US accident tolerant fuels to begin tests

15 February 2018

US-based Global Nuclear Fuel (GNF) said on 8 February that it had manufactured and shipped batches of test assemblies of its IronClad and Armor accident tolerant fuels (ATFs) for installation at Southern Nuclear Operating Company’s two-unit Hatch nuclear plant in early 2018. The lead test assemblies were engineered and manufactured at GNF’s facility in Wilmington, North Carolina.

GNF, a GE-led joint venture with Hitachi Ltd, is working with both Southern Nuclear and Exelon Generation to insert lead test assemblies utilising an iron-chromium-aluminum fuel cladding material (IronClad) and coated zirconium fuel cladding (Armor) into several reactors over the next few years.

The IronClad lead test assemblies will be the first fuel developed through the US Department of Energy’s (DOE’s) Enhanced Accident Tolerant Fuel programme to be installed in a commercial nuclear reactor. “We are exploring many technologies for our advanced fuel portfolio but believe that our expertise and experience with ferritic steel and coated zirconium cladding will enable us to put this enhanced solution to work more quickly for our customers,” said GNF CEO Amir Vexler. GNF developed the Armor coating, which is applied to a standard zirconium fuel rod, to provide debris resistance and more oxidation resistance than conventional zirconium cladding. 

GNF said the IronClad material is designed to provide substantial oxidation resistance and excellent material behaviour over a range of conditions. The low oxidation rates of this material at higher temperatures further improves safety limit margins. The Armor coated zirconium cladding provides enhanced protection of fuel rods against debris fretting. It also provides oxidation resistance and superior material behaviour over a range of conditions making it an attractive technology to improve safety limit margins and abrasion resistance. 

The installation of IronClad material at the Hatch boiling water reactors (BWRs) includes two variations of the iron-chromium-aluminium material. One material will be in fuel rod form but will not be fuelled while the other material is in the form of a solid bar segment. Armor lead test assemblies that contain fuelled coated zirconium rods will be installed in the same reload at Plant Hatch. Lead test assemblies that include both IronClad and Armor fuelled rods are planned for 2019 installation at Exelon Generation’s single unit Clinton nuclear plant, also a BWR.  

The US Nuclear Energy Institute (NEI) on 5 February sent a comment letter to the   Nuclear Regulatory Commission (NRC) on the industry’s path forward to full ATF deployment. The plan aims for phased implementation in a commercial reactor in the early to mid-2020s. “This schedule is of key importance in the decisions our members will need to make when evaluating the ATF safety benefits against the costs of adopting this technology,” NEI Technical Advisor Andrew Mauer said the letter.

NRC published a draft project plan outlining its preliminary strategy to prepare for ATF licence applications for comment in December 2017. In its comment letter, NEI said that the industry finds many aspects of the draft plan commendable but that “a more transformational shift in the NRC’s fuel licensing approach is needed.” NEI suggested that NRC should leverage the DOE’s existing advanced modelling and simulation (M&S) capacity which did not exist 20 years ago.

The DOE's programme to develop accident-tolerant nuclear fuel was launched in 2012, with the aim of developing new cladding materials and new fuel materials that can better tolerate the loss of active cooling in the core, while maintaining or improving fuel performance and economics during normal operation.

Three concepts for advanced fuels are currently under development and qualification with three fuel vendors funded by DOE: France’s Framatome, GNF and Westinghouse. A fourth vendor, Lightbridge, is developing an advanced metallic fuel concept with potential accident tolerant characteristics without DOE support.
 



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