US General Atomics has completed its first round of testing at Idaho National Laboratory (INL) on unfuelled samples of a new high-temperature ceramic fuel cladding. This is part of a series of tests with US Department of Energy (DOE) to commercialise the SiGA fuel cladding early next decade.
General Atomics is developing cladding made from silicon carbide (SiC). This ceramic material can withstand temperatures up to 3800°F – 500°F higher than the melting point of the zirconium alloy currently widely used in operating light water reactors. SiGA’s multi-layered SiC composite cladding structure is sealed with a fully-SiC joining process, enabling exceptional stability during operational temperature cycling.
The first set of unfuelled SiGA rodlets that completed a 120-day irradiation cycle in INL’s Advanced Test Reactor showed no initial signs of structural damage, leakage, or significant mass changes. These rodlets will now undergo additional post-irradiation examination at the lab to better inform future experiments.
“This testing provides initial validation that SiGA cladding can effectively contain the fuel and any fission products that are produced under irradiation and high temperature conditions,” said Christina Back, Vice President of Nuclear Technologies & Materials at General Atomics Electromagnetic Systems (GA-EMS). “This is a key milestone on SiGA cladding’s development path to enhance the safety of the existing US fleet of light water reactors.”
GA-EMS President Scott Forney said the test results “offer critical, quantifiable, and independent validation that our SiC cladding technology is on the right path to provide a safe, suitable, accident tolerant fuel cladding solution for the nuclear fleet.” It is a key milestone on the development path to enhance the safety of light water reactors, particularly during an unlikely event of an accident and could also do the same for the future generation of advanced nuclear power systems, he noted.
Previous testing at the lab demonstrated the rodlets’ performance at elevated accident temperatures. They were also exposed to high temperature steam conditions and remained intact under loss-of-coolant conditions that caused zircalloy rods to fail and burst under the same conditions.
Additional irradiation experiments on the SiGA rodlets are in research reactors at INL, Oak Ridge National Laboratory (ORNL), and the Massachusetts Institute of Technology (MIT) to help verify cladding’s material properties and strength.
General Atomics is progressing through three types of irradiation experiments – unfuelled, non-uranium fuelled, and uranium fuelled rodlets. Future testing on fuelled SiGA rodlets in INL, ORNL, and MIT research reactors will eventually lead to irradiation in commercial power reactors using full-length, 12-foot fuel rods in the next six years. The performance data will be used to support Nuclear Regulatory Commission licensing.
DOE previously supported the development and demonstration of SiGA cladding through its Accident Tolerant Fuel Programme From FY25, SiGA cladding will be funded through DOE’s new Next Generation Fuels Programme, which supports industry through financial assistance and lab-based research and development by focusing on developing and maturing longer-term, high-risk, high-reward fuel concepts.
“We look forward to continuing our partnership with the DOE and the national labs to accelerate the irradiation testing to demonstrate the performance of fuelled SiGA cladded rods. The planned test series progressively builds up performance data to show that SiGA cladding can effectively contain the fuel and any gasses that are produced when subjected to irradiation and high temperature,” said Dr Christina Back, Vice President of GA-EMS Nuclear Technologies and Materials. “In parallel, we are scaling up to full size, 12-foot long SiGA rods and will then be doing the irradiation testing in actual commercial reactors with deployment targeted for the mid-2030 timeframe. We remain committed to bringing SiGA’s unique safety and efficiency benefits to the nation’s nuclear fleet.”
