General Atomics, Framatome join for fuel channel work

The fuel channel in a boiling water reactor (BWR) surrounds the fuel rods and assemblies for structural stability and to direct water over the fuel rods to ensure efficient cooling and heat transfer. These are currently made of zirconium alloy, the same material used for the tubes that hold the fuel pellets. Framatome said replacing zirconium alloys with silicon carbide could provide "substantial temperature and oxidation resistance to significantly reduce the amount of hydrogen that could be generated in the unlikely event of a severe accident".

GA originally developed its SiGA silicon-carbide composite - a ceramic material reinforced with flexible silicon carbide fibres - for its Energy Multiplier Module (EM2) small modular reactor design. This is a modified version of its Gas-Turbine Modular Helium Reactor (GT-MHR) design. The EM2 employs a 500 MWt, 265 MWe helium-cooled fast-neutron high-temperature reactor operating at 850 degrees Celsius. This would be factory manufactured and transported to the plant site by truck.

The partners will evaluate the feasibility of using SiGA in fuel channel applications through thermomechanical and corrosion testing. The long-term goal is to demonstrate the irradiation of a full-length fuel channel in support of licensing and commercialisation. The use of silicon carbide in fuel channels could facilitate the removal of about 40% of the zirconium metal in BWR fuel designs.

"Efforts to increase nuclear plant economics must look at more than just the fuel rods," said Christina Back, GA vice president of nuclear technology and materials. "This project begins the process of developing a fully robust core by deploying modern materials for critical in-core components."

Framatome is conducting this research as part of its PROtect enhanced accident tolerant fuel (EATF) programme. Last year, it delivered lead fuel assemblies with PROtect EATF technologies to two US reactors and one European reactor. These assemblies included Framatome's chromium-coated cladding and chromia-enhanced pellet solutions.

Framatome is one of three companies - the others are Global Nuclear Fuel and Westinghouse - working with the US Department of Energy (DOE) to commercialise their accident tolerant fuel concepts by 2025. The DOE's ATF programme was launched following the 2011 Fukushima Daiichi accident and aims to demonstrate performance by inserting ATF technology into a commercial reactor by 2022, and bring advanced fuel concepts to market by 2025. This accelerated timeframe is critical if ATFs are to benefit the current fleet of operating nuclear reactors, many of which are currently licensed to operate into the 2030s.