United States Nuclear Regulatory Commission - Protecting People and the Environment

Lead Test Assemblies

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Lead test assembles (LTAs) are fuel assemblies that contain design features or materials that have not been approved for unrestricted use1 in the reactor core. LTA irradiation campaigns provide knowledge of and experience with irradiated material properties and performance, which is critical for qualifying analytical codes and methods and for developing the design bases to license new fuel material or design features for unrestricted use. In particular, the campaigns are intended to accomplish the following tasks:

  • collection of data to characterize irradiated material properties and performance;
  • provision of irradiated material for subsequent hot-cell examination, characterization, and research;
  • demonstration of in-reactor performance.

LTAs have been loaded in operating reactor cores safely over the past several decades. Licensees may request a license amendment to insert LTAs, or they may be inserted without additional NRC approval through the change process in 10 CFR 50.59.

To clarify and provide regulatory certainty around the use of 10 CFR 50.59 with LTAs, the NRC issued a guidance letter to industry on June 24, 2019.

Several U.S. power reactor licensees have inserted LTAs with ATF technologies, which are listed below. Other technologies may be loaded into LTAs and inserted in reactor cores in the future.

Chromium-coated Cladding

Plant Licensee Fuel Vendor Date Inserted
Hatch Southern Nuclear GNF Spring 2018
Byron Exelon Westinghouse Spring 2019
Vogtle Southern Nuclear Framatome Spring 2019
ANO Entergy Framatome Fall 2019
Clinton Exelon GNF Fall 2019

Doped Pellets

Plant Licensee Fuel Vendor Date Inserted
Byron Exelon Westinghouse Spring 2019
Vogtle Southern Nuclear Framatome Spring 2019
ANO Entergy Framatome Fall 2019

FeCrAl Cladding

Plant Licensee Fuel Vendor Date Inserted
Hatch Southern Nuclear GNF Spring 2019
Clinton Exelon GNF Fall 2019

Uranium Silicide Pellets

Plant Licensee Fuel Vendor Date Inserted
Byron Exelon Westinghouse Spring 2019

1The term "unrestricted use" means that, unlike LTAs, the fuel has been approved for use at a plant without limits on quantity or placement within the core (except for those limits that are part of the approval). License amendments for approval of unrestricted use are commonly called "fuel transitions." Similar terms sometimes used include "batch quantities", "batch loads", and "reload quantities" of fuel assemblies.

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Page Last Reviewed/Updated Thursday, July 23, 2020