grant opportunity aims to bolster research "that will result in the fabrication of 12-foot SiC cladding fuel rods for irradiation testing in research reactors" according to the DOE. The initiative intends to complete research, fabrication, insertion, irradiation, and post-irradiation examinations by 2030.

Responding to questions from Nuclear News about the research reactors to be used, DOE contracting officer Jeff Rigby said, "We anticipate that applicants will be able to use the [Idaho National Laboratory] Advanced Test Reactor (ATR), the [Oak Ridge National Laboratory] High Flux Isotope Reactor (HFIR), the [Massachusetts Institute of Technology] Research Reactor (MITR), and/or other university research reactors for their silicon carbide cladding irradiation campaigns."

The DOE is accepting applications for the grants until December 7.

Accident tolerant fuel: The Nuclear Regulatory Commission lists zirconium alloys, aluminum, and stainless steel as materials often used in cladding-a protective layer of metal that surrounds the fuel in a fuel rod. However, researchers have been investigating possible alternatives for decades.

Research into new types of cladding took on a sense of urgency in 2011, when a 9.1 magnitude earthquake and resulting tsunami caused meltdowns in three reactors at Japan's Fukushima Daiichi nuclear power plant. According to reports, metals in the cladding oxidized when the reactor cores overheated, which led to explosive hydrogen gas escaping into the reactor buildings.

In 2012, Congress appropriated funds to establish what would become known as the Accident Tolerant Fuel (ATF) program, an initiative to develop fuel systems that could withstand a loss of cooling in a reactor core for a longer period of time than the uranium oxide-zirconium alloy systems in wide use.

SiC is an alternative to conventional cladding materials. The NRC cites the material's ability to maintain structural integrity and withstand steam oxidation at high temperatures as benefits.

To date, three U.S. companies have explored SiC as cladding material through the ATF program:

General Atomics, maker of SiGA SiC composite fuel tubes.

Westinghouse, which partnered with General Atomics in 2019 to study the use of SiGA fuel cladding tubes with its own EnCore uranium silicide fuel pellets.

Framatome, which partnered with General Atomics in 2020 to examine the use of SiC as cladding for fuel used in boiling water reactors.

Additionally, according to Rigby, "Related R&D has also been conducted through university projects under the Nuclear Energy University Program (NEUP) and small business projects under the DOE Office of Science's Small Business Innovation Research (SBIR) program. These efforts have focused on silicon carbide cladding concepts for light water reactors, including silicon carbide/silicon carbide composite rod and hybrid silicon carbide/zircaloy rod concepts."

Questions regarding silicon carbide: Along with its benefits, SiC also poses difficulties that the NRC notes on its website. These include the material's permeability to gases produced in the fission process and challenges with fabricating SiC tubing-issues that future research would presumably address.

Moreover, SiC systems are not the only accident tolerant fuel technologies that have been developed or researched. Companies within the United States have considered several alternatives, including the following:

Zirconium alloy cladding coated with chromium.

"Doped" fuel pellets-pellets with chromium or another material added.

Uranium nitride fuel pellets.

Extruded metallic fuel-a blend of uranium and zirconium housed within a zirconium alloy cladding.

Iron-chromium-aluminum (FeCrAl) cladding.

In response to Nuclear News' question regarding the choice of SiC systems as the focus of the current grant opportunity, Rigby said, "Silicon carbide (SiC/SiC) cladding has been a focus of research funding because of its potential to significantly improve nuclear fuel safety, particularly through its high-temperature performance and oxidation resistance. This focus is reinforced by the House Appropriations Committee's continued endorsement in fiscal year 2026 and, most recently, FY 2027, recognizing the progress achieved to date and demonstrating strong congressional support for advancing the technology toward commercial deployment. At the same time, DOE continues to pursue other next-generation fuel technologies."

More information about the silicon carbide cladding grants can be found on the initiative's page on grants.gov.